U.S. patent application number 12/922970 was filed with the patent office on 2011-04-21 for system and method for producing and determining cooling capacity of two-phase coolants.
This patent application is currently assigned to THE TRUSTEES OF THE UNIVERSITY OF PENNSYLVANIA. Invention is credited to Lance B. Becker, Diana Bull, Joshua W. Lampe.
Application Number | 20110088413 12/922970 |
Document ID | / |
Family ID | 41091540 |
Filed Date | 2011-04-21 |
United States Patent
Application |
20110088413 |
Kind Code |
A1 |
Lampe; Joshua W. ; et
al. |
April 21, 2011 |
SYSTEM AND METHOD FOR PRODUCING AND DETERMINING COOLING CAPACITY OF
TWO-PHASE COOLANTS
Abstract
The invention provides systems and devices for producing
two-phase coolants such as an ice slurry. Also provided are methods
for producing two-phase coolants, and methods for using the
two-phase coolants to lower the temperature or maintain a low
temperature in any subject, system, object, device, or application
where particular low temperatures are desired. Also provided are
systems for determining the cooling capacity of two-phase
coolants.
Inventors: |
Lampe; Joshua W.;
(Philadelphia, PA) ; Becker; Lance B.;
(Philadelphia, PA) ; Bull; Diana; (Philadelphia,
PA) |
Assignee: |
THE TRUSTEES OF THE UNIVERSITY OF
PENNSYLVANIA
Philadelphia
PA
|
Family ID: |
41091540 |
Appl. No.: |
12/922970 |
Filed: |
March 19, 2009 |
PCT Filed: |
March 19, 2009 |
PCT NO: |
PCT/US09/37679 |
371 Date: |
December 13, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61037949 |
Mar 19, 2008 |
|
|
|
Current U.S.
Class: |
62/68 ;
62/340 |
Current CPC
Class: |
F28D 15/0233 20130101;
F28F 13/00 20130101; C09K 5/066 20130101; F25C 1/00 20130101; F25C
2301/002 20130101 |
Class at
Publication: |
62/68 ;
62/340 |
International
Class: |
F25C 1/18 20060101
F25C001/18; F25C 1/00 20060101 F25C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2008 |
WO |
US2008/080435 |
Claims
1. A method for producing a flowable ice slurry comprising the
steps of: supercooling a liquid; moving the supercooled liquid in a
stable flow through a passage; and disturbing the stable flow of
the supercooled liquid, thus inducing ice nucleation in the
supercooled liquid and producing a flowable ice slurry.
2. The method of claim 1, wherein the moving step comprises moving
the supercooled liquid in a stable flow through a tube or pipe.
3. The method of claim 1, wherein the supercooling step comprises
supercooling a saline solution.
4. The method of claim 1, wherein the disturbing step comprises
producing a flowable ice slurry comprising from about 0% to about
60% ice.
5. The method of claim 1, wherein the disturbing step comprises
fluctuating a pressure of the supercooled liquid in the
passage.
6. The method of claim 5, wherein the disturbing step further
comprises introducing an impinging jet of a second supercooled
liquid into the stable flow of the supercooled liquid.
7. The method of claim 6, wherein the disturbing step is performed
in a substantially closed system in which the second supercooled
liquid is mixed with the supercooled liquid or in an at least
partially open system in which the second supercooled liquid
impinges against a substantially static surface of the supercooled
liquid.
8. The method of claim 1, wherein the disturbing step comprises
ultrasonically disturbing the stable flow.
9. The method of claim 1, wherein the disturbing step comprises
generating an eddy or vortex in the stable flow.
10. The method of claim 1, wherein the disturbing step comprises
creating at least one stagnation point in the stable flow.
11. The method of claim 10, wherein the disturbing step comprises
contacting the stable flow with at least one ice crystal.
12. The method of claim 10, wherein the disturbing step comprises
contacting the stable flow with at least one trip.
13. The method of claim 12, wherein the disturbing step comprises
contacting the stable flow with at least one trip positioned near a
center of the flow of the supercooled liquid.
14. The method of claim 12, wherein the disturbing step comprises
contacting the stable flow with at least one trip positioned near a
periphery of the flow of the supercooled liquid.
15. The method of claim 12, wherein the trip generates an eddy or a
vortex.
16. The method of claim 10, wherein the trip is selected from the
group consisting of a post design trip, a cross-wire trip, a tooth
design trip, a central tooth design trip, a sticky sphere trip, a
pyramidal trip, a surface roughness trip, a teeth combination trip,
a dimpled tube trip, and a cone with blades trip, or combinations
thereof.
17. The method of claim 1, further comprising the step of removing
heat from the ice slurry.
18. The method of claim 17, wherein the heat removing step
comprises contacting the ice slurry with a heat exchanger.
19. The method of claim 1, further comprising the step of lowering
the free energy of the stable flow with the use of an
interface.
20. The method of claim 1, wherein the supercooling step comprises
the steps of: supercooling a concentrated liquid; supercooling
water or a less concentrated liquid; and, mixing the supercooled
concentrated liquid and the supercooled water or less concentrated
liquid to form a supercooled liquid.
21. The method of claim 1, wherein the moving step comprises moving
the supercooled liquid in a laminar flow through the passage.
22. The method of claim 1, wherein the moving step comprises moving
the supercooled liquid in a turbulent flow through the passage.
23. A method for producing a flowable ice slurry comprising the
steps of: supercooling a concentrated liquid; supercooling water or
a less concentrated liquid; mixing the supercooled concentrated
liquid and the supercooled water or less concentrated liquid to
form a supercooled solution; moving the supercooled solution in a
stable flow through a passage; and disturbing the stable flow of
the supercooled solution, thus inducing ice nucleation in the
supercooled solution and producing a flowable ice slurry.
24. The method of claim 23, wherein the concentrated liquid is
saline.
25. A system for producing an ice slurry, comprising: a heat
exchanger configured to supercool a liquid solution; a passage
coupled to receive a stable flow of the supercooled liquid solution
from the heat exchanger; and means associated with the passage for
disturbing the stable flow of the supercooled liquid in the passage
and inducing ice nucleation in the supercooled liquid, thus
producing a flowable ice slurry.
26. The system of claim 25, said disturbing means comprising a jet
configured to introduce an impinging supercooled liquid into the
supercooled liquid solution.
27. The system of claim 25, said disturbing means comprising an
ultrasound transducer.
28. The system of claim 25, said disturbing means comprising at
least one stagnation point.
29. The system of claim 28, wherein the stagnation point is a
trip.
30. The system of claim 29, wherein the trip is positioned near a
center of the flow of the supercooled liquid solution.
31. The system of claim 29, wherein the trip is selected from the
group consisting of a post design trip, a cross-wire trip, a tooth
design trip, a central tooth design trip, a sticky sphere trip, a
pyramidal trip, a surface roughness trip, a teeth combination trip,
a dimpled tube trip, and a cone with blades trip, or combinations
thereof.
32. The system of claim 25, said disturbing means comprising at
least one eddy or vortex shedding point.
33. The system of claim 25, wherein the passage comprises at least
one interface to lower a free energy of the supercooled liquid
solution.
34. The system of claim 25, further comprising an inlet positioned
to introduce supercooled water for mixing with the liquid
solution.
35. The system of claim 25, further comprising a second heat
exchanger coupled to receive ice slurry from the disturbing means
and configured to remove heat from the ice slurry.
36. A device for inducing ice nucleation in a supercooled liquid,
comprising: a conduit configured to be coupled to a source of
supercooled liquid, the conduit defining a passage positioned to
receive a stable flow of the supercooled liquid; and at least one
stagnation point associated with the conduit and positioned to
disturb the stable flow of the supercooled liquid, the at least one
stagnation point being configured to induce ice nucleation in the
supercooled liquid, thus producing a flowable ice slurry.
37. The device of claim 36, wherein the at least one stagnation
point comprises a trip.
38. The device of claim 37, wherein the trip is positioned near a
center of the passage.
39. The device of claim 37, wherein the trip is selected from the
group consisting of a post design trip, a cross-wire trip, a tooth
design trip, a central tooth design trip, a sticky sphere trip, a
pyramidal trip, a surface roughness trip, a teeth combination trip,
a dimpled tube trip, and a cone with blades trip, or combinations
thereof.
40. The method of claim 1, wherein the disturbance comprises a seed
piece of ice that presents a substantially stable heterogeneous
nucleation site.
41. The method of claim 6, wherein the second supercooled liquid is
different from the supercooled liquid.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/037,949, filed Mar. 19, 2008 and International
Application No. PCT/US2008/080435, filed Oct. 20, 2008. The
disclosure of each application is incorporated by reference herein,
in its entirety and for all purposes.
FIELD
[0002] The invention relates generally to the field of
refrigeration and cooling. More specifically, the invention relates
to systems for producing a coolant such as a two-phase coolant and
to systems for measuring the cooling capacity of coolants such as
two-phase, liquid-solid coolants.
BACKGROUND
[0003] Numerous industries require cooling systems for a large
variety of applications. In many cases, refrigerant chemicals or
machines are used to generate cold air or ice for a desired
application. Although various cooling systems have been proposed,
there remains a need in the art for improved cooling systems.
SUMMARY
[0004] In one aspect, the invention provides systems for producing
a two-phase coolant. The system comprises a first container, a
homogenizer coupled to receive a first fluid from the first
container, a valve positioned to control flow of the first fluid
from the first container to the homogenizer and, a second container
coupled to deliver a second fluid to the homogenizer. The first
container can be configured to maintain the first fluid at a
temperature below the atmospheric freezing point of the first fluid
and can be pressurized at a level sufficiently high to cause
substantially instantaneous freezing of the first fluid upon its
release from the first container. The second container can be
configured to maintain the second fluid at a temperature below the
atmospheric freezing point of the first fluid. The homogenizer can
comprise an aperture for efflux of the produced coolant.
[0005] In an additional aspect, the invention provides methods for
producing a coolant such as a two-phase coolant. The methods
comprise admixing a microparticalized solid produced by releasing
from a pressurized container a first fluid cooled to a temperature
below its atmospheric freezing point with a carrier fluid cooled to
a temperature below the atmospheric freezing point of the first
fluid. It is preferred that the pressure in the container is
sufficiently high to cause substantially instantaneous freezing of
the first fluid upon release from the container. In some aspects,
the microparticalized solid is ice. The first fluid or carrier
fluid can be aqueous or nonpolar. Aqueous fluids can be a
physiologically compatible buffer, or can comprise one or more
salts, sugars, biomolecules, surfactants, or emulsifiers.
[0006] The invention also provides methods for inducing hypothermia
in a subject. The methods can comprise administering to the subject
a pharmaceutically acceptable microparticulate two-phase coolant in
an amount effective to induce hypothermia in the subject. The
subject can be any animal, and is preferably a human being. The
hypothermia can be systemic or can be localized to one or more
particular organs, tissues, locations, cavities, spaces, or regions
in the body.
[0007] The invention further provides methods for cooling
perishable goods. The methods can comprise producing a
microparticulate two-phase coolant and exposing perishable goods to
the coolant. Perishable goods can be a food or beverage product,
chemical, drug, or pharmaceutical compound or composition, cells,
tissues, biological fluids, organs, and the like.
[0008] The invention further provides methods for cooling devices.
In some preferred aspects, the devices are weapons. The methods can
comprise producing a microparticulate two-phase coolant and
exposing the device to the coolant. Exemplary weapons include guns,
cannons, and weaponized lasers.
[0009] Also provided are methods for cooling rooms. Such methods
can comprise producing a microparticulate two-phase coolant,
exposing air to the coolant, and circulating the cooled air
throughout at least one room.
[0010] In another aspect, the invention provides a system for
determining the cooling capacity of a two-phase, solid-liquid
coolant. A length of conduit with known heat transfer
characteristics receives a flow of two-phase, solid-liquid coolant
at a prescribed volumetric flow rate. A heat source is positioned
to transfer heat to the coolant flowing through the interior of the
conduit. At least one heat flux sensor and at least one temperature
sensor are positioned on the conduit to measure heat transfer to
the coolant and coolant temperature as functions of the distance
traveled by the coolant through the conduit interior. Electronics
coupled to the temperature and heat flux sensors compute the
cooling capacity of the coolant using the heat transfer to the
coolant and coolant temperature change measured in the conduit.
[0011] In an additional aspect, the invention provides a system to
detect solid void fraction and solid particle size in a two-phase,
solid-liquid coolant. A conduit of a predetermined length with
known heat transfer characteristics having an interior and an
exterior and an inlet and an outlet receives a flow of a two-phase,
solid-liquid coolant at a prescribed volumetric flow rate. A heat
source is positioned to transfer heat to the coolant flowing
through the interior of the conduit. The conduit has at least one
heat flux sensor positioned to measure heat transfer to the coolant
as a function of distance traveled by the coolant through the
conduit. The conduit further has at least one temperature sensor
positioned to measure coolant temperature in the conduit interior
as a function of distance traveled by the coolant through the
conduit. Electronics coupled to the temperature and heat flux
sensors determine the solid void fraction and solid particle size
of the coolant using the measured heat transfer and
temperature.
[0012] In an additional aspect, the invention provides a method of
determining the cooling capacity of a two-phase, solid-liquid
coolant. Heat is transferred to a prescribed volumetric flow of a
two-phase, solid-liquid coolant flowing through a conduit of a
predetermined length having an interior and an exterior and known
heat transfer characteristics. The heat transfer to the flow of
coolant in the conduit and the coolant temperature are measured as
a function of distance traveled by the coolant through the conduit.
The cooling capacity of the coolant is calculated using the
measured heat transfer and coolant temperature.
[0013] In an additional aspect, a method of detecting solid void
fraction and solid particle size in a two-phase, solid-liquid
coolant is provided. Heat is transferred to a prescribed volumetric
flow of a two-phase, solid-liquid coolant flowing through a conduit
of a predetermined length having an interior and an exterior and
known heat transfer characteristics. The heat transfer to the flow
of coolant in the conduit and the temperature of the coolant in the
conduit are measured as a function of distance traveled by the
coolant through the conduit. The measured heat transfer and coolant
temperature are correlated with the coolant solid void fraction and
solid particle size, and the coolant solid void fraction and solid
particle size are calculated.
[0014] The invention also features systems and devices for
producing a two phase coolant such as an ice slurry. In one aspect,
a system for producing an ice slurry is provided, which comprises a
low concentration saline, such as a commercially available, 0.45%,
0.9% or 3.0% physiological saline solution, a coolant such as dry
ice or a compressed gas, a heat exchanger configured to control the
freezing temperature of the low concentration saline, and a heat
source positioned to heat the ice slurry that forms as the saline
freezes. The heat exchanger can comprise two concentric tubes, with
the inner tube configured for ice slurry formation and flow, and
the outer tube configured to comprise the coolant for cooling the
inner tube to allow a portion of the low concentration saline to
freeze, resulting in an ice slurry comprising liquid phase and
solid phase (frozen) low concentration saline solution. The ice
slurry can comprise about 0.001%, 5%, 10%, 15%, 20%, 25%, 30%, 35%,
40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or more
solid phase ice. The heat exchanger can alternatively comprise a
heat pipe such as an annular heat pipe.
[0015] In some aspects, devices for producing an ice slurry can
comprise a housing comprising a heat exchanger comprising at least
one coolant and configured to control the freezing temperature of a
fluid such as a low concentration saline, a driveshaft which can be
configured to rotate, at least one scraper blade coupled to the
driveshaft and configured to scrape ice from the side walls of the
heat exchanger, an internal disk coupled to the heat exchanger and
configured to hold the bearing at an end of the driveshaft, a
mixing vessel housing coupled to the housing comprising the heat
exchanger and comprising a mixing vessel, and a mixing vessel
configured to receive ice slurry from the heat exchanger and to
receive a high concentration saline solution, and comprising a
mixing blade.
[0016] The heat exchanger can comprise two concentric tubes, with
the inner tube configured for ice slurry formation and flow, and
the outer tube configured to comprise the coolant for cooling the
inner tube to allow a portion of the low concentration saline to
freeze, resulting in a low concentration saline-ice slurry
comprising liquid phase saline and solid phase ice. The heat
exchanger can alternatively comprise a heat pipe such as an annular
heat pipe. The low concentration saline can be a commercially
available, medical grade saline solution such as a 0.45%, 0.9%, or
3.0% physiological saline solution. The high concentration saline
can be a commercially available, medical grade saline solution such
as 3.0%, 5.0%, or 7.5%% physiological saline solution.
[0017] The device can further comprise pumps. For example, the
device can comprise a first pump configured to transport the ice
slurry through one or more components of the device, and can
comprise a second pump configured to pump coolant through the heat
exchanger. Any suitable coolant can be used, such as dry ice, dry
ice-alcohol slurry, a compressed gas, freezing point depressed
water, ethylene glycol, or polyethylene glycol.
[0018] The invention also provides kits for producing an ice
slurry, for example, by using the systems, devices, and methods
described and exemplified herein. In some aspects, the kits
comprise a low concentration saline solution, at least one coolant,
a heat exchanger configured to control the freezing temperature of
the saline, and a high concentration saline solution. The coolant
can be any suitable coolant such as dry ice or a compressed gas.
The low concentration saline can be a commercially available,
medical grade saline solution such as a 0.45%, 0.9%, or 3.0%
physiological saline solution. The high concentration saline can be
a commercially available, medical grade saline solution such as a
3.0%, 5.0%, 7.5%% physiological saline solution.
[0019] The heat exchanger can comprise two concentric tubes, with
the inner tube configured for ice slurry formation and flow, and
the outer tube configured to comprise the coolant for cooling the
inner tube to allow a portion of the low concentration saline to
freeze, resulting in an ice slurry comprising liquid phase saline
solution and a solid phase of ice. The heat exchanger can
alternatively comprise a heat pipe such as an annular heat
pipe.
[0020] The invention also provides methods for producing an ice
slurry. Generally, the methods comprise contacting a low
concentration saline solution with a heat exchanger comprising at
least one coolant and configured to control the freezing
temperature of the saline solution. Upon contact of the saline
solution with the heat exchanger, a portion of the saline solution
freezes within the heat exchanger, and the remainder of the saline
solution remains in the liquid state to form an ice slurry. After
formation of the ice slurry, the methods comprise the step of
admixing a high concentration saline solution with the ice
slurry.
[0021] The heat exchanger can comprise two concentric tubes, with
the inner tube configured for ice slurry formation and flow, and
the outer tube configured to comprise the coolant for cooling the
inner tube to allow a portion of the low concentration saline to
freeze, resulting in an ice slurry comprising liquid phase and
frozen low concentration saline solution. The heat exchanger can
alternatively comprise a heat pipe such as an annular heat pipe.
The low concentration saline can be a commercially available,
medical grade saline solution such as a 0.45%, 0.9%, or 3.0%
physiological saline solution. The high concentration saline can be
a commercially available, medical grade saline solution such as a
3.0%, 5.0%, or 7.5% physiological saline solution. The ice slurry
can comprise about 0.001%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%,
45%, 50%, 55%, 60%, 65%, 70% or more solid phase saline.
[0022] The invention also provides methods for inducing hypothermia
in a subject. The methods comprise administering to the subject an
effective amount of a pharmaceutically acceptable ice slurry
produced by contacting a low concentration saline solution with a
heat exchanger comprising at least one coolant and configured to
control the freezing temperature of the saline solution wherein a
portion of the saline solution freezes within the heat exchanger,
and the remainder of the saline solution remains in the liquid
state to form an ice slurry, and admixing a high concentration
saline solution with the ice slurry. The subject can be any animal
and is preferably a human. The hypothermia can be systemic
throughout the body of the subject, or can be localized to a
particular organ, tissue, location, cavity, space or region in the
body of the subject.
[0023] The invention further provides methods for producing a
flowable ice slurry that comprise the steps of supercooling a
liquid, moving the supercooled liquid in a stable flow through a
passage and disturbing the stable flow of the supercooled liquid,
thus inducing ice nucleation in the supercooled liquid and
producing a flowable ice slurry. In some aspects, the moving step
can comprise moving the supercooled liquid in a stable flow through
a tube or pipe. The moving step can comprise moving the supercooled
liquid in a laminar flow through the passage, or in a turbulent
flow through the passage.
[0024] In some preferred aspects, the supercooling step comprises
supercooling a saline solution. The flowable ice slurry produced by
these methods preferably comprises from about 0% to about 80% ice.
The flowable ice slurry can also comprise from about 0% to about
60%, or from about 0% to about 30% ice. The flowable ice slurry can
also comprise at least about 20%. In some aspects, the methods
further comprise the step of removing heat from the ice slurry, for
example, by contacting the ice slurry with a heat exchanger. In
some aspects, the methods further comprise the step of lowering the
free energy of the stable flow.
[0025] The disturbing step can comprise fluctuating a pressure of
the supercooled liquid in the passage, and can further comprise
introducing an impinging jet of a second supercooled liquid into
the stable flow of the supercooled liquid. The second supercooled
liquid is optionally different from, or the same as, the
supercooled liquid. The disturbing step is optionally performed in
a substantially closed system in which the second supercooled
liquid is mixed with the supercooled liquid or in an at least
partially open system in which the second supercooled liquid
impinges against a substantially static surface of the supercooled
liquid.
[0026] In some aspects, the disturbing step comprises
ultrasonically disturbing the stable flow. In other aspects, the
disturbing step comprises generating an eddy or vortex in the
stable flow. In other aspects, the disturbing step comprises
introducing an interface with a contact angle that preferably
lowers the free energy barrier. In other aspects, the disturbing
step comprises introducing a seed piece of ice which can create a
heterogeneous nucleation site. In yet other aspects, the disturbing
step comprises contacting the stable flow with at least one
stagnation point. The stagnation point can be, for example, at
least one ice crystal. The stagnation point can also be, for
example, at least one trip.
[0027] The trip can be positioned near the center of the flow of
the supercooled liquid, or positioned near a periphery of the flow
of the supercooled liquid. In some aspects, the trip can generate
an eddy or a vortex. Preferred examples of suitable trips can be
selected from the group consisting of a post design trip, a
cross-wire trip, a tooth design trip, a central tooth design trip,
a sticky sphere trip, a pyramidal trip, a surface roughness trip, a
teeth combination trip, a dimpled tube trip, and a cone with blades
trip, or combinations thereof.
[0028] In some aspects of the methods, the supercooling step
comprises the steps of supercooling a concentrated liquid,
supercooling water and, mixing the supercooled concentrated liquid
and the supercooled water to form a supercooled liquid.
[0029] The invention also provides methods for producing a flowable
ice slurry comprising the steps of supercooling a concentrated
liquid, supercooling water or supercooling a less concentrated
liquid, mixing the supercooled concentrated liquid and the
supercooled water or less concentrated liquid to form a supercooled
solution, moving the supercooled solution in a stable flow through
a passage, and disturbing the stable flow of the supercooled
solution, thus inducing ice nucleation in the supercooled solution
and producing a flowable ice slurry. The concentrated liquid is
preferably saline.
[0030] The invention also provides systems for producing an ice
slurry, comprising a heat exchanger configured to supercool a
liquid solution, a passage coupled to receive a stable flow of the
supercooled liquid solution from the heat exchanger, and means
associated with the passage for disturbing the stable flow of the
supercooled liquid in the passage and inducing ice nucleation in
the supercooled liquid, thus producing a flowable ice slurry. In
some aspects, the disturbing means comprise a jet configured to
introduce an impinging supercooled liquid into the supercooled
liquid solution. In other aspects, the disturbing means comprise an
ultrasound transducer. In other aspects, the disturbing means
comprise at least one eddy or vortex shedding point. In other
aspects, the disturbing step comprises introducing an interface
with a contact angle that preferably lowers the free energy
barrier. In other aspects, the disturbing step comprises
introducing a seed piece of ice which can create a heterogeneous
nucleation site In yet other aspects, the disturbing means comprise
at least one stagnation point such as a trip.
[0031] The trip can positioned near the center of the flow of the
supercooled liquid solution or a periphery of the flow of the
supercooled liquid solution. Preferred examples of suitable trips
can be selected from the group consisting of a post design trip, a
cross-wire trip, a tooth design trip, a central tooth design trip,
a sticky sphere trip, a pyramidal trip, a surface roughness trip, a
teeth combination trip, a dimpled tube trip, and a cone with blades
trip, or combinations thereof.
[0032] The systems can comprise at least one interface to lower a
surface energy of the supercooled liquid solution. The systems can
further comprise an inlet positioned to introduce supercooled water
for mixing with the liquid solution. The systems can further
comprise a second heat exchanger coupled to receive ice slurry from
the disturbing means and configured to remove heat from the ice
slurry.
[0033] The invention also provides devices for inducing ice
nucleation in a supercooled liquid, comprising a conduit configured
to be coupled to a source of supercooled liquid, the conduit
defining a passage positioned to receive a stable flow of the
supercooled liquid, and at least one stagnation point, or at least
one eddy or vortex shedding point, or at least one interface with a
contact angle that lowers the free energy barrier associated with
the conduit and positioned to disturb the stable flow of the
supercooled liquid, the at least one stagnation point, at least one
eddy or vortex shedding point, or at least one interface being
configured to induce ice nucleation in the supercooled liquid, thus
producing a flowable ice slurry. The at least one stagnation point,
at least one eddy or vortex shed point, or at least one interface
can comprise a trip. The trip can be positioned near the center of
the passage. Preferred examples of suitable trips can be selected
from the group consisting of a post design trip, a cross-wire trip,
a tooth design trip, a central tooth design trip, a sticky sphere
trip, a pyramidal trip, a surface roughness trip, a teeth
combination trip, a dimpled tube trip, and a cone with blades trip,
or combinations thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 shows a schematic view of an exemplary embodiment of
a two-phase coolant production system.
[0035] FIG. 2 shows a schematic diagram of an exemplary embodiment
of a system to measure solid void fraction and particle size in a
two-phase, liquid-solid coolant.
[0036] FIG. 3 shows a graphic diagram of the effect of particle
size on heat flux measurement.
[0037] FIG. 4A-C shows a schematic diagram of two nozzle
embodiments adapted for the generation of ice from a pressurized
liquid. The shaded areas are surfaces that may be heated or coated
with non-stick substances to impede internal ice formation and
blockage of the nozzle outlets.
[0038] FIG. 5 shows a schematic of an embodiment of a two phase
coolant production system that utilizes phase changes as opposed to
electrical refrigeration to promote freezing.
[0039] FIG. 6A-B shows an exploded view of one embodiment of a two
phase coolant production device.
[0040] FIG. 7A-B shows an embodiment of a housing for the various
components of a two phase coolant production device.
[0041] FIG. 8 shows an embodiment of a heat exchanger that can be
used in the coolant production assembly shown in FIG. 6.
[0042] FIG. 9 shows an embodiment of a driveshaft that can be used
in the coolant production assembly shown in FIG. 6.
[0043] FIG. 10 shows an embodiment of an ice scraper blade that can
be used in the coolant production assembly shown in FIG. 6.
[0044] FIG. 11A-C shows an embodiment of an internal disk that can
be used in the coolant production assembly shown in FIG. 6.
[0045] FIG. 12A-C shows an embodiment of a two phase coolant mixing
blade that can be used in the coolant production assembly shown in
FIG. 6.
[0046] FIG. 13 shows an embodiment of a mixing vessel that can be
used in the coolant production assembly shown in FIG. 6.
[0047] FIG. 14 shows an embodiment of a mixing vessel housing that
can be used in the coolant production assembly shown in FIG. 6.
[0048] FIG. 15 shows an embodiment of a heat exchanger comprising
an annular heat pipe that can be used in the coolant production
assembly shown in FIG. 6.
[0049] FIG. 16 shows a schematic diagram of an exemplary embodiment
of a system to measure solid void fraction and particle size in a
two-phase, liquid-solid coolant, which system comprises a heat
pipe.
[0050] FIG. 17A-B shows the heat flow and temperature profile
generated by the creation of slurry from a heat exchange
device.
[0051] FIG. 18A-B shows the heat flow and temperature profiles
illustrating the effect of a frozen plug in the coolant lines on
the operation of a slurry production system.
[0052] FIG. 19A-C shows the heat flow and temperature profile
illustrating the effect of a change in rotation rate of ice scraper
blades on the operation of an ice slurry production system.
[0053] FIG. 20 shows a schematic of an embodiment of a disturbance
nucleation system having a primary and a secondary cooler.
[0054] FIG. 21A-B shows a representative data set showing ice
nucleation initiated via two disturbance methodologies.
[0055] FIG. 22 shows various trip embodiments for inducing ice
nucleation, including (A) post; (B) cross-wire; (C) tooth; (D)
central tooth; (E) sticky sphere; (F) pyramidal; (G) surface
roughness; (H) teeth combination; (I) dimpled tube; and (J) cone
with blades.
[0056] FIG. 23 shows an exemplary embodiment of an ice nucleation
chamber.
[0057] FIG. 24 shows frontal and cross sectional views of
embodiments of trip holders and a spacer that can be used in an ice
nucleation chamber.
[0058] FIG. 25 shows a frontal view of an embodiment of an ice
nucleation chamber.
[0059] FIG. 26 shows an embodiment of a custom hose barb with an
o-ring mate surface.
[0060] FIG. 27 shows a cross-sectional view of an exemplary
embodiment of an ice nucleation chamber.
[0061] FIG. 28 shows a back view of an embodiment of an ice
nucleation chamber.
[0062] FIG. 29A-B shows the front and cross-sectional views of an
embodiment of a post trip design holder.
DETAILED DESCRIPTION
[0063] Various terms relating to the systems, methods, and other
aspects of the present invention are used throughout the
specification and claims. Such terms are to be given their ordinary
meaning in the art unless otherwise indicated.
[0064] Various publications, including patents, published
applications, technical articles and scholarly articles are cited
throughout the specification. Each of these cited publications is
incorporated by reference herein, in its entirety and for all
purposes.
[0065] It has been discovered in accordance with aspects of the
present invention that freezing point depression can be harvested
to spontaneously freeze a fluid, which can be microparticalized and
mixed with a carrier fluid to form an ice slurry. It has further
been discovered that the size of the microparticles can be
controlled and fine-tuned to serve a particular application. In
addition, it has been discovered that the resultant slurry can be
maintained and transported in a controlled environment to prevent
undesired melting of the frozen particles, to prevent clumping, and
to prevent intermixing of the frozen fluid contents with the
carrier fluid. It has also been discovered that the admixing of
salt after the formation of ice crystals in commercially available
ice slurry production devices will render the slurry more
pumpable.
[0066] Accordingly, the invention provides cooling systems,
including systems for producing a two-phase coolant. The figures
illustrate exemplary embodiments of the inventive systems. In one
exemplary aspect shown in FIG. 1, the system comprises a first
container 10. The first container comprises at least one aperture
12 for introducing first fluid 14 into the container. First fluid
14 is releasably retained within the container 10. First container
10 also comprises at least one additional aperture 16 for releasing
first fluid 14 from the container. First container 10 is coupled to
homogenizer 18 such that first fluid 14 is received by the
homogenizer. Optionally, first container 10 is coupled to
homogenizer 18 by a first tube 20.
[0067] In some aspects, the system comprises valve 22 positioned to
control flow of the first fluid 14 from the first container 10 to
the homogenizer 18. The valve can optionally be coupled to
container 10, first tube 20, or homogenizer 18. A gasket 24, which
is optional, can be attached to the first container 10 at second
aperture 16, to first tube 20, to valve 22, or to homogenizer 18.
Since the couplings of the constituents of the system may not
completely form a fluid or airtight seal, gasket 24 is utilized to
form a seal between the coupled constituents.
[0068] The valve 22 can be a nozzle. An atomizer or nozzle can be
used to create micron-sized droplets of the fluid of interest. The
fluid is expected to undergo phase transition from liquid to solid
when released from the nozzle once droplet pressure returns to
atmospheric.
[0069] FIG. 4 shows a schematic diagram of exemplary nozzle
structures that may be used in the present invention to facilitate
particalized ice production. FIG. 4A shows a cross section of a
nozzle with multiple apertures. FIG. 4B shows a cross section of a
nozzle with a single aperture. FIG. 4C shows a top view of the
single aperture nozzle. The nozzle 44, for example, can have a
plurality of small apertures 46 present to form a fine mist from
the exiting fluid. A needle valve 48 can be used to restrict flow
of fluid through the nozzle to control flow rate. In another
example, the nozzle 50 has only a single aperture 52, but has
internal geometry such that the liquid exiting the hole will have
substantial rotational velocity, dramatically increasing the
kinetic energy present in the flow, thereby resulting in the
formation of a fine mist. Nozzle 50 can also comprise a needle
valve 54 to control fluid flow through the nozzle.
[0070] It is preferred that the nozzle maintains high enough
pressure through the fluid's exit such that the fluid will not
begin to change phase, e.g., freeze, inside of the nozzle.
Solidification of the fluid inside the nozzle can potentially cause
clogging of the fluid flow space 56 of the nozzle or clogging of
the apertures. To reduce the possibility of phase change occurring
before the fluid exits the nozzle, the apertures 46 can be
cone-shape, with the outlet 58 being the narrowest diameter.
[0071] In the event that a cone-shape is insufficient to keep the
fluid from freezing in the nozzle, at least two non-limiting
alternative strategies can be used to reduce or eliminate
solidification and nozzle obstruction. The first is to use
resistive heating elements (not shown) to create a small thermal
boundary layer in the flow near the nozzle wall 56. This boundary
layer will not freeze, and can keep the flow continuing smoothly
through the exit. The second is to use a hydrophobic coating on the
nozzle to reduce the adhesion energy between the exiting fluid and
the nozzle wall. This hydrophobic coating can also attract other
hydrophobic elements that may be present in the exiting liquid,
which can further serve to reduce the adhesion energy between the
exiting fluid and the nozzle wall.
[0072] As shown in FIG. 1, the system also comprises second
container 26. Second container 26 can be separate from or
concentric with or otherwise associated with first container 10.
FIG. 1 shows the separate configuration of the two containers. The
second container comprises at least one aperture 28 for introducing
second fluid 30 into the container. Second fluid 30 is releasably
retained within the container 26. Second container 26 also
comprises at least one additional aperture 32 for releasing second
fluid 30 from the container. Second container 26 is coupled to
homogenizer 18 such that second fluid 30 is received by the
homogenizer. Optionally, second container 26 is coupled to
homogenizer 18 by a second tube 34. A gasket (not shown), which is
optional, can be attached to the second container 26 at aperture
28, to second tube 34, or to homogenizer 18.
[0073] The containers can be fabricated from any material suitable
in the art, including but not limited to plastic, glass, rubber,
metal, ceramic, and the like. The containers can be transparent,
translucent, opaque, or impenetrable to light. Gasket can be
comprised of any material suitable in the art, including but not
limited to elastomers such as silicon, and carbon-based elastomeric
polymers, thermoplastic elastomers, nitrile butadiene rubber, butyl
rubber, siloxanes, ethylene-propyldiene monomer, and the like.
[0074] Homogenizer 18 will function to produce a uniform desired
particle size and desired slurry density, e.g., ratio of solid
particulate matter to fluid. Homogenizer 18 can comprise at least
one aperture 36 for receiving the solidified fluid 14 released from
first container 10, and at least one aperture 38 for receiving the
second fluid 30 released from second container 26. In some aspects,
a single aperture can receive both the solidified fluid 14 released
from first container 10, and the second fluid 30 released from
container 26. Homogenizer 18 can comprise at least one aperture 40
for releasing two-phase coolant produced in the homogenizer.
Optionally, third tube 42 can be coupled to homogenizer 18 via
aperture 40. Third tube 42 can be used to deliver the coolant to a
particular location such as those described and exemplified
herein.
[0075] Optionally, the system may comprise a pump (not shown). The
pump can be coupled to first container 10, second container 26, or
homogenizer 18. Although forces such as gravity, and pressure
released from container 10 can transport solidified first fluid 14
or second fluid 30 to homogenizer 18, in some aspects, it may be
preferable to facilitate transport by use of a pump.
[0076] In the packaging process of the liquid into the first
container, the container will be filled to a less than full volume.
For example, filled with fluid to about one half of the total
volume, although greater or lesser amounts of fluid are possible.
The container can then be sealed, and attached to a gas cylinder
about at the required pressure. Any suitable gas can be used to
provide the pressure, including oxygen, carbon dioxide, nitrogen,
or argon. The gas is then transferred to the first container to
provide the required pressure. The amount of pressure can be varied
to accommodate variables such as the type or volatility of the
fluid, the fluid's atmospheric freezing point, and the like.
Because the container is sealed, the pressure can be maintained at
the desired level for an extended period of time. The pressure seal
can be broken when the nozzle is opened to begin the spray.
[0077] The pressure from the first container can be used to provide
the force for the flow to the homogenizer, and can be used to drive
or entrain the fluid from the second container. If the containers
are concentric, then the second fluid will be entrained by the
velocity of the spray leaving the nozzle. In addition, the motion
of the spray can optionally be varied to create a low pressure
area, which in turn will siphon fluid from the second tank. A third
option is to couple the pressure in the second tank to a nozzle
outlet to increase pressure at the exit from the nozzle due to the
expanding ice and gas. The pressure can then be harnessed to
increase the pressure in the second container. The flow from the
second container can travel under the nozzle, picking up
micro-particulate ice on its path into the delivery system.
[0078] Also featured in accordance with exemplary aspects of the
present invention are methods for producing coolants, including
two-phase coolants. Generally, the methods comprise admixing a
particalized solid with a carrier fluid. The particalized solid is
preferably microparticalized and more preferably nanoparticalized,
and is produced by releasing from a pressurized container a first
fluid that has been cooled to a temperature below its atmospheric
freezing point. It is preferable that the first fluid freezes into
the solid substantially instantaneously. The freezing can proceed,
for example, in an adiabatic manner. Any means suitable in the art,
such as those described and exemplified herein, can be used to
particalize the frozen fluid. The pressure in the container is
maintained at a level to cause freezing point depression. The
carrier fluid is also cooled to a temperature below the atmospheric
freezing point of the first fluid. The mixing of the particalized
frozen first fluid with the carrier fluid according to this aspect
produces a slurry, i.e., a two-phase solution that can be used as a
coolant in any suitable application, such as those described and
exemplified herein. In some highly preferred aspects, the two-phase
solution is homogenized to include a uniform particle size and/or
uniform ratio of solid to fluid.
[0079] In some aspects, the first fluid and/or the carrier fluid is
aqueous, or substantially aqueous. The aqueous fluid can be water,
alcohol, or a physiologically compatible buffer such as, but not
limited to, Hanks solution, Ringer's solution, or physiological
saline buffer. The first fluid and/or carrier fluid can comprise at
least one salt, monosaccharide, or polysaccharide, or a biomolecule
such as nucleic acids, polypeptides, and lipids, or an analog,
homolog, or derivative of any of the above. Any salt,
monosaccharide, or polysaccharide known or suitable for the
particular needs of the application can be used.
[0080] The first fluid and/or carrier fluid can comprise at least
one emulsifier. Any emulsifier known or suitable for the particular
needs of the application can be used. U.S. FDA-approved emulsifiers
are highly preferred, particularly with respect to therapeutic or
food-based applications of the resultant ice slurry. Some
non-limiting examples of such emulsifiers include glycerol, soya
oil, and egg lecithin.
[0081] The first fluid and/or carrier fluid can comprise at least
one surfactant. Any surfactant known or suitable for the particular
needs of the application can be used. U.S. FDA-approved surfactants
are highly preferred. For example, families of surfactants made of
Polyethylene Oxide (PEO) and Polypropylene Oxide (PPO), or
Polyethylene Glycol (PEG) and Polypropylene Glycol (PPG) subunits
are particularly preferred. These surfactants have been shown to be
non-toxic, are generally regarded as safe, and have also been
proven to be protective in cases of cell damage or micro-bubble
embolization. Two families of surfactants are very highly
preferred: the Poloxamer surfactants (PEG and PPG copolymer
surfactants); and the Pluronic surfactants (PEO and PPO copolymer
surfactants).
[0082] In some aspects, the first fluid and/or the carrier fluid is
nonpolar, for example, an organic solvent. Any nonpolar fluid known
or suitable for the needs of the application can be used.
Non-limiting examples of these fluids include Perftoran, and
perfluoro-x-anes, such as perfluorodecane and perfluorohexane. The
two-phase coolant can comprise any ratio of solid to fluid suitable
for the particular needs of the application. For example, the ratio
may range from 0.001% solid to 99.999% solid and correspondingly
99.999% fluid to 0.001% fluid. At least about 10% solid void
fraction in the fluid is preferred. More preferable is at least
about 15% solid void fraction, more preferably at least about 20%
solid void fraction, more preferably at least about 25% solid void
fraction, more preferably at least about 30% solid void fraction,
more preferably at least about 35% solid void fraction, more
preferably at least about 40% solid void fraction, more preferably
at least about 45% solid void fraction, more preferably at least
about 50% solid void fraction, and still more preferably at least
about 55% solid void fraction can be used. At least about 60% solid
void fraction in the fluid is even more preferred, and still higher
percentages are even more preferred. Because it is preferred to
maximize cooling in a given volume, it is highly desirable to
provide the highest percentage of the solid void fraction as can be
achieved given the materials chosen to comprise the resultant
slurry. In some cases, chemical lubricants (emulsifiers and
surfactants) and/or particle size controls can be used to enhance
the level of solid void fraction.
[0083] The invention also features methods for using a coolant such
as a two-phase coolant produced by the inventive systems and
methods. The coolant can be used to cool or maintain a particular
temperature in any application where lower temperatures or
temperature maintenance is desired.
[0084] Thus, the invention provides methods for inducing or
maintaining hypothermia in a subject. Such methods generally
comprise administering to a subject in need thereof a
pharmaceutically acceptable coolant such as a two-phase coolant
produced according to any of the inventive methods described or
exemplified herein. The coolant is administered to the subject in
an amount effective to induce hypothermia. The effective amount may
be dependent on various factors that are expected to be known in
the art. Non-limiting examples of such factors include the species,
height, weight, age of the subject, and the like. Administration
can proceed by any means suitable for the particular application to
which the coolant is being used. For example, the coolant can be
administered intravenously, intramuscularly, intraperitoneally,
topically, orally, nasopharyngeally, anally, vaginally, into the
thoracic cavity, into the lungs, into other corporeal spaces,
regions, and the like. Intravenous administration is highly
preferred.
[0085] The methods can be used in any subject. Preferably, the
methods are used in mammals such as horses, cows, pigs, dogs, cats,
rabbits, rats, hamsters, and mice. The methods are preferably
beneficially employed in humans.
[0086] The hypothermia can be systemic, meaning that hypothermia
can be induced and/or maintained throughout the entire body of the
subject. Alternatively, the hypothermia can be directed to a
particular location or locations of the body, for example, to a
particular organ, appendage, cavity, space, or region.
[0087] Also provided are methods for rapidly cooling or maintaining
a cool temperature for perishable goods. Such methods generally
comprise producing a coolant such as a two-phase coolant according
to any of the inventive methods described or exemplified herein,
and exposing the perishable goods to the coolant. Perishable goods
refers to any product, compound, or composition that has a finite
shelf life. Non-limiting examples of perishable goods include food
products such as meats, fish, produce, milk and milk products,
confectionaries, beverages, and the like, pharmaceuticals,
vitamins, minerals, volatile chemicals, radionuclides, biomolecules
such as nucleic acids, polypeptides, and lipids, cells, tissues,
organs, and biological fluids such as blood, blood serum, urine,
saliva, sweat, milk, and the like.
[0088] Also featured are methods for rapidly cooling heat
generating devices such as a weapon or high powered electronics.
The methods generally comprise producing a coolant such as a
two-phase coolant according to any of the inventive methods
described or exemplified herein, and exposing the weapon to the
coolant. Any weapon or sub-part of a weapon such as a gun barrel
can be cooled using the inventive method. Non-limiting examples of
suitable weapons include guns, cannons, and electromagnetic pulse
generators. Weaponized lasers can also be cooled according to the
inventive methods. The weapons can be hand-held, or those attached
to equipment such as a plane, helicopter, or vehicle. Non-limiting
examples of high powered electronics are computers, appliances,
micro-electronic devices, power transformers, and the like.
[0089] The invention also features methods for cooling a room. The
methods generally comprise producing a coolant such as a two-phase
coolant according to any of the inventive methods described or
exemplified herein, exposing air to the coolant such that the
temperature of the air is lowered, and circulating the cooled air
throughout the room. The air can be exposed to the coolant
according to any means suitable in the art. Similarly, the cooled
air can be circulated according to any means suitable in the art,
such as a fan. The invention contemplates that multiple rooms can
simultaneously be cooled through the inventive methods. For
example, through appropriate duct work, the cooled air can be
circulated to multiple rooms, including all rooms of a particular
building, at the same time.
[0090] The invention also features methods for non-lethal crowd
control. The high volume and pressure pumping of the two phase
coolant, for example, out of a water cannon can be used to disperse
rioting crowds through the creation of severe discomfort through
the rapid cooling caused by full body exposure to the two phase
coolant.
[0091] The invention also features a method for improvement of fire
control or suppression methods. The high volume and pressure
pumping of the two phase coolant out of, for example, a fire hose
may improve fire fighting procedures as the environmentally
friendly two phase coolant can draw more heat out of the fire,
reducing the energy of the combustion process, making the fire
easier to control and suppress. Additionally the release of ice
slurry from fire sprinkler systems can have the same effect on the
fire.
[0092] The invention also features methods for the protection of
structural elements during extreme heat. Non-limiting examples of
extreme heat are: a building fire, space craft atmosphere re-entry,
or metal foundry equipment. In extreme heat events, the heat can
exceed the limits of the structural members, resulting in building
collapse, space craft disintegration, or failure of mechanical
systems. If members of these systems were designed in conjunction
with a high volume two phase coolant production system to provide
integrated heat transfer conduits, the members may be cooled
directly during the heating event, lengthening the time to
structural failure.
[0093] Additionally the invention features methods for personal
cooling systems. Personal cooling may improve personal performance
during physical activity or otherwise help prevent corporeal
over-heating. Non-limiting examples of personal cooling systems are
personal misters, bench misters for sports teams, body cooling
systems as may be worn under other clothing, equipment, helmets,
gloves, shoes, and the like to cool the desired portion of the
body.
[0094] Additionally the invention features methods for the removal
or safe handling of toxic gases. As a liquid's temperature is
reduced, the amount of gas that can be dissolved in the liquid
increases. The described methods may be used to create a two phase
air scrubbing liquid. This liquid can then be used to quickly
filter air that has been exposed to any of a variety of toxic
gasses, non-limiting examples of which are, carbon monoxide, poison
gas, radio-active gas, radio-active particulate, asbestos
particulate, and the like. An alternative aspect of the same device
can allow for the safe handling of weapons that contained such
gases.
[0095] Additionally the invention features methods to rapidly
induce deep hypothermia for the induction of a cryostasis state.
This method may be employed for medical benefit in hospitals, or
alternatively may be employed to induce stasis for long term space
travel. The location of the deep hypothermia induction may require
different embodiments of the two phase coolant production system.
Systems designed for use in space may use the vacuum of space as
its primary coolant.
[0096] In any of the above-described methods, or other methods to
which the invention can be adapted, the rate of cooling can be
controlled. Cooling can thus proceed slowly or rapidly, at a
uniform rate, or at a staggered rate, for example, rapidly for a
period of time, followed by a slow period. The rate of cooling can
be determined and adjusted according to the particular needs of the
application. The rate of cooling can be controlled according to any
means suitable in the art. Suitable methods for controlling the
rate of cooling include, but are not limited to, adjusting the
delivery rate of the slurry or adjusting the ice content of the
slurry. The method used to control these parameters can depend on
the particular configuration of the device, but can include
changing the pumping rate, or the percentage that a valve or nozzle
is open. It is contemplated that cooling systems provided by this
invention can advantageously be used for a large variety of
additional applications. Some non-limiting examples of such
applications include storage, shipping, and air conditioning in
various industries. Additional applications can be found, for
example, in the health care industry, where cooling of patients is
gaining recognition as a therapy to improve outcomes for trauma,
cardiac arrest, ischemic injury and the like. Cooling is also
advantageous for devices that generate excess levels of heat that
could damage components of the device. Such devices include
computers, weapons, tools, motors, vehicles, and the like.
[0097] Refrigerant chemicals or machines are optionally used to
generate cold air or ice in some applications. But because many
refrigerant chemicals such as chlorofluorocarbons are toxic and can
potentially damage the environment, such cooling systems are less
preferred than those embodiments described herein that can be
operated without the use of refrigerant chemicals. Similarly,
because many commercial air conditioning or refrigeration units can
use large amounts of energy, potentially taxing energy grids during
peak demand, such cooling systems are less preferred than those
embodiments described herein that can be operated without the use
of large amounts of energy.
[0098] Two-phase, solid-liquid coolants of the type described
herein can be beneficially employed for a variety of uses,
including medical, refrigeration, and HVAC applications, crowd
control, and fire suppression, among others. In some applications,
it is particularly beneficial to verify the quality, i.e., cooling
capacity, of such coolants at the site of action where the coolant
is applied. A quality assurance system that will allow the reliable
use of two-phase coolant systems in various applications is
therefore desirable.
[0099] Cooling capacity in two-phase, solid-liquid coolants
correlates to the void fraction and particle size of the coolant
solids. Particle detection devices employing ultrasound or light
scattering are optionally used to make measurements for determining
cooling capacity. In applications in which significant power and
computational requirements may not be available, or in which a
clean, stable environment may not be available, it is beneficial to
have a quality assurance system with minimal power and
computational demands that can be scaled for different applications
in unpredictable environments, such as battlefield, emergency, or
marine settings.
[0100] As shown in FIG. 2, in a preferred embodiment a system 100
for determining the cooling capacity of a two-phase, solid-liquid
coolant is provided, including a conduit 110 having an interior 111
and an exterior 112, a predetermined length, and known heat
transfer characteristics. The conduit can be made from a metal such
as copper, aluminum, or stainless steel. The conduit can be rifled
to cause laminar mixing of the coolant as it travels through the
quality measuring device. The internal dimension of the rifled
conduit device can be of the same dimension as the entry and exit
tube, which can vary based on the application. By way of example
but not of limitation, a gastrointestinal delivery system can have
a larger conduit than an intravenous delivery system. The external
diameter of the conduit preferably will not exceed twice the inner
diameter. The conduit 110 further has an inlet 113 and an outlet
114 adapted respectively to receive and discharge a predetermined
volumetric flow of coolant, which flows through the interior 111 of
the conduit 110. A heat source 120 is positioned relative to the
conduit 110 to transfer heat to the coolant flowing through the
conduit interior 111. The heat source for the device optimally can
be provided in the form of a series of resistive thermal devices
(RTD) powered with an electric current. The RTDs can be
micro-fabricated into the wall of the conduit, or can be attached
to the interior or exterior of the conduit as well. The RTDs can be
controlled so that a constant temperature is maintained. In
addition the RTD can have built-in heat flux and temperature
sensors. At least one heat flux sensor 121 and at least one
temperature sensor 122 are positioned on the conduit 110. Sensor
wires 123 connect the sensors 121 and 122 with an electronics
element 130, typically a computer or other semiconductor
device.
[0101] In operation, a predetermined volumetric flow of a
two-phase, solid-liquid coolant, preferably an aqueous slurry of
ice, is drawn from the output of a coolant delivery system and
directed to the inlet 113 of the conduit 110. Preferably, the
coolant flow to the conduit 110 is drawn from a source as near as
possible to the point of application of the coolant so that the
cooling capacity of the coolant at the application point is
determined. Heat is transferred by the heat source 120 to the
coolant flowing within the conduit interior 111. The exterior 112
of the conduit 110 preferably is maintained at a constant
temperature. It is also preferable that a substantially uniform
cross-sectional distribution of solid and phases in the coolant is
maintained as the coolant passes through the conduit 110. Rifling
or vanes can be present in the conduit to induce mixing to ensure
homogeneity of the fluid.
[0102] The heat flux and temperature sensors 121, 122 measure heat
transfer and coolant temperature as functions of the distance the
coolant travels within the conduit interior 111. Signals are
transmitted through the sensor wires 123 from the sensors 121, 122
to the electronics element 130, such as a computer. The electronics
element 130 is provided with correlations of the measured heat flux
to the coolant and coolant temperature with coolant properties,
including cooling capacity, solids void fraction, and solids
particle size. Using the measured heat flux and temperature values,
the electronics element calculates the relevant coolant properties.
As shown in FIG. 3, decreasing solid particle size correlates to an
increase in measured heat flux.
[0103] Also featured in accordance with the present invention are
systems and methods for portable on-demand production of a
two-phase coolant. One obstacle to providing rapid cooling, for
example, to induce therapeutic hypothermia in the field is finding
a power source large enough to cool liquids such as a saline
solution to form ice in the short time span that is available to
treat a patient. In addition, in the therapeutic setting, this
power need is complicated by the fact that cooling of the patient
ideally begins outside of the hospital, meaning that the large
power source needs to be available on emergency vehicles.
[0104] By way of example, for two liters of aqueous saline to be
cooled from about room temperature to the freezing point,
approximately 0.degree. C., with one of the two liters needing to
be frozen to ice, the total energy required would be about 550
kilo-joules. To carry out this process in about 5 minutes would
require more than 1.8 kilo-watts of energy, assuming ideal
conditions. Refrigeration units that provide that type of cooling
power are available, but generally require special 220 volt wiring
and are generally large and heavy, weighing hundreds of pounds.
Moreover, as conditions are often not ideal, it is likely that
these estimated power needs represent a significant
under-estimation of the actual power that would be required. Thus,
the requisite refrigeration units in reality are likely to be even
heavier and require more power to operate. The size and power
requirement limitations would limit the ability to produce a two
phase coolant in an emergent setting in a hospital building, and
severely limit, if not prohibit the ability to produce such
coolants from an emergency vehicle within the time constraints of a
medical emergency.
[0105] To overcome such limitations, one possible solution can be
to create the two phase coolant before it is needed, and to store
it. Advance preparation could significantly reduce the flow rates
of the coolant, thereby reducing the power consumption. Two phase
coolants such as slurry lose their preferred ice particle shape and
pumpability characteristics, however, upon storage, thereby
reducing the therapeutic value of the coolant. An aqueous ice
slurry is in a constant state of phase change between the ice and
liquid forms of water. Over time, the dendritic nature of the ice
crystals is restored and the slurry would no longer be able to be
moved, even pumped, within the tight constraints of, for example,
an intravenous tube.
[0106] It has been discovered in accordance with the present
invention that the stored thermodynamic energy of, for example,
compressed gasses or dry-ice, can be harnessed for the portable
on-demand production of two phase coolant. However, such use of
thermodynamic energy for cooling liquids creates temperatures below
the eutectic point of salt water, which results in an ice slurry
having a temperature much lower than 0.degree. C., which could be
harmful to a patient. This challenge was overcome by the discovery
that use of one or more heat exchangers can control the freezing
temperature of the aqueous saline. The use of heat exchangers
provides the additional advantage of also allowing for the use of
stored cooling in the form of dry-ice sublimation, or liquid
evaporation. An overview of the use of heat exchangers is
illustrated in FIG. 5. More details of embodiments of the inventive
systems are provided below with reference to FIGS. 6-14.
[0107] The pressure drop, heat flow, and mass flow rates of the
heat exchanger can be modified by scaling its linear dimensions.
The skilled artisan can, for example, consult the introductory
chapter of John E Hesselgreaves' Compact Heat Exchangers:
Selection, Design and Operation (Elsevier Science Ltd. 2001) for
guidance in this regard. Any dimensions of devices described or
exemplified herein are intended to be illustrative, and not
limiting. Accordingly, dimensions can vary, for example, according
to the particular system, device, application, or needs of a
particular user or application.
[0108] In one aspect, the two phase coolant productions systems
utilize medical grade saline solutions, which generally contain
from about 0.45% to about 7.5% solute, to create a sterile
ice-saline slurry on demand for inducing hypothermia in a patient.
For example, the sterile ice slurry produced can be used to quickly
induce therapeutic hypothermia for patient protection during sudden
death, heart attack, stroke, heat stroke, septic shock, hemorrhagic
shock or any medical condition wherein uncontrolled metabolic
injury is a concern.
[0109] As shown in FIG. 6A-B, two phase coolant production systems
can comprise several principle component parts assembled into a
slurry production device 200. An exploded view of an example of a
suitable assembly configuration is provided. FIG. 6B shows a 90
degree rotation of the configuration shown in FIG. 6A. The figure
shows a housing 220, heat exchanger 240, driveshaft 260, ice
scraper blade 280, internal disk 300, mixing blade 320, mixing
vessel 340, and a mixing vessel housing 360. The assembly can
further comprise gaskets and connectors such as screws or snap fits
(not shown).
[0110] In some aspects, the systems comprise a housing 220
configured to contain the principle components of the two phase
coolant production system. The housing can be comprised of any
suitable material such as metal, plastic, rubber, silica, polymers,
glass, wood, and the like. The housing can be insulated. Plastic is
a preferred material. As shown in FIG. 7, the housing can comprise
a lumen 222 for containing the components of the two phase coolant
production system. FIG. 7A shows one exemplary exterior
configuration of the housing. FIG. 7B shows a cut-away view of the
housing, showing an example of a configuration of additional
components of the slurry production system within the housing. The
components can be fastened to the housing according to any means
suitable in the art. Preferably, the components are reversibly
assembled to allow the components to be periodically cleaned and/or
sterilized.
[0111] The housing can also comprise apertures, which can be used,
for example as a coolant inlet 226 and a coolant outlet 224, as
well as an inlet 230 for fluid that is to be frozen into the ice
component of a resultant ice slurry and an outlet 228 for the ice
slurry. The apertures can optionally comprise connectors configured
for connecting the housing to fluid containers, slurry storage
containers, tubing for delivery of the slurry, additional
components of the system, and the like. Connectors can be any
connector suitable in the art for the purpose to which it is being
used.
[0112] The housing preferably comprises a heat exchanger 240. The
heat exchanger can comprise a length L and a diameter D (FIG. 7B).
In some preferred aspects, the heat exchanger can comprise one or
more tubes, preferably concentric tubes, that separate the coolant
from the fluids that comprise the two phase coolant.
[0113] As shown in FIG. 8, the heat exchanger 240 can comprise one
tube. The tube has a lumen 244 through which the fluids that
comprise the two phase coolant can flow, and the ice phase of the
slurry being produced can be formed on the sidewalls 246 of the
lumen. The coolant flows between the housing 220 and the heat
exchanger tube 240. The heat exchanger tubes can range in length
from about 1 inch to about 24 inches, although shorter or longer
tubes can be used. Preferably, the tubes are about 1 inch to about
6 inches long. The inner tube can range in diameter from about 0.25
inches to about 2 inches. Preferably, the inner tube diameter is
about 0.5 inches. The outer tube can range in diameter from about
0.5 inches to about 2.5 inches. Preferably, the outer tube diameter
is about 0.8 inches. In one non-limiting example of a single heat
exchange tube, tube length L is about 6 inches and diameter D is
about 0.75 inches.
[0114] The heat exchanger tubes can be fabricated from any material
suitable in the art, and the material chosen may depend on the use
to which the system is being put. The heat exchanger tube can
comprise a metal such as stainless steel, platinum, or titanium.
Preferably, the heat exchanger material is stainless steel. The
inner and outer tubes can be comprised of the same material or
different materials. The outer tube can be comprised of stainless
steel, platinum, titanium, Nylon, polycarbonate, Teflon, or Tygon.
Preferably, the material is insulating and sterilizable, such as
polycarbonate.
[0115] The heat exchanger tube is contained within the housing, and
the walls of the heat exchanger tube are directly contacted with
the coolant flowing through or otherwise present in the housing
lumen. The tube can be fastened to the housing, or can be free
floating within the housing. The coolant cools the heat exchanger
tube to a temperature sufficient to freeze the fluid that contacts
the sidewalls of the heat exchanger tube. In addition, the cooling
of the fluid can result in the freezing of fluid not in direct
contact with the heat exchanger tube sidewalls. The coolant can be
any coolant suitable in the art for freezing the fluid of interest.
Non-limiting examples of coolant include dry ice-alcohol slurry,
compressed refrigerant gases such as Freon and ammonia,
polyethylene glycol, polypropylene glycol, water, freezing point
depressed water such as sodium chloride saline or potassium formate
saline or dextrose solutions, alcohols, and the like.
[0116] The tube of the heat exchanger preferably comprises a
driveshaft 260, for example, as shown in FIG. 9. The driveshaft can
comprise an axle 262 to allow the driveshaft to rotate within the
heat exchanger inner tube. The driveshaft can further comprise one
or more scraper blade holders 264 to reversibly fasten one or more
scraper blades to the driveshaft. The drive shaft can further
comprise one or more channels 266 to facilitate the flow and
transport of fluid and the forming ice slurry through the heat
exchanger. The channels can be cut into the distal end of the
driveshaft at an angle to provide pulsatile flow through downstream
components of the slurry production assembly. One of the challenges
of creating a coolant of this type is the propensity of the ice
particles to aggregate and coalesce, ruining the pumpability of the
slurry. Blunt obstructions in the slurry flow path provide flow
stagnation points, which in turn provide locations for ice particle
aggregation. Pulsatile flow can help reduce or even eliminate any
ice particle jamming that is likely to occur with the dendritic ice
crystals. In addition, the driveshaft provides appropriate means of
connection with the mixing blade 268.
[0117] The driveshaft can be fastened to the heat exchanger or to
the housing. The driveshaft can rotate clockwise, counterclockwise,
or in combinations thereof. The driveshaft can rotate at any speed
suitable in the art. The driveshaft rotation speed can be
correlated to the number of ice scraping blades. For example, from
analysis of the water freezing process, it was determined that the
ice interface can preferably be scraped from about every thirtieth
to about every fifth of a second. In some preferred aspects, the
ice interface is scraped every twentieth of a second. Therefore, a
driveshaft having one scraping blade can preferably rotate at about
1200 rpm. A driveshaft with two scraping blades can preferably
rotate at about 600 rpm. A driveshaft with three scraping blades
can preferably rotate at about 400 rpm. A driveshaft with four
scraping blades can preferably rotate at about 300 rpm. This
relationship between number of scraping blades and the rpm of the
driveshaft can continue to any number of scraping blades. In more
preferred aspects, the driveshaft rotates from about 0.0001 to
about 200 rpm. Rotation can be effectuated according to any means
suitable in the art, including the use of a motor. In some
embodiments, a battery or AC powered motor of appropriate power can
be attached to the proximal end of the driveshaft 262. In other
embodiments, a turbine blade can be attached to the proximal end of
the driveshaft 262. This driveshaft can be powered by a pump that
is used to pump fluid through the device.
[0118] The driveshaft can comprise one or more scraper blades 280,
as illustrated in FIG. 10. The scraper blades are configured to
remove the formed ice from the sidewalls of the inner tube. Each
scraper blade can optionally comprise one or more apertures 282.
The apertures can allow for the scraped ice particles to pass
freely through the scraper blade. The apertures can range in size
from about 1/16 inch to about 1/2 inch wide and from about 1/4 inch
to about 8 inches long. Preferably, the apertures are about 1/8
inch wide and 3/4 inch long.
[0119] Free passage through the scraper blade can help to ensure
homogeneity of the resultant slurry. The scraper blade can be
comprised of any material suitable in the art, including metal,
plastic, rubber, glass, polymers, silica, and the like. The ends of
the scraper blades that contact the ice formed on the sidewalls of
the inner tube can be tapered. The scraper blades can be configured
as an auger. In the auger configuration, the scraper blades serve
at least two purposes. In one aspect, the auger blades can serve to
scrape the ice off of the heat exchange interface and can be used
to transport the saline slurry through the device. The auger
embodiment can advantageously require fewer pumps, and thus less
electrical power to operate. The number of auger scraper blades can
vary from one to many. The number of blades can be determined
according to different variables, including by relating the desired
slurry flow rate, the auger parameters (lead, lead angle, and mean
auger diameter), and the desired RPM of the motor.
[0120] In some aspects, a slurry production assembly can comprise
an internal disk 300, as shown in FIG. 11A-C. Figures A-C show
different view angles of the internal disk. The internal disk can
hold the bearing near the end of the driveshaft. The internal disk
can comprise one or more apertures 302 to allow the produced
ice-saline slurry to pass through the disk to subsequent components
of the device. In addition, the disk comprises two faces for
compressive forces to seal the device together, comprises the
distal end of the heat exchanger, and comprises the proximal end of
the mixing vessel. Optionally, gaskets can be used between the
distal end of the heat exchanger and the disk, and between the
proximal end of the mixing vessel and the disk.
[0121] The slurry production assembly comprises, in some aspects, a
mixing blade 320. One non-limiting example of a mixing blade
configuration is shown in FIG. 12A-C. FIG. 12A shows a side-view of
the mixing blade, FIG. 12B shows a top-view of the mixing blade,
and FIG. 12C shows a three-dimensional perspective of the whole
mixing blade. This blade is configured to mix and/or finely
homogenize the ice slurry produced in the heat exchanger, which
will be dendritic ice slurry, and a high concentration saline. The
blade shape can be designed to create turbulent (chaotic) mixing of
the slurry and the high concentration saline. In some aspects, the
mixing blade is configured to push the slurry out radially, in turn
forcing the high concentration saline into the more central
volume.
[0122] The ice particles initially formed to comprise the ice
slurry generally comprise sharp, dendrite-like edges. The shape of
the formed ice can impede or even prevent transport pumping of the
slurry through tubes, for example, for delivery to a patient. It
has been discovered that smoothing of the ice particle shape, which
can occur in either the primary ice formation process or in a
secondary smoothing process can overcome the problems of
transporting ice slurry comprising dendritic ice crystals. This
described secondary process could be added to many commercially
available slush production devices making the slurry more pumpable
or drinkable. Non-limiting examples of currently available slush
production devices are: the ORS-1075HS HUSH-SLUSH.RTM. (O.R.
Solutions, Inc., Chantilly, Va.) system, SLURPEE.RTM. machines
(7-Eleven), slushie machines, frozen alcoholic beverage machines,
systems for building refrigeration using two phase coolants, and
the like.
[0123] It has further been discovered that smoothing of ice
particle shape can be effectuated by controlled heating of the ice
slurry, by addition of an effective amount of a high concentration
saline to the slurry, or by addition of an effective amount of a
non-frozen liquid. The addition of a small amount of heat to the
slurry, which can occur by heat flux or liquid flux, while the
slurry is being agitated can lead to the development of smooth ice
particles. The amount of heating required can depend, for example,
on the desired flow rate of the slurry. The heat can be added by
maintaining a wall temperature higher than the slurry average
temperature. Non-limiting wall temperatures can range from about
0.degree. to about 40.degree. Celsius, with both the low range 0-4
degrees Celsius and 30-40 degrees being preferred. The two
preferred temperature ranges correspond to differing heating areas,
with the larger heating area corresponding to the lower wall
temperature.
[0124] The high concentration saline can comprise from about 1 to
about 10 percent solute, including commercially available 3.5%, 5%,
and 7.5% medical grade saline. The saline can comprise one or more
of the following non-limiting solutes, which are preferably
pharmaceutically acceptable or physiological salts or sugars,
non-limiting examples of which include: sodium chloride, sodium
lactate, potassium phosphate, calcium chloride, potassium chloride,
sodium phosphate, potassium diphosphate, potassium formate,
glucose, and dextrose.
[0125] Controlled heating of the ice slurry and/or the addition of
a high concentration saline to the ice slurry can be effectuated in
any component of the slurry production assembly. In one preferred
aspect, the assembly comprises a dedicated component for smoothing
of the ice particles, for example, a mixing vessel. The mixing
vessel can be configured according to any shape and size suitable
in the art. In one highly preferred aspect, the mixing vessel is
cone-shaped, as shown in FIG. 13.
[0126] A mixing vessel 340 can comprise an inlet 342 for ice slurry
formed in the heat exchanger that passes through the internal disk.
The mixing vessel can also comprise an outlet 344 for effluent of
the refined slurry, for example, to be administered to a patient.
In some aspects, the vessel can comprise an inlet 346 or a
plurality of inlets to allow for the addition of high concentration
saline to the vessel lumen. The mixing vessel can house the mixing
blade. In some aspect the vessel can be heated to smooth the shape
of the ice crystals. Non-limiting examples of methods to heat the
mixing vessel include incorporating thermal resistive devices into
the mixing vessel wall, passing a warm fluid around the exterior of
the mixing vessel wall, or having the mixing vessel wall be
comprised of a heat pipe, wherein the heat pipe could provide a set
wall temperature higher than the slurry temperature. The vessel can
be manufactured from any material suitable in the art, such as
metal, plastic, rubber, silica, polymers, glass, and the like, and
can optionally be insulated.
[0127] In some embodiments, the slurry production assembly can
comprise a mixing vessel housing 360. An example of a vessel
housing configured to contain a mixing cone is shown in FIG. 14.
The vessel housing component can be configured to hold components
of the assembly on the distal side of the internal disk, and can be
reversibly fastened to the main housing of the assembly, providing
the compression that seals all of the different compartments and
holds the entire assembly together. In some preferred aspects, the
vessel housing comprises one or more apertures 362 to allow the
high concentration slurry to pass through the vessel housing and
into the mixing vessel. In some preferred aspects, the vessel
housing comprises one or more outlets 364 for the effluent of the
produced slurry from the slurry production assembly. In some highly
preferred aspects, the outlet can comprise a fitting 366 for
connection to a tube such as an intravenous tube, for
administration of the slurry to a patient. Any fitting suitable in
the art can be used, such as an IV luer connector. Other
non-limiting possible connectors include: standard plumbing
connectors for use with building cooling, perishable goods cooling,
or fire suppression sprinkler systems, connectors appropriate for
cooling of weapons such as lasers, guns, canons, and
electro-magnetic pulse generators, connectors appropriate for fire
hoses and water cannons, connectors appropriate for personal
cooling systems such as cooling caps, cooling vests or personal
mister systems, connectors appropriate for personnel misting
systems (sports team benches), connectors appropriate for cryogenic
stasis systems, connectors appropriate for cooling of foundry
equipment, connectors appropriate for structural element cooling
under extreme conditions such as building frame cooling during fire
or space craft protection during damaged heat shield re-entry,
connectors appropriate for air scrubbing systems, connectors
appropriate for improved toxic gas containment and transport,
connectors appropriate for minimally invasive surgical instruments
for use in organ preservation during prolonged surgeries,
connectors appropriate for storage tank deposition, connectors
appropriate for localized medical cooling such as a gastro
intestinal tube, or tubing for lung lavage or tubing for slurry
emission into the nasopharyngeal, oral, aural, anal or vaginal
cavities, connectors appropriate for slurry emission into
intraperitoneal or intrathoracic spaces, or connectors appropriate
for emission into any other physiological space or region.
[0128] In some aspects, the slurry production system, such as the
assemblies described and exemplified herein, comprise four volumes.
The first volume contains low concentration saline and is cooled so
that ice forms in the saline. In some preferred aspects, the slurry
can comprise from about 10 to about 90% ice, although higher or
lower percentages can be produced, depending on, among other
things, the particular needs of the application. More preferably,
the slurry comprises from about 20 to about 80% ice, more
preferably from about 30 to about 70% ice, more preferably from
about 40 to about 60% ice, and more preferably from about 50 to
about 60% ice.
[0129] The second volume can surround the first volume and can be
separated by the configuration of the heat exchanger. This second
volume is where the coolant is re-circulated. Preferably, the
coolant and the saline have opposite flow directions to create a
counter-current heat exchanger. The coolant can be circulated
through a phase change refrigeration unit where the heat is
removed. Preferably, the refrigeration unit is non-electrical, but
can also be electrical.
[0130] The third volume is where the ice slurry produced from the
heat exchanger is heated or mixed with the high concentration
saline. Controlled heating or mixing of the ice particles with
additional salt smoothes the ice particles can make the slurry
pumpable. The mixing blade can be present in the third volume.
[0131] The fourth volume can surround the third volume and is where
the high concentration saline is introduced into the assembly. The
volume is configured to allow the high concentration saline to flow
freely to all surfaces of the mixing vessel. This facilitates
uniform mixing, and also reduces drag as the ice slurry flows
through the vessel. The completed ice slurry travels out of the end
of the vessel. In some aspects, the slurry can be pumped through
one or more of the components of the assembly, and/or it can be
pumped through a tube for administration to a patient.
[0132] In a counter current heat exchanger configuration, coolant
flow rate and saline flow rate can be physically related based on
the void fraction of ice that is desired. In addition, heat
transfer equations can be complicated by changing temperatures in
the heat exchanger wall as a function of distance through the
device. In addition, energy may be required to pump the coolant
liquid. To optimize configuration and operation of a slurry
production system, it has been discovered that annular heat pipes
can be used as a heat exchanger in the system. Accordingly, in some
preferred aspects, the heat exchanger can be a heat pipe,
preferably an annular heat pipe.
[0133] According to an exemplary embodiment, a heat pipe is
essentially a self contained, surface tension driven, heat pump.
When a temperature gradient is imposed across a heat pipe, heat is
conducted and convected across the heat pipe, allowing as much as
100.times. the heat transfer as may occur through conduction alone.
An additional benefit of heat pipe technology is that, through
control of the internal pressure at manufacturing, the heat pipe
can be tuned to have a desired evaporation or condensation
temperature. This makes it possible to provide a surface with a set
constant temperature without any additional control or feedback.
Thus, the heat pipe provides an additional advantage of reducing or
eliminating any requirement to pump a coolant and provides a
further advantage of having a heat exchanger surface with a
constant wall temperature. This advantageously will allow
production of even smaller and more portable slurry production
systems and devices, as well as systems and devices that require
fewer pumps and therefore require less electrical power to
operate.
[0134] An example of a heat pipe heat exchanger configuration is
shown in FIG. 15, which provides a cross sectional view. The heat
pipe is preferably annular, and in this view has been cut in half
along the central axis. In the configuration shown, the liquid in
the heat pipe condenses on the side of the coolant and then is
wicked toward the saline side, where the coolant may evaporate. The
evaporation temperature can be maintained between about 0.degree.
and about -20.degree. C. The coolant can be a compressed gas such
as liquid nitrogen, or it can be alcohol mixed with dry ice. The
heat pipe can provide an even temperature at the saline side even
if there are temperature gradients at the coolant side. The coolant
can be contained in a second larger annulus in which the heat pipe
nests.
[0135] FIG. 16 illustrates a modification of the system shown in
FIG. 2. In the cross sectional view of the system shown in FIG. 16,
the heat pipe includes an annulus which has been cut in half along
its central axis. In this configuration, the evaporative side of
the heat pipe 400 can be proximal to the heater 402. The condensing
side of the heat pipe can be proximal to the side of the slurry.
The condensing liquid can heat the slurry melting the ice. The
measurement techniques described above can be used. The
condensation temperature can range from about 0.degree. to about
60.degree. C.
[0136] Ice slurry production can be optimized by nucleating ice
from a supercooled saline solution that is outside of a primary
heat exchanger. For example, generally when slurry is produced
inside of a heat exchanger, a nucleation event occurs in a
supercooled solution, but this event is not continuous, meaning
that the ice formed must primarily be obtained by scraping the
surface of the heat exchanger, rather than from the ice forming in
the solution on a continuing basis due to nucleation. In this the
present invention, the supercooled state is stabilized, and then
ice is nucleated with disturbances. It is advantageous to create
the ice outside of the primary heat exchanger since the
maintainability and efficiency of the heat exchanger are lower when
ice is produced in the heat exchanger. Thus, in some aspects, the
invention provides systems for generating ice from a supercooled
solution (a liquid solution cooled to a temperature below the
freezing point of the solution), for example, by creating a
disturbance in the flow of the solution. Such a disturbance can be
made using ultrasound, change in roughness, a change in turbulence,
and the like. Ice nucleation often occurs more easily at
pre-existing interfaces because surfaces allow particles to
nucleate by lowering the surface energy and hence decreasing the
free energy barrier; a change in the contact angle between the
phases can influence the surface energy.
[0137] In some aspects, the slurry generating system can be
configured as shown in FIG. 20. For example, the system 500 can
comprise at least one heat exchanger. A primary cooler 502 can be
utilized to supercool a solution 504 without inducing ice
nucleation. The primary cooler can, for example, be a counter
current scraped surface heat exchanger (as described and
exemplified herein), an annular heat pipe, or can be any
refrigeration technology capable of cooling a saline solution to a
temperature below its freezing point.
[0138] Ice nucleation can be induced in the supercooled solution,
for example, by disturbing the stable flow. The stable flow can be
a laminar flow or a turbulent flow. The flow disturbances 506 can
be induced through methods such as ultrasound, flow stagnation
points, introduction of a seed piece of ice, the use of bubbles,
eddy or vortex shedding geometries (for example pyramidal shapes),
angle adjustments of physical objects to adjust wetting (contact
angle), physical object material changes to adjust wetting, or a
change in the momentum of the fluid flow (by changing the diameter
through which fluid flows), other flow disturbance means, or any
combination of the above. These disturbances can initiate
heterogeneous nucleation in the solution to form an ice slurry 508.
The disturbances can be spatially isolated from the primary cooler,
for example in an ice nucleation chamber 510 connected to the
primary cooler. Total ice fraction as well as particle size can be
controlled by the continued removal of heat from the slurry with an
optional secondary cooler 512 after the onset of nucleation.
[0139] In some aspects, the flow disturbance can be a local
pressure fluctuation, for example, from an impinging supercooled
fluid jet, or from ultrasonic waves.
[0140] A supercooled jet of fluid impinging on a fluid bed of
supercooled liquid can induce heterogeneous nucleation. In this
aspect, it is believed that the pressure fluctuations induced by
jet/droplet impact on the fluid bed can lead to local fluctuations
in the equilibrium freezing temperature leading to heterogeneous
ice nucleation.
[0141] The probability that an impinging jet will induce
heterogeneous ice nucleation can be increased through the
introduction of a gas bubble on the surface of the fluid body. The
bubble should preferably be stable on the fluid bed, which provides
practical limits on the characteristic length scale of the bubble.
In such aspects, ice crystallization may initiate on the bubble
interface while the bubble is under the impinging supercooled fluid
jet, or while the bubble is adjacent to the impinging supercooled
fluid jet. Additionally, the collapse of the bubble under the
pressure of the impinging jet may cause local fluctuations in the
equilibrium freezing temperature leading to heterogeneous ice
nucleation. This mechanism may also be applicable to the use of
ultrasound to induce ice crystal nucleation.
[0142] It is believed that ultrasound induces ice crystal formation
through the collapse of a cavitation bubble. As a microbubble
collapses, the local pressure gradient can be greater than 1 GPa.
This local high pressure field can lead to a localized increased
equilibrium freezing temperature which leads to ice nucleation. In
addition, in the post bubble collapse period, there is an area of
relative negative pressure which also leads to a localized increase
in equilibrium freezing temperature. There is evidence of a
secondary nucleation process that may be a product of buoyancy
force induced bubble motion. Regardless, secondary ice nucleation
effects are not explained by the collapse of a cavitation bubble,
as the time scales are too long. Generally, ultrasonic nucleation
of ice crystals is highly dependent on the amount of gas dissolved
in the liquid, and requires roughly 5 degrees Kelvin of
supercooling. Degassed liquids exhibit a significantly reduced
tendency to form ice crystals due to ultrasonic pulses. The
concepts are described, for example, in Zhang et al.,
"Ultrasonic-induced nucleation of ice in water containing air
bubbles", Ultrasonics Sonochemsitry 10(2003) 71-76; and, Ohsaka et
al., "Dynamic nucleation of ice induced by a single stable
cavitation bubble Appl. Phys. Lett. 73, 129 (1998). These
references are incorporated by reference herein.
[0143] In some aspects, one or more ice crystals can be used to
induce ice nucleation. Ice can be used in at least two manners to
induce spontaneous nucleation of a supercooled liquid. The first is
the creation of a stagnation point using an ice body. The
stagnation point itself can be sufficient to induce heterogeneous
nucleation. The construction of an ice body provides the added
benefit that the ice body can be colder than the supercooled fluid,
and can therefore absorb some heat from the fluid while maintaining
an ice crystal structure. Additionally, the addition of an ice seed
particle can be used. Heterogeneous nucleation is a stochastic
process, and therefore the required number of seed particles may
correlate inversely with the amount of supercooling. Therefore, the
higher the amount of supercooling, the smaller the number of ice
seed particles required to induce heterogeneous nucleation. It is
also possible that the crystal structure of the ice body or seed
particle could provide the foundation for crystallization of the
supercooled liquid. By implanting a stable ice crystal into the
supercooled solution, the radius condition necessary to create an
ice nucleus from the solution is relaxed since ice growth can
initiate off of an already formed surface. The ice crystal can be
from any material, including dry ice.
[0144] In some aspects, stagnation points, eddy or vortex shedding,
flow separation, or interface locations in the solution flow can be
used to facilitate ice nucleation. For example, stagnation points,
eddy or vortex shedding, flow separation, or interfaces with
distinct contact angles can be caused by one or more trips. Trips
can comprise any suitable configuration, including but not limited
to the configurations shown in FIG. 22.
[0145] FIG. 22A shows a post design trip. Post trips create a
centralized fluid stagnation point, increase the velocity of the
flow by decreasing the available cross section, and/or provide an
interface to lower the free energy barrier. Posts can have any
width or diameter suitable to affect flow velocity, ice particle
size, ice particle shape, and total ice slurry yield. The post
preferably is centered in the ice flow tube, allowing the cooled
solution and formed ice slurry to flow between the ice flow tube
side walls and the outer surface of the post. The post can have any
suitable length, and in some preferred aspects, spans the length of
the tube that carries the supercooled effluent from the primary
cooler. The post trip configuration can be optimized according to
the needs of the application, for example, by varying the diameter
of post, the diameter of the post as a function of length (i.e.,
making a cone), the material used to fabricate the post (e.g.,
plastic, metal, foam, and the like), the surface properties of post
(e.g., rough or smooth), the length of post (e.g., thin/disk-like,
or very long), the tip characteristics (rounded, flat, sliced at an
angle), and the like.
[0146] FIG. 22B shows a cross-wire design trip. Cross-wires can
create a flow disturbance with small to insignificant stagnation
points, can cause changes in local flow through eddy or vortex
shedding, and/or can provide an interface to lower the free energy
barrier. The main change in flow will occur in the center of the
flow where all the wires cross; here will be located the largest
stagnation point, but the crossing of all of the wires also creates
many surface planes and crevices from which nucleation can be
facilitated due to the creation of lower surface energy through
increased interaction with contact angles. The cross-wire trip
configuration can be optimized according to the needs of the
application, for example, by varying the number of wires, by using
either round or rectangular wire, by varying the diameter of wire
(thick wire can produce stagnation points), by elongating the
profile to extend down the length of the tube, by varying the
surface properties (rough or smooth), by varying the material the
wire is fabricated from (stainless steel, ceramic, plastic, etc),
by varying the cross location (peripheral rather than central), or
by using blades instead of wire, the blades having edges arranged
in a similar pattern, and the like.
[0147] FIG. 22C shows a tooth design trip. Teeth can create
peripheral stagnation points, cause change in local flow through
eddy or vortex shedding, and/or provide an interface to lower the
free energy barrier. When using teeth, the main change in flow will
occur at the peripheral sections of the flow. The tooth design trip
configuration can be optimized according to the needs of the
application, for example, by varying the number of teeth, varying
the edges of teeth (round versus straight), making the teeth
three-dimensional, for example, to take on a pyramidal shape,
varying the angle of teeth (can be bent toward or away from flow),
varying the angle of entire object (for example, setting at 45
[deg]), varying the surface properties of the teeth (rough or
smooth), varying the material the teeth or trip on the whole is
fabricated from (stainless steel, ceramic, plastic, and the like),
changing the open diameter through which the fluid flows by
changing the radial height of the teeth, elongating the profile to
extend down the length of the tube, or simplifying the shape to
posts sticking out of the tube side wall or having blades running
length of the tube side wall, and the like.
[0148] FIG. 22D shows a central tooth design trip, with several
possible design variations, including a rounded tooth
configuration, a pointed tooth configuration, and a saw-blade
configuration. A central tooth, similar to the post, can create
central stagnation points, cause changes in the local flow through
eddy or vortex shedding, and/or provide an interface to lower the
free energy barrier. The central tooth design varies the basic post
design to enhance eddy or vortex shedding, and in some ways can be
considered a fusion of the Cross-Wire Design (FIG. 22B) and the
Post Design (FIG. 22A). The central tooth configuration can be
optimized according to the needs of the application, for example,
by varying the number of teeth, varying the edges of teeth (rounded
versus straight), making the teeth three-dimensional, for example,
to take on a pyramidal shape, varying the angle of teeth (can be
bent toward or away from flow), varying the angle of entire object
(for example, setting at 45 [deg]), varying the surface properties
of the teeth(rough or smooth), varying the material tooth teeth or
trip on the whole is fabricated from (stainless steel, ceramic,
plastic, and the like), varying the diameter of trip, or elongating
the profile to extend the length of the tube or shorten the tube to
a thin shape, and the like.
[0149] FIG. 22E shows a sticky sphere trip design. The sticky
sphere can cause changes in local flow through eddy or vortex
shedding, and/or provide an interface to lower the free energy
barrier. The main change in flow will occur in the center of the
flow. This trip design is believed to induce turbulent flow, and
can be considered to relate to a three dimensional variation of the
cross-wire trip (FIG. 22B). The sticky sphere trip configuration
can be optimized according to the needs of the application, for
example, by varying the diameter of sphere, the shape of the sphere
(sphere, ellipsoid, cube, and the like), the number, length, and
diameter of the spines, the tip properties of spines, the angle the
spines protrude from the anchoring body, the material used to
fabricate the spines and/or the anchoring body (stainless steel,
ceramic, plastic, and the like), and/or the roughness properties of
the spines and/or base, and the like. A simplified sticky sphere
version can have a Star-of-Bethlehem-type shape.
[0150] FIG. 22F shows a pyramidal trip design. The pyramidal trip,
similar to the tooth design shown in FIG. 22C can create flow
disturbance with small to insignificant stagnation points, cause
change in local flow through eddy or vortex shedding, provide
interface to lower free energy barrier, and can increase ice yield
by having multiple shed points distributed along the length and/or
radius of the flow tube. The pyramidal trip configuration can be
optimized according to the needs of the application, for example,
by varying the number of pyramids, the shape of pyramids (e.g.,
tetrahedral), by making the edges round versus straight, by varying
the angle of pyramid attachment (e.g., facing toward or away from
the flow direction), by varying the surface properties (rough or
smooth), varying the material used to fabricate the pyramid
(stainless steel, ceramic, plastic, and the like), varying the
spacing of pyramids along the length of the tube or around the
circumference of the tube, or including more than one pyramid at a
certain position in the tube, and the like.
[0151] FIG. 22G shows a surface roughness trip design. The surface
roughness trip can create flow disturbance with small to
insignificant stagnation points, cause change in local flow through
eddy or vortex shedding, and/or provide micro-interfaces to lower
free energy barrier. The roughness creates many surface planes and
crevices from which nucleation can be facilitated due to the
creation of lower surface energy through increased interaction with
contact angles. The surface roughness trip configuration can be
optimized according to the needs of the application, for example,
by varying level (course to fine) of roughness, the degree of
roughness increasing or decreasing as function of length, the total
length of rough area, or the material used to create a rough
surface (stainless steel, ceramic, plastic, and the like), and the
like.
[0152] FIG. 22H shows a teeth combination trip configuration. The
teeth combination provides the synergistic benefits of the tooth
designs shown in FIGS. 22C and 22D. The combination trip can
increase slurry yield by having multiple eddy or vortex shed points
distributed along the length and radius of the flow tube. This
combination can be optimized according to the needs of the
application, for example, as each of the tooth designs described
above can be optimized. In addition, this trip can be optimized by
using different combinations of tooth designs, such as combinations
of rounded teeth and pointed teeth, and the like.
[0153] FIG. 22I shows a dimpled tube trip configuration. The
dimpled tube trip can create flow disturbance with small to
insignificant stagnation points (if the structure is hollow as
shown in the figure), or with a central stagnation point (if the
structure is solid as in the post designs shown in FIG. 22A), can
cause flow separation at one or more dimple interfaces (causing the
fluid to detach from the surface of the object) and result in
eddies and vortices, and provides an interface to lower the free
energy barrier. This trip design can by optimized according to the
needs of the application, for example, by varying the number of
dimples or the depth of dimples, by elongating the profile to
extend the length of the tube, by varying the surface properties of
each dimple (rough or smooth), and/or varying the material used to
fabricate the trip (e.g., stainless steel, ceramic, plastic, and
the like), and the like.
[0154] FIG. 22J shows a cone with blades trip configuration. The
cone with blade trip can cause changes in local flow through eddy
or vortex shedding, and can provide an interface to lower the free
energy barrier. The main change in flow can occur in the center of
the flow. This trip is a variation on the Post Design described
above, which can enhance eddy or vortex shedding. The cone can be
optimized according to the needs of the application, for example,
by varying the length of the cone, the number of blades, the height
of the blades, the surface properties of the blades (rough or
smooth), and/or the material used to fabricate the cone and/or
blade, and the like.
[0155] Inducing ice nucleation outside of the primary cooling
system provides several benefits. The need to scrape a surface as
ice forms can be reduced or eliminated, although it may be
desirable in some aspects to continue to utilize scraping to reduce
the effect of ice fouling on the heat transfer rate, which in turn
reduces system wear, system cost, system weight, and system size
(no motor). The elimination of the ice fouling problem also
increases the overall efficiency of the system. The cooling systems
are also easier to model because the heat transfer is better
understood physically and mathematically. Also, this makes it
possible to nucleate the ice in a tube with the diameter of an
intravenous tube, eliminating the difficulty of transitioning the
particulate flow from a large diameter to a small diameter before
administering to a patient.
[0156] According to another or alternative aspect of this invention
ice slurry production can be optimized by combining two solutions.
The concentration of a solution determines its the freezing point
by increasing the entropic penalty associated with the freezing
process. Any solution maintained at a temperature below its
freezing point is a supercooled solution. A more concentrated
solution can achieve lower temperatures, through freezing point
depression relative to less concentrated solutions. Since the
maintainability and efficiency of scraped surface heat exchangers
are lower when ice is produced in situ, it is advantageous to
create the ice outside of this device.
[0157] Thus, ice slurry can be generated by combining a
concentrated supercooled solution (solution A) with, for example,
cooled water (or a cooled solution less concentrated than solution
A) (solution B), to create a solution with the desired
concentration (solution C) that will have a temperature that is
below the freezing point for solution C (i.e., an already
supercooled solution C). This supercooled product, solution C, can
then have ice nucleation induced, for example, using the methods
described and exemplified herein such as in the manner of combining
two fluids (solution A and solution B), or in a secondary scraped
surface heat exchanger directly before slurry utilization site. The
desired concentration of solution C will dictate the combination
rates of solution A with solution B, and it will also dictate the
freezing point of the product. The freezing point of the product
will dictate the required temperatures of the two solutions (A and
B) to be combined to form the product solution C.
[0158] Ice nucleation can take place in a specialized nucleation
region of the inventive systems. For example, the nucleation region
can comprise one or more stagnation points, one or more eddy or
vortex shedding points, or one or more interfaces such as the trips
described and exemplified herein. The nucleation region can be a
nucleation chamber configured as shown in FIG. 23.
[0159] The nucleation chamber 600 can be comprised of any suitable
material such as a plastic, metal, ceramic, wood, and the like, and
will comprise at least one lumen 602 having a width or diameter
D'-1 through which a solution such as a supercooled saline solution
can flow to facilitate ice nucleation and slurry formation. The
chamber can comprise a space 604 having a width or diameter D'-3
and a length or depth D-2 sufficient to house, among other things,
one or more trip holders 606A and 606B, as well as an optional
spacer 618, having, for example, a length or depth D-1. The chamber
can also comprise a space 620 for an o-ring. In some preferred
aspects, the back of the chamber can comprise a drip shoulder 616
that comprises an overhang so that liquid passing through the
chamber does not drip down the rear face of the chamber. The
falling slurry and/or solution can then be collected. However, the
drip shoulder can be replaced by another o-ring surface that can
then interface with the slurry delivery system.
[0160] In some aspects, the chamber can comprise an aperture 614
that can be used to allow ice and/or slurry to be removed from the
chamber, for example, to analyze for concentration, crystal size
and shape, temperature, and the like. In some aspects, the aperture
can be an interface for a hose barb to allow ice removal to be
facilitated by vacuum. The interface can comprise threads 628
compatible with threads on a hose barb, including hose barbs that
are commercially available. The trip holder, which is shown in more
detail in FIG. 24, can comprise a slot 610 having a width or
diameter D'-2 to fit one or more trips, and can comprise one or
more apertures 608 through which a fastener can be placed to
prevent the trip holder from rotating or otherwise shifting out of
place. For example, the fastener can attach to an aperture 612 in
the chamber wall or housing.
[0161] FIG. 24 shows different views of the components that the
space as shown in FIG. 23 (604) can comprise, including the trip
holder and spacer. For example, FIG. 24A shows a frontal view of
trip holder 606A. This orientation shows the location of the
apertures 608, the slot 610 for holding a trip, and the width or
diameter D'-1 and D'-3. FIG. 24B shows a frontal view of trip
holder 606B and the location of apertures 608. FIG. 24C shows a
frontal view of a "blank" having a width or diameter D'-1, which
can fit into the slot 610 of trip holder 606A when a post-design
trip is used. FIG. 24D shows a cross sectional view of trip holders
606A and 606B (shown in FIGS. 24A and B) having a width or diameter
D'-3, and shows the location of lumen 602 and aperture 608, the
slot 610 having a width or diameter D'-2. FIG. 24E shows the
frontal view of a spacer having a width or diameter D'-3, as well
as a lumen 602 for the supercooled solution to flow. The spacer can
be fabricated from any suitable material, and in some preferred
aspects, is fabricated from the same material used to make the
chamber housing.
[0162] A frontal view of the ice nucleation chamber is shown in
FIG. 25. This view shows the location of the lumen 602 through
which a supercooled solution can flow, the o-ring space 620, space
604 having width or diameter D'-3, and aperture 608. Also shown are
apertures 646 for a fastener that can fasten a hose barb such as
the barb shown in FIG. 26 to the front of the chamber.
[0163] In some aspects, the chamber is configured to receive
supercooled solution from a primary cooler. Thus, for example,
supercooled solution can flow through a tube from the cooler into
the nucleation chamber, as allowed for by a fitting, for example
fitting 366 shown in FIG. 14. To minimize or eliminate loss of
supercooled fluid from the tube, and to ensure a smooth transition
into the nucleation chamber, a hose barb may be used. One exemplary
hose barb is shown in FIG. 26. The hose barb 640 can have a tip 642
onto which a tube or hose can be reversibly attached and a lumen
644 to allow the supercooled solution to flow through the barb into
the lumen of the chamber 602. The base 648 of the hose barb can
mate with an o-ring found on a distinct surface, and can comprise
one or more apertures 646 for fasteners to fasten the hose barb to
the chamber.
[0164] The aperture 614 near the back of the chamber for removing
ice and/or slurry samples is shown in more detail in FIG. 27. This
figure shows an example of a hose barb 650 having threads 652
compatible with the threads 628 in the chamber. The aperture near
the back of the chamber can be bored to allow a vacuum attachment
that can be used to separate nucleated ice from the solution. This
can be used to determine ice mass fraction from the increase in
solution concentration
[0165] A frontal view of the back of the chamber is shown in FIG.
28. The back has an aperture 602 having width or diameter D'-1 for
the formed ice slurry to pass through and out of the nucleation
chamber. There are also apertures 654 for fasteners to attach. FIG.
28 indicates the back wall having a region removed so the liquid
and/or slurry can be collected instead of running down the back
face of the nucleation chamber. However, this back surface can also
have an optional o-ring space present to accommodate the interface
of the nucleation chamber to the slurry delivery device.
[0166] The post design holder is shown in FIG. 29. FIG. 29A shows a
frontal view of a back configuration that can be used when using
non-post trips. The post design trip holder can have an aperture
656 having width or diameter D'-4 corresponding to the diameter of
the post trip and into which the post trip can be placed. D'-4 can
be smaller than D'-1. There are also apertures 654 that align with
the apertures 654 shown in FIG. 28, which can allow for fasteners
to fasten the post design trip holder to the nucleation chamber.
FIG. 29B shows a side view of a back configuration that can be used
when using post trips. The aperture 656 with width or diameter D'-4
for post placement and the apertures 654 for fastening to the
nucleation chamber are shown.
[0167] Systems and devices for producing ice slurry preferably will
have monitoring instrumentation capable of identifying modes of
failure upon processing and analysis to be completed either real
time or after operation, and preferably will have appropriate
mechanisms for responding to various modes of failure. The systems
and devices can have performance standards set forth from
calculations as well as experimental calibration, and deviations
from these standards can be utilized to alter or control the
operation of the device.
[0168] For example, uncharacteristic changes in heat flow can cause
the system to systematically evaluate temperature, rotation rate,
and torque, individually and/or then in combination, to identify
the cause of the system failure. The cause can then optionally be
translated and brought to the attention of the user so the failure
can be addressed.
[0169] Temperature measuring devices can include, but are not
limited to, thermocouples, non-limiting examples of which include
K, J, T, and E type thermal resistive devices (RTD's), or infrared
instrumentation. The rotary torque can be measured using a variety
of methods, including moment arm, slip ring, and rotary transformer
methods. The rotation rate sensor, or angular displacement sensor,
can also utilize a variety of sensing methods and can operate in a
variety of ranges. The instrumentation to measure rotation rate and
rotary torque can be in the form of a single sensor, and can be
provided with a variety of sensor ranges. Such instrumentation is
known in the art. All measurements can be transmitted to a computer
for data acquisition and analysis.
[0170] Ice slurry generating systems and devices preferably have a
target heat transfer coefficient that can be altered by changing
the mass flow rates in the system. Thus, optimal ice slurry
production can have a target heat transfer coefficient that, if not
met, will indicate a failure in the system.
[0171] Analysis of the coolant and ice slurry (product)
temperatures, measured at either the inlet, outlet, or both, or at
any other location, allows for system monitoring that can trigger
operation of a failure mode should the coolant or product
temperatures rise above or fall below a working or optimized range
for the device. Such a failure mode will be comprised of
adjustments in the operation of the system to bring the coolant and
product temperatures within the appropriate range.
[0172] The rate of temperature change can also serve as an
indicator of a failure mode. A change in the temperatures of the
coolant and ice slurry product can result in a change of the heat
transfer coefficient.
[0173] Other data points that can be subject to monitoring to
optimize operation of the slurry production system include ice
fouling from the exchanger. A change in the operation of ice
removal can result in a change of the heat transfer coefficient. In
addition, the generated slurry can be monitored based on at least
three properties, individually or in any combination, including (1)
ice mass concentration; (2) ice particle size; and (3) ice particle
shape. These three properties can determine the rheologic
properties of the slurry, the melt temperature range and the pump
power requirements. Variations of these properties outside of
accepted optimal ranges can trigger a series of adjustments
designed to bring these properties of the ice slurry back to within
acceptable ranges.
[0174] The invention also provides methods for producing an ice
slurry using the ice slurry production systems described and
exemplified herein. In some detailed aspects, the methods comprise
contacting a fluid such as a low concentration saline solution with
a heat exchanger for a time sufficient to allow a portion of the
fluid to freeze and form an ice slurry, and then admixing a higher
concentration saline solution with the ice slurry. The heat
exchanger can comprise two concentric tubes, or it can be a heat
pipe such as an annular heat pipe. The high concentration saline
solution smoothes the formed ice crystals to allow the slurry to be
pumpable. In an alternative aspect, the methods comprise contacting
a fluid such as a lower concentration saline solution with a heat
exchanger for a time sufficient to allow a portion of the fluid to
freeze and form an ice slurry, and then contacting the ice slurry
with a heat source for a period of time sufficient to smooth the
ice crystals in the slurry. The methods can be used to produce ice
slurry on any scale, small or large, for example, for
administration to a patient, or for fire suppression or crowd
control.
[0175] The invention also provides methods for using a two-phase
coolant such as the ice slurry produced by the inventive ice slurry
production systems and devices. The ice slurry can be used to cool
or maintain a particular temperature in any application where lower
temperatures or temperature maintenance is desired.
[0176] In a highly preferred aspect, the invention features methods
for inducing or maintaining hypothermia in a subject comprising
administering to a subject in need thereof a pharmaceutically
acceptable ice slurry such as an ice slurry produced by the
inventive ice slurry production systems and methods described or
exemplified herein. The ice slurry is administered to the subject
in an amount effective to induce or maintain hypothermia. The
effective amount may be dependent on various factors. Non-limiting
examples of such factors include the species, height, weight, age
of the subject, condition being treated and the like.
Administration can proceed by any means suitable for the particular
application to which the coolant is being used. For example, the
coolant can be administered intravenously, intramuscularly,
topically, orally, nasopharyngeally, anally, vaginally, into
intraperitoneal or intrathoracic spaces, into other physiological
spaces or regions, and the like. Intravenous administration is
highly preferred.
[0177] The methods can be used in any subject. Preferably, the
methods are used in mammals such as horses, cows, pigs, dogs, cats,
rabbits, rats, hamsters, and mice. The methods are preferably
beneficially employed in humans.
[0178] The hypothermia can be systemic, meaning that hypothermia
can be induced and/or maintained throughout the entire body of the
subject. Alternatively, the hypothermia can be directed to a
particular location or locations of the body, for example, to a
particular organ, appendage, cavity, space, or region.
[0179] Also provided are methods for rapidly cooling or maintaining
a cool temperature for perishable goods. Such methods generally
comprise producing an ice slurry using any of the ice slurry
production systems, devices, and methods described and exemplified
herein, and exposing the perishable goods to the ice slurry.
Non-limiting examples of perishable goods include food products
such as meats, fish, produce, milk and milk products,
confectionaries, beverages, and the like; pharmaceuticals;
vitamins; minerals; volatile chemicals; radionuclides; biomolecules
such as nucleic acids, polypeptides, and lipids, cells, tissues,
organs; and biological fluids such as blood, blood serum, urine,
saliva, sweat, milk, and the like.
[0180] Also featured are methods for rapidly cooling heat
generating devices such as a weapon. The methods comprise producing
an ice slurry using any of the ice slurry production systems,
devices, and methods described or exemplified herein, and exposing
the weapon or components thereof to the ice slurry. Any weapon or
sub-part of a weapon such as a gun barrel can be cooled using the
inventive method. Non-limiting examples of suitable weapons include
guns, cannons, and electromagnetic pulse generators. Weaponized
lasers can also be cooled according to the inventive methods. The
weapons can be hand-held, or they can be those attached to
equipment such as a plane, helicopter, or vehicle.
[0181] The following examples are provided to describe exemplary
aspects of the invention in greater detail. They are intended to
illustrate, not to limit, the invention.
EXAMPLE 1
On-Demand Production of Saline Ice Slurry
[0182] In this prophetic example, a device is prepared for
on-demand production of a micro-particulate two-phase (solid and
fluid) coolant. The device includes two containers of fluid that
may be separate or concentric. One container is pressurized and the
other is not. The device is used to produce a uniform and
homogenized saline ice slurry.
[0183] The container can be filled with water that can contain
varying concentrations of salts, surfactants, and/or emulsifiers.
The container will be pressurized to a level high enough to induce
instantaneous expansion of the liquid upon release from the
container. The pressurized container will not be entirely full of
fluid, instead leaving a large volume, expected to be about 50%, to
the gas phase. The pressurized container and its contents will then
be refrigerated to a temperature below the atmospheric pressure
freezing point of the fluid.
[0184] A specialized nozzle can be attached to the end of the
pressurized container. This nozzle will create a fine mist of the
fluid as the fluid is expelled from the bottle. As the pressure is
released, the fluid will spontaneously change to the solid phase
(e.g., freeze) because its temperature is held below its
atmospheric pressure freezing point. The formed ice crystals will
be processed in a homogenizer, where they will be mixed with a
carrier fluid that was released from the second tank.
Homogenization ensures tunable ice particle size and chemical
smoothing.
[0185] The second container will contain a fluid compatible with
the solidified fluid from the first container in order to form the
desired ice slurry. For example, the second container can contain
water, salts, surfactants and other emulsifiers. As above, the
second container and its contents will be refrigerated to a
temperature below the atmospheric pressure freezing point of the
fluid from container 1. The fluid from the second container,
however, will remain in the fluid phase, even at the low
temperature, because of the absence of pressure.
[0186] The cooled fluid from the second container will then be
pumped into the homogenizer and mixed with the ice particles
created from the first container. The fluid thus will serve as a
carrier fluid for the micro-particulate ice for delivery to a
desired location and use for a desired purpose.
[0187] There can be a pressure connection between the homogenizer
outlet and the second container. In this case, the excess pressure
from the first container that was used to cause freezing point
depression is used upon release to pump the fluid from the second
container into the homogenizer. A schematic illustration is
provided in FIG. 1.
EXAMPLE 2
Low-Electrical Production of On-Demand High or Low Volume Saline
Ice Slurry
[0188] In this prophetic example, a device is prepared for
on-demand production of a micro-particulate two-phase (solid and
fluid) coolant in high or low volumes. The device may include large
scale versions of the devices previously described as well as large
volumes of primary coolant such as a compressed gas or dry ice. The
primary separation between Example 1 and Example 2 is the provision
or slurry without the requirement of electrical power.
[0189] In situations where the availability of electrical power may
limit the previously described use of a two phase coolant the
described devices and methods may be used to overcome the
electrical power limitation. In this example, which is pictured in
FIG. 5, one of the slurry production devices described herein has
been scaled to sizes effective to the particular cooling tasks. In
addition, an appropriate volume of primary coolant is also
available. The primary coolant is pumped through the Coolant Heat
exchanger where a secondary coolant is cooled to a similar or
slightly warmer temperature. The secondary coolant is pumped or is
wicked to the Slurry Production Device. In the slurry production
device the secondary coolant cools the saline water to its freezing
point. Ice is scraped off of the heat exchanger surface and ice
nucleates in the bulk liquid. Ice particle size is controlled by
ice scraper blades and mixing. The saline and slurry are pumped
through the slurry production device and delivered by means
appropriate to the task.
EXAMPLE 3
Quality of a Two-Phase (Solid-Liquid) Coolant
[0190] In this prophetic example, an in-line system is proposed for
assuring the quality of a two-phase (solid-liquid) coolant delivery
system, preferably just prior to the site of coolant application.
The system is intended to address the concern that the quality of
the coolant will alter in transit from slurry creation to site of
action due to melting of the solid phase.
[0191] The device will consist of a tube with known heat transfer
characteristics that has a series of heat flux and temperature
sensors embedded at predetermined positions along the length of the
tube. The environment outside of the tube will be held at a known
temperature. An aqueous ice slurry will be passed through the tube
at a prescribed volumetric flow rate and the heat flux and
temperature will be measured as a function of distance traveled by
the coolant down the tube. The ice void fraction will be calculated
by measuring the total amount of heat that will enter the coolant
slurry. The ice particle size will be correlated from the time that
was required to transfer that much heat. These calculations will be
made on a computer connected to the series of sensors.
[0192] The calculation of the ice void fraction will be made as
follows. The fluid will be well-mixed within the tube as a function
of the tube design, and the temperature within the tube will stay
very close to the freezing point of the liquid, until all of the
ice is melted. The heat flux will therefore primarily go to the
melting of the ice. Once the ice is melted the temperature of the
liquid will begin to rise, and this will be detected by the
temperature sensors. Therefore, based on the location of the
initial rise in temperature of the fluid in the tube, the measured
heat flux as a function of the length of the tube, and volumetric
flow rate the ice percentage will be estimated using a relationship
such as Equation 1:
.DELTA.Q.sub.slurry=m.sub.slurryC.DELTA.T+%.sub.icem.sub.slurry.lamda..s-
ub.ice
where .DELTA.Q.sub.slurry is the heat energy gained from the
heater, m.sub.slurry is the mass of the slurry, C is the heat
capacity of the liquid phase of the slurry, .DELTA.T is the change
of temperature of the slurry, %.sub.ice is the ice percentage, and
.lamda..sub.ice is the latent heat for the phase change from ice to
liquid.
[0193] The calculation of the average ice particle size will come
from an empirically-derived correlation. A heat transfer equation
(Equation 2) that will explain the method for measuring the average
slurry particle size is:
{dot over (Q)}=hA.DELTA.T
where {dot over (Q)} is the heat entering the slurry in units of
watts (heat flow), h is the convective heat transfer coefficient in
units of W/m.sup.2K, and .DELTA.T is the temperature difference
between the inner tube wall and the bulk fluid temperature. The
coefficient h will be a function of the fluid volumetric flow rates
and fluid physical properties as well as the size and distribution
of the ice particles in the slurry. It is expected that the value
of h will increase with decreasing average particle size when the
ice percentage is fixed. As the particle size decreases, the number
of particles will increase as will the interfacial area available
for phase change from solid to liquid assuming that the volume is
fixed. An example of the difference in the measured values that one
may expect under these conditions is given in FIG. 3.
EXAMPLE 4
Heat Exchanger Construction and Ice Slurry Production
[0194] General Device Characteristics: A counter current scraped
surface heat exchanger similar to the embodiment illustrated in
FIG. 6 was constructed and used to generate ice slurry. The device
had a heat exchange surface area of 0.011 m.sup.2, an annular gap
of 4.94 mm, and eight scraping blades.
[0195] The primary coolant was either 70% or 46% potassium formate.
The primary coolant was cooled in a distinct heat exchanger loop
composed of copper coils submerged in a dry ice/propanol mixture.
The dry ice/propanol mixture created a uniform -70.degree. C. bath
through which the potassium formate passed. The potassium formate
entered the counter current heat exchanging device at a temperature
below the freezing point of the product. The product in the cases
presented is either 10% NaCl by mass (10% saline) or 1% NaCl by
mass (1% saline).
[0196] All exposed lines were insulated. The range of mass flow
rates for coolant and product were (respectively): 0.011-0.002
[kg/sec] and 0.006-0.001 [kg/sec]. In general, the product entered
the counter current heat exchanger at room temperature. The central
impeller shaft was rotated at a constant 100 rpm.
[0197] The heat flow of the system, when no ice was being produced,
was calculated using the following equation (Equation 3):
HeatFlux={dot over (Q)}=C.sub.p{dot over
(m)}(T.sub.out-T.sub.in)
where C.sub.p is the specific heat and {dot over (m)} is the mass
flow rate in [kg/sec]. The temperatures of the coolant (T.sub.in
and T.sub.out) and the product (T.sub.in and T.sub.out) were
measured with K type thermocouples and were recorded with a Sper
Scientific 4 Channel Datalogging Thermometer. If the event included
the generation of ice, the following equation (Equation 4) was used
to obtain a representational heat flux:
HeatFlux.sub.ConsideringIce={dot over (Q)}=(C.sub.p{dot over
(m)}(T.sub.out-T.sub.in))(100-%.sub.ice)+{dot over
(m)}.lamda.%.sub.ice
where .lamda. is the latent heat for the phase change from ice to
liquid.
[0198] Ice Slurry Production. The scraped surface heat exchanger
described above was used to produce ice slurry. The coolant was 70%
potassium formate and the product was 10% NaCl.
[0199] FIG. 17A shows the heat flow data for both the coolant and
product, as derived using Equations 3 and 4. FIG. 17B traces the
temperature profiles as a function of time. The temperature plot
(FIG. 17B) shows the product was supercooled below the freezing
point; the degree of supercooling, in part, determines the
concentration of ice produced during spontaneous generation.
Spontaneous generation of ice particles occurred (indicated
temporally by the vertical line in FIG. 17A-B) and the temperature
of the product out increases, indicating the release of the heat of
fusion to make the ice. FIG. 17A shows this by indicating an
increase in the heat flow of the product out by the concentration
of ice produced. The product out temperature remained at the
freezing point of the product, and scraping of ice particles from
the heat exchanger wall occurred after the spontaneous generation
event.
[0200] Failure Mode Identification: The device had monitoring
instrumentation capable of identifying modes of failure upon
processing and analysis. The physical device had performance
standards set forth from calculations as well as experimental
calibration, and deviations from these standards were utilized to
alarm the user to a change in the operation of the device.
Uncharacteristic changes in heat flow prompted a systematic
evaluation of temperature, rotation rate, and torque (individually
and then in concert) to identify the cause of the system
failure.
[0201] FIG. 18 shows a representative data set from the scraped
surface heat exchanger for which a failure occurred in the form of
a frozen coolant line. The coolant was 46% potassium formate and
the product was 1% NaCl.
[0202] Section 1 of FIG. 18A shows a large change in the heat flow
of the system for both the coolant and the product. This change was
accompanied by a dramatic rise in the product out temperature as
well as the coolant in temperature, while the coolant bath
temperature remained constant (indicating the bath was not
exchanging heat with the coolant) (FIG. 18B). The increase in
coolant bath temperature, shown in section 2, was then correlated
with a decrease in coolant in temperature, indicating the release
of a frozen plug from the coolant lines.
[0203] FIG. 19A-C shows a representative data set illustrating
failure in the form of a defective methodology for removing ice
from the heat exchanging surface. The coolant was 46% potassium
formate and the product was 1% NaCl.
[0204] FIG. 19A shows a change in the heat flow of the system
similar to FIG. 18A-B; however, it was not correlated with a large
change in the entering coolant temperature, and the coolant bath
temperature continued to change (indicating heat was being
exchanged with the coolant). The change in heat flow was
accompanied by a rise in the product out temperature (FIG. 19B) as
well as a decrease in the coolant out temperature. FIG. 19C is a
representation of what occurred to the scraper rotation rate during
the drop in heat flow shown in FIG. 19A; the correlation in time
indicates that the change in heat flow was a result of the change
in scraper rotation rate.
EXAMPLE 5
Supercooling a Saline Solution
[0205] General Device Description. A counter current scraped
surface heat exchanger similar to the embodiment illustrated in
FIG. 6 was constructed and used to generate ice slurry. The device
had a heat exchange surface area of 0.011 m.sup.2, an annular gap
of 4.94 mm, and eight scraping blades. The product flows out of the
counter-current heat exchanger into an insulated 1/4 inch inner
diameter tube. The product exits the tube and falls into a
collection beaker.
[0206] The primary coolant was 70% potassium formate. The primary
coolant was cooled in a distinct heat exchanger loop composed of
copper coils submerged in a dry ice/propanol mixture. The dry
ice/propanol mixture created a uniform -70.degree. C. bath through
which the potassium formate passed. The potassium formate entered
the counter current heat exchanging device at a temperature below
the freezing point of the product. The product in the case
presented is 4.7% NaCl by mass (4.7% saline).
[0207] All exposed lines were insulated. The range of mass flow
rates for coolant and product were (respectively): 0.011-0.002
[kg/sec] and 0.006-0.001 [kg/sec]. In general, the product entered
the counter current heat exchanger below room temperature but well
above the freezing point. The central impeller shaft was rotated at
a constant 100 rpm.
[0208] The heat flow of the system, when no ice was being produced,
was calculated using Equation 3 from Example 4, above. The
temperatures of the coolant and the product measured with K type
thermocouples and were recorded with a Sper Scientific 4 Channel
Datalogging Thermometer.
[0209] If the event included the generation of ice, the mass
concentration of ice was found by measuring the increase in density
of the saline solution. While ice was being generated a vacuum was
drawn on the system to separate the saline from the ice particles
with a 40 micron filter. The slurry separated saline solution was
collected in a flask and the density of this solution was found by
fitting a mass versus volume plot of measured data points. The
density of the saline solution corresponds uniquely to a mass
fraction of salt dissolved in water, i.e., the concentration of the
saline. Published literature showing the relationship between
density and concentration was used to identify the concentration of
the slurry saline. Since the pure water ice had to be pulled out of
the original saline solution, the change in saline concentration is
an indicator of the mass fraction of ice in the slurry as is shown
in the following equation (Equation 5):
MassFraction ice = % ice = 1 - C o C s ##EQU00001##
where C.sub.o is the original saline concentration and C.sub.s is
the concentration of the saline in the slurry. The following
equation (Equation 6) was used to obtain a representational heat
flow for the slurry:
HeatFlow.sub.ConsideringIce={dot over (Q)}=(C.sub.p{dot over
(m)}(T.sub.out-T.sub.in))(1-%.sub.ice)+({dot over
(m)}.lamda..sub.ice+C.sub.p,ice{dot over
(m)}T.sub.out)%.sub.ice
where .lamda..sub.ice is the latent heat of the phase change from
solid to liquid.
EXAMPLE 6
Ice Generation using a Seed
[0210] The identified regions in FIG. 21 show the use of an ice
seed to initiate heterogeneous nucleation. A seed ice cube, held at
a temperature below the freezing point of the solution, was placed
in the flow of a supercooled solution produced as from a two phase
coolant device as described in Example 5 and shown in FIG. 6 as it
was falling into the collection container.
[0211] Ice crystals then started to form on this seed during the
sections highlighted on FIG. 21; the seed ice was removed once
crystals started to form. With the presence of crystals in the
solution, nucleation nucleuses were now present in the bulk to
initiate heterogeneous nucleation in the collection beaker. In the
identified sections of FIG. 21, the saline out temperature is below
the freezing point, and hence is supercooled, and the heat flow
plot (FIG. 21A) shows the increased heat flow that is obtained when
ice is present in the product. FIG. 21B shows the temperature
profile.
[0212] Two time periods are identified on FIG. 21 as sections where
nucleation was initiated by the use of a seed ice cube; this is
because the collection beaker for the product was changed. When a
new beaker without any ice crystals was placed under the falling
product there were no nucleation nucleuses available at first, and
so no ice was being produced. Again a seed ice cube, held at a
temperature below the freezing point of the solution, was placed in
the path of the supercooled solution as it was falling into the
collection container and was removed directly after there were
freely floating visible ice crystals in the collection beaker (time
period of ice cube introduction lasted approximately 5
seconds).
EXAMPLE 7
Ice Generation Off of a Physical Surface
[0213] While heterogeneous nucleation was occurring in the
collection beaker, a physical object was placed in the end section
of the device flow tube, in this embodiment it was the tip of a
thermocouple probe. FIG. 21 has identified the section during which
heterogeneous nucleation has initiated from the insertion of the
object. In the identified section of FIG. 21, the saline out
temperature is below the freezing point, and hence is supercooled,
and the heat flow plot (FIG. 21A) shows the increased heat flow
that is obtained when ice is present in the product. Approximately
30 seconds after ice nucleation was initiated, the object was
removed from the flow path. Ice nucleation continued since there
were nucleation nucleuses, in the form of ice crystals, already
present in the flow path.
[0214] The time period during which the vacuum system was turned on
to collect the slurry solution is also highlighted in FIG. 21.
There was a measured increase in the concentration of the saline.
According to Equation 5, from Example 5, the ice mass fraction was
calculated to be 0.30.
[0215] The present invention is not limited to the embodiments
described and exemplified above, but is capable of variation and
modification within the scope and range of equivalents of the
appended claims.
* * * * *