U.S. patent application number 14/209387 was filed with the patent office on 2015-03-26 for closed loop ice slurry refrigeration system.
The applicant listed for this patent is J. Peter Clark, III. Invention is credited to J. Peter Clark, III.
Application Number | 20150083374 14/209387 |
Document ID | / |
Family ID | 51625395 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150083374 |
Kind Code |
A1 |
Clark, III; J. Peter |
March 26, 2015 |
Closed Loop Ice Slurry Refrigeration System
Abstract
A closed loop refrigeration system comprises an ice slurry
mixture which comprises ice, water, and a freezing point
depressant. The system also comprises a first storage device for
storing the ice slurry mixture, and an agitator disposed in the
first storage device. The agitator agitates the ice slurry mixture
in at least an intermittent manner. The system further comprises a
first conduit connecting the first storage device and a heat load,
and a first pump disposed on the first conduit for pumping the ice
slurry mixture through the first conduit from the first storage
device to the heat load. At least some of the ice melts in the heat
load. The system also comprises a second conduit connecting the
heat load and a second storage device. The second storage device is
connected to the first storage device. The system further comprises
a second pump disposed on the second conduit for pumping the ice
slurry mixture containing the melted ice through the second conduit
from the heat load to the second storage device.
Inventors: |
Clark, III; J. Peter; (Oak
Park, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Clark, III; J. Peter |
Oak Park |
IL |
US |
|
|
Family ID: |
51625395 |
Appl. No.: |
14/209387 |
Filed: |
March 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61851921 |
Mar 14, 2013 |
|
|
|
Current U.S.
Class: |
165/104.31 ;
165/104.19 |
Current CPC
Class: |
F25D 17/02 20130101;
F25C 2301/002 20130101 |
Class at
Publication: |
165/104.31 ;
165/104.19 |
International
Class: |
F25D 17/02 20060101
F25D017/02 |
Claims
1. A closed loop refrigeration system, comprising: an ice slurry
mixture comprising ice, water, and a freezing point depressant; a
first storage device for storing the ice slurry mixture; an
agitator disposed in the first storage device, wherein the agitator
agitates the ice slurry mixture in at least an intermittent manner;
a first conduit connecting the first storage device and a heat
load; a first pump disposed on the first conduit for pumping the
ice slurry mixture through the first conduit from the first storage
device to the heat load, wherein at least some of the ice melts in
the heat load; a second conduit connecting the heat load and a
second storage device, the second storage device connected to the
first storage device; and a second pump disposed on the second
conduit for pumping the ice slurry mixture containing the melted
ice through the second conduit from the heat load to the second
storage device.
2. The system of claim 1, where the freezing point depressant
comprises a low carbon glycol or the corresponding polyglycol.
3. The system of claim 2, where the low carbon glycol is selected
from the group consisting of ethylene glycol, propylene glycol,
butylene glycol, a corresponding polyglycol, and a mixture
thereof.
4. The system of claim 2, where the low carbon glycol is propylene
glycol.
5. The system of claim 1, further comprising an ice slurry
generator, the ice slurry generator connected to the first and
second storage devices.
6. The system of claim 1, further comprising a vibrator disposed on
the first or second conduit, the vibrator vibrating the ice slurry
mixture contained in the conduit.
7. A closed loop refrigeration system, comprising: an ice slurry
mixture comprising about 5-60% ice, about 20-95% water, and about
0-50% a freezing point depressant; a first storage device for
storing the ice slurry mixture; an agitator disposed in the first
storage device, wherein the agitator agitates the ice slurry
mixture in at least an intermittent manner; a heat load; a first
transporter for transporting the ice slurry mixture from the first
storage device to the heat load; and a second transporter for
transporting the ice slurry mixture from the heat load to a second
storage device, the second storage device connected to the first
storage device.
8. The system of claim 7, where the freezing point depressant is
propylene glycol.
9. The system of claim 7, where the freezing point depressant is
about 10-50% of the ice slurry mixture.
10. The system of claim 7, where the ice is about 20-35% of the ice
slurry mixture.
11. The system of claim 7, where the first or second transporter is
a pump.
12. The system of claim 7, where the first or second transporter is
a progressing cavity pump.
13. The system of claim 7, further comprising an ice slurry
generator, the ice slurry generator connected to the first and
second storage devices.
14. The system of claim 13, wherein the ice slurry mixture from the
heat load is transported to the ice slurry generator for
regenerating the ice slurry mixture.
15. A method, comprising the steps of: providing an ice slurry
mixture comprising about 5-60% ice, about 20-95% water, and about
0-50% a freezing point depressant in a first storage device;
agitating the ice slurry mixture stored in the first storage device
in at least an intermittent manner; pumping the ice slurry mixture
through a first conduit from the first storage device to a heat
load, wherein at least some of the ice melts in the heat load;
pumping the ice slurry mixture containing the melted ice through a
second conduit from the heat load to a second storage device.
16. The method of claim 16, where the pumping is with a progressing
cavity pump.
17. The method of claim 16, further comprising generating the ice
slurry mixture and introducing the ice slurry mixture to the first
storage device.
18. The method of claim 16, further comprising vibrating the ice
slurry mixture contained in the conduit.
19. The method of claim 16, further comprising regenerating the ice
slurry mixture containing the melted ice after the ice slurry
mixture containing the melted ice is pumped from the heat load to
the second storage device.
Description
RELATED APPLICATION
[0001] The present application claims priority from provisional
patent application No. 61/851,921, filed Mar. 14, 2013. That filing
is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present disclosure relates to a new and improved closed
loop refrigeration system using ice slurries.
BACKGROUND OF THE INVENTION
[0003] Refrigeration systems are commonly used to cool an air
space, cool equipment, and to keep food or perishables at chilled
temperatures. Conventional refrigeration systems typically consist
of three components: a compressor, a condenser and an evaporator,
as well as various piping, valves and controls that connect all the
components. These components work together to cycle a refrigerant
through the refrigeration system. The compressor compresses the
refrigerant so that it turns from gas to liquid at a relatively
high temperature. The condenser then transfers this heat to the
atmosphere. The resulting cold liquid refrigerant is then sent to
the evaporator, which removes the heat from the cabinet or space by
turning the liquid refrigerant into a gas. That refrigerant gas is
returned to the compressor and the refrigeration cycle is
repeated.
[0004] One problem faced with such systems is that the cooling and
refrigeration process requires large amounts of electrical energy
to operate. This places a high demand on electric utilities during
on-peak periods, usually during waking hours of the weekday.
Utilities must provide enough generating capacity to meet this
demand. Evenings and weekends are off-peak demand periods and much
less of the total generating capacity is used then. To encourage a
better or more uniform demand for electric power, many utilities
charge a reduced rate for electricity used during off-peak periods.
Thus, there is an ongoing demand to find ways to shift or transfer
as much as possible of required electrical consumption to off-peak
periods to take advantage of the reduced rates.
[0005] One method that is known in the field of refrigeration
systems is the use of an ice slurry (see, e.g., U.S. Pat. No.
4,584,843). Specifically, known methods for refrigeration in a
process where an aqueous liquid is fed through a freeze exchanger
in indirect heat exchange with a refrigerant to convert at least
part of the aqueous liquid to ice. Such methods further include
feeding the aqueous liquid-ice mixture from the freeze exchanger to
an ice storage tank to provide an ice slurry and aqueous liquid
therein, and removing cold aqueous liquid from the ice storage tank
for feeding through a heat exchanger in indirect heat exchange with
a fluid to be cooled and used for cooling purposes, with the now
warmed aqueous liquid exiting from the heat exchanger and returning
to the ice storage tank to be cooled by contact with the ice
therein.
[0006] Existing approaches, however, each run into one or more
system or processing limitations which make them unacceptable for
certain existing refrigeration applications. For instance, in
certain processing applications, an excess of ice can have an
adverse impact on the operation of the system, e.g., due to
agglomeration and clogging. Alternative systems provide for the use
of other refrigerants which have adverse environmental impacts
(e.g., due to unavoidable leakage over time) as well as undue costs
(e.g., due to the high volume of refrigerant and the cost of
replacement involved). Thus, there is a need for an improved
refrigeration system to reduce these shortcomings.
DEFINITION OF TERMS
[0007] The following terms are used in the claims of the patent as
filed and are intended to have their broadest plain and ordinary
meaning consistent with the requirements of the law.
[0008] An ice slurry mixture means "a phase changing refrigerant."
A multicomponent ice slurry mixture means "a phase changing
refrigerant including micro-crystals formed and suspended within a
solution of water and a freezing point depressant." Slurry ice has
greater heat absorption compared with single phase refrigerants
because the melting enthalpy (latent heat) of the ice is also
used.
[0009] A freezing point depressant means "a solute to water which
decreases the freezing point of the water, such as ethylene glycol,
propylene glycol, various alcohols (Isobutyl, ethanol), salts
(CaCl.sub.2, NaCl) and sugar (sucrose, glucose)."
[0010] A closed loop refrigeration system means "a refrigeration
system in which the coolant may be recycled continuously."
[0011] A heat load means "the amount of heat entering the area to
be controlled by the refrigeration system."
[0012] An agitator means "an apparatus for mixing a liquid or
liquid solid mixture."
[0013] Where alternative meanings are possible, the broadest
meaning is intended. All words used in the claims set forth below
are intended to be used in the normal, customary usage of grammar
and the English language.
OBJECTS AND SUMMARY OF THE INVENTION
[0014] It is herein provided a new and improved closed loop
refrigeration system that uses ice slurries.
[0015] In one aspect, a closed loop refrigeration system comprises
an ice slurry mixture which comprises ice, water, and a freezing
point depressant. The system also comprises a first storage device
for storing the ice slurry mixture, and an agitator disposed in the
first storage device. The agitator agitates the ice slurry mixture
in at least an intermittent manner. The system further comprises a
first conduit connecting the first storage device and a heat load,
and a first pump disposed on the first conduit for pumping the ice
slurry mixture through the first conduit from the first storage
device to the heat load. At least some of the ice melts in the heat
load. The system also comprises a second conduit connecting the
heat load and a second storage device. The second storage device is
connected to the first storage device. The system further comprises
a second pump disposed on the second conduit for pumping the ice
slurry mixture containing the melted ice through the second conduit
from the heat load to the second storage device.
[0016] In another aspect, a closed loop refrigeration system
comprises an ice slurry mixture which comprises about 5-60% ice,
about 20-95% water, and about 0-50% a freezing point depressant.
The system also comprises a first storage device for storing the
ice slurry mixture, and an agitator disposed in the first storage
device. The agitator agitates the ice slurry mixture in at least an
intermittent manner. The system further comprises a heat load, a
first transporter for transporting the ice slurry mixture from the
first storage device to the heat load, and a second transporter for
transporting the ice slurry mixture from the heat load to a second
storage device. The second storage device is connected to the first
storage device.
[0017] In a further aspect, a method comprises providing an ice
slurry mixture comprising about 5-60% ice, about 20-95% water, and
about 0-50% a freezing point depressant in a first storage device,
and agitating the ice slurry mixture stored in the first storage
device in at least an intermittent manner. The method also
comprises pumping the ice slurry mixture through a first conduit
from the first storage device to a heat load. At least some of the
ice melts in the heat load. The method also comprises pumping the
ice slurry mixture containing the melted ice through a second
conduit from the heat load to a second storage device.
[0018] It should be noted that not every embodiment of the claimed
invention will accomplish each of the objects of the invention set
forth above. In addition, further objects of the invention will
become apparent based the summary of the invention, the detailed
description of preferred embodiments, and as illustrated in the
accompanying drawings. Such objects, features, and advantages of
the present invention will become more apparent in light of the
following detailed description of a best mode embodiment thereof,
and as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 shows a system schematic of a preferred embodiment of
a configuration of a closed loop refrigeration system operating in
accord with the present invention during off peak power consumption
hours.
[0020] FIG. 2 shows a system schematic of a preferred embodiment of
a configuration of a closed loop refrigeration system operating in
accord with the present invention during peak power consumption
hours.
[0021] FIGS. 3 a-b show cross sectional views of a standard elbow
and a lead in chamfer elbow, respectively, with the chamfered lead
in reducing steps in the ID size of the flow path for a conduit
section in accord with the present invention.
[0022] FIG. 4 shows a system schematic of another preferred
embodiment of a configuration of a closed loop refrigeration system
operating in accord with the present invention during peak power
consumption hours.
[0023] FIG. 5 shows a system schematic of a preferred embodiment of
a configuration of a closed loop refrigeration system operating in
accord with the present invention during off peak power consumption
hours.
[0024] FIG. 6 shows an example thermocouple engagement for
monitoring operation of a section of conduit during operation in
accord with the present invention.
[0025] FIG. 7 is a table showing temperature versus time plot for
various locations during an initial closed loop evaluation
according to an embodiment of the present invention.
[0026] FIG. 8 is a table showing temperature versus time plot for a
peristaltic ice pumping experiment in accordance with an embodiment
of the present invention.
[0027] FIG. 9 is a table showing a time versus temperature plot for
Reversible Path In/Out of storage in accord with an embodiment of
the present invention.
[0028] FIG. 10 is a table showing close up detail of the sub-zero
temperature range for the time versus temperature plot for
Reversible Path In/Out of storage in accord with an embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
[0029] Set forth below is a description of what is currently
believed to be the preferred embodiment or best examples of the
invention claimed. Future and present alternatives and
modifications to this preferred embodiment are contemplated. Any
alternatives or modifications which make insubstantial changes in
function, in purpose, in structure or in result are intended to be
covered by the claims in this patent.
[0030] Practically all modern refrigeration systems are closed
loop, meaning that the refrigerant is enclosed (as opposed to being
purposefully vented into the atmosphere) in the system and thus
must fill all the coils and piping. A typical supermarket has
3,000-4,000 pounds of refrigerant in all its various refrigerated
display cases, walk-in coolers, etc. Despite all precautions, some
refrigerant inevitably leaks from the system, causing environmental
damage and incurring substantial maintenance and repair expenses as
well as the high cost of replacement refrigerant. For example, some
synthetic refrigerants cost hundreds of dollars per pound, and
refrigeration systems may lose up to 30-0.40% of its refrigerants
in a single year. The same issues apply to refrigeration systems
used in home and auto air conditioners, which often need service
and refilling.
[0031] Typical known refrigerants include water, ice, hydrocarbons,
propane, butane, ammonia, chlorofluorocarbons, freon,
hydrochlorofluorocarbon, hydrofluorocarbon, methyl formate, methyl
chloride, sulfur dioxide, etc. Some of these refrigerants such as
water and ice were found to be problematic, in part because ice
tends to agglomerate and clog the refrigeration system.
Furthermore, ice refrigeration systems can be quite expensive.
[0032] Additionally, a number of these refrigerants were found to
be harmful when leaked into the environment (e.g., toxic, ozone
depletion, global warming, etc.). To help reduce the volume of
environmentally unfriendly refrigerants used (and leaked to the
environment), secondary loop refrigeration systems were designed. A
secondary loop refrigeration system has two refrigeration circuits:
a primary refrigeration circuit and a secondary refrigeration
circuit. Consequently, a secondary loop refrigeration system
incorporates two different refrigerants to provide cooling: a
primary refrigerant in the primary refrigeration circuit and a
secondary refrigerant in the secondary refrigeration circuit.
[0033] In a secondary loop refrigeration system, one circuit is
used to cool the other circuit (which is used to cool the target
air space or equipment). Thus, there may be multiple compressors
and heat exchangers that link the two circuits. The configuration
of secondary loop refrigeration systems is subject to various
designs as known in the art. Typically, the primary refrigeration
circuit remains in a machine room and is used to cool the secondary
refrigeration circuit (which is used to cool the target air space
such as the supermarket refrigerator or industrial equipment,
etc.)
[0034] By using the primary refrigerant to cool the secondary
refrigerant, the overall volume of the refrigerant needed to cool a
target space is reduced compared to a conventional refrigeration
system.
[0035] The primary refrigerant may be a synthetic or natural
chemical.
[0036] The secondary refrigerant may be water when used above its
freezing point. Many cooling functions require temperatures close
to or below the freezing point of water, in which case substances
are added to water to lower its freezing point, much like
anti-freeze in an automobile. Sodium chloride, calcium chloride,
low carbon glycols, such as ethylene glycol, propylene glycol,
butylene glycol and polyglycols thereof, and alcohol are all
examples of freezing point depressants that can be used in
circulating water-based cooling solutions. However, salt solutions
can be corrosive and glycol solutions may have increased viscosity
if the concentration of glycol is high.
[0037] Carbon dioxide can also be used as a secondary refrigerant.
However, carbon dioxide systems operate at higher pressures than
other refrigerants, which demands special piping and fittings.
[0038] Brine (salt-based) or water solution refrigerants in
secondary loop systems operate at relatively low pressures, but
still require substantial pumps, valves and piping.
[0039] As such, both known conventional and secondary loop
refrigeration systems have a number of shortcomings (i.e.,
refrigerant harmful to environment, excess refrigerant needed,
substantial piping, etc.). Thus, there is a need for an improved
refrigeration system to reduce these shortcomings.
[0040] It has been discovered that the use of ice slurries in a
closed loop refrigeration system reduces many of the shortcomings
found in current conventional refrigeration systems and current
secondary loop refrigeration systems.
[0041] FIG. 1 shows a closed loop refrigeration system 10 according
to one embodiment of the present invention that uses an ice slurry
which comprises ice, water and propylene glycol. There is also
present an ice slurry generator or ice maker 12 for generating the
ice slurry. A storage device 14 is provided for storing the ice
slurry. The storage device includes an agitator 16 that agitates
the ice slurry in an intermittent matter to prevent agglomeration.
The agitation of the slurry can be further aided by the use of a
mixer 18 which is also used to receive slurry supply from the
storage device 14 for mixing with warmer ice slurry returning from
the heat load 26. Additionally, a peristaltic pump 20 is used to
pump the ice slurry from the ice slurry generator along a first
conduit 22 to the storage device and/or along a second conduit 24
to a heat load 26. At least some of the ice melts in the heat load.
A vibration motor (not shown) is used for vibrating said first
and/or second conduit to help prevent the ice from agglomerating.
In addition, a second pump 28 is used to pump the ice slurry from
the heat load (thus containing melted ice) along a third conduit 30
to the ice slurry generator for regenerating the ice slurry in
mixer 18 or in melt storage device 32, depending upon the system
demands (e.g., heat load 26 demands or whether operation is
occurring peak electricity hours).
[0042] As shown in FIG. 2, an embodiment of the present invention
provides for interruption, decrease or stoppage of the ice maker 12
to accommodate for load demands (e.g., to decrease ice maker usage
during more expensive electricity hours). In such an instance, the
continuing generation of the ice slurry is provided by the extra
ice slurry previously generated and stored in the storage device
14, which is combined with the warmed ice slurry returning from the
heat load 26. In this manner, it can be observed that the closed
loop configurations system can maintain a ice slurry supply for
heat load 26 in the absence of the constant operation of ice maker
12. Of course, those of ordinary skill will understand that this
operation will also permit a reduced, as opposed to a stopped
operation of the ice make 12 so as to lessen (rather than stopping)
the draw of electricity during peak hours.
[0043] This closed loop refrigeration system according to one
embodiment of the present invention can be employed in a secondary
loop refrigeration system as the secondary circuit. The various
elements of the embodiments of the invention will be described in
more detail below.
[0044] Ice Slurries
[0045] Ice slurries are a type of phase change material that can
transfer heat. A phase change occurs when ice melts, water boils or
wax melts. Makes energy to cause such a change, called the heat of
fusion or the heat of vaporization. 144 BTU/lb is required to melt
ice as compared to 1 BTU/lb per degree Fahrenheit of so-called
sensible heat for water. (Sensible heat is the amount of heat that
is added or lost by a substance due to a change in temperature.)
Thus, ice has a superior thermal capacity compared to water.
[0046] Since it is difficult to circulate pure ice, it has been
discovered that ice in the form of an ice slurry can be circulated
through a refrigeration system. However, it has been found that the
ice slurry comprises small, smooth ice crystals that are capable of
flowing in a slurry through very small tubes; otherwise, it will
aggregate easily and prevent circulation at high ice loading.
Acceptable ice slurries include those described in U.S. Pat. Nos.
6,244,052; 6,413,444; 6,547,811; 7,389,653; 7,422,601; and U.S.
Patent Publication Nos. 2009/0125087; 2009-0255276, all of which
are herein incorporated by reference.
[0047] Ice slurries may also be generated using any conventional
ice slurry generator known in the art, including the Lanikai frozen
drink machine or other scraped surface heat exchangers.
[0048] Ice slurries (or ice slurry mixture) used in one embodiment
of the present invention comprise a mixture of ice, water and
propylene glycol. In one example, ice can be present in an amount
up to 60% (e.g., ice loadings of 20-30%, 30-40%, 40-50%, 50-60%,
etc.). In another example, propylene glycol can be present in an
amount up to 50%, and preferably no more than 50% or whatever is
the eutectic composition of the freezing point depressdant. (The
eutectic point is that temperature and composition at which a
mixture freezes without separation into two phases.) In a further
example, water is present in the remaining amount (e.g., 40%, 50%,
60%, etc.).
[0049] In one embodiment, the ice is first formed as small, smooth
crystals and stored as a concentrated slurry (e.g., 40-60% ice
loading) that is too thick to circulate by itself. When ready for
use, the stored concentrated ice slurry is diluted to about 20-30%
ice loading at the appropriate temperature by mixing with another
medium (e.g., a return melted slurry).
[0050] Experiments have shown that slurries with 20% ice loading
have approximately the same viscosity as pure water at the same
temperature, but yet have enhanced heat transfer coefficients. As
such, high ice loading is desirable to maximize the thermal
capacity of the ice slurry. Slurries of 20-35% ice loading have
been found to circulate well while providing good thermal capacity.
In use, all the ice eventually melts and the solution warms
slightly, adding some sensible heat to the heat of fusion.
[0051] The use of an ice slurry refrigerant in a closed loop
refrigeration system is more environmentally friendly than
refrigerants used in a conventional refrigeration system.
Additionally, using an ice slurry refrigerant in a closed loop
refrigeration system uses fewer parts and is simpler to control
than a conventional refrigeration system.
[0052] Additionally, combined with the lower flow required for a
given heat load, the use of an ice slurry refrigerant in a
secondary loop system has lower capital, maintenance and operating
costs than does a brine or carbon dioxide system.
[0053] Components
[0054] The concentrated ice slurry is stored in a storage device
14, which may be any conventional storage container known in the
art. The storage device includes an agitator 16, which can be any
conventional mixing device known in the art. During storage,
intermittent gentle agitation is applied to prevent aggregation of
ice crystals.
[0055] A peristaltic pump 20 can be used to pump the ice slurry
from the ice slurry generator along a first conduit 22 to the
storage device. A peristaltic pump or progressing cavity pump 28
can also be used to pump the ice slurry along a second conduit to a
heat load. It has been discovered that the "pulsing" action of
peristaltic pump (as opposed to a centrifugal pump) helps to
prevent the ice in the ice slurries from aggregating and clogging
the conduits.
[0056] In addition, it has also been discovered that using a
vibration motor along the conduits can also help prevent the ice in
the ice slurries from agglomerating and clogging the conduits. This
is especially true when using vibration to promote flow of the
concentrated ice slurry from the storage device.
[0057] Any conventional conduits known in the art can be used with
the various embodiments of the present invention.
[0058] The heat load represents any device in which the target air
space is being cooled (e.g., refrigerator or jacketed vessel,
etc.). At least some of the ice in the ice slurry will melt in the
heat load.
[0059] Any conventional pumps known in the art (or a peristaltic
pump) can be used to pump the ice slurry from the heat load (thus
containing melted ice) along a third conduit to the ice slurry
generator for regenerating the ice slurry.
[0060] Modes
[0061] Furthermore, the advantage of reduction in energy when using
the embodiments of the present invention can be realized by
operating the disclosed technology in different modes (i.e., by
coordinating the power requirements of the refrigeration system
with the different electricity rates charged during the day and
night). For example, the power requirements of the refrigeration
system can be operated in accordance with the daily fluctuations in
energy prices (i.e., off peak vs. peak rates).
[0062] Energy is needed to power the compressors in a refrigeration
cycle that produces cold temperature. The cost of electricity in
most places is a function of demand because electricity suppliers
and utilities have a variety of sources, which have a range of
efficiencies and costs. The largest and most efficient power
plants--coal, nuclear or gas heated, are used to supply the base
load, while smaller more flexible peak shaving units are employed
when demand exceeds base load. Utilities typically price
electricity to penalize use at peak times (i.e., daytime) and
motivate use at off-peak times (i.e., evening). Sometimes the
difference between night and day, or peak and off-peak, rates can
be a factor of two.
[0063] To take advantage of the lower off-peak rates, it is
advantageous to operate the refrigeration compressors in the
present disclosure only when rates are low, and storing the cold
temperature. Making ice is one way to store the cold temperature
and is used in ice-making units, where water is typically frozen
around metal coils filled with refrigerant. The cold temperature is
recovered when needed by circulating water past the coils, melting
the ice and cooling the water, which then circulates as a heat
transfer medium to where it is needed (i.e., air coolers, heat
exchangers or process chillers).
EXAMPLES
[0064] By way of illustration, the present disclosure will be
described in more detail in the drawings, photos and pages that
follow. One skilled in the art will realize that many various
designs are possible under the present disclosure and that these
examples are only illustrative and not meant to include all such
possibilities. In addition to the advantages discussed above, these
examples also illustrate use of an auger freezer (instead of
conventional freezer), the absence of size reduction step, the
absence of valves to control flow of slurry, and the absence of
ripening or crystal modification step. One skilled in the art will
appreciate that there are many other advantages of the present
disclosure.
[0065] Definitions: ice slush was straight from a Lanikai machine
12. Ice slurry was processed with the intent to increase the
ability to flow and be pumped. ID: inside diameter. OD: outside
diameter.
[0066] Setup (Materials and Equipment) includes a Lanikai frozen
drink machine; a MasterFlex peristaltic pump; an Electric drill,
0-550 RPM; Variac; a tile saw pump; a heated water bath; Coleman
coolers (2); thermocouples, T type, Omega 5TC-TT-T-36-72 (8); a
measurement computing USB--Temp ID:02; a digital thermometer,
Digisense ID:428763; a graduated cylinder; a stopwatch; a stir rod;
and a paint mixer.
Example 1
Night Mode
[0067] An aqueous solution of a freezing point depressant, such as
propylene glycol is mixed in a large container. A Lanikai is filled
with the mixed solution until there is approximately 1 cm of
standing solution in the Lanikai holding tank. The fill pump fills
the holding tank up to the proper level. All three tubes are set in
the peristaltic pump heads. The smaller diameter tubing should be
on a separate pump from the two larger tubes. The mixed output tube
is directed at the heat exchanger cooler and the pure ice is sent
to the ice storage cooler. The heat exchanger cooler is filled with
solution and the circulation pump is turned on. The heat load
source is then turned on and the load pump is heated. Subsequently,
the Lanikai output valve is opened and all peristaltic pumps are
turned on and control knobs adjusted to desired settings.
Example 2
Day Mode
[0068] The tubing from the head #2 (the tubing going to ice
storage) on peristaltic pump #1 is removed. Head #1 is kept intact.
The tubing in ice storage is moved to a location it will not touch
the mixer, but is adequate enough to extract uniform slurry. The
output nozzle on Lanikai faceplate is closed. The direction of
peristaltic pump #1 is reversed, and the flow of peristaltic pump
#2 is readjusted to desired thickness.
Example 3
Slush Flow Control Experiments
[0069] The closed loop slurry system requires a controlled flow of
ice slush throughout the system. Initial experiments were performed
to evaluate different methods of ice slush flow control from the
Lanikai frozen drink machine. The following experiments were
performed with a 10% by volume concentration solution of propylene
glycol mixed with tap water.
[0070] The Lanikai machine features a main valve on the front face
plate that allows dispensing of the ice slush. The main valve
consists of a sliding cylinder sealed by o-rings that can be
infinitely adjusted between fully open and fully closed. When fully
opened, the diameter of the orifice is approximately 1'' in
diameter. By varying the position of the valve and therefore the
orifice size, the flow of ice slush can be controlled. However, the
valve position that generates approximately 300 mL/min output flow
was found to jam and stop flowing after approximately 2-3 minutes
of flow at 300 mL/min through the orifice. The flow rate was found
to gradually decrease until flow became essentially zero or
"jammed". The ice slush just inside the outlet of the Lanikai is
visible due to the clear front plate. When a jam occurs, the ice
slush visually appeared to be a high concentration of ice which
likely caused the stoppage of flow or an "ice jam". The flow can be
restarted by opening the valve and in effect creating a larger
orifice.
[0071] The opening below the main valve on the front plate of the
Lanikai can be fitted with a section of 1'' ID rigid tubing, bonded
to the opening and then connected to a piece of 1'' ID flexible
tubing. Placing the flexible over the rigid tubing is intended to
increase the ability of the ice slush to flow by eliminating the
step which would otherwise be created when using certain standard
fluid fitting connectors. Flow through the flexible tubing can be
controlled by varying the height of the opening and overall length
of the tube relative to the Lanikai and therefore varying the
static fluidic pressure differential and amount of friction. These
two variables were experimentally adjusted to control the flow rate
to approximately 300 mL/min. However; the rate was found to slow
after several minutes and eventually stop almost completely or form
an "ice jam" as previously discussed. A vibrator motor was
connected to the flexible tubing to vibrate the ice slush along the
tubing. The vibration was found to have two effects: both to
increase the flow rate and to increase the consistency of the
output flow rate over time. An experiment was performed where the
Lanikai machine was run continuously for several hours and the
output flow rate measured every 15 minutes. Over the 6 hour period,
flow rate ranged between 252 and 292 mL/min. The Lanikai machine
with a flexible tube was connected and coupled to a vibrator motor
as described above the closed loop system requires controlled flow
of ice slush at various locations. Depending on the final closed
loop configuration, changing the relative height of the ice slush
output may not always be feasible or easily controlled. To allow
more flexibility in system design, the ice slush flow can be
controlled by connecting a peristaltic pump to the outlet spout of
the Lanikai faceplate and then fully opening the main valve on the
Lanikai. A MasterFlex peristaltic pump (7523-10 drive with 7518-00
head) with W' OD.times.0.375'' ID (McMaster 5554K16) was connected
to the outlet of the Lanikai via a W' push to connect fitting
(McMaster 51055K22) and run continuously for over an hour
successfully.
[0072] In this example, the output of the Lanikai was connected to
the peristaltic pump via the Yi'' tubing and a push to connect
connector.
[0073] Ice slush flow can also be controlled using a rotating auger
similar to a setup found in a food processing feeder bin. An auger
drive system was prototyped and evaluated experimentally by driving
the 1''.times.17'' auger drill bit (Menards 2423429) inside a
section of 1'' ID rigid PVC tubing (McMaster 49035K25). With
approximately 60% ice concentration, the ice flow can be controlled
by varying the rotation speed of the auger down to zero RPM which
corresponds to zero mL/min. If ice concentration drops below a
critical value, the ice slush can flow through the pipe even with
zero auger rotation. The critical value of ice concentration is
dependent in part to the location of the auger relative to the
outlet spout on the Lanikai machine. When configured with the auger
drive approximately 150 mm below the output spout on the Lanikai
faceplate, the non-rotating auger can control ice slush flow. The
maximum flow created by the auger is limited and is less than
proportional to theoretical rate calculated by multiplying the
linear speed at which the helix translates axially through the tube
by the cross sectional volume of the void in the auger. As a
result, the ice slush will be constantly mixed by the helix of the
rotating auger as the ice slush translates along the tube.
[0074] A number of different auger drive and peristaltic pump
configurations were experimentally evaluated. An experiment was
performed with a section of clear PVC pipe attached to the Lanikai
and the 1'' connected to an electric drill. The auger approximates
a progressing cavity pump, which could serve in a larger embodiment
of the invention.
[0075] In the previously described experiments, ice slush from the
Lanikai was found to flow well through 1'' tubing and pipes
provided total flow lengths were limited to approximately 500-1000
mm and in pathways with less than 180.degree. of total directional
change. It was also noted that steps in the ID size of the flow
path negatively impacted the ability of the ice slush to flow.
Standard PVC pipes and connectors create a step in the ID where the
pipe meets the connector. The step was reduced by creating a
lead-in chamfer as shown in FIGS. 3 a-b, such reduction of step
being useful for either of the first conduit 22 or second conduit
24.
Example 4
Closed Loop Experiments
[0076] An initial closed loop system configuration was evaluated
experimentally. The system evaluated featured two ice slush flow
control mechanisms (a driven auger and a peristaltic pump) as well
as a submersible pump. The ice slush from the Lanikai machine was
driven at approximately 300 mL/min into the storage container. From
the storage container, the ice slush was pumped into one leg of a
wye fitting and then into the simulated heat load. A submersible
pump was at the bottom of the heat exchanger and pumped the melted
slush both into a flow control valve and then into other leg of the
wye fitting as well as back into the storage reservoir of the
Lanikai. The FIGS. 1 and 2 show a schematic view of this setup.
Thermocouples were placed at different locations along the fluid
flow path in the system.
[0077] This initial evaluation was started with room temperature
fluid in the return reservoir of the Lanikai, ice storage as well
as the heat exchanger; however, the Lanikai was allowed to run and
create a -5.5.degree. C. ice slush prior to opening the main valve
on the Lanikai. The main valve was opened at approximately sample
950 in the DAQ record and is evident by the rapid drop in Lanikai
outlet temperature. Due to limitations in this configuration, no
automated slush agitation exists in the ice storage container.
Throughout the test, the ice storage container was manually
agitated using a stirring rod or by spinning a paint mixer at
approximately 100 RPM near the storage outlet to the peristaltic
pump. The drop in temperature at approximately sample 1060 in the
DAQ record can likely be attributed to the point at which manual
mixing was increased such that fresh ice slush from the Lanikai had
been mixed with the warmer slush already in the ice storage
container.
[0078] FIG. 7 shows the temperature versus time plot for the
various locations during an initial closed loop evaluation from May
12, 2012 (non calibrated values reported). The variation in the
"Out of Heat Exchanger" temperature is a result of the
configuration used to refill the Lanikai reservoir. The submersible
pump used to refill the reservoir is only turned on when the
reservoir is below a minimum level.
Example 5
Peristaltic Ice Slush Pumping Experiment
[0079] An experiment was performed to evaluate the ability of the
peristaltic pump to move ice slush continuously for several hours.
A section of Yz'' OD.times.0.375'' ID tubing (McMaster 5554K 1 6)
was connected to outlet of the Lanikai via a shim section of 1''PVC
pipe and a Yz'' NPTF reducing tee fitting and a Yz'' push to
connect to Yz'' NPTM fitting (McMaster 51055K22). To simplify this
experiment, the flow circuit was reduced so that the ice slush was
pumped directly to the "heat load" cooler where a submerged pump
pumped the melted ice slush back to the Lanikai reservoir.
[0080] Flow rate of the slush into the heat exchange cooler was
recorded and measured manually with a stopwatch and graduated
cylinder throughout the test. Temperature was also monitored via
thermocouple at various locations. At approximately data point 7500
the peristaltic pump was turned off in an attempt to create an `ice
jam` at the outlet of the Lanikai. After 20 minutes, the
peristaltic pump was turned on again with no evidence of irregular
ice slush flow. The heat exchanger was not fully melting the ice
slush and therefore the melted slush being pumped back into the
Lanikai continued to decrease in temperature. And as a result, ice
slush temperature being pumped into the heat exchanger also
continued to decrease as evident by the three temperature traces
(RESERVOIR, LANK CLOSE, INTO HEAT EXCH) decreasing between
approximately 0 and 4500. During this time period, the flow rate
was measured 5 times and varied between 140 and 152 mL/min.
[0081] At approximately data point 4300, it was noticed that the
ice slush in the flexible tubing was separated by air pockets
making up for approximately 30% of the volume in the tubing. The
air pockets were likely caused by the ice slush becoming thick
(cold) as discussed previously. The temperature at the Lanikai
outlet when the ice pockets were noticed was -6.8.degree. C. At
this point, warmer (room temperature) melted ice slush was added to
the heat exchanger and therefore raised the temperature of the
outlet slush again. Repeating this test with the same setup and
more closely observing the ice slush flow rate obtained given a
constant peristaltic pump setting may indicate the temperature at
which the ice slush is no longer able to be pumped with a given
setup. Based on these results, it is reasonable to expect the
coldest temperature for this setup to be approximately -7 to
-8.degree. C.
[0082] FIG. 8 shows the temperatures versus time throughout the
test.
Example 6
Ice Slush Auger, Storage and Waring Blender Experiments
[0083] Bench testing was performed to evaluate the effect of
storing ice slush overnight. A 48 Qt (45.4 L) size Colman cooler
(Sears 80529711) filled with approximately half way with ice slush
was stored for approximately 8 hours in the ambient lab
environment. The cooler used incidentally had four 2'' diameter
holes in the cover that remained unsealed during the test and the
cooler lid was also slightly propped open. Some kind of mild
agitation will be needed to prevent icebergs from forming in the
stored slush. Additionally, using an intermittent agitation method
should also be considered to prevent adding too much energy into
stored ice and therefore reducing the cooling capacity.
Example 7
Closed Loop "Reversible Path In/Out of Storage"
[0084] A slightly different system architecture was put together to
further improve the control over the system and simplify the
required components. The main feature of this architecture is that
the ice slush pathway between one of the peristaltic pumps 20 or 28
and the storage container 14 allows for either forward or reverse
ice slush flow depending on the intended day or night mode
operation. Temperatures throughout the flow loop can be recorded
via thermocouples placed inside the tubing at various locations.
FIGS. 4 and 5 show a block diagram of the system flow path in this
configuration, as well as the thermocouple location and ID
numbers.
[0085] The thermocouples were placed in the following locations
identified by their location in the schematics: [0086] Channel
0--Lanikai Reservoir Tank 32 [0087] Channel 1--Ambient [0088]
Channel 2--Lanikai Output 22 [0089] Channel 3--High Ice 14 [0090]
Channel 4--Mixed Output to Heat Load 24 [0091] Channel 5--High Ice
Storage 14 [0092] Channel 6--Fill Tube 10
[0093] This system was first run in night mode for 2 hrs 45 min,
followed by day mode operation for 1 hr. During night mode,
Peristaltic Pump One was set to 100 mL/min such that the two pump
heads combined were pumping 200 mL/min of ice slush from the
Lanikai machine. The mixing drill with a rectangular mixing head
was set to a slow, constant speed. At the same time, Peristaltic
Pump Two was set to 50 mL/min creating a lower ice concentration
ice slurry mix flowing into the heat exchanger. At the transition
to day mode operation, the tubing from Head One on Peristaltic Pump
One was removed to allow free ice slush flow through that
segment.
[0094] The main valve of the Lanikai was closed to prevent back
flow and Peristaltic Pump Two was slowed to 30 mL/min given that
the ice concentration of the ice slush in storage had decreased
slightly due to melting (this was detected by an increase in
thermocouple #4 temperature as well as a visual assessment of the
ice slush flowing into the heat exchanger. The plot of FIG. 9 below
shows the resulting temperatures from the two modes of
operation.
[0095] The plot of FIG. 10 shows a close up of the sub-zero
temperature range for the same experiment. The ice slush
temperature flowing into the heat exchanger varied between
approximately -4.degree. C. and -2.6.degree. C. throughout the
test. Excluding the brief period during the transition between the
two modes, the ice slush temperature remained constant during the
transition to day mode.
Example 8
Lanikai Power Consumption
[0096] The power characteristics of the Lanikai machine were
characterized with an off the shelf "Kill-A-Watt EZ Plug Power
Meter." An experiment was conducted where the Lanikai was connected
to the power meter, filled with room temperature propylene glycol
mix and then turned on. Cold compressor on the Lanikai machine is
controlled via a belt tension switch that is coupled to the main
drive auger inside the main chamber. As the contents in the chamber
cool, the ice concentration increases causing the torque on the
auger to increase. When the torque reaches a certain limit the
condenser is switched off. The time period from initial startup to
when the compressor was first turned off was recorded as well as
the temperature of the contents at that point. The following table
1 summarizes the findings.
TABLE-US-00001 TABLE 1 Initial Final Temperature Compressor
Temperature Date (c.) `ON` Time (c.) kWH Jun. 20, 2012 23 50 min -5
Jun. 25, 2012 23.5 45 min 21 sec -5 0.66 Jun. 26, 2012 21.2 40 min
16 sec -5.2 0.59
[0097] Both a peristaltic pump and an auger drive were found to
successfully control the flow of ice slush in the system. Both the
peristaltic pump and auger drive appear to allow precise flow
control; however, the auger requires a certain minimum ice
concentration to maintain control of the flow rate. Use of the main
valve or addition of a gate valve after the auger could prevent ice
concentrations from dropping below the critical valve.
Additionally, when an auger drive is used, the vertical distance
between the auger and the ice slush distance should be considered
and minimized where possible to prevent fluid separation in the ice
slush along the vertical distance.
Example 9
Thermocouple Setup
[0098] FIG. 6 shows how a thermocouple can be inserted into a
section of flexible tubing as could be used with conduits such as
the first 22 or second 24 conduit. Create a small 2-4 mm long slit
in the flexible tubing then insert a section of a metal tube with
the tip ground to a sharp point through the slit in the flexible
tubing. Insert the thermocouple though the cannula of the metal
tube, then pull the section of metal tubing through the ID of the
flexible tubing.
[0099] Thermocouple Calibration. As part of the experimentation
described herein, a three point calibration was performed as
described in Table 2:
TABLE-US-00002 TABLE 2 Degrees C. Digisense Ch 0 Ch 1 Ch 2 Ch 3 Ch
4 Ch 5 Ch 6 Ch 7 Ambient 21.5 23.13 22.95 23.74 22.78 -- 21.19
22.36 22.32 Water & 12.92 13.6 13.66 13.67 13.76 -- 12.76 12.86
12.83 Slurry Mix -- Slurry -6.39 -5.25 -5.24 -4.57 -5.19 -- -6.07
-5.59 -5.73 Location for Lanikai Ambient Bottom of Lanikai NA Into
Out of Into 12 MAY 2012 Resevoir Under Storage Outlet Storage Heat
Head Test Table Container Spout Container Load Load
[0100] The above description is not intended to limit the meaning
of the words used in the following claims that define the
invention. Rather, it is contemplated that future modifications in
structure, function or result will exist that are not substantial
changes and that all such insubstantial changes in what is claimed
are intended to be covered by the claims. Likewise, it will be
appreciated by those skilled in the art that various changes,
additions, omissions, and modifications can be made to the
illustrated embodiments without departing from the spirit of the
present invention. All such modifications and changes are intended
to be covered by the following claims.
* * * * *