U.S. patent application number 13/247707 was filed with the patent office on 2012-07-26 for heat pipe system having common vapor rail.
Invention is credited to Khanh Dinh.
Application Number | 20120186787 13/247707 |
Document ID | / |
Family ID | 46543287 |
Filed Date | 2012-07-26 |
United States Patent
Application |
20120186787 |
Kind Code |
A1 |
Dinh; Khanh |
July 26, 2012 |
HEAT PIPE SYSTEM HAVING COMMON VAPOR RAIL
Abstract
A heat pipe has a plurality of conduits. Each conduit has an
evaporator section extending laterally from a first open end of the
conduit, a condenser section extending laterally from a second open
end of the conduit, and a liquid return section connected to the
evaporator section at a position away from the first open end and
connected to the condenser section at a position away from the
second open end. The liquid return section of at least one conduit
is distinct from the liquid return section of another of the
conduits. A common vapor manifold extends between the first and
second open ends of each of said plurality of conduits so vapors
produced in the evaporator sections can flow from the first open
ends through the common vapor manifold to the second open ends
without flowing through the conduits.
Inventors: |
Dinh; Khanh; (Gainsville,
FL) |
Family ID: |
46543287 |
Appl. No.: |
13/247707 |
Filed: |
September 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61436076 |
Jan 25, 2011 |
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Current U.S.
Class: |
165/104.26 |
Current CPC
Class: |
F28D 15/06 20130101;
F28D 15/0266 20130101; Y02B 30/56 20130101; Y02B 30/563 20130101;
F28D 21/0014 20130101; F28F 2210/10 20130101; F28D 2015/0216
20130101; F24F 12/002 20130101; F28D 15/0275 20130101; F24F 12/003
20130101; F28F 1/32 20130101 |
Class at
Publication: |
165/104.26 |
International
Class: |
F28D 15/04 20060101
F28D015/04 |
Claims
1. A heat pipe comprising: a plurality of conduits, each conduit
including an evaporator section extending laterally from a first
open end of the respective conduit, a condenser section extending
laterally from a second open end of the respective conduit, and a
liquid return section, the liquid return section for each conduit
being connected to the evaporator section at a position away from
the first open end and connected to the condenser section at a
position away from the second open end so the evaporator and
condenser section are in fluid communication with one another
through the liquid return section for flow of liquid condensed in
the condenser section to the evaporator section, the liquid return
section of at least one conduit being distinct from the liquid
return section of another of the conduits; and a common vapor
manifold in fluid communication with and extending between the
first and second open ends of each of said plurality of conduits so
vapors produced in the evaporator sections can flow from the first
open ends through the common vapor manifold to the second open ends
without flowing through the conduits.
2. A heat pipe as set forth in claim 1 wherein the vapor manifold
comprises first and second legs, the first open ends of said
plurality of conduits opening into the first leg and the second
open ends of said plurality of conduits opening into the second
leg, the manifold further comprising a vapor passage connecting the
first and second legs to one another for flow of vapors evaporated
in the evaporator sections to the condenser sections through the
common vapor manifold.
3. A heat pipe as set forth in claim 3 wherein said plurality of
conduits are arranged so they are spaced apart vertically from one
another, the first leg of the common vapor manifold extends to a
position that is higher in elevation than the highest of the first
open ends, and the second leg of the common vapor manifold extends
to a position that is higher in elevation than the highest of the
second open ends.
4. A heat pipe as set forth in claim 3 wherein the vapor passage
connects to the first leg of the common vapor manifold at an
elevation above the highest of the first open ends and the vapor
passage connects to the second leg at an elevation above the
highest of the second open ends.
5. A heat pipe as set forth in claim 1 wherein said plurality of
conduits are arranged so they are spaced apart vertically from one
another and the common vapor manifold has an inverted U-Shape.
6. A heat pipe as set forth in claim 1 wherein the evaporator
sections have a horizontal orientation.
7. A heat pipe as set forth in claim 1 wherein the condenser
sections are inclined downward from the second open ends.
8. A heat pipe as set forth in claim 1 wherein said plurality of
conduits are made of tubing no larger in diameter than 1/2 inch
tubing.
9. A heat pipe as set forth in claim 8 wherein the length of each
of said plurality of conduits is in the range of about 100 to about
250 inches.
10. A heat pipe as set forth in claim 1 wherein the length of each
of said plurality of conduits is in the range of about 100 to about
250 inches.
11. A heat pipe as set forth in claim 1 wherein the second end of
each of said plurality of conduits is at an elevation that is
higher than an elevation of the first end of the respective
conduit.
12. A heat pipe as set forth in claim 1 wherein the conduits are
U-Shaped and the evaporator sections have a horizontal
orientation.
13. A heat pipe as set forth in claim 1 wherein the conduits are
substantially straight.
14. A heat pipe system comprising a frame and a plurality of heat
pipes as set forth in claim 13 supported by the frame, the heat
pipes being arranged relative to one another so the evaporator
sections of the heat pipe conduits are positioned to form an array
of evaporator sections on a first side of the frame and the
condenser sections of the heat pipe conduits are positioned to form
an array of condenser sections on a second side of the frame
opposite the first side of the frame.
15. A heat pipe system as set forth in claim 14 further comprising
a plurality of fins in thermal communication with the heat pipe
conduits, the fins including a first set of fins in the array of
evaporator sections and a second set of fins in the array of
condenser sections, the first and second sets of fins being spaced
from one another.
16. A heat pipe system as set forth in claim 14 installed in a duct
system of an HVAC system, wherein the array of evaporator sections
is in a first duct of the duct system and the array of condenser
sections is in a second duct of the duct system, one of the first
and second ducts leading to an inlet of the HVAC system and the
other of the first and second ducts extending from an outlet of the
HVAC system.
17. A heat pipe as set forth in claim 1 further comprising fins
connected to the conduits in the evaporator section to facilitate
heat transfer and fins connected to the conduit in the condenser
section to facilitate heat transfer, the liquid return section and
common vapor manifold being free of fins.
18. A heat pipe as set forth in claim 1 further comprising a
working fluid contained in the conduits and common vapor
manifold.
19. A heat pipe as set forth in claim 19 wherein the heat pipe
contains no more than a 35% charge of the working fluid.
20. A heat pipe as set forth in claim 1 in combination with a
cooling coil, the evaporator sections of the conduits being
disposed in the path of air flowing into the cooling coil and the
condenser sections of the conduits being disposed in the path of
air downstream of the cooling coil.
21. A heat pipe as set forth in claim 1 in combination with another
substantially identical heat pipe nested within the heat pipe.
22. A heat pipe as set forth in claim 1 wherein the common vapor
manifold has a U-shaped configuration and at least a portion of the
common vapor manifold is on the same side of the heat pipe as at
least one of the liquid return sections of the conduits.
23. A heat pipe as set forth in claim 1 wherein the evaporator
sections and condenser sections are configured so they are doubled
back on themselves.
24. A heat pipe as set forth in claim 23 wherein the common vapor
manifold has an inverted U-shape and is on the same side of the
heat pipe as the liquid return sections of the conduits.
25. A heat pipe as set forth in claim 23 wherein the conduits have
a horizontal U-shaped configuration and the common vapor manifold
has an evaporator leg adjacent and connected to the evaporator
sections, a condenser leg adjacent and connected to the condenser
sections, and a vapor passage extending between the evaporator leg
and condenser leg, the evaporator leg being positioned inside a
portion of the evaporator sections of the conduits and the
condenser leg being positioned outside a portion of the condenser
sections.
26. A heat pipe as set forth in claim 1 further comprising a valve
moveable between first and second operating positions, the valve
producing relatively less resistance to flow of vapor through the
common vapor manifold in the first position and relatively more
resistance to flow of vapor through the common vapor manifold in
the second position.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. provisional
application No. 61/436,076 filed Jan. 25, 2011, the entire contents
of which are hereby incorporated by reference.
FIELD OF INVENTION
[0002] The present invention relates generally to passive heat
transfer devices and more particularly to heat pipes, which are
closed loop systems using the high heat of evaporation/condensation
associated with a phase changing working fluid to efficiently
transfer large amounts of heat and which require no or only small
energy input.
BACKGROUND
[0003] Heat pipes are closed loop heat exchangers that rely on a
phase change of a working fluid to absorb heat by evaporation and
release heat by condensation. A liquid working fluid (e.g., water,
Freon, or the like) is vaporized in the evaporator portion of a
heat pipe using heat absorbed from the environment. The vapor flows
into the condenser portion of the heat pipe where it is condensed,
releasing heat into the environment. Liquid condensed in the
condenser is returned to the evaporator (e.g., by gravity,
capillary action, pump, etc.) where it is evaporated again. In use
the working fluid is continuously vaporized in the evaporator
portion of the heat pipe and continuously condensed in the
condenser portion of the heat pipe such that heat is absorbed from
the environment by the evaporator, transferred to the condenser,
and then released into the environment by the condenser. This
process cools the environment surrounding the evaporator and heats
the environment surrounding the condenser. Heat pipes can be
extremely efficient at transferring large amounts of heat and can
operate with only a limited difference between the temperatures of
the evaporator and condenser portions of the system. Heat pipes
also require no moving parts and typically require little or no
maintenance.
[0004] One practical application for heat pipes is in
de-humidification systems that pre-cool air in the inlet stream of
a cooling coil (e.g., in the HVAC system for a commercial or
residential building) and re-heat the outlet air stream from the
cooling coil. The heat pipe can be configured to extend from one
side of the cooling coil to its opposite side so the evaporator
portion is in the cooling coil inlet stream and the condenser
portion is on the opposite side of the cooling coil in the cooling
coil outlet stream. For example, heat pipes can wrap around the
sides and/or over the top of the cooling coil so the evaporator
portion of the heat pipe is in the inlet stream and the condenser
portion of the heat pipe is in the outlet stream. Pre-cooling the
air as it enters the cooling coil allows the cooling coil to cool
the air to a significantly lower temperature without using much if
any additional energy. The overly cooled output air stream from the
cooling coil is then heated by the condenser portion of the heat
pipe system to a comfortably cool temperature. Over cooling the air
in this manner increases the amount of moisture condensed from the
air stream as it flows through the cooling coil. This combination
of heat pipe and cooling coil provides a low cost, low maintenance
dehumidification system.
[0005] Heat pipes can also be used to recover heat that would
otherwise be lost in exhaust from an HVAC system during cold
weather. For example, a heat pipe can be installed in the duct
system of an HVAC system so the heat pipe extends into two
adjoining ducts, one of which is being used to exhaust warmer stale
air from the building and the other of which is used to convey
cooler fresh air from outside the building to the HVAC system. Heat
from the warm exhaust is captured by evaporation of the working
fluid in the part of the heat pipe exposed to the exhaust and
transferred to the cool inlet air by condensation of the working
fluid in the part of the heat pipe exposed to the inlet stream.
Thus, heat that would otherwise be lost to the outside of the
building is used to pre-heat the cool inlet air, which means less
energy is required by the heater of the HVAC system to heat the
fresh air to a comfortable temperature. The heat pipes can be
designed so when the cooling coil is operating in warm weather heat
is transferred from the relatively warm inlet air to relatively
cool stale exhaust air. Using the heat pipes to recapture heat from
the warm exhaust in cold weather and recapture coolness from the
cool exhaust in warm weather reduces the load on the heater and
cooling coil and reduces energy required by the HVAC.
[0006] Various improvements to the prior art heat pipes are been
made and will be described in the detailed description below.
SUMMARY
[0007] One aspect of the invention is a heat pipe. The heat pipe
includes a plurality of conduits. Each conduit has an evaporator
section extending laterally from a first open end of the respective
conduit, a condenser section extending laterally from a second open
end of the respective conduit, and a liquid return section. The
liquid return section for each conduit is connected to the
evaporator section at a position away from the first open end and
connected to the condenser section at a position away from the
second open end so the evaporator and condenser section are in
fluid communication with one another through the liquid return
section for flow of liquid condensed in the condenser section to
the evaporator section. The liquid return section of at least one
conduit is distinct from the liquid return section of another of
the conduits. The heat pipe has a common vapor manifold in fluid
communication with and extending between the first and second open
ends of each of said plurality of conduits so vapors produced in
the evaporator sections can flow from the first open ends through
the common vapor manifold to the second open ends without flowing
through the conduits.
[0008] Other objects and features will in part be apparent and in
part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective of one embodiment of a heat
pipe;
[0010] FIG. 2 is front elevation of the heat pipe;
[0011] FIG. 3 is a right side elevation of the heat pipe with a
portion of a conduit broken away to show a phase changing working
fluid;
[0012] FIG. 4 is a left side elevation of the heat pipe with a
portion of a conduit broken away to show the phase changing working
fluid;
[0013] FIG. 5 is a top plan view of the heat pipe in combination
with a cooling coil;
[0014] FIG. 6 is perspective of one embodiment a heat pipe nested
within another heat pipe;
[0015] FIG. 7 is a perspective of a heat pipe having a common vapor
manifold configured to wrap around the side of a cooling coil;
[0016] FIG. 8 is a perspective of a heat pipe having evaporator
sections and condenser sections configured to double back on
themselves;
[0017] FIG. 9 is a perspective of another embodiment of a heat
pipe;
[0018] FIG. 10 is a perspective of a system including a plurality
of heat pipes;
[0019] FIG. 11 is a perspective of the system illustrated in FIG.
10 in a frame with fins;
[0020] FIG. 12 is a schematic illustrating the system of FIGS. 10
and 11 installed in the duct system of an HVAC system;
[0021] FIG. 13 is a perspective of another embodiment of a heat
pipe;
[0022] FIG. 14 is a top plan view of a set of heat pipes including
the heat pipe illustrated in FIG. 13;
[0023] FIG. 14A is a top plan view of another embodiment of set of
heat pipes including the heat pipe illustrated in FIG. 13; and
[0024] FIG. 15 is a schematic illustrating a system having the set
of heat pipes in FIG. 14 installed in the duct system on an HVAC
system.
[0025] Corresponding reference characters indicate corresponding
parts throughout the drawings.
DETAILED DESCRIPTION
[0026] Referring to FIGS. 1-5, one embodiment of a heat pipe,
generally designated 101, includes a plurality of conduits 103
containing a working fluid (e.g., water, Freon or another
refrigerant), some of which exists as a vapor V and some of which
exists as a liquid L, as illustrated in FIGS. 3 and 4. Each of the
conduits 103 includes an evaporator section 105 extending laterally
from an open end 107 of the conduit and a condenser section 109
extending laterally from another open end 111 of the conduit. Each
of the conduits also includes a liquid return section 113 for flow
of liquid L condensed in the condenser section 109 to the
evaporator section 105.
[0027] As illustrated in the drawings, the liquid return section
113 for each conduit 103 is connected to the evaporator section 105
at a position away from the open end 107 of the evaporator section.
For example, the liquid return section 113 is suitably connected to
the evaporator section 105 at an end of the evaporator section
opposite the open end 107. The liquid return section 113 is also
connected to the condenser section 109 at a position away from the
open end 111 of the condenser section (e.g., at an end of the
condenser section opposite the open end 111 of the condenser
section) so the evaporator section 105 and condenser section of
each conduit 103 are in fluid communication with one another
through the respective liquid return section. The liquid return
section 113 of at least one conduit 103 is distinct from the liquid
return section of another of the conduits. As illustrated, for
example, each conduit 103 has its own liquid return section 113,
meaning the liquid return section for each conduit is distinct from
the liquid return sections of all the other conduits.
[0028] The evaporator sections 105, condenser sections 109, and
liquid return sections 113 are each suitably substantially straight
sections of the respective conduit 103, although this is not
required to practice the invention. The sections 105, 109, 113 can
be connected to one another using a 90 degree elbow connector or
other suitable connector. The conduits 103 could also be formed by
bending a single segment of pipe to produce the various sections
105, 109, 113 of the conduit. The evaporator sections 105 of the
conduits 103 suitably have a horizontal orientation. At least a
portion of the condenser section 109 for each conduit 103 is at an
elevation higher than the elevation of the evaporator section 105
of the respective conduit 103. For example, as illustrated in FIG.
2, the open end 111 of the condenser section 109 is suitably at an
elevation above the elevation of the open end 107 of the evaporator
section 105 for each of the conduits 103. The condenser sections
109 are inclined downward from their open ends 111 so gravity
assists flow of liquid L condensed in the condenser section toward
the liquid return section 113. The liquid return sections 113 can
suitably have an orientation inclined downward from the condenser
sections 109 to the evaporator sections 105. In the illustrated
embodiment, however, the liquid return sections 113 are
substantially horizontal. Further, the degree of inclination in any
of the various parts of the conduit 103 is suitably relatively
slight (e.g., about 1 percent slope). Moreover, conduits that do
not have any slope are within the broad scope of the invention.
[0029] Although the embodiment illustrated in the drawings has a
configuration in which gravity drives or assists flow of condensed
liquid L through the heat pipe 101 to the evaporator sections 105,
condensed liquid can be returned to the evaporator portion of a
heat pipe without any gravity assistance and/or against gravity
using various internal wicking features and/or pumps known to those
skilled in the art without departing from the scope of the
invention.
[0030] As illustrated in FIGS. 1-5, the conduits 103 are suitably
generally U-shaped and have a substantially horizontal orientation.
In particular, the difference in elevation between the highest part
of the conduit 103 (e.g., at openings 111 in the illustrated
embodiment) and the lowest part of the conduit (e.g., evaporator
section 105 and/or at the openings 107) is suitably no more than
about 10 percent of the overall length of the conduit, meaning the
conduit has a substantially horizontal orientation. The conduits
103 are arranged so they are spaced vertically from one another, as
illustrated in FIG. 1. For example, the conduits 103 are suitably
stacked generally one on top of the other so they each have an
identical U-shaped footprint when viewed from the top, as
illustrated in FIG. 5. The conduits 103 may lie directly on top of
one another so the top of one conduit is in contact with the bottom
of another conduit within the broad scope of the invention. In the
illustrated embodiment, however, the conduits 103 are retained in
spaced relation from one another and fins extend vertically between
the conduits. Referring to FIG. 1, one set of fins 121 is connected
to the evaporator sections 105 of the conduits 103 to facilitate
absorption of heat from the environment. Another set of fins 123 is
connected to the condenser sections 109 of the conduit to
facilitate release of heat to the environment. The fins 121, 123
are suitably large thin metal plates that extend continuously
between the conduits 103 such that the conduits are embedded in the
fins. The sets of fins 121, 123 extend continuously along
substantially the entire length of the evaporator sections 105 and
condenser sections 109. Only some of the fins 121, 123 are shown in
FIG. 1 to show the conduits better. The liquid return sections 113
are substantially free of fins to limit heat transfer between the
working fluid in the liquid return sections and the
environment.
[0031] The heat pipe 101 is suitably configured so the evaporator
sections 105 are positioned on one side of a space 131 for
receiving a cooling coil 135 (FIG. 5) and the condenser sections
are positioned on the opposite side of the space. In FIG. 5, the
heat pipe 101 is illustrated in combination with a cooling coil 135
(broadly a "cooling system"). The cooling coil 135 is conventional
except for the heat pipes 101 and need not be described or
illustrated in detail. Those skilled in the art will recognize the
cooling coil 135 is suitably part of a conventional air
conditioning system (not shown). The evaporator sections 105 of the
heat pipe 101 collectively form an array of evaporator sections
disposed in the path of air incoming to the evaporator of the
cooling system for pre-cooling air before it arrives at the
evaporator. The condenser sections 109 of the heat pipe 101
collectively form an array of condenser sections disposed in the
air path downstream of the evaporator of the cooling system for
re-heating overly cooled air to a temperature that is suitable for
the occupants of a building cooled by the cooling system.
[0032] The conduits 103 are suitably made of relatively long narrow
tubing. For example, the conduits 103 are suitably made of tubing
no larger than 1 inch tubing, more suitably no larger than 5/8
inche tubing, more suitably no larger than 1/2 inch tubing and can
in some cases be made of tubing no larger than 3/8 inch tubing. As
illustrated in FIG. 5, the evaporator sections 105 and condenser
sections 109 are generally parallel to one another and spaced from
one another by a distance D1 that is at least about 2 feet, more
suitably at least about 4 feet, still more suitably in the range of
about 4 to about 10 feet, and still more suitably in the range of
about 6 to about 8 feet. The length L1 of the liquid return
sections 113 of the conduits is suitably about equal to the
distance D1. The evaporator and condenser sections 105, 109 are
suitably about equal in length. Each of the evaporator and
condenser sections 105, 109 has a length L2 suitably in the range
of about 25 to about 150 inches, more suitably in the range of
about 50 to about 125 inches, and still more suitably in the range
of about 75 to about 100 inches, with each of the foregoing lengths
being suitable when the conduits are made from 1/2 inch tubing. If
larger tubing is used, the lengths can be increased even more
without experiencing a significant loss in efficiency.
[0033] The overall length of the flow path through the conduits 103
from the condenser opening 111, through the condenser section 109,
liquid return section 113, and evaporator section 105 to the
evaporator opening 107 is suitably in the range of about 50 inches
to about 300 inches, more suitably in the range of about 60 to
about 250 inches, more suitably in the range of about 100 to about
250 inches, more suitably in the range of about 125 to about 225
inches, and still more suitably in the range of about 150 to about
200 inches, with each of the foregoing lengths being suitable when
the conduits are made from 1/2 inch tubing. Those skilled in the
art will recognize the lengths described above for the conduits and
the various parts thereof are fairly long flow paths for a heat
pipe made of 1/2 inch tubing. Again, if larger tubing is used, the
lengths can be increased even more without experiencing a
significant loss in efficiency. For example, when the tubing is 5/8
inch diameter tubing, the overall length of the flow path through
the conduits 103 from the condenser opening, through the condenser
section 109, liquid return section 113, and evaporator section 105
to the evaporator opening 107 is suitably in the range of about 100
inches to about 500 inches, more suitably in the range of about 200
inches to about 500 inches, and still more suitably in the range of
about 200 inches to about 400 inches. As another example, when the
tubing is 3/8 inch diameter tubing, the overall length of the flow
path through the conduits is suitably in the range of about 12
inches to about 200 inches, more suitably in the range of about 12
inches to about 100 inches, and still more suitably in the range of
about 12 inches to about 60 inches, and still more suitably in the
range of about 24 inches to about 60 inches. As still another
example, when the tubing is in the range of about 5/16 to 7 mm
diameter tubing, the overall length of the flow path through the
conduits is suitably in the range of about 12 inches to about 50
inches. It costs substantially more to make heat pipes using larger
diameter tubing than it does with smaller diameter tubing, so it is
desirable to use the smallest diameter tubing that does not result
in an unacceptably inefficient heat pipe. But the improvements
described herein can also improve the efficiency for heat pipes in
which the dimensions for the lengths and diameters of the conduits
vary from those listed above within the scope of the invention.
[0034] The heat pipe 101 also has a common vapor manifold 151 in
fluid communication with the open ends 107, 111 of each of said
plurality of conduits 103 and extending between the open ends of
the conduits so vapors V produced in the evaporator sections 105
can flow from the open ends 107 of the evaporator sections 105
through the common vapor manifold to open ends 111 of the condenser
sections 109 without flowing through the conduits. Because the
vapor V can return to the condenser sections 109 without flowing
through the conduit, there is much less resistance to flow of
liquid from the condenser sections to the evaporator sections 105
because counterflow of vapor and liquid L in the conduits 103 is
greatly reduced or eliminated. The common vapor manifold can have
many different configurations within the broad scope of the
invention. As illustrated, the common vapor manifold 151 is an
inverted U-shaped conduit having a generally upright evaporator leg
153, a generally upright condenser leg 155, and a generally
horizontal vapor passage 157 connecting the legs to one another so
they are in fluid communication with one another through the vapor
passage. The evaporator leg 153 and the condenser leg 155 are
suitably substantially straight (e.g., vertical) sections of
tubing. The vapor passage 157 is also a substantially straight
section of tubing having the same diameter as the legs 153, 155.
Although the legs and vapor passage of the manifold are straight in
the illustrated embodiment, other configurations are possible
within the broad scope of the invention. The vapor passage 157 can
be connected to the legs 153, 155 of the vapor manifold 151 using a
90 degree elbow connection or other suitably connecting means.
Similarly, a single piece of tubing can be bent into an inverted
U-shape to form the common vapor manifold 151 within the scope of
the invention.
[0035] The tubing for the common vapor manifold 151 suitably has a
diameter that is larger than the diameter of the conduits 103, as
in the illustrated embodiment. In one embodiment, the conduits 103
can be made from 0.5 inch or 3/8 inch copper tubing while the
common vapor manifold 151 is made from larger diameter 5/8 inch or
0.5 inch copper tubing, respectively. However, the cross sectional
flow area of the vapor manifold 151 can be much larger than
described above or be the same or smaller than the cross sectional
flow area a conduit 103 within the scope of the invention. It is
also understood the conduits 103 and manifold 151 are not required
to have any particular cross sectional shape within the broad scope
of the invention.
[0036] The open ends 107 of the evaporator sections 105 open into
the evaporator leg 153 of the manifold 151. The open ends 111 of
the condenser sections 109 open into the condenser leg 155 of the
manifold 151. In the illustrated embodiment, the evaporator leg 153
of the common vapor manifold 151 extends to a position that is
higher in elevation than the highest of the open ends 107 of the
evaporator sections 105. For example, the manifold 151 suitably
extends a distance H1 (FIG. 3) above the highest of the open ends
107 of the evaporator sections 105. Likewise, the condenser leg 155
leg of the common vapor manifold 151 extends to a position that is
higher in elevation than the highest of the open ends 111 of the
condenser sections 109. The vapor passage 157 connects to the
evaporator leg 153 at an elevation above the highest of the open
ends 107 of the evaporator sections 105 and connects to the
condenser leg 155 at an elevation above the highest of the open
ends 111 of the condenser sections 109. The vapor passage 157 of
the illustrated embodiment is also at an elevation that is higher
than the highest of the generally horizontal conduits 103. An
opening 137 (FIG. 1) for receiving the cooling coil 135 as it
slides relative to the heat pipe 101 into the space 131 is formed
between the legs 153, 155 and under the vapor passage 157 of the
vapor manifold. Like the liquid return sections 113 of the conduits
103, the common vapor manifold 151 is suitably substantially free
of fins to limit heat transfer between the heat pipe 101 and the
environment except at the evaporator and condenser sections 105,
109.
[0037] When the cooling coil 135 is on, air flows into the cooling
coil and is cooled. Meanwhile, the evaporator sections 105 of the
heat pipe 101 are exposed to the relatively warm air flowing into
the cooling coil 135, represented in FIG. 5 by arrows A. Heat from
the warm inlet air is absorbed by the fins 121 and evaporator
sections 105. This process cools the air before it reaches the
cooling coil 135. The absorbed heat causes liquid phase working
fluid L to evaporate in the evaporator sections 105. Vapors V
produced in the evaporator sections 105 flow into the evaporator
leg 153 of the vapor manifold 151 through the openings 107, up to
the vapor passage 157, across the vapor passage to the condenser
leg 155, down into the condenser leg 155, and then into the
condenser sections 109 through the openings 111. Because the air
was pre-cooled by the evaporator sections 105 before reaching the
cooling coil 135, the cooling coil can cool the air down to a
temperature significantly below the temperature to which it would
be cooled if there were no heat pipe present, but with little or no
additional energy consumption. Because the air is cooled by the
cooling coil 135 to this lower temperature, significantly more
water vapor is condensed and removed from the air flowing through
the cooling coil.
[0038] As this is occurring, the condenser sections 109 are exposed
to the cold outlet air stream from the cooling coil 135,
represented by arrows B in FIG. 5. As the cold air outlet stream
flows through the fins 123, it absorbs heat released from the
condenser sections 109 of the heat pipe 101 through condensation of
the working fluid in the condenser sections. The interaction of the
cold air from the cooling coil 135 and the condenser sections 109
warms the air to a comfortable temperature and produces
condensation of the working fluid in the condenser sections of the
heat pipe 101. The liquid L condensed in the condenser sections
flows from the condenser sections 109 to the evaporator sections
105 through the respective liquid transfer sections 113. The air
warmed by the condenser sections 109 has lower relative humidity
than it would without the heat pipe 101. Moreover, the heat pipe
dehumidifies the air with little or no additional energy
consumption.
[0039] Because the common vapor manifold 151 allows vapors
evaporated in the evaporator sections to flow to the condenser
sections through the vapor manifold, there is less resistance to
flow of liquid L through the conduits 103 to the evaporator
sections 105 and there is less resistance to flow of vapor V to the
condenser sections 109 because of the relative absence of counter
flowing vapor and liquid in any section of the heat pipe 101. This
increases the speed at which vapor V and liquid L flows through the
heat pipe 101 and thereby allows the heat pipe 101 to perform
efficiently even when the overall length of the conduits 103 is
relatively long and the inner diameter of the conduits is
relatively small (e.g., as described above). Moreover, the heat
pipe 101 can perform efficiently with a relatively low charge of
working fluid. For example, the charge of working fluid can
suitably be in the range of about 15 percent to about 60 percent,
more suitably in the range of about 15 percent to about 45 percent,
more suitably in the range of about 15 percent to about 30 percent,
and still more suitably in the range of about 20 percent to about
30 percent. In other examples, the interior surface of the tubing
has grooves (which those skilled in the art will recognize aids
flow of liquid through the tubing by capillary action) and the
charge of working fluid can suitably be in the range of about 20
percent to about 50 percent, more suitably in the range of about 20
percent to about 45 percent, more suitably in the range of about 25
percent to about 40 percent, and still more suitably in the range
of about 25 to 35 percent. Grooved tubing typically works better
with a slightly larger charge of working fluid compared to tubing
that is smooth on the inside. As further examples, the charge of
working fluid is suitably less than about 40 percent, still more
suitably less than about 35 percent, and still more suitably no
more than about 30 percent. As those skilled in the art know, the
amount of charge is the weight of working fluid (liquid+vapor) in
the system expressed as a percentage of the weight of liquid phase
working fluid that would completely fill the interior volume of the
heat pipe. It is understood that larger charges than those
specified above may be used within the broad scope of the
invention. Accordingly, the performance of the heat pipe 101 can be
equivalent to conventional heat pipe having significantly more
expensive larger diameter tubing for the conduits and requiring a
higher volume of working fluid. It is understood the improvements
described herein can also improve efficiency of the heat pipes with
the charge of working fluid varies from the amounts described above
without departing from the scope of the invention.
[0040] As illustrated in FIG. 1, the system 101 can include a valve
161 installed in the common vapor manifold 151 for selectively
reducing flow of vapor through the common vapor manifold. The valve
161 is suitably moveable (e.g., manually or via an electronic
control system, not shown) between first and second operating
positions such that there is relatively less resistance to flow of
vapor through the common vapor manifold 151 in the first position
(e.g., a fully open position) and relatively more resistance to
flow of vapor through the common vapor manifold in the second
position (e.g., a fully closed position). Thus, the valve provides
the ability to adjust the efficiency of the system from a higher
heat transfer efficiency for better dehumidification to a lower
heat transfer efficiency. It may be desirable to operate in a lower
heat transfer efficiency mode when the air flowing into the system
is already relatively dry and less dehumidification is desired. The
valve 161 is optional. Although the valve illustrated in FIG. 1 is
a manually operated ball valve, it is understood it will often be
desirable to use an electronically controlled valve so the valve
can be operated from a remote position (e.g., by a processor). If
desired the valve 161 can be positionable at one or more additional
operating positions intermediate the first and second positions
(e.g., an infinite number of positions between a fully closed
position and a fully open position) to provide greater control over
the amount of fluid flowing through the common vapor manifold
151.
[0041] FIG. 6 illustrates another embodiment of a heat pipe system,
generally designated 101'. This system 101' includes multiple heat
pipes 101 nested together so they work in tandem. In FIG. 6, there
are two heat pipes 101 in the system 101' and each of the two heat
pipes is exactly the same as the heat pipe 101 in FIG. 1 except one
of the heat pipes is slightly smaller than the other so it can nest
inside the other. It is understood there could be more than two
heat pipes nested together without departing from the scope of the
invention. The system 101' operates in a manner that is
substantially the same as the system 101 in FIG. 1, except the
system 101' has a greater capacity to transfer heat because of the
multiple heat pipes 101 working in tandem.
[0042] FIG. 7 illustrates another embodiment of a heat pipe system,
generally designated 101''. This heat pipe is substantially
identical to the heat pipe 101 illustrated in FIG. 1, except as
noted. The heat pipe 101'' has a common vapor rail 151'' having a
vapor passage 157'' configured to extend from the top of the
evaporator leg 153 to the top of the condenser leg 155 along a path
that matches the U-shaped contour of the conduits 103. Accordingly,
a portion of the common vapor manifold 151'' is on the same side of
the heat pipe 101'' as at least one (e.g., all) of the liquid
return sections 113 of the conduits 103. As illustrated in FIG. 7,
the vapor passage 157'' extends from the top of the evaporator leg
153 along and above the evaporator section 105, liquid return
section 113, and condenser section 109 of the uppermost conduit.
The vapor passage 157'' is configured so it wraps around the same
side of the cooling coil 135 as the conduits. This allows the heat
pipe 157'' to be installed around the cooling coil 135 without
requiring the vapor rail 151'', and in particular the vapor passage
157'' thereof, to be passed over the top of the cooling coil. This
can be desirable, for example, when the cooling coil 135 is already
installed and obstructions would prevent or make it difficult to
move the vapor passage 157 for the embodiment illustrated in FIG. 1
over the top of the cooling coil to wrap the conduits 103 around
the sides of the cooling coil during installation of the heat pipe.
The heat pipe 101'' illustrated in FIG. 7 can also be nested with
one or more similar heat pipes in a manner analogous to the nesting
illustrated in FIG. 6.
[0043] Another embodiment of a heat pipe, generally designated
101''', is illustrated in FIG. 8. This heat pipe 101''' is
substantially identical to the heat pipe 101 illustrated in FIG. 1
except as noted. The conduits 103''' of this heat pipe 101''' have
evaporator sections 105''' and condenser sections 109''' that
double back on themselves so the open ends 107''', 111' are at the
same end of the system as the liquid return sections 113 of the
conduits. The overall shape of the conduits 103''' is that of a
horizontal U, with the doubled back evaporator and condenser
sections 105''', 109''' forming the sides of the U and the liquid
return sections 113''' forming the bottom of the U. The overall
length of the conduits 103''' is suitably the same as the lengths
of the conduits 103 described above. However, doubling back of the
evaporator sections 105''' and condenser sections 109 requires the
working fluid to flow double the length of the cooling coil to flow
through the condenser section and through the evaporator section.
Accordingly, the heat pipe 101''' in FIG. 8 is particularly
suitable for small and medium sized cooling coils. The common vapor
manifold 151''' is substantially similar to the vapor manifold 151
described above, but it is at the same end of the heat pipe 101'''
as the liquid return sections 113 of the conduits 103'''.
Accordingly, similar to the embodiment illustrated in FIG. 7, there
is no need to pass the common vapor rail 151''' over the top of the
cooling coil 135 during installation.
[0044] The evaporator sections 105''' and condenser sections 109'''
are suitably horizontal (e.g., perfectly horizontal or
substantially free of any incline), as illustrated. Each evaporator
section 105''' is suitably doubled back in such a way that the end
107''' of the evaporator section is spaced inward from the end of
the liquid return section 113 connected to the evaporator section.
Each condenser section 109''' is suitably doubled back in such a
way that the end 111''' is spaced outward from the end of the
liquid return section that is connected to the condenser section.
Accordingly, when the heat pipe 101''' is installed for use with
cooling coil 135, each evaporator section 105''' includes a first
portion 105a''' adjacent the opening 107''' and a second portion
105b''' remote from the opening 107''' and upstream of the first
portion in the cooling coil intake stream. Likewise, each condenser
section 109''' includes a first portion 109a''' adjacent the
opening 111''' and a second portion 109b''' remote from the opening
111''' that is upstream of the first portion in the flow out of the
cooling coil. The evaporator leg 153''' of the common vapor
manifold 151''' is positioned inside the portions 105b'''' of the
evaporator sections 105''' that are remote from the open ends
107'''. The condenser leg 155''' of the common vapor manifold
151''' is positioned outside the portions 109b''' of the condenser
sections 109''' that are remote from the open ends 111'''. When the
heat pipe 101''' is in use, this arrangement causes temperature
gradients to form in the conduits 103''' that pump the working
fluid through the heat pipe 101'''. In particular, evaporator
portion 105b''' will be warmer than portion 105a''' and condenser
portion 109a''' will be warmer than portion 109b'''. The thermal
gradients pump working liquid L from the warmer portion toward the
cooler portion.
[0045] Another embodiment of a heat pipe, generally designated 201,
is illustrated in FIG. 9. Except as noted, this heat pipe 201 is
substantially identical in construction to the heat pipe 101
described above. The heat pipe includes a common vapor manifold 251
that is analogous to the manifold 151 describe above. However, the
conduits 203 of this heat pipe 201 are substantially straight all
the way from one end 107 to the other 111 instead of U-shaped.
Consequently, the ends 107, 111 of the conduits 203 are spaced much
farther from one another and the vapor manifold 251 has a much
longer vapor passage 257 than is the case for the heat pipe 101.
The entire vapor manifold 251, including the evaporator leg 253,
condenser leg 255, and vapor passage 257, and the conduits 203 are
oriented on a common plane. In this embodiment, the evaporator
sections 205 are in-line with the condenser sections 209. The heat
pipe 201 includes a first set of fins 221 on the evaporator
sections 205 and a second set of fins 223 on the condenser sections
209. Only some of the fins 221, 223 are shown in FIG. 6. The liquid
return section 213 is a short segment of the conduit 203 that is
substantially free of fins positioned between the evaporator and
condenser sections 205, 209. As illustrated, the conduits 203 and
vapor passage 257 are substantially horizontal in orientation. It
is noted however the conduits 203 could be inclined slightly
downward from the condenser sections to the evaporator sections to
provide gravity assistance for liquid flow from the condenser
sections toward the evaporator sections within the scope of the
invention.
[0046] One embodiment of system 271 including a plurality of the
heat pipes 201 is illustrated in FIGS. 10 and 11. The system 271 is
suitable for transporting heat between two different and parallel
ducts in a ventilation system and includes a frame 273 (FIG. 11)
and a plurality of the heat pipes 201 supported by the frame. The
heat pipes 201 are arranged relative to one another so an array 275
of evaporator sections 205 is formed on one side of the system and
an array 281 of condenser sections 209 is formed on the other side
of the system. As illustrated in FIG. 10, for example, the heat
pipes 201 are arranged so the conduits 203 of the plurality of heat
pipes are parallel to one another. Further, the evaporator sections
205 of the heat pipes 201 are in side-by-side relation to one
another in the evaporator array 275 and the condenser sections 209
are also in side-by-side relation to one another in the condenser
array 281. The fins 221 in the evaporator array 275 (FIG. 11) are
spaced from the fins 223 in the condenser array 209 by a gap 225
aligned with the liquid return sections 213 of the conduits 203.
The fins 221, 223 suitably extend continuously between adjacent
heat pipes 201, as illustrated in FIG. 11.
[0047] The system 271 can be installed in the duct system 291 of an
HVAC (not shown) as illustrated schematically in FIG. 12. The side
having the evaporator array 275 is installed in an inlet duct 293
conveying exterior air toward the HVAC. The side having the
condenser array 281 is installed in an adjacent duct 295. Air in
the ducts 293, 295 flows in opposite directions as indicated by
arrows A and B. During the summer, the system 271 transfers heat
from relatively warm air being taken into the HVAC system from
outside the building through one of the ducts 293 to relatively
cooler stale air from inside the building that is being exhausted
to outside the building by the HVAC system through the other duct
295. This saves energy by pre-cooling the intake air before it
reaches the cooling coil using the already cooled stale air being
exhausted by the HVAC.
[0048] In winter, the system 271 can be operated in heat recovery
mode by reversing the direction of heat transfer through the heat
pipes 201. For example, the stale air from inside is now being
vented to the exterior through the duct 295 is now relatively
warmer while colder fresh air from the exterior of the building is
conveyed to the HVAC through the adjacent duct 293. Because of the
reversal of the direction of the temperature gradient between the
sides of the system 271, what was the evaporator array 275 in the
summer now functions as a condenser array and what was the
condenser array 281 in the summer now functions as an evaporator
array. The warm exhaust air flowing through the exhaust duct 295
evaporates the working fluid in the evaporator array 281 while the
colder air in the inlet duct 293 condenses the working fluid in the
condenser array 275. The heat captured from the warmer exhaust air
by evaporation of the working fluid is transferred to the other
side of the heat pipe system 271 where it pre-heats the colder
inlet air before it arrives at the HVAC. Consequently,
significantly less energy is required to heat the colder incoming
air than would be required without the heat pipe system 271.
[0049] Significantly, no tilting mechanism is required to reverse
flow of the liquid phase working fluid through the heat pipe system
271. This is contrary to some prior art heat pipe based heat
recovery modules in which a complicated tilting system and more
costly flexible ducts are needed to adjust the inclination of the
conduits and use gravity to overcome resistance to flow of the
liquid phase working fluid associated with counterflowing vapors in
the conduits. Instead, whenever the condenser array 275 is in a
relatively warmer environment and the evaporator array 281 is in a
relatively cooler environment, the flow of the working fluid
through the system 271 automatically reverses and the condenser
sections function as evaporator sections while the evaporator
sections functions as condenser sections. This is because the
common vapor manifold 251 sufficiently reduces resistance to flow
of liquid phase working fluid in the conduits 203 that natural
liquid pumping forces produced by the thermal gradient are
sufficient to produce flow of liquid between the condenser array
275 and evaporator array without requiring any gravitationally
induced flow in the conduits. Accordingly, the conduits 203 can
remain in the same horizontal orientation for operation in summer
and winter.
[0050] Another embodiment of a heat pipe, generally designated 301,
is illustrated in FIG. 13. The heat pipe includes first and second
sets of conduits 303a, 303b. Each conduit 303 in the first and
second sets 303a, 303b extends between opposite open ends and is
spaced vertically from the other conduits in the same set. The
conduits suitably have the lengths and diameters specified above
for the conduits 103 of the heat pipe 101 in FIG. 1. The conduits
303 are suitably all substantially straight, although this is not
required to practice the invention. The conduits 303 of the first
set 303a are in generally side-by-side relation with the conduits
of the second set 303b and are spaced laterally from the conduits
of the second set by a gap 305. The heat pipe 301 includes two
vapor manifolds 311', 311'' each of which includes a pair of legs
315, 317 and a vapor passage 321 extending between and in fluid
communication with the legs. The legs and vapor passages of the
first manifold are designated with a single prime (') after the
reference number while the legs and vapor passage of the second
manifold are designated with a double prime ('') after the
reference number.
[0051] The first leg 315' of the first manifold 311' is at one end
of the conduits 303 of the first set 303a while the second leg 317'
of the first manifold is at the opposite end of the conduits of the
second set 303b. The vapor passage 321' extends across the gap 305
and between the legs 315', 317'. The vapor passage 321' is in fluid
communication with the legs 315', 317' and allows vapor to flow
through the manifold 311' between the end of the conduits 303 of
the first set 303a and the ends of the conduits of the second set
303b on the opposite side of the heat pipe 301 without flowing
through any of the conduits of the first or second sets. The second
vapor manifold 311'' is substantially identical to the first 311'
except that its legs 315'', 317'' are connected to the ends of the
conduits 303 opposite the ends to which the legs 315', 317' of the
first manifold 311' are connected. The vapor passages 321', 321''
of the manifolds 311', 311'' are suitably substantially straight
and criss-cross one another as they extend over the top of the gap
305.
[0052] The heat pipe 301 is suitable for use in a heat transfer
system used to transfer heat between two different ducts of a
ventilation system. Although the heat pipe 301 can be the only heat
pipe in the ventilation system within the scope of the invention,
it is possible to combine the heat pipe 301 with various other heat
pipes to create a set of heat pipes that work together in the
ventilation system. For example, FIG. 14 is a top plan view of a
set of heat pipes that can be supported by the frame 273 of the
heat transfer system illustrated in FIG. 11 instead of the six heat
pipes 201 in that embodiment. There are four heat pipes in FIG. 14.
The first heat pipe 301 is the heat pipe illustrated in FIG. 13.
The second heat pipe 401 is substantially similar to the heat pipe
301 illustrated in FIG. 13 except that it is dimensioned to nest
with the first heat pipe 301. As illustrated in FIG. 14, the
conduits of the second heat pipe 401 are positioned in the gap 305
between the first and second sets 303a, 303b of conduits for the
first heat pipe 301. The third and fourth heat pipes 201 in FIG. 14
are each substantially identical to the heat pipe 201 illustrated
in FIG. 9 and described above. The conduits for the third and
fourth heat pipes are each positioned in the gap between the
conduits of the first and second set for the second heat pipe 401.
It is understood that another heat pipe similar to the heat pipe
301 could be nested within the second heat pipe 401 instead of or
in addition to the third and fourth heat pipes 201 in FIG. 14.
[0053] As illustrated schematically in FIG. 15, a heat transfer
system 571 including the frame 273 described above supports the
four heat pipes 301, 401, 201, 201 illustrated in the FIG. 14 so
the conduits extend from a position within the first duct 293 to a
position within the second duct 295 different from the first duct
in a manner similar to what is illustrated in FIG. 12. However, in
contrast to the embodiment illustrated in FIG. 12, the airflow A, B
in the ducts 293, 295 is in the same direction instead of in
opposite directions. Many HVAC systems use a parallel flow
arrangement through adjacent ducts instead of counterflow and the
system illustrated in FIG. 15 can provide significant advantages
when there is parallel flow. When the heat transfer system 571 is
used in parallel flow situations as illustrated in FIG. 15, the
heat pipes operate more efficiency because vapors are exchanged
between the first and second sets of conduits 303 for heat pipe 301
and heat pipe 401.
[0054] Without exchange of working fluid between the upstream and
downstream heat pipes in a parallel flow situation, as illustrated
in FIG. 15, the evaporator and condenser sections of the heat pipe
on the upstream side would be exposed to a relatively large
temperature difference. Each heat pipe farther downstream would be
exposed to a smaller temperature difference because the of heat
already transferred between the two air streams by the one or more
heat pipes farther upstream before the air arrives at the
downstream heat pipe. Further, the heat pipes on the downstream end
of the system may operate inefficiently because of the smaller
temperature difference.
[0055] On the other hand, in the heat pipes 301, 401 in the system
571 illustrated in FIGS. 14 and 15 vapor flows through the
manifolds 351 from the warmer end of the system in each duct 293,
295 to the cooler end of the system in the opposite duct. This
helps establish and maintain temperature driven pumping forces that
circulate the working fluid through the heat pipe. It also helps
ensure that each of the heat pipes 301, 401, 201, 201 is exposed to
a temperature difference that supports efficient operation of the
heat pipe.
[0056] FIG. 14A is a top plan view of another set of heat pipes
that can be supported by the frame 273 of the heat transfer system
illustrated in FIG. 8 instead of the six heat pipes 201 in that
embodiment. There are three heat pipes in FIG. 14A. The first heat
pipe 301 is the heat pipe illustrated in FIG. 13. The second and
third heat pipes 401, 501 are substantially similar to the heat
pipe 301 illustrated in FIG. 13 except the second heat pipe 401 is
dimensioned to nest with the first heat pipe 301 and the third heat
pipe 501 is dimensioned to nest within the second heat pipe. The
heat pipes illustrated in FIG. 14A operate in a similar manner to
those illustrated in FIG. 14 except the vapor manifolds of the
third heat pipe 501 also allow vapor exchange to occur which can
further augment efficiency of a heat transfer system using the heat
pipes 301, 401, 501.
[0057] It is also noted that any of the vapor manifolds described
for any of the embodiments described herein can optionally include
a valve similar to the valve 161 illustrated FIG. 1 and described
above to reduce the capacity of the heat pipes. Again, the valves
can be electronically actuated valves (e.g., solenoid valves) to
facilitate control of the valve by a processor, although the valve
in FIG. 1 is illustrated as a manually operated ball valve.
[0058] When introducing elements of the ring binder mechanisms
herein, the articles "a", "an", "the" and "said" are intended to
mean that there are one or more of the elements. The terms
"comprising", "including" and "having" and variations thereof are
intended to be inclusive and mean that there may be additional
elements other than the listed elements. Moreover, the use of
"forward" and "rearward" and variations of these terms, or the use
of other directional and orientation terms, is made for
convenience, but does not require any particular orientation of the
components.
[0059] As various changes could be made in the above without
departing from the scope of the invention, it is intended that all
matter contained in the above description and shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *