Method using heat pipes with multiple evaporator/condenser zones and heat exchangers using same

Abstract

Elongated, smaller-diameter tube heat pipes have an airflow arrangement that allows for short distances between evaporating and condensing sections of the heat pipe. The heat pipe is exposed to multiple alternate hot and cold zones adjacent to each other. Each evaporator zone accepts input heat to cause evaporation of the working fluid in the wick of the immediate vicinity. The vapor produced moves to either side by local pressure differences to condense in the two adjacent condenser zones where it is absorbed by the wick as a liquid and flows in the wick back to adjacent evaporator zones at each side. Each evaporator zone creates two fluid loops whereby evaporated working fluid splits up left and right, condenses in adjacent condenser zones and flows back to the evaporator zone as a liquid within the wick. Therefore, the overall tube length can be increased indefinitely, without traditional degradation of performance.

Description

FIELD OF THE INVENTION

The present invention relates to using efficient small diameter heat pipes with multiple evaporator/condenser zones in a single heat pipe.

BACKGROUND OF THE INVENTION

Heat pipe technology is old art incorporating the use of an evacuated sealed metal pipe partially filled with a working fluid. A wide variety of working fluids may be used; they are selected to be compatible with the temperature regime of the two heat transfer pairs between which heat is being transferred. The heat source must be able to evaporate the working fluid while the heat sink must be able to condense the vapor back into a liquid. Heat pipes also typically contain an internal wick coating to return condensed working fluid back to the heated evaporator zone. While heat pipes are relatively inexpensive to manufacture and offer orders of magnitude effective thermal conductivity as compared to solid copper of similar size, there are some limitations to their physical construction for proper operation.

Heat pipes typically degrade in performance as the tube length increases. Increasing tube diameter can help alleviate this issue, but larger tubes come with their own inefficiencies. It is known that smaller tubes offer greater efficiency, but in heat pipes smaller tubes restrict the length of the tube. Longer heat pipes of smaller diameter, if practical, would offer an opportunity to construct cost-competitive compact and efficient air-to-air heat exchangers.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to use smaller diameter tube heat pipes with an airflow arrangement that allows for short distances between evaporating and condensing sections of the heat pipe.

It is also an object to increase the overall tube length indefinitely, without traditional degradation of performance.

Other objects will become apparent by the following description of the invention.

SUMMARY OF THE INVENTION

The method of this invention utilizes smaller-tube heat pipes with an airflow arrangement that allows for short distances between evaporating and condensing sections of the heat pipe. Therefore, the overall tube length can be increased indefinitely, without traditional degradation of performance. Length of each tube is infinitely variable. While tube diameters of each heat pipe may vary, typical tube diameters may be ⅛ inch to 2 inches in diameter, although they can be smaller than ⅛ inch in diameter or more than 2 inches in diameter.

Traditional heat pipes have one evaporator end where input heat is added and one condenser end where heat is extracted. In contrast, in the heat pipe method of this invention, a heat pipe is exposed to multiple alternate hot and cold zones adjacent to each other by external means. So, although the heat pipe itself is of traditional construction, it no longer has a single evaporator end and a single condenser end. The operation is similar to that of a string of short heat pipes laid end to end, but the single long small diameter heat pipe is more practical and of much lower cost to manufacture. In operation, each evaporator zone accepts input heat to cause evaporation of the working fluid in the wick of the immediate vicinity. The vapor produced moves to either side by local pressure differences to condense in the two adjacent condenser zones where it is absorbed by the wick as a liquid and flows in the wick back to adjacent evaporator zones at each side. Thus each evaporator zone creates two fluid loops, whereby evaporated working fluid splits up left and right, condenses in the adjacent condenser zones and flows back to the evaporator zone as a liquid within the wick.

In an alternate embodiment of the heat pipe of this invention, additional torus shaped (like a donut or washer) plugs are added internally to partition each pair or grouping of pairs of heat/cool zones from the adjacent one. The central openings in the plugs allow gas pressures to equalize As the plugs may be rigid and extended to the inside of the heat pipe housing, they would partition the wick layer by actually cutting it or squeezing it against the housing. The plugs may also be resilient such as an elastomer/rubber in which case the wicking internal layer would also be squeezed so as to limit liquid flow within the heat/cool zone. The solid walls of the plugs act as a dam to hold liquid between hot/cold sections of pipe. The purpose of these added plugs is also to counteract any gravitational effects due to sagging or bowing of a long heat pipe or not being horizontally level thereby inducing the puddling of liquid which can result in the wick. Note that the vapor flow would be mainly confined to flow from hot to cold region within the partitioned sections, but the central hole will permit some vapor flow to adjacent regions to equalize any positional or temporal imbalances along the heat pipe.

A heat pipe used by the method of this invention by creating alternate adjacent evaporator/condenser pairs along its length can be applied to a variety of applications such as removing heat from electronics or in medical equipment or chemical manufacture. Liquid-to-liquid, liquid-to-air, contact surface-to-contact surface, or air-to-air heat transfer can be accommodated. In this invention, air-to-air heat exchangers for HVAC application will be discussed.

Although other configurations are possible, the heat exchangers of this invention are configured in a geometry not unlike that of fin tube heat exchangers commonly used in cooling coils, steam heating, and similar applications. The long small diameter heat pipes run parallel to each other preferable through common fins; they are passive independent entities and therefore not interconnected fluidically. They are placed in the same positions of the long parallel runs in a similar fin tube unit. One or more heat pipes can be used forming a flat rectangular array.

Multiple rows of heat pipes can also be configured, preferably staggering the heat pipes in each row. A four sided housing around the sides of the heat pipe/fin unit leaves the fins exposed on top and bottom completing the heat pipe heat exchanger (HPHE).

In a preferred embodiment, triangular crossection manifolds as described in U.S. Pat. No. 6,182,747 of Stark are attached on top and bottom of the heat pipe/fin unit. Since the manifolds have divider flanges which seal along the ends of the heat pipe heat exchanger (HPHE) fins, they automatically create the multiple adjacent evaporator/condenser zones along the heat pipes. By selecting the orientation of the bottom manifold relative to the top manifold, either parallel flow or crossflow heat exchangers can be configured.

In an alternate system for dehumidification, a single triangular manifold is used on top of the heat pipe heat exchanger (HPHE). A cooling coil is placed underneath the heat pipe heat exchanger (HPHE) with baffles maintaining the same zone separations as that of the triangular manifold. Under the cooling coil section is a drain pan with baffles separating each evaporator/condenser pair such that incoming air passes through each input manifold passageway and through the heat pipe heat exchanger (HPHE), then down through the cooling coil, then reversing direction through the drip pan, up through the cooling coil, further up through the heat pipe heat exchanger (HPHE), and then discharging through the exhaust part of the manifold. This flow constitutes a two-pass dehumidification cycle.

In an alternate embodiment of manifold construction, optional integral dampers are used in the triangular manifold. In this embodiment, the air is allowed to pass through dampers in the manifold walls, without going through the dehumidification process. The benefit here is to relieve the pressure drop and subsequent energy penalty when dehumidification is off. The preferred embodiment uses a triangular shaped manifold to conserve material. However, any shape of manifold is acceptable, so long as it is essentially one continuous zig-zagging wall that separates the incoming and outgoing air streams

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can best be understood in connection with the accompanying drawings. It is noted that the invention is not limited to the precise embodiments shown in drawings, in which:

FIG. 1 is an annotated side schematic representation of a traditional heat pipe and method associated therewith.

FIG. 2 is a side crossectional detail of a section of heat pipe as used in a method of this invention with multiple adjacent evaporator/condenser zones.

FIG. 2A is a side crossectional detail of an alternate embodiment of heat pipe as used in a method of this invention whereby internal plugs are added separating each pair or grouping of pairs of heat/cool zones.

FIG. 3 is a perspective view of a heat pipe/fin assembly of this invention.

FIG. 4 is a perspective view of a heat pipe heat exchanger (HPHE) of this invention.

FIG. 5 is a perspective view of a prior art triangular manifold as used in one embodiment of this invention.

FIG. 6 is a perspective view of the manifold of FIG. 5 when viewed from a different angle.

FIG. 7 is a heat pipe heat exchanger (HPHE) of this invention with manifolds attached on top and bottom thereof.

FIG. 8 illustrates the parallel flow configuration which results from the heat pipe heat exchanger with manifolds of the configuration of FIG. 7.

FIG. 9 shows the cross flow which results by re-orienting the bottom or top manifold relative to the other manifold as shown in FIG. 7.

FIG. 10 is a perspective view of an alternate embodiment for a dehumidification system configured with a heat pipe heat exchanger (HPHE).

FIG. 11 illustrates the two-pass air flow pattern through the dehumidification system of FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates the operation of a typical prior art heat pipe with a single divider externally separating evaporator from the condenser section. Note the one-way internal vapor flow to the right in the open center and the reverse liquid flow in the wick.

FIG. 2 shows a section of heat pipe using the multiple adjacent evaporator/condenser (hot/cold) sections method along the entire length of a heat pipe 1. The outer side 2 is shown as a rigid finned tube with an internal wick 3 bonded to it. Baffles or partitions 4 keep the external hot 5 and cold 6 flows or regions separated. Vapor 8 evaporates into the central section and partitions into a right and a left drift to the adjacent cold condensing section 6 from each hot evaporating section 5. FIG. 2 also shows the direction of liquid flow within wick 3 in both directions toward adjacent evaporator 5 sections. This flow generates short loops of vapor/liquid within the heat pipe, which negates the inherent inefficiency associated with conventionally used long heat pipes of small diameter.

FIG. 2A shows an alternate embodiment of heat pipe 51 wherein each pair or grouping of pairs of heat/cool zones 55 are internally isolated by a torus shaped plug 57 which limits liquid flow within wick 53 to the length of a heat/cool zone. For example, FIG. 2A shows respective torus shaped plugs 57 separating each heat/cool zone 55 from each other heat/cool zone 55. However, each pair of torus shaped plugs 57 can separate groups of two or more heat/cool zones 55 from other groups of heat/cool zones 55 or from a single heat/cool zone 55. Vapor 58 is also largely limited to loop from hot to cold zone within this region although a small amount of vapor can flow to adjacent regions through the central hole in plugs 57. This embodiment has the ability to counteract pooling or puddling of liquid within wick 53 along the heat pipe due to gravity in cases of significant deviation from horizontal positioning as well as any buckling or sagging of the long heat pipe 51.

FIG. 3 shows a heat pipe/fin unit 10 with three heat pipes 1 and multiple parallel fins placed transverse to heat pipes 1 and intimately attached to each. In this embodiment, the outer heat pipe wall is smooth and the fins 12 are shared among the three heat pipes 1. Many more than 3 heat pipes can be used, and multiple rows can also be configured with shared or not shared fins 12. A single heat pipe can be used as well.

FIG. 4 illustrates how the addition of two end panels 18 and 19 as well as side panels 16 and 17 transform heat pipe/fin assembly 10 into a functioning heat pipe heat exchanger (HPHE) 15.

FIGS. 5 and 6 are two views of a prior art triangular sheet metal manifold 22 that is used with heat pipe heat exchanger (HPHE) 15. The manifolds 22 have adjacent open and blocked sections on either side. Manifolds 22 seal to the top and bottom edges of fins 12 in their vicinity when placed in contact with heat pipe heat exchanger (HPHE 15).

FIG. 7 shows one manifold 22 attached to the top of heat pipe heat exchanger (HPHE) 15 and one at the bottom. FIG. 7 also illustrates the blocking panels 25 of top manifold 22 being in registration with those of bottom manifold 22. The open sections are also in registration.

This configuration results in the parallel air flow 27 shown in FIG. 8. The alternate crossflow 29 of FIG. 9 is achieved by having open panels in bottom manifold 22 in registration with blocking panels 25 in top manifold 22.

The alternate embodiment of the dehumidification system 35 of FIG. 10 uses a single triangular manifold 22 atop heat pipe heat exchanger (HPHE) 15 with a rectangular cooling coil 37 underneath and a drip pan 39 at the bottom. Cooling coil 37 has internal baffles 38 in registration with manifold 22 partitions above to continue the separation of flow regions. With the internal baffles, the two-pass air flow through the dehumidifier is achieved. In the prior art dampers are used to bypass air from one side of the manifold to the other, but they are not integral to the manifold as shown in the new invention.

In the foregoing description, certain terms and visual depictions are used to illustrate the preferred embodiment. However, no unnecessary limitations are to be construed by the terms used or illustrations depicted, beyond what is shown in the prior art, since the terms and illustrations are exemplary only, and are not meant to limit the scope of the present invention.

It is further known that other modifications may be made to the present invention, without departing the scope of the invention, as noted in the appended Claims.

Claims

1. A heat pipe heat exchanger comprising at least one elongated small diameter heat pipe with multiple evaporator/condenser zones in a single heat pipe having a wick associated therewith;

said at least one elongated, smaller-diameter tube heat pipe having an external arrangement providing short distances between evaporating and condensing sections of said at least one heat pipe;

said at least one heat pipe being exposed to multiple alternate hot evaporator and cold condenser zones adjacent to each other, wherein each evaporator zone accepts input heat to cause internal evaporation of the working fluid in a wick region of said wick in an immediate vicinity of each said evaporation zone;

said at least one heat pipe producing vapor moving to either side of said at least one heat pipe by local pressure differences to condense in the two adjacent condenser zones, where said vapor is absorbed by said wick as a liquid and flows said liquid in said wick back to adjacent evaporator zones at each side of said at least one heat pipe;

each said evaporator zone creating two fluid loops whereby evaporated working fluid splits up left and right, condensing in adjacent condenser zones and said working fluid flows back to the respective evaporator zone as a liquid within said wick,

whereby the overall tube length of said at least one heat pipe can be increased indefinitely, without traditional degradation of performance.

2. The heat pipe heat exchanger as in claim 1, wherein said at least one elongated heat pipe is a plurality of elongated heat pipes laid parallel to each other.

3. The heat pipe heat exchanger as in claim 1, wherein said vapor produced moves to either side by local pressure differences to condense in the two adjacent condenser zones where said vapor is absorbed by said wick as a liquid and flows in the wick back to adjacent evaporator zones at each side, wherein further each said evaporator zone creates two fluid loops whereby evaporated working fluid splits up left and right, condensing in respective adjacent condenser zones and flows back to the evaporator zone as a liquid within the wick.

4. The heat pipe heat exchanger of claim 3, wherein said heat pipe heat exchanger is an air to air heat pipe heat exchanger.

5. The heat pipe heat exchanger of claim 3, wherein said heat pipe heat exchanger is a liquid to liquid heat pipe heat exchanger.

6. The heat pipe heat exchanger of claim 3, wherein said heat pipe heat exchanger is a liquid to air heat pipe heat exchanger.

7. The heat pipe heat exchanger of claim 3, wherein said heat pipe heat exchanger is an air to liquid heat pipe heat exchanger.

8. The heat pipe heat exchanger of claim 1, wherein said heat pipe heat exchanger comprises partitions separating each said evaporator/condenser hot and cold zones.

9. The heat pipe heat exchanger as in claim 2, wherein said plurality of heat pipes run parallel to each other through common fins; said parallel heat pipes being passive independent entities and not being interconnected fluidically.

10. The heat pipe heat exchanger as in claim 9, wherein said plurality of heat pipes form a flat rectangular array.

11. The heat pipe heat exchanger as in claim 9, wherein multiple rows of heat pipes are staggered in each row.

12. The heat pipe as in claim 9, further comprising a four sided housing around the sides of the heat pipe/fin unit, leaving respective fins exposed on top and bottom portions of said heat pipe heat exchanger.

13. The heat pipe heat exchanger as in claim 12, further comprising at least one air flow manifold being provided on each said top and bottom portions of said heat pipe heat exchanger.

14. The heat pipe heat exchanger as in claim 13, wherein each said manifold on said respective top and bottom portions of said heat pipe are triangular manifolds with divider flanges sealing along the ends of respective fins thereby creating said multiple adjacent evaporator/condenser zones along each said the heat pipes.

15. The heat pipe heat exchanger as in claim 14, wherein air flow through each pair of said manifolds is parallel flow, relative to each other

16. The heat pipe heat exchanger as in claim 14, wherein air flow through each pair of said manifolds is cross flow, relative to each other

17. The heat pipe heat exchanger of claim 1, wherein in said heat pipe heat exchanger at least one respective pair of hot evaporator and cold condenser zones are internally isolated by a torus shaped plug, said torus shaped plug limiting liquid flow within said wick to the length of each respective hot evaporator and cold condenser zone;

each said torus shaped plug having a central hole permitting vapor to flow therethrough to respective adjacent hot evaporator and cold condenser zones;

thereby counteracting pooling or puddling of said liquid within said wick along said heat pipe heat exchanger due to gravity in cases of significant deviation from horizontal positioning, buckling or sagging of said heat pipe heat exchanger.

18. The heat pipe heat exchanger of claim 17, wherein said at least one respective pair of hot evaporator and cold condenser zones are a plurality of groups of pairs of hot evaporator and cold condenser zones.

19. The heat pipe heat exchanger of claim 1 further comprising a dehumidification system having a cooling coil being placed underneath said heat pipe heat exchanger with baffles maintaining respective zone separations, wherein further under said cooling coil section is provided a drain pan with baffles separating each respective evaporator/condenser pair such that incoming air passes through each respective input manifold passageway and through said heat pipe then down through said cooling coil, then reversing direction through a drip pan, up through a cooling coil, further up through said heat pipe, and then discharging through an exhaust port of said manifold, wherein the air flow is a two-pass dehumidification cycle.

20. The heat pipe heat exchanger as in claim 19, wherein said manifold is triangular.

21. The heat pipe heat exchanger as in claim 19, further comprising at least one damper therein

22. The heat pipe heat exchanger of claim 13, further comprising at least one damper in said manifold.

23. The heat pipe heat exchanger as in claim 1 further comprising said heat pipe being a rigid finned tube with fins transferring heat outward.

24. A heat pipe heat exchanger comprising at least one elongated small diameter heat pipe with multiple evaporator/condenser zones in a single heat pipe;

said at least one elongated, smaller-diameter tube heat pipe having an airflow arrangement providing short distances between evaporating and condensing sections of said at least one heat pipe;

said at least one heat pipe being exposed to multiple alternate hot evaporator and cold condenser zones adjacent to each other within said heat pipe, wherein each evaporator zone in said heat pipe accepts input heat to cause evaporation of the working fluid;

said at least one heat pipe producing vapor moving to either side of said at least one heat pipe by local pressure differences to condense in two adjacent condenser zones;

each said evaporator zone creating two fluid loops whereby evaporated working fluid splits up left and right, condensing in adjacent condenser zones and said working fluid flows back to the respective evaporator zone as a liquid,

said heat pipe having external partitions separating respective hot and cold air flows, wherein vapor evaporating into a section partitions into a right and a left drift to a respective adjacent condensing section from each respective evaporating section, wherein liquid flows in both directions toward adjacent evaporator sections, wherein said flow generates short loops of vapor/liquid within said heat pipe.

whereby the overall tube length of said at least one heat pipe can be increased indefinitely, without traditional degradation of performance.

25. The heat pipe heat exchanger of claim 24, wherein in said heat pipe heat exchanger said at least one respective pair of hot evaporator and cold condenser zones are internally isolated by a torus shaped plug, said torus shaped plug limiting liquid flow within said heat pipe heat exchanger to the length of each respective hot evaporator and cold condenser zone;

each said torus shaped plug having a central hole permitting vapor to flow therethrough to respective adjacent hot evaporator and cold condenser zones;

thereby counteracting pooling or puddling of said liquid within said heat pipe heat exchanger due to gravity in cases of significant deviation from horizontal positioning, buckling or sagging of said heat pipe heat exchanger.

26. The heat pipe heat exchanger of claim 25, wherein said at least one respective pair of hot evaporator and cold condenser zones are a plurality of groups of pairs of hot evaporator and cold condenser zones.

27. A method of heat exchange comprising the steps of providing at least one elongated small diameter heat pipe with multiple evaporator/condenser zones in a single heat pipe;

providing said at least one elongated, smaller-diameter tube heat pipe with an airflow arrangement providing short distances between evaporating and condensing sections of said at least one heat pipe;

exposing said at least one heat pipe to multiple alternate hot evaporator and cold condenser zones adjacent to each other, wherein each evaporator zone accepts input heat to cause evaporation of the working fluid in a region in an immediate vicinity of each said evaporation zone;

using said at least one heat pipe to produce vapor and moving said vapor to either side of said at least one heat pipe by local pressure differences to condense in the two adjacent condenser zones, where said vapor is absorbed as a liquid and flows back to adjacent evaporator zones at each side of said at least one heat pipe;

each said evaporator zone creating two fluid loops whereby evaporated working fluid splits up left and right, condensing in adjacent condenser zones and said working fluid flows back to the respective evaporator zone as a liquid within said evaporator zone,

whereby the overall tube length of said at least one heat pipe can be increased indefinitely, without traditional degradation of performance.

28. The method of heat exchange as in claim 27, further comprising the step of providing a plurality of elongated heat pipes laid parallel to each other.

29. The method of heat exchange as in claim 27, wherein said vapor produced moves to either side by local pressure differences to condense in the two adjacent condenser zones where said vapor is absorbed by a wick in said at least one heat pipe as a liquid and flows in the wick back to adjacent evaporator zones at each side, wherein further each said evaporator zone creates two fluid loops whereby evaporated working fluid splits up left and right, condensing in respective adjacent condenser zones and flows back to the evaporator zone as a liquid within the wick.

30. The method of heat exchange as in claim 27 further system comprising the steps of:

placing a cooling coil being placed underneath said heat pipe heat exchanger with baffles maintaining respective zone separations to provide dehumidification,

providing a drain pan under said cooling coil section; passing incoming air through each respective input manifold passageway and through said heat pipe then down through said cooling coil, then reversing direction through a drip pan, up through a cooling coil, further up through said heat pipe, and then discharging through an exhaust part of said manifold, wherein the air flow is a two-pass dehumidification cycle.

31. The method as in claim 27, wherein in said heat pipe heat exchanger at least one respective pair of hot evaporator and cold condenser zones are internally isolated by a torus shaped plug, said torus shaped plug limiting liquid flow within said wick to the length of each respective hot evaporator and cold condenser zone;

each said torus shaped plug having a central hole permitting vapor to flow therethrough to respective adjacent hot evaporator and cold condenser zones;

thereby counteracting pooling or puddling of said liquid within said wick along said heat pipe heat exchanger due to gravity in cases of significant deviation from horizontal positioning, buckling or sagging of said heat pipe heat exchanger.

32. The method as in claim 31, wherein said at least one respective pair of hot evaporator and cold condenser zones are a plurality of groups of pairs of hot evaporator and cold condenser zones.