Thermoelectric device with evaporating/condensing heat exchanger

• US 5,737,923 A
• Filed: 10/17/1995
• Issued: 04/14/1998
• Est. Priority Date: 10/17/1995
• Status: Expired due to Term

• Current Assignee: Marlow Industries, Inc. (Coherent Corp.)
• Original Assignee: Marlow Industries, Inc. (Coherent Corp.)
• Inventors: Gilley, Michael D., Webb, Ralph L.
• Primary Examiner(s): Sollecito, John M.
• Application Number:
  US08/544,169
• Time in Patent Office: 910 Days
• Field of Search: 62/3.2, 62/3.3, 62/3.6, 62/3.7, 165/104.33, 165/104.26, 165/133, 165/911, 165/517
• US Class Current: 62/3.7
• CPC Class Codes: F25B 21/02 using Peltier effect; using Nernst-Ettinghausen effect
• CPC Class Codes: F28B 9/08 for collecting and removing condensate
• CPC Class Codes: F28D 15/0233 the conduits having a particular shape, e.g. non-circular cross-section, annular F28D15/0241, F28D15/0266 take precedence
• CPC Class Codes: F28D 15/0266 with separate evaporating and condensing chambers connected by at least one conduit; Loop-type heat pipes; with multiple or common evaporating or condensing chambers F28D15/043 takes precedence
• CPC Class Codes: F28F 1/128 Fins with openings, e.g. louvered fins
• CPC Class Codes: F28F 13/187 especially adapted for evaporator surfaces or condenser surfaces, e.g. with nucleation sites
• CPC Class Codes: F28F 17/005 Means for draining condensates from heat exchangers, e.g. from evaporators F28B9/08 takes precedence
• CPC Class Codes: H10N 10/13 characterised by the heat-exchanging means at the junction
• CPC Class Codes: Y10S 165/517 Roughened surface
• CPC Class Codes: Y10S 165/911 Vaporization

Abstract

A thermoelectric heat transfer system having a thermoelectric device and a heat exchanger with an evaporating surface and a condensing surface. A working fluid is sealed within the heat exchanger. The thermoelectric device includes a thermally conductive hot plate and a thermally conductive cold plate with thermoelectric elements disposed therebetween and the thermoelectric elements are electrically coupled in series and thermally coupled in parallel. The evaporating surface of the heat exchanger is thermally coupled with the hot plate. A fluid flow path to allow working fluid in its vapor phase to flow from the evaporating surface to the condensing surface and working fluid in its liquid phase to flow from the condensing surface to the evaporating surface.

Claims

1. A thermoelectric device and heat exchanger comprising:

a plurality of thermoelectric elements for transferring thermal energy;

first and second thermally conductive plates having the thermoelectric element disposed therebetween;

a working fluid contained within the heat exchanger;

the heat exchanger having a first, sealed chamber with a first surface for evaporating the working fluid and a second, sealed chamber with a second surface for condensing the working fluid located remote from the first, evaporating surface;

the second, sealed chamber having a plurality of hollow tubes with an enhanced heat transfer surface formed on the interior of each hollow tube;

each hollow tube coupled with a manifold to form a portion of the second, sealed chamber;

a plurality of convection cooling fin disposed on the exterior of the hollow tubes whereby the fins transfer heat from the hollow tubes to an environment surrounding the second, sealed chamber;

the first, evaporating surface comprising an enhanced heat transfer surface to promote boiling of the working fluid on the first evaporating surface; and

the first surface of the heat exchanger thermally coupled with the first conductive plate of the thermoelectric device.

2. The thermoelectric device and heat exchanger of claim 1 wherein the heat exchanger further composes:

first, sealed chamber and the second, sealed chamber with a fluid flow path disposed between the first chamber and the second chamber;

the first, evaporating surface forming a part of the first chamber and the second, condensing surface formed as a part of the second chamber;

the first conductive plate of the thermoelectric device attached to the first, evaporating surface on the exterior of the first chamber; and

the fluid flow path communicating working fluid between the first chamber and the second chamber in response to heat transferred from the thermoelectric device through the first, evaporating surface to the first chamber.

3. The thermoelectric device and heat exchanger of claim 1 wherein the first, evaporating surface further comprises an enhanced heat transfer surface having a porous metal coating with a thickness of 0.2 to 2.0 mm and a void fraction of 40% to 70% with the thermoelectric device coupled to the first, evaporating surface opposite from the enhanced heat transfer surface.

4. The thermoelectric device and heat exchanger of claim 1 wherein the first, evaporating surface further comprises:

an enhanced heat transfer surface having a plurality of fins with each fin having a height in the range of approximately 0.030 to 0.050 inches and spacing of adjacent fins in the range of approximately 30 to 60 fins per inch; and

each fin having a tip and the tips of the fins bent to form a plurality of fluid reentry cavities with an opening in the range of 0.001 to 0.005 inches between the tip of one fin and the side of an adjacent fin.

5. The thermoelectric device and heat exchanger of claim 1 wherein the enhanced heat transfer surface of the second, sealed chamber further comprises a plurality of alternating tips and flutes to improve the thermal efficiency of the second surface.

6. The thermoelectric device and heat exchanger of claim 1 further comprising

an enhanced heat transfer surface formed as part of the convection cooling fins to improve the thermal efficiency of the adjacent condensing surface.

7. The thermoelectric device and heat exchanger of claim 1 further comprising the heat exchanger formed in part from material selected from the group consisting of aluminum, aluminum alloys, ceramics, cermets, composites, and copper alloys.

8. The thermoelectric device and heat exchanger of claim 1 further comprising the heat exchanger formed in part from copper.

9. The thermoelectric device and heat exchanger of claim 1 further comprising:

a heat sink thermally coupled with the second conductive plate of the thermoelectric device;

the heat sink having a surface area substantially larger than the surface area of the second conductive plate; and

the heat sink spaced a selected distance from the first, evaporating surface with the thermoelectric device disposed therebetween.

10. The thermoelectric device and heat exchanger of claim 1 wherein the working fluid comprises water.

11. The thermoelectric device and heat exchanger of claim 1 wherein the working fluid comprises an alcohol.

12. The thermoelectric device and heat exchanger of claim 1 wherein the working fluid comprises methanol.

13. The thermoelectric device and heat exchanger of claim 1 wherein the working fluid comprises a refrigerant selected from the group consisting of ammonia, ethyl chloride, methyl chloride, sulphur dioxide, fluorocarbons, hydrocarbons, halogenated hydrocarbons and hydrofluorocarbon (HFC) compounds.

14. The thermoelectric device and heat exchanger of claim 1 wherein the working fluid comprises a non-CFC refrigerant.

15. The thermoelectric device and heat exchanger of claim 1 further comprising a port for adding and removing the working fluid from the heat exchanger.

16. The thermoelectric device and heat exchanger of claim 1, further comprising at least one pressure relief device to release a portion of the working fluid from the heat exchanger if the pressure of the working fluid exceeds a preselected value in response to heat transferred from the thermoelectric device.

17. A thermoelectric heat transfer system comprising:

a thermoelectric device having a hot plate and a cold plate with a plurality of thermoelectric elements disposed therebetween;

the thermoelectric elements electrically coupled in series with each other and thermally coupled in parallel with respect to the hot plate and the cold plate;

an electrical circuit providing electrical power to the thermoelectric elements to transfer heat energy between the hot plate and the cold plate depending upon the direction of electrical current flow through the thermoelectric elements;

a heat load thermally coupled with the cold plate;

a heat exchanger containing a working fluid;

the heat exchanger having a first, sealed chamber with a first surface for evaporating the working fluid and a second, sealed chamber with a second surface for condensing the working fluid located remote from the first, evaporating surface;

the second, sealed chamber having a plurality of hollow tubes with an enhanced heat transfer surface formed on the interior of each hollow tube;

each hollow tube coupled with a manifold to form a portion of the second, sealed chamber;

a plurality of convection cooling fins disposed on the exterior of the hollow tubes whereby the fins transfer heat from the hollow tubes to an environment surrounding the second, sealed chamber;

the first, evaporating surface comprising an enhanced heat transfer surface to promote boiling of the working fluid on the first, evaporating surface; and

the first surface of the heat exchanger thermally coupled with the hot plate of the thermoelectric device to allow heat transfer from the thermoelectric device through the enhanced heat transfer surface of the first, evaporating surface to the working fluid.

18. The thermoelectric heat transfer system of claim 17 wherein the heat load comprises an electronic circuit.

19. The thermoelectric heat transfer system of claim 17 wherein the heat load comprises a microprocessor for a computer.

20. The thermoelectric heat transfer system of claim 17 wherein the heat load comprises a heat sink thermally coupled with the cold plate, the heat sink disposed within an enclosed structure and the thermoelectric device coupled with the heat sink opposite from the enclosed structure.

21. The thermoelectric heat transfer system of claim 20 wherein the enclosed structure is selected from the group consisting of a thermoelectric refrigerator, a portable personal cooler, or an organ transport container.

22. The thermoelectric heat transfer system of claim 17 wherein the heat exchanger further comprises:

the first sealed chamber and the second sealed chamber having a fluid flow path disposed between the first sealed chamber and the second sealed chamber;

the first evaporating surface forming a part of the first sealed chamber and the second, condensing surface forming a part of the second sealed chamber;

the hot plate of the thermoelectric device coupled with the first evaporating surface to transfer heat from the thermoelectric device to the working fluid through the first evaporating surface; and

the fluid flow path communicating working fluid between the first sealed chamber and the second sealed chamber.

23. The thermoelectric heat transfer system of claim 17 wherein the heat exchanger further comprises:

the first sealed chamber and the second sealed chamber having a fluid flow path disposed between the first sealed chamber and the second chamber; and

the fluid flow path providing a communication path to allow evaporated working fluid to flow from the first sealed chamber to the second sealed chamber and condensed working fluid to flow from the second sealed chamber to the first sealed chamber.

24. The thermoelectric heat transfer system of claim 17 further comprising:

the first sealed chamber and the second sealed chamber having a fluid flow path for communicating working fluid between the first sealed chamber and the second sealed chamber; and

the fluid flow path formed from flexible material to allow adjusting the location of the second sealed chamber with respect to the first sealed chamber.

25. The thermoelectric heat transfer system of claim 21 wherein the second condensing surface of the heat exchanger further comprises a plurality of generally hollow U-shaped tubes with an enhanced heat transfer surface formed on the interior of each hollow U-shaped tube.

26. The thermoelectric heat transfer system of claim 17 wherein the second, condensing surface further comprises a plurality of alternating tips and associated flutes to form the enhanced heat transfer surface to improve the thermal efficiency of the condensing surface.

27. The thermoelectric heat transfer system of claim 17 further comprising:

a plurality of fins formed as part of the convection cooler; and

a plurality of slots formed in each fin and a projection extending from each fin at an acute angle relative to the direction of an air flow through the convection cooler whereby the projection and slots cooperate with each other to provide an enhanced heat transfer surface to improve the thermal efficiency of the adjacent condensing surface.

28. A method for increasing the heat transfer efficiency of a thermoelectric device having a plurality of thermoelectric elements disposed between a first thermally conductive plate and a second thermally conductive plate with the thermoelectric elements electrically coupled in series with respect to each other and thermally coupled in parallel with respect to the thermally conductive plates, comprising the steps of:

forming a heat exchanger having a first, sealed chamber and a second, sealed chamber;

forming a fluid flow path between the first chamber and the second chamber;

forming a first evaporating surface having an enhanced heat transfer surface as a part of the first chamber;

forming the second chamber from a plurality of hollow tubes with an enhanced heat transfer surface disposed on the interior of each hollow tube;

coupling each hollow tube with a manifold to form a portion of the second, sealed chamber;

attaching a plurality of convection cooling fins to the exterior of the hollow tubes whereby the fins transfer heat from the hollow tubes to the environment surrounding the second, sealed chamber;

placing a working fluid within the heat exchanger and sealing the heat exchanger to prevent undesired escape of the working fluid;

thermally coupling the first evaporating surface with the first thermally conductive plate to allow heat transfer from the thermoelectric device to the enhanced heat transfer surface of the first, evaporating surface;

providing electrical power to the thermoelectric elements to transfer heat energy from the second thermally conductive plate to the first thermally conductive plate;

transferring heat energy from the first thermally conductive plate to the first evaporating surface to evaporate the working fluid;

communicating the evaporated working fluid from the first chamber to the second chamber through the fluid flow path;

condensing the evaporated working fluid on the second condensing surface in the second chamber; and

returning the condensed working fluid to the first chamber through the fluid flow path.

29. The method of claim 28 further comprising the steps of forming an enhanced heat transfer surface on the first evaporating surface by placing a porous metal coating on the first evaporating surface with a thickness of 0.2 to 2.0 millimeters and a void fraction of 40% to 70% to enhance heat transfer from the thermoelectric device to the enhanced heat transfer surface.

30. The method of claim 28 further comprising the steps of:

fabricating an enhanced heat transfer surface on the first evaporating surface by forming the first evaporating surface from a selected metal alloy;

forming a plurality of fins extending from the first evaporating surface with each fin having a tip at a height in the range of approximately 0.030 to 0.050 inches and spacing the fins in the range of approximately 30 to 60 fins per inch on the first evaporating surface; and

bending the tips of the fins to form a plurality of fluid cavities with openings in the range of approximately 0.001 to 0.005 inches between the tip of one fin and the side of an adjacent fin.

31. The method of claim 28 further comprising the steps of forming a plurality of alternating tips and flutes as part of the second, condensing surface to provide the enhanced heat transfer surface to improve the thermal efficiency of the condensing surface.

32. The method of claim 28 further comprising the steps of:

forming a plurality of alternating tips and flutes as part of the second condensing surface; and

selecting the height of each tip and the width between adjacent tips to allow surface tension of working fluid condensed on the respective tips to drain the condensed working fluid into the associated flute whereby a portion of each tip remains exposed to evaporated working fluid without forming a boundary layer of liquid on the respective portion of the tip.