Thermoelectric refrigerator with evaporating/condensing heat exchanger

• US 6,003,319 A
• Filed: 04/10/1998
• Issued: 12/21/1999
• 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): Bennett, Henry
• Assistant Examiner(s): SHULMAN, MARK S
• Application Number:
  US09/058,269
• Time in Patent Office: 620 Days
• Field of Search: 62/3.6, 62/3.7, 62/3.64, 62/430, 165/104.21
• 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 refrigerator with a 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. The thermoelectric elements are preferably 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 is provided 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. The configuration of the heat exchanger will optimize heat transfer by the working fluid from the thermoelectric device.

Claims

1. A thermoelectric refrigerator having a thermoelectric heat transfer system to maintain temperature within an interior portion of the thermoelectric within a selected range, comprising:

a thermoelectric device with a plurality of thermoelectric elements for transferring thermal energy therethrough;

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

the first thermally conductive plate disposed within the interior portion of the thermoelectric refrigerator;

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;

the second condensing surface located remote from the first evaporating surface;

the first evaporating surface of the heat exchanger thermally coupled with the second conductive plate of the thermoelectric device;

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

the fluid flow path communicating the working fluid between the first chamber and the second chamber; and

the working fluid cooperating with the thermoelectric elements to transfer heat energy from the first thermally conductive plate through the thermoelectric elements, the second thermally conductive plate, the first evaporating surface to the second condensing surface of the heat exchanger.

2. The thermoelectric refrigerator of claim 1 wherein the first, sealed chamber further comprises:

a first portion and a second portion;

the first portion having a generally reduced interior volume to minimize the amount of working fluid required to fill the first portion and to maximize contact between the working fluid in its liquid phase and the first evaporating surface;

the second portion coupled to and disposed above the first portion when the thermoelectric heat transfer system is installed at a selected location within the thermoelectric refrigerator; and

the second portion sized larger than the first portion to accommodate collection of the working fluid in its vapor phase.

3. The thermoelectric refrigerator of claim 1 wherein the first evaporating surface further comprises an enhanced heat transfer surface to promote boiling of the working fluid by the first evaporating surface.

4. The thermoelectric refrigerator of claim 1 wherein the second condensing surface further comprises an enhanced heat transfer surface to improve thermal efficiency of the condensing surface.

5. The thermoelectric refrigerator of claim 1 wherein the second condensing surface further comprises an enhanced heat transfer surface having a plurality of alternating tips and flutes to improve thermal efficiency of the condensing surface.

6. The thermoelectric refrigerator of claim 1 further comprising a convection cooler disposed on the exterior of the heat exchanger adjacent to the second condensing surface.

7. The thermoelectric refrigerator of claim 1 further comprising:

a convection cooler disposed on the exterior of the heat exchanger adjacent to the second condensing surface; and

a plurality of fins formed as part of the convection cooler.

8. The thermoelectric refrigerator 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, copper and copper alloys.

9. The thermoelectric refrigerator of claim 1 further comprising:

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

the thermoelectric refrigerator having a storage area from which the heat sink removes thermal energy.

10. The thermoelectric refrigerator of claim 1 wherein the working fluid comprises a hydroflourocarbon generally designated as R134A.

11. The thermoelectric refrigerator of claim 1 wherein the working fluid comprises hydrofluoroether having the general formula C₄ F₉ OCH₃.

12. The thermoelectric refrigerator of claim 1 wherein the working fluid comprises a refrigerant selected from the group consisting of ammonia, methanol, ethyl chloride, methyl chloride, sulphur dioxide, water, alcohol, fluorocarbons, hydrocarbons, halogenated hydrocarbons and hydrofluorocarbon (HFC) compounds.

13. The thermoelectric refrigerator of claim 1 wherein the working fluid comprises a non-CFC refrigerant.

14. The thermoelectric refrigerator of claim 1 further comprising a port for adding and removing the working fluid from the first chamber.

15. The thermoelectric refrigerator of claim 1 wherein the heat load comprises a heat sink thermally coupled with the first conductive plate and the heat sink disposed within the thermoelectric refrigerator.

16. A method for increasing the heat transfer efficiency of a thermoelectric refrigerator having thermoelectric heat transfer system including a thermoelectric device with 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 first and second thermally conductive plates, comprising the steps of:

thermally coupling the first thermally conductive plate with a heat sink;

placing the heat sink within the thermoelectric refrigerator with the second chamber having a plurality of hollow tubes;

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

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

forming a first evaporating surface as a part of the first chamber and forming a second condensing surface as a part of the second 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 second thermally conductive plate;

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

transferring heat energy from the second thermally conductive plate to the first evaporating surface to convert the working fluid from its liquid phase to its vapor phase;

communicating the working fluid in its vapor phase from the first chamber to the second chamber through the fluid flow path;

condensing the working fluid in its vapor phase on the second condensing surface in the second chamber; and

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

17. The method of claim 16 wherein forming the second sealed chamber further comprises the steps of:

forming the plurality of hollow tubes with an enhanced heat transfer surface on the interior of each hollow tube;

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

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.

18. The method of claim 16 further wherein forming the first sealed chamber further comprises the steps of:

forming a first portion of the first sealed chamber with a relatively small fluid volume to increase contact between the working fluid in its liquid phase and the first evaporating surface; and

forming a second portion of the first sealed chamber with a larger fluid volume to accomodate a mixture of working fluid in its liquid phase and vapor phase.

19. A thermoelectric refrigerator defined in part by an enclosed structure having five walls and an opening to an interior of the enclosed structure and a door assembly mounted on the opening for selectively controlling access to the interior of the enclosed structure and a thermoelectric heat transfer system comprising:

a thermoelectric device with first and second thermally conductive flat plates lying in generally parallel planes;

a heat exchanger with a first evaporating section and a second condensing section, the first evaporating section coupled to the second thermally conductive plate;

the second condensing section disposed above and connected to the first evaporating section by a fluid flow path extending therebetween;

the evaporating section further comprising a first portion and a second portion coupled together to form a fluid tight chamber;

the first portion having a reduced fluid volume with respect to the second portion;

the second portion coupled to and disposed above the first portion;

the second portion having a fluid volume sized larger than the first portion to accommodate communication of working fluid in its vapor phase with the fluid flow path; and

a heat sink coupled to the first thermally conductive plate of the thermoelectric device.

20. The thermoelectric refrigerator of claim 19 wherein the thermoelectric heat transfer system further comprises means for circulating air within the interior of the enclosed structure over the heat sink.

21. The thermoelectric refrigerator of claim 20 further comprising:

the thermoelectric device mounted on one wall of the enclosed structure; and

the condensing section of the heat exchanger disposed on the exterior of the enclosed structure above the thermoelectric device.

22. A thermoelectric refrigerator defined in part by an enclosed structure and a thermoelectric heat transfer system for controlling the temperature within the enclosed structure, comprising:

the enclosed structure having three side walls, a top, a bottom and an opening to the interior of the enclosed structure;

a door assembly mounted on the opening for controlling access to the interior of the enclosed structure;

an air plenum disposed on the top of the enclosed structure;

the thermoelectric heat transfer system mounted one of the side walls;

the thermoelectric heat transfer system further comprising a condensing section disposed within the air plenum;

a heat sink disposed within the interior of the enclosed structure;

a first air circulation fan disposed adjacent to the heat sink to circulate air within the interior of the enclosed structure past the heat sink;

the air plenum having an air intake louver and an air exhaust louver;

an air intake fan located inside the air plenum; and

an air diverter to create an airflow path from the air intake louver, through the air intake fan, across the condensing section, and out of the air plenum through the exhaust louver.