Systems and methods for thermal management through use of ammonium carbamate

• US 9,863,725 B1
• Filed: 02/27/2013
• Issued: 01/09/2018
• Est. Priority Date: 02/29/2012
• Status: Active Grant

• Current Assignee: US Department of The Air Force (U.S. Department Of Defense)
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Dudis, Douglas S., Schmidt, Joel E., Miller, Douglas J.
• Primary Examiner(s): Rivera, Carlos A
• Assistant Examiner(s): Diaz, Marcos O
• Application Number:
  US13/778,675
• Time in Patent Office: 1,777 Days
• Field of Search: 502 56, 422109, 165 10, 16510412, 16510432, 16510417
• CPC Class Codes: A47J 36/28 Warming devices generating the heat by exothermic reactions, e.g. heat released by the contact of unslaked lime with water
• CPC Class Codes: B65D 81/3484 Packages having self-contained heating means, e.g. heating generated by the reaction of two chemicals warming devices A47J36/24
• CPC Class Codes: F25J 2205/24 using regenerators, cold accumulators or reversible heat exchangers
• CPC Class Codes: F28D 1/0472 the conduits being helically or spirally coiled
• CPC Class Codes: F28D 15/00 Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies F28D17/00, F28D19/00, F28D20/00 take precedence
• CPC Class Codes: F28D 20/003 using thermochemical reactions
• CPC Class Codes: F28D 20/0034 using liquid heat storage material
• CPC Class Codes: F28D 20/0056 using solid heat storage material F28D20/0052 takes precedence
• CPC Class Codes: F28D 20/02 using latent heat
• CPC Class Codes: F28D 2021/0022 for chemical reactors
• CPC Class Codes: F28D 5/02 in which the evaporating medium flows in a continuous film or trickles freely over the conduits
• CPC Class Codes: F28F 23/00 Features relating to the use of intermediate heat-exchange materials, e.g. selection of compositions heat-transfer, heat-exchange or heat-storage materials C09K5/00
• CPC Class Codes: F28F 27/00 Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus control arrangements in general G05
• CPC Class Codes: Y02E 60/14 Thermal energy storage

Abstract

Ammonium carbamate-based methods and systems for management of thermal loads, particularly low-quality, high-flux thermal loads. The increase in temperature in heat sensitive devices is mitigated by the endothermic decomposition of ammonium carbamate into carbon dioxide and ammonia gases. This process has an energy density an order of magnitude greater than conventional thermal management materials and is particularly useful for temperatures between 20° C. and 100° C. Systems incorporating ammonium carbamate may be controlled by regulating the fluid flow, overhead pressure, temperature, or combinations thereof.

Claims

1. An ammonium carbamate-based thermal management system comprising:

a flow controller comprising a control unit, a coolant fluid for absorbing heat from a thermal load, a coolant fluid circulation pump, a flow valve, and at least one temperature sensor, wherein the coolant fluid circulation pump is fluidly coupled to the thermal load, and wherein the flow controller is configured to regulate a flow of the coolant fluid from the thermal load;

a primary heat exchanger coupled to the flow controller, wherein the primary heat exchanger comprises ammonium carbamate and a non-aqueous heat transfer fluid that is non-reactive with the ammonium carbamate, wherein the primary heat exchanger is configured to transfer heat from the coolant fluid to the heat transfer fluid and the ammonium carbamate, and wherein the ammonium carbamate endothermically decomposes into ammonia gas and carbon dioxide gas upon the transfer of heat from the coolant fluid;

a vacuum source coupled to the primary heat exchanger, wherein the vacuum source is configured to provide the primary heat exchanger with a pressure lower than atmospheric pressure; and

a pressure controller coupled to the primary heat exchanger and to the vacuum source, wherein the pressure controller is configured to maintain pressures lower than atmospheric pressure in the primary heat exchanger to remove the ammonia gas and the carbon dioxide gas from the primary heat exchanger, thereby regulating an overhead pressure within the ammonium carbamate-based thermal management system.

2. The ammonium carbamate-based thermal management system of claim 1 wherein the vacuum source comprises a vacuum pump and a valve.

3. The ammonium carbamate-based thermal management system of claim 1 further comprising at least one heating element between the primary heat exchanger and the vacuum source, wherein the heating element is configured to prevent the ammonia gas and the carbon dioxide gas from combining to reform ammonium carbamate prior to removal from the ammonium carbamate-based thermal management system.

4. The ammonium carbamate-based thermal management system of claim 1 further comprising a storage chamber.

5. The ammonium carbamate-based thermal management system of claim 4 wherein the storage chamber further comprises a reservoir liquid in which at least one of the ammonia gas and the carbon dioxide gas are soluble.

6. The ammonium carbamate-based thermal management system of claim 1 further comprising a redirection component, wherein the redirection component is configured to direct the ammonia gas or the carbon dioxide gas from the vacuum source to at least one secondary application.

7. The ammonium carbamate-based thermal management system of claim 1 further comprising a secondary heat exchanger coupled to the vacuum source, wherein the secondary heat exchanger is configured to exothermically combine the ammonia gas and the carbon dioxide gas to form regenerated ammonium carbamate, and wherein the regenerated ammonium carbamate is transferred back into the primary heat exchanger.

8. The ammonium carbamate-based thermal management system of claim 1 wherein the primary heat exchanger further comprises a circulation mechanism.

9. The ammonium carbamate-based thermal management system of claim 1, wherein the heat transfer fluid comprises a non-solvent heat transfer fluid, whereby the ammonium carbamate forms a suspension in the non-solvent heat transfer fluid.

10. The ammonium carbamate-based thermal management system of claim 1, wherein the heat transfer fluid comprises a heat transfer solvent, whereby the ammonium carbamate forms a solution in the heat transfer solvent.

11. The ammonium carbamate-based thermal management system of claim 1, wherein the primary heat exchanger comprises a plurality of coils configured such that the coolant fluid flows through the plurality of coils, and wherein an exterior surface of the plurality of coils is in contact with the heat transfer fluid.

12. The ammonium carbamate-based thermal management system of claim 1, wherein the primary heat exchanger comprises a plurality of thermally conductive structures configured such that heat from the coolant fluid is transferred to the thermally conductive structures, and wherein an exterior surface of the thermally conductive structures is in contact with the heat transfer fluid.

13. The ammonium carbamate-based thermal management system of claim 1, wherein the thermal load is selected from the group consisting of an electronic component, an avionic system, an antenna, a laser, a battery, and a fuel cell.

14. An ammonium carbamate-based thermal management system comprising:

a thermal load selected from the group consisting of an electronic component, an avionic system, an antenna, a laser, a battery, and a fuel cell;

an ammonium carbamate-based heat exchanger comprising ammonium carbamate and a non-aqueous heat transfer fluid, wherein heat absorbed into the heat transfer fluid causes an endothermic decomposition of ammonium carbamate into ammonia gas and carbon dioxide gas;

a circulation loop comprising a coolant fluid and a coolant fluid circulation pump, wherein the circulation loop is fluidly coupled to the thermal load and the ammonium carbamate-based heat exchanger, and wherein the coolant fluid absorbs heat away from the thermal load and transfers heat to the ammonium carbamate-based heat exchanger; and

a control system comprising

a pressure controller coupled to the ammonium carbamate-based heat exchanger, wherein the pressure controller regulates pressure within the ammonium carbamate-based heat exchanger at a level less than atmospheric pressure, and facilitates transfer of the ammonia gas and carbon dioxide gas formed by the endothermic decomposition of ammonium carbamate out of the ammonium carbamate-based heat exchanger;

a flow valve in the circulation loop to regulate a flow of the coolant fluid; and

at least one temperature sensor for sensing a temperature of the coolant fluid, wherein the control system is configured to control a rate of the endothermic decomposition of ammonium carbamate by controlling operation of the pressure controller, the flow valve, and/or the coolant fluid circulation pump.