Method for thermal management through use of ammonium carbamate

• US 9,677,817 B1
• Filed: 02/27/2013
• Issued: 06/13/2017
• 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): Berhanu, Etsub
• Assistant Examiner(s): Class-Quinones, Jose O
• Application Number:
  US13/778,685
• Time in Patent Office: 1,567 Days
• Field of Search: 16510412, 16510417, 16510418, 165138, 62 4, 622592, 422198
• 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. A method for managing thermal loads comprising the steps of:

providing an ammonium carbamate-based thermal management system comprising a flow controller, a primary heat exchanger coupled to the flow controller, a vacuum source coupled to the primary heat exchanger, and a pressure controller coupled to the primary heat exchanger and the vacuum source, wherein the primary heat exchanger comprises ammonium carbamate;

applying heat from a thermal load to the ammonium carbamate-based thermal management system, wherein heat from the thermal load is absorbed into a coolant fluid to provide a heated coolant fluid, wherein the heated coolant fluid is introduced into the primary heat exchanger using the flow controller, and wherein the thermal load is within a temperature range greater than or equal to about 20°

C. and less than or equal to about 100°

C.;

transferring heat from the heated coolant fluid to the ammonium carbamate, wherein the ammonium carbamate endothermically decomposes into ammonia gas and carbon dioxide gas;

adjusting an overhead pressure of the primary heat exchanger, a system temperature of the primary heat exchanger, or a coolant fluid flow rate to achieve a desired amount of heat transfer from the thermal load to the ammonium carbamate; and

removing the ammonia gas and the carbon dioxide gas from the ammonium carbamate-based thermal management system using the vacuum source, the vacuum source being controlled by the pressure controller.

2. The method of claim 1 wherein the vacuum source comprises a vacuum pump.

3. The method of claim 1 wherein the vacuum source comprises a pressure differential between an overhead pressure inside the ammonium carbamate-based thermal management system and an exterior atmospheric pressure.

4. The method of claim 1 wherein the primary heat exchanger further comprises a heat transfer fluid and a circulation mechanism.

5. The method of claim 4 wherein the heat transfer fluid further comprises a non-solvent heat transfer fluid, the ammonium carbamate forming a suspension in the non-solvent heat transfer fluid.

6. The method of claim 4 wherein the heat transfer fluid further comprises a heat transfer solvent, the ammonium carbamate forming a solution in the heat transfer solvent.

7. The method of claim 6 wherein transferring heat from the coolant fluid further comprises absorbing at least a portion of the thermal load into the heat transfer solvent.

8. The method of claim 1 wherein removing the ammonia gas and the carbon dioxide gas further comprises venting the ammonia gas and the carbon dioxide gas to a storage chamber.

9. The method of claim 8 wherein the storage chamber comprises at least one reservoir liquid in which at least one of the ammonia gas and the carbon dioxide gas are soluble.

10. The method of claim 1 further comprising providing at least one heating element, 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.

11. The method of claim 1 further comprising redirecting at least one of the ammonia gas and the carbon dioxide gas from the vacuum source to at least one secondary application.

12. The method of claim 1 further comprising:

directing the ammonia gas and the carbon dioxide gas into a secondary heat exchanger;

exothermically combining the ammonia gas and the carbon dioxide gas to form regenerated ammonium carbamate; and

transferring the regenerated ammonium carbamate back into the primary heat exchanger.

13. The method 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. A method for managing heat transfer of a thermal load, comprising:

providing an ammonium carbamate-based thermal management system comprising

an ammonium carbamate-based heat exchanger comprising ammonium carbamate and a 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, 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, or the flow valve;

absorbing heat generated at the thermal load into the coolant fluid, 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, and wherein a thermal load temperature is within a temperature range greater than or equal to about 20°

C. and less than or equal to about 100°

C.;

transferring heat from the heated coolant fluid to the ammonium carbamate, wherein the ammonium carbamate endothermically decomposes into ammonia gas and carbon dioxide gas;

adjusting an overhead pressure of the ammonium carbamate-based heat exchanger, a system temperature of the ammonium carbamate-based heat exchanger, or a coolant fluid flow rate to achieve a desired amount of heat transfer from the thermal load to the ammonium carbamate; and

removing the ammonia gas and the carbon dioxide gas from the ammonium carbamate-based thermal management system using a vacuum source, the vacuum source being controlled by the pressure controller.

15. The method of claim 14, wherein removing the ammonia gas and the carbon dioxide gas further comprises venting the ammonia gas and the carbon dioxide gas to a storage chamber.

16. The method of claim 15, wherein the storage chamber comprises at least one reservoir liquid in which at least one of the ammonia gas and the carbon dioxide gas are soluble.

17. The method of claim 14, further comprising providing at least one heating element, 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.

18. The method of claim 14, further comprising redirecting the ammonia gas or the carbon dioxide gas from the vacuum source to at least one secondary application.

19. The method of claim 14, further comprising:

directing the ammonia gas and the carbon dioxide gas into a secondary heat exchanger;

exothermically combining the ammonia gas and the carbon dioxide gas to form regenerated ammonium carbamate; and

transferring the regenerated ammonium carbamate back into the ammonium carbamate-based heat exchanger.