Supersonic vapor compression and heat rejection cycle
View Patent ↗Method and apparatus for cooling a fuel cell stack. The cooling system uses vaporization cooling of the fuel stack and supersonic vapor compression of the vaporized coolant to significantly increase the temperature and pressure of the liquid coolant flowing through a heat exchanger. By increasing the heat rejection temperature of the coolant delivered to the heat exchanger, the heat transfer area of the heat exchanger can be reduced and the mass flow rate of coolant can also be reduced. The increased fluid pressure is used to circulate the coolant through the cooling system, thereby eliminating the circulation pump associated with conventional systems.
1. A method of cooling a heat source with a cooling circuit, comprising:
circulating a first liquid stream through the heat source of the cooling circuit, the heat source transferring heat to said first liquid stream, wherein at least a portion of said first liquid stream vaporizes for providing a vapor stream and a second liquid stream at an outlet of the heat source;
circulating said vapor stream and said second liquid stream to a vapor separator that separates said vapor stream from said second liquid stream;
accelerating said separated vapor stream to supersonic velocity with an accelerating unit;
introducing an inlet liquid stream to said supersonic vapor stream, wherein said supersonic vapor stream transfers momentum to said inlet liquid stream for producing an outlet liquid stream;
circulating said outlet liquid stream through a first heat exchanger for transferring heat therefrom, thereby reducing a temperature of said outlet liquid stream; and
circulating said outlet liquid stream to the heat source, wherein the heat source is a fuel cell stack.
2. The method of claim 1 , further comprising:
splitting said outlet liquid stream with a valve into a liquid sub-stream and said inlet liquid stream;
circulating said liquid sub-stream through the heat source; and
circulating said inlet liquid stream for contacting said vapor stream.
3. The method of claim 2 , further comprising mixing said liquid sub-stream with said second liquid stream for providing said first liquid stream prior to circulating said first liquid stream through the heat source.
4. The method of claim 2 , further comprising circulating said inlet liquid stream through a second heat exchanger for reducing the temperature thereof, wherein said second heat exchanger is downstream of said first heat exchanger.
5. The method of claim 1 , wherein said second liquid stream constitutes said inlet liquid stream for momentum transfer thereto.
6. The method of claim 1 , further comprising cooling said inlet liquid stream prior to said momentum transfer.
7. The method of claim 6 , further comprising heating said vapor stream prior to momentum transfer therefrom.
8. The method of claim 6 , wherein said vapor stream is heated by said outlet liquid stream.
9. The method of claim 1 , wherein said accelerating unit comprises a vapor inlet receiving said vapor stream, a liquid inlet receiving said inlet liquid stream at an inlet temperature and pressure, a supersonic vapor nozzle for accelerating said vapor stream to supersonic velocity in response to expansion thereof, an acceleration chamber where said vapor stream transfers momentum to said inlet liquid stream, and an ejector for condensing said vapor stream and ejecting said outlet liquid stream at an outlet temperature and pressure, wherein said outlet temperature and pressure are greater than said inlet temperature and pressure.
10. The method of claim 5 , further comprising circulating said inlet liquid stream through a second heat exchanger to cool said inlet liquid stream prior to said momentum transfer.
11. A method of cooling a heat source with a cooling circuit, comprising:
circulating a first liquid stream to the heat source of the cooling circuit, the heat source transferring heat to said first liquid stream, wherein at least a portion of said first liquid stream vaporizes for providing a vapor stream and a second liquid stream at an outlet of the heat source;
circulating said vapor stream and said second liquid stream to a vapor separator that separates said vapor stream from said second liquid stream;
accelerating said separated vapor stream to supersonic velocity with an accelerating unit;
introducing an inlet liquid stream at an inlet temperature and pressure to said supersonic vapor stream, wherein said supersonic vapor stream transfers momentum to said inlet liquid stream to result in a liquid outlet stream at an outlet temperature and pressure, wherein said outlet temperature and pressure are greater than said inlet temperature and pressure;
circulating said liquid outlet stream directly into and through a first heat exchanger for reducing a temperature of said liquid outlet stream; and
circulating said liquid outlet stream to the heat source, wherein the heat source is a fuel cell stack.
12. The method of claim 11 , further comprising:
splitting said liquid outlet stream into a liquid sub-stream and said inlet liquid stream;
circulating said liquid sub-stream through the heat source; and
circulating said inlet liquid stream for contacting said vapor stream.
13. The method of claim 12 , further comprising mixing said liquid sub-stream with said second liquid stream for providing said first liquid stream prior to circulating said first liquid stream through the heat source.
14. The method of claim 12 , further comprising circulating said inlet liquid stream through a second heat exchanger for reducing the temperature thereof, wherein said second heat exchanger is downstream said first heat exchanger.
15. The method of claim 11 , wherein said second liquid stream constitutes said inlet liquid stream for momentum transfer thereto.
16. The method of claim 11 , further comprising cooling said inlet liquid stream prior to said momentum transfer.
17. The method of claim 16 , further comprising heating said vapor stream prior to momentum transfer therefrom.
18. The method of claim 16 , wherein said vapor stream is heated by said liquid outlet stream.
19. The method of claim 11 , wherein said accelerating unit comprises a vapor inlet receiving said vapor stream, a liquid inlet receiving said inlet liquid stream at said inlet temperature and pressure, a supersonic vapor nozzle for accelerating said vapor stream to supersonic velocity in response to expansion thereof, an acceleration chamber where said vapor stream transfers momentum to said inlet liquid stream, and an ejector for condensing said vapor stream and ejecting said liquid outlet stream at said outlet temperature and pressure.
20. A method of cooling a structure with a cooling circuit, comprising:
circulating a cooling fluid to the structure, wherein the structure transfers heat to said cooling fluid to vaporize said cooling fluid to a stream that is partial vapor and partial liquid;
circulating said partial liquid and partial vapor streams to a vapor separator, wherein said vapor separator separates said partial liquid stream from said partial vapor stream;
circulating said partial liquid stream back to the structure;
circulating said partial vapor stream and an inlet liquid to a nozzle unit, wherein said nozzle unit accelerates and combines said partial vapor stream and said inlet liquid to form an outlet liquid stream;
circulating said outlet liquid stream to at least one heat exchanger, said at least one heat exchanger reducing temperature and pressure of said outlet liquid stream; and
sending a first portion of said outlet liquid stream to the structure for combination with said partial liquid stream and a second portion of said outlet liquid stream to said nozzle unit as said inlet liquid, wherein the structure is a fuel cell stack.