Cooling system for high density heat load

1. A cooling system for transferring heat from a heat load, the cooling system comprising:

a two-phase working fluid;

a pump configured to increase the pressure of the working fluid without substantially increasing the enthalpy of the working fluid;

an air-to-fluid heat exchanger in fluid communication with the pump and in thermal communication with the heat load;

a fluid-to-fluid heat exchanger having a first fluid path in fluid communication with the air-to-fluid heat exchanger and the pump, and a second fluid path, the first and second fluid paths being in thermal communication with one another;

a second heat transfer system in fluid communication with the second fluid path and comprising:

a second portion of the fluid-to-fluid heat exchanger;

a single phase working fluid; and

a pump;

wherein the air-to-fluid heat exchanger is configured so that heat from air passing through the air-to-fluid heat exchanger causes at least a portion of the two-phase working fluid to change phase from a liquid to a gas within the air-to-fluid heat exchanger; and

a controller configured to prevent condensation on the air-to-fluid heat exchanger by controlling the amount of heat transferred to the second fluid path so that a temperature of the two-phase working fluid within the air-to-fluid heat exchanger is above a dew point temperature of the air passing through the air-to-fluid heat exchanger.

2. The cooling system of claim 1 , further comprising a flow regulator positioned between the pump and the air-to-fluid heat exchanger in fluid communication with the first fluid path.

3. The cooling system of claim 1 , further comprising a working fluid receiver in fluid communication between the fluid-to-fluid heat exchanger and the pump.

4. The cooling system of claim 1 , further comprising a working fluid flow regulating valve in fluid communication between the pump and the air-to-fluid heat exchanger and a working fluid receiver in fluid communication between the fluid-to-fluid heat exchanger and the pump.

5. A cooling system for transferring heat from a heat load to an environment, the cooling system comprising:

a first cooling cycle containing a two-phase working fluid; and

a second cooling cycle thermally connected to the first cooling cycle;

wherein the first cooling cycle comprises:

a pump configured to increase the pressure of the working fluid without substantially increasing the enthalpy of the working fluid;

an air-to-fluid heat exchanger in fluid communication with the pump and in thermal communication with the heat load;

a second heat exchanger having a first fluid path for the working fluid in fluid communication with the air-to-fluid heat exchanger and the pump, and a second fluid path comprising a portion of the second cooling cycle;

wherein the first and second fluid paths are in thermal communication with one another;

wherein the first cooling cycle is configured so that air heated by the heat load and flowing through the air-to-fluid heat exchanger causes the two-phase working fluid to at least partially change phase from a liquid to a gas within the air-to-fluid heat exchanger; and

wherein the second cooling cycle comprises a chilled water system in thermal communication with the environment and wherein the second cooling cycle is configured to maintain a temperature of the two-phase working fluid entering the air-to-fluid heat exchanger above a dew point of the air flowing through the air-to-fluid heat exchanger.

6. The cooling system of claim 5 , further comprising a working fluid receiver in the first cooling cycle between the second heat exchanger and the pump.

7. The cooling system of claim 5 , further comprising a working fluid flow regulating valve in fluid communication between the pump and the air-to-fluid heat exchanger and a working fluid receiver in fluid communication between the second heat exchanger and the pump.

8. A cooling system for transferring heat from a heat load to an environment, the cooling system comprising:

a working fluid pump configured to increase the pressure of a two-phase working fluid without substantially increasing the enthalpy of the working fluid;

an air-to-fluid heat exchanger connected to the pump and having a fluid path in thermal communication with the heat load;

a second heat exchanger having first and second fluid paths in thermal communication with one another, wherein the first fluid path is configured to provide fluid communication from the air-to-fluid heat exchanger to the pump, and wherein the second fluid path is adapted to thermally connect the air-to-fluid heat exchanger in the first fluid path to a chilled water cooling system that is in thermal communication with the environment;

wherein the air-to-fluid heat exchanger is configured so that air flowing along the fluid path heats the working fluid and causes the working fluid to at least partially change phase from a liquid to a gas within the air-to-fluid heat exchanger; and

a controller configured to maintain a temperature of the working fluid at a location fluidly between the second heat exchanger and the air-to-fluid heat exchanger above a dew point temperature of air passing through the air-to-fluid heat exchanger so that the cooling system removes only sensible heat from the air passing there through to prevent condensation on the air-to-fluid heat exchanger.

9. The cooling system of claim 8 , further comprising a working fluid receiver in fluid communication between the second heat exchanger and the pump.

10. The cooling system of claim 8 , further comprising a working fluid flow regulating valve in fluid communication between the pump and the air-to-fluid heat exchanger and a working fluid receiver in fluid communication between the second heat exchanger and the pump.

11. A heat transfer system, comprising:

a first heat transfer subsystem adapted to circulate there through a first working fluid selected from the group consisting of chlorofluorocarbons, hydrofluorocarbons and hydrochlorofluorocarbons, and comprising

an air-to-fluid heat exchanger disposed in a fluid path configured to be in thermal communication with a heat load;

a pump configured to increase the pressure of the first working fluid without substantially increasing the enthalpy of the first working fluid; and

at least a portion of a second heat exchanger;

a second heat transfer subsystem comprising

at least a second portion of the second heat exchanger; and

a third heat exchanger;

wherein the second heat transfer subsystem is adapted to circulate a second working fluid there through, wherein the second working fluid is selected from the group consisting of water, water-ethylene glycol and water-propylene glycol; and

wherein the first heat transfer subsystem is adapted to cause at least a portion of the first working fluid to undergo a phase change from a liquid to a gas in the air-to-fluid heat exchanger; and

a system controller configured to prevent condensation on the air-to-fluid heat exchanger by maintaining a temperature of the first working fluid leaving the second heat exchanger above a dew point temperature of air that passes through the air-to-fluid heat exchanger.

12. The system of claim 11 , wherein the heat load is a room.

13. The system of claim 11 , wherein the heat load is an electronics cabinet.

14. The system of claim 11 , further comprising a flow regulator associated with the plurality of the air-to-fluid heat exchanger and which is adapted to control an amount of first working fluid flowing through the air-to-fluid heat exchanger.

15. The system of claim 14 , wherein the flow regulator is adapted to control the amount of first working fluid flowing through the air-to-fluid heat exchanger independently of fluid pressure.

16. The system of claim 14 , wherein the flow regulator is adapted to maintain a substantially constant flow of first working fluid through the air-to-fluid heat exchanger.

17. The system of claim 14 , further comprising a receiver in fluid communication with the first heat transfer subsystem and adapted to accumulate a portion of the first working fluid.

18. The system of claim 17 , wherein the receiver is adapted to accumulate a portion of the first working fluid based upon temperature and/or heat load.

19. The system of claim 14 , wherein the first heat transfer subsystem comprises a plurality of air-to-fluid heat exchangers, and further comprising a flow regulator associated with each of the plurality of air-to-fluid heat exchangers, wherein each flow regulator is adapted to limit an amount of first working fluid flowing through an associated one of the plurality of air-to-fluid heat exchangers.

20. The system of claim 11 , wherein the second heat exchanger is selected from the group consisting of: a tube-in-tube heat exchanger, a shell and tube heat exchanger and a plate and frame heat exchanger.

21. The cooling system of claim 11 , further comprising a working fluid receiver in the first heat transfer subsystem between the second heat exchanger and the pump.

22. The cooling system of claim 11 , further comprising a working fluid flow regulating valve in fluid communication between the pump and the air-to-fluid heat exchanger and a working fluid receiver in fluid communication between the second heat exchanger and the pump.

23. A cooling system for removing heat from a high density heat load, comprising:

a first heat transfer system comprising

a two-phase working fluid;

a plurality of air-to-fluid heat exchangers configured to transfer heat from the heat load to the working fluid so that at least a portion of the working fluid changes phase from a liquid to a gas within at least one of the air-to-fluid heat exchangers;

a working fluid flow regulator fluidly coupled with at least one of the plurality of air-to-fluid heat exchangers and configured to limit the maximum working fluid flow to the at least one air-to-fluid heat exchanger;

a working fluid receiver configured to hold working fluid based on at least one of working fluid temperature, cooling system load and a combination thereof;

a pump configured to increase the pressure of the working fluid without substantially increasing the enthalpy of the working fluid; and

a first portion of a fluid-to-fluid heat exchanger;

wherein the pump is in fluid communication with the working fluid receiver, the first portion of the fluid-to-fluid heat exchanger, and the plurality of air-to-fluid heat exchangers;

a second heat transfer system comprising

a second portion of the fluid-to-fluid heat exchanger;

a single-phase working fluid; and

a second pump;

wherein the second pump is in fluid communication with the second portion of the fluid-to-fluid heat exchanger;

wherein the first heat transfer system is thermally coupled to the second heat transfer system by the fluid-to-fluid heat exchanger; and

a cooling system controller configured to monitor a dew point temperature of air flowing through the air-to-fluid heat exchanger, maintain a temperature of the two phase working fluid entering one or more of the plurality of air-to-fluid heat exchangers above the dew point temperature, and prevent condensation on the plurality of air-to-fluid heat exchangers.

24. The system of claim 23 , wherein the air-to-fluid heat exchangers are located at least partially within an enclosure and the high density heat load is created by electronics within the enclosure, the enclosure having a forced air flow path across the electronics and through one or more of the air-to-fluid heat exchangers.

25. The system of claim 24 , wherein first heat transfer system is configured so that the two-phase working fluid is cooled in the fluid-to-fluid heat exchanger upstream from the receiver and pump, then flows from the pump through the regulating valves and then into each air-to-fluid heat exchanger where at least a portion of the working fluid is heated to a boil, and then returns to the fluid-to-fluid heat exchanger where it is once again cooled.

26. The system of claim 23 , wherein the single-phase working fluid is selected from the group consisting of: water, water-ethylene glycol, and water-propylene glycol.

27. The system of claim 23 , further comprising a working fluid flow regulator associated with each air-to-fluid heat exchanger and configured to limit a maximum working fluid flow to its associated air-to-fluid heat exchanger.