REGENERATIVE PREHEATER FOR PHASE CHANGE COOLING APPLICATIONS

Abstract

A method for cooling an information technology system, comprising: receiving a flow of at least a subcooled liquid phase change refrigerant; cooling the information technology system by sensible heat transfer in an evaporator, to produce at least gaseous refrigerant; and exchanging heat from the at least gaseous refrigerant from the evaporator to the subcooled liquid phase change refrigerant. The phase change refrigerant may be a hydrofluorocarbon ether having a boiling point of 30-65° C. at 1-12 bar.

Claims

1. A manifold for a phase change refrigerant cooling system, comprising: an inlet port configured to receive a flow of phase change refrigerant comprising a liquid phase; an outlet port configured to output a flow of the phase change refrigerant comprising a liquid phase and a gas phase, warmed with respect to the received flow of the phase change refrigerant; a cold conduit configured to distribute the phase change refrigerant comprising the liquid phase from the inlet port to a plurality of cooling loops, each cooling loop warming the phase change refrigerant with at least one evaporator, such that the phase change refrigerant exiting the cooling loop comprises a liquid phase and a gas phase; a hot conduit configured to receive the warmed phase change refrigerant from the plurality of cooling loops, and convey it to the outlet port; a primary heat exchanger, comprising: a liquid phase change refrigerant inlet configured to receive a liquid phase change refrigerant having a first subcool from a pump; a warm phase change refrigerant outlet configured to supply a mixed liquid phase and gas phase refrigerant to a condenser; an inlet port interface configured to supply the flow of the phase change refrigerant comprising the liquid phase having a second subcool to the inlet port, the second subcool being less than the first subcool; and an outlet port interface configured to interface with the outlet port, receive the flow of the phase change refrigerant comprising a liquid phase and a gas phase, wherein the primary heat exchanger transfers heat from the received flow of the phase change refrigerant comprising the liquid phase and the gas phase to the liquid phase change refrigerant having the first subcool, to produce the liquid phase change refrigerant having the second subcool; a plurality of secondary heat exchangers, each respective secondary heat exchanger being configured to transfer heat from the warmed phase change refrigerant from a respective cooling loop to a portion of the phase change refrigerant comprising a liquid phase from the cold conduit, whereby a subcooling of the phase change refrigerant comprising a liquid phase entering the respective cooling loop is reduced with respect to the phase change refrigerant comprising a liquid phase; a controllable bypass valve, configured to control a bypass flow of a portion of the phase change refrigerant from the inlet port to the outlet port, without the bypass flow passing through the cold conduit or the hot conduit; and a control configured to control the controllable bypass valve dependent on a subcool of the cold conduit.

2. A phase change refrigerant cooling system, comprising: an inlet port configured to receive a flow of at least a liquid phase change refrigerant; an outlet port configured to output a flow of heated phase change gaseous refrigerant comprising a liquid phase and a gas phase; a cold conduit configured to distribute the at least liquid phase change refrigerant from the inlet port to at least two successive evaporators in a cooling loop; a hot conduit configured to receive the heated phase change refrigerant comprising the liquid phase and the gas phase from the at least two successive evaporators in the cooling loop; a heat exchanger, configured to transfer heat from the heated phase change refrigerant comprising the liquid phase and the gas phase to the at least liquid phase change refrigerant, whereby a subcooling of the at least liquid phase change refrigerant is reduced; a controllable bypass valve, configured to control a bypass flow of liquid phase change refrigerant from the inlet port mixed with the heated phase change refrigerant from the hot conduit flowing to the outlet port that does not pass through the heat exchanger; and an automated controller, configured to adjust a valve to control an amount of subcool of the cold conduit.

3. A heat exchanger for a phase change refrigerant cooled electronic system, comprising: an inlet port configured to receive a flow of phase change refrigerant having a first subcool below a boiling point of the phase change refrigerant; an outlet port configured to output a flow of heated phase change refrigerant comprising a gas phase; an interface cold port configured to supply the phase change refrigerant having a second subcool below the boiling point of the phase change refrigerant to an evaporator; an interface hot port configured to receive the heated phase change refrigerant comprising a gas phase from the evaporator; a heat exchanger, configured to transfer heat from the heated phase change refrigerant from the evaporator to the liquid phase change refrigerant having the first subcool, to reduce the subcool and transform the liquid phase change refrigerant having the first subcool to the liquid phase change refrigerant having the second subcool; a first valve, configured to control a mixing of a portion of the phase change refrigerant having the first subcool below the boiling point of the phase change refrigerant from the inlet port with the heated phase change refrigerant comprising the gas phase from the evaporator, for efflux through the outlet port as the heated phase change refrigerant comprising the gas phase, the mixed portion of the phase change refrigerant bypassing the heat exchanger; and a controller, configured to adjust a level of the second subcool with a second valve.

4. (canceled)

5. The heat exchanger of claim 3, further comprising a pump configured to pressurize the subcooled phase change refrigerant to transport it up a height gradient from a reservoir to the heat exchanger, wherein a subcooling of the phase change refrigerant is greater at the reservoir than at the heat exchanger.

6. The heat exchanger of claim 3, wherein the controller comprises a control system configured to maintain the phase change refrigerant entering the heat exchanger at a subcooled level.

7. The heat exchanger of claim 3, wherein the second valve is proximate to the evaporator and is configured to control a flow of the phase change refrigerant based on a temperature difference, further comprising a second heat exchanger configured to transfer heat from the heated phase change refrigerant comprising the gas phase from the evaporator, to the phase change refrigerant having the second subcool below the boiling point of the phase change refrigerant.

8-9. (canceled)

10. A method for cooling an information technology system, comprising: receiving a flow of at least a subcooled liquid phase change refrigerant through an inlet port and returning a warmed flow through an outlet port; cooling the information technology system by sensible heat transfer in a plurality of evaporators in series, each respective evaporator being configured to produce a warmed at least gaseous phase change refrigerant from a received portion of the flow of at least subcooled liquid phase change refrigerant; exchanging heat from the warmed at least gaseous phase change refrigerant from the plurality of evaporators in series to the received flow of that at least a subcooled liquid phase change refrigerant with at least one first heat exchanger; controlling a flow of phase change refrigerant that bypasses the at least one first heat exchanger from the inlet port to the outlet port to form a mixture of the warmed at least gaseous phase change refrigerant with the at least the subcooled liquid phase change refrigerant using a controllable bypass valve controlled dependent on a subcool of mixture of the warmed at least gaseous phase change refrigerant with the at least the subcooled liquid phase change refrigerant; and controlling a thermodynamic characteristic of the received flow of the at least a subcooled liquid phase change refrigerant with a second valve.

11. The method of claim 10, wherein the heat is exchanged from the warmed at least gaseous phase change refrigerant from the evaporator to the subcooled phase change refrigerant with the first heat exchanger having a cold plate.

12. The method of claim 10, further comprising normalizing the amount of subcooling to compensate for difference in height.

13. The method of claim 10, further comprising: pumping the subcooled phase change refrigerant up a height gradient from a reservoir to a second heat exchanger, wherein a subcooling of the phase change refrigerant is greater at the reservoir than at the second heat exchanger; heating the pumped subcooled phase change refrigerant with heat from the warmed at least gaseous phase change refrigerant in the second heat exchanger; distributing the heated pumped phase change refrigerant through a cold channel in a manifold to the inlet port; receiving the warmed at least gaseous phase change refrigerant from the outlet port into a warm channel in the manifold; and supplying the collected warmed at least gaseous phase change refrigerant from the warm channel in the manifold to the second heat exchanger.

14. The method of claim 10, wherein said controlling comprises controlling the heat exchanging to maintain the phase change refrigerant at a predetermined subcooled level.

15. (canceled)

16. The method of claim 10, wherein said controlling comprises controlling a flow of the phase change refrigerant with the second valve proximate to the plurality of evaporators in series operated based on a temperature difference.

17. (canceled)

18. The method of claim 10, wherein said controlling comprises controlling the exchanging of heat from the warmed at least gaseous phase change refrigerant from the evaporator to the subcooled phase change refrigerant dependent on a subcool condition of phase change refrigerant entering the evaporator.

19. The method of claim 10, wherein said controlling comprises controlling the exchanging of heat from the warmed at least gaseous refrigerant from the evaporator to the subcooled phase change refrigerant dependent on sensing a cavitation of refrigerant.

20. The method of claim 10, wherein said controlling comprises controlling the exchanging of heat from the warmed at least gaseous refrigerant from the evaporator to the subcooled phase change refrigerant to maintain at least a portion of liquid refrigerant in the at least gaseous refrigerant, wherein a terminal evaporator of the plurality of evaporators in series receives a flow of phase change refrigerant comprising a liquid phase and a gas phase.

21. The method according to claim 10, wherein the information technology system has a plurality of cooling loops, each cooling loop comprising a respective plurality of evaporators in series, the plurality of cooling loops having different heights with respect to a common pump, each cooling loop being fed by a different respective first heat exchanger, further comprising separately controlling a subcool of the received portion of the flow of at least subcooled liquid phase change refrigerant from each respective heat exchanger.

22. The manifold according to claim 1, further comprising a coolant distribution unit comprising the pump, the condenser, and a liquid phase change refrigerant reservoir.

23. (canceled)

24. The manifold according to claim 1, wherein each cooling loop comprises a plurality of evaporators in series, each evaporator being configured to cool a central processing unit of a server in a rack, wherein at least one cooling loop has a different height with respect to the pump.

25. The phase change refrigerant cooling system according to claim 2, further comprising at least one additional heat exchanger, each additional heat exchanger being associated with an additional cold conduit configured to distribute the at least liquid phase change refrigerant from the inlet port to at least two successive evaporators in a respective additional cooling loop, and an additional hot conduit configured to receive the heated phase change refrigerant comprising the liquid phase and the gas phase from the at least two successive evaporators in the additional cooling loop, each additional heat exchanger being configured to transfer heat from the at least two successive evaporators to the at least liquid phase change refrigerant from the inlet port, whereby a subcooling of the at least liquid phase change refrigerant entering the additional cooling loop is reduced.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG. 1 shows a schematic diagram of an embodiment of the present invention.

[0058] FIG. 2 shows a prior art schematic of components of the rack scale cooling system and the relative location of the instrumentation.

[0059] FIG. 3 shows a P-h diagram of Novec 7000 (Extracted from a 3M® datasheet).

[0060] FIG. 4 shows the variation of degree of subcooling in the reservoir and the supply pressure with the reservoir pressure in the embodiment according to FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] As shown in FIG. 1, the system includes three main parts, servers 40. 50, a coolant distribution unit (CDU) 10, and a manifold 36. There could be other configurations of the CDU, e.g., there can be no reservoir, the location of reservoir can be different, the pump can be a gear pump, etc.

[0062] The servers are deployed on a rack. Each server hosts multiple central processing units (CPU), and each CPU is associated with a phase change cooler (evaporator) 44, 46, 54, 56.

[0063] The CDU 10 is deployed at the bottom of the rack (i.e., at the highest gravity-induced pressure) and is responsible for supplying the coolant (e.g., Novec/HFE-7000 or another refrigerant or phase change fluid) to the manifold 36 via a centrifugal pump 16 and transferring the absorbed heat in the secondary loop returned by line 22, and fed with line 20, by the coolant to a chilled water loop 18 from the building (primary loop) through a heat exchanger (HX) 30.

[0064] As shown in FIG. 1 The CDU 10 has a pump 16 (which may also be centrifugal or a gear pump or other type of pump), which draws refrigerant from a reservoir 14, to feed a manifold 36 through line 20. The manifold provides a cold line 24, which distributes liquid refrigerant to the various servers. The hot line 26 returns gaseous refrigerant and often some liquid to the condenser 12, which as a cold water loop 18 for cooling the refrigerant. The cooled refrigerant is accumulated in the reservoir 14. The cold water loop 18 cools the refrigerant to e.g., 30° C., dependent on the operating pressure and phase change refrigerant employed. Ideally, the fluid is cooled to just below the corresponding saturation temperature of the refrigerant in the condenser. Other configurations are of course possible.

[0065] Each server receives a flow of refrigerant from the cold line 24 of the manifold 36 and returns gaseous refrigerant and often some liquid to the hot line 26 of the manifold 36.

[0066] A heat exchanger 32, 34 is provided for each server 40, 50 loop, and optionally a heat exchanger 30 is provided at the entry to the manifold 36. The heat exchanger 32, 34 may be an integral part of the manifold, e.g., specifically designed to facilitate heat transfer from the hot line 26 to the cold line 24.

[0067] The heat exchanger 30, when provided, reduces the subcooling of the refrigerant. Subcooling is the number of degrees below the boiling point a volatile fluid is in. That is, the fluid in the reservoir 14 is below the boiling point of the refrigerant, e.g., Novac 7000, and as delivered to the cold line 24 is below the fluid boiling point. By transferring heat from the hot line 26 to the cold line 24, the cold line 24, the refrigerant entering the server 40, 50 loop is closer to its boiling point. Likewise, the heat exchangers 32, 34 heat the cold refrigerant entering the server loop 40, 50 in line 42, 52, with heat from the evaporators 44, 46, 54, 56 to further reduce the subcooling.

[0068] Therefore, the evaporators, and especially the initial evaporators in the server loop 44, 54, transfer a smaller portion of heat through sensible heat transfer, and a higher portion through latent heat transfer, than a corresponding system, e.g., as shown in FIG. 2, which does not have the heat exchangers. Because the heat exchangers 32, 34 as shown in FIG. 1 are proximate to the evaporators 44, 46, 54, 56, and thus the lines 20 and 22 are cooler and hold a more dense fluid or fluid-gas mixture than if the heat exchangers were displaced from the evaporators, or for example, the CDU 10 run with less subcooling. This arrangement compensates for gravitational and line pressure drop induced changes in subcool degree, and ensures that the feed line 20 entering the manifold is a cool liquid.

[0069] In another embodiment, the heat exchangers 32, 34 are replaced with thermoelectric heat pumps, which, though dissipative, are more controllable and potentially allow thermodynamically unfavorable heat transfer.

[0070] FIG. 2 shows a prior art phase change cooling system which lacks heat exchangers associated with the evaporators.

[0071] FIG. 3 shows a P-h diagram of Novec 7000 (Extracted from a 3M® datasheet).

[0072] FIG. 4 shows the variation of degree of subcooling in the reservoir and the supply pressure with the reservoir pressure in the embodiment according to FIG. 2.

[0073] One skilled in the art will readily appreciate that the specific methods and results discussed are merely illustrative of the invention as described more fully in the claims which follow thereafter.

REFERENCES

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