WO2008027931A2

WO2008027931A2 - Manifold for a two-phase cooling system

Info

Publication number: WO2008027931A2
Application number: PCT/US2007/077045
Authority: WO
Inventors: Charles Tilton; Donald Tilton; Tony Hyde; Paul Knight; Bryan Darton
Original assignee: Isothermal Systems Research, Inc.
Priority date: 2006-08-29
Filing date: 2007-08-28
Publication date: 2008-03-06
Also published as: US20080093054A1; WO2008027931A3

Abstract

A manifold for a two-phase cooling system for efficiently transferring coolant within a multi-phase cooling system. The manifold for a two-phase cooling system generally includes an extended manifold having a supply chamber and a return chamber in thermal communication with one another to provide for efficient coolant transfer between a thermal server and a spray module.

Description

APPLICATION

FOR UNITED STATES LETTERS PATENT

SPECIFICATION

TO ALL WHOM IT MAY CONCERN:

BE IT KNOWN THAT WE, Charles L. Tilton, a citizen of the United States, Donald E. Tilton, a citizen of the United States, Tony E. Hyde, a citizen of the United States, Paul A. Knight, a citizen of Canada, Bryan M. Darton, a citizen of the United States, and Brian P. Dunhamn, a citizen of the United States, have invented a new and useful manifold for a two-phase cooling system of which the following is a specification: Manifold For A Two-Phase Cooling System

CROSS REFERENCE TO RELATED APPLICATIONS I hereby claim benefit under Title 35, United States Code, Section 119(e) of United States provisional patent application Serial Number 60/841,056 filed August 29, 2006 (Docket No. ISR-662). The 60/841,056 application is currently pending. The 60/841,056 application is hereby incorporated by reference into this application.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable to this application.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to fluid distribution manifolds for two- phase liquid cooling systems and more specifically it relates to a manifold for efficiently transferring coolant within a multi-phase cooling system.

Description of the Related Art

Any discussion of the related art throughout the specification should in no way be considered as an admission that such related art is widely known or forms part of common general knowledge in the field. Modern electronic devices (e.g. microprocessors, circuit boards and power supplies) and other heat producing devices have significant thermal management requirements. Conventional dry thermal management technology (e.g. forced air convection using fans and heat sinks) simply is not capable of efficiently thermally managing modern electronics.

Single-phase liquid thermal management systems (e.g. liquid cold plates) and multi-phase liquid thermal management systems (e.g. spray cooling, pool boiling, flow boiling, jet impingement cooling, falling-film cooling, parallel forced convection, curved channel cooling and capillary pumped loops) have been in use for years for thermally managing various types of heat producing devices.

Spray cooling technology is being adopted today as the most efficient option for thermally managing electronic systems. United States Patent No. 5,220,804 entitled High Heat Flux Evaporative Spray Cooling to Tilton et al. describes the earlier versions of spray technology, as it relates to cooling electronics. United States Patent No. 6,108,201 entitled Fluid Control Apparatus and Method for Spray Cooling to Tilton et al. also describes the usage of spray technology to cool a printed circuit board. United State Patent No. 6,958,911 entitled Low Momentum Loss Fluid Manifold System to Cader et al. describes a manifold system for providing coolant to spray modules.

The liquid coolant typically used within a spray cooling system is a dielectric fluid (e.g. perfluorocarbons and hydrofluoroethers) having a low vaporization temperature at standard atmospheric pressure. One common brand of dielectric liquid coolant for two- phase thermal management systems is a perfluorocarbon manufactured by Minnesota Mining and Manufacturing Company (3M^®) under the federally registered trademark FLUORINERT^®.

Because of the inherent issues in the related art, there is a need for a new and improved manifold for a two-phase cooling system for an efficient coolant transfer system.

BRIEF SUMMARY OF THE INVENTION

The general purpose of the present invention is to provide a manifold for a two- phase cooling system that has many of the advantages of the coolant manifolds used in two-phase coolant systems mentioned heretofore. The invention generally relates to a coolant transfer manifold which includes an extruded manifold having a supply chamber and a return chamber in thermal communication with one another.

There has thus been outlined, rather broadly, some of the features of the invention in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and that will form the subject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction or to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.

An object is to provide a manifold for a two-phase cooling system for efficiently transferring coolant within a multi-phase cooling system.

Another object is to provide a manifold for a two-phase cooling system that utilizes an extruded structure for the manifold. An additional object is to provide a manifold for a two-phase cooling system that provides a supply chamber and a return chamber that co-exist in a single manifold structure.

A further object is to provide a manifold for a two-phase cooling system that is cost effective to produce and efficient to install.

Another object is to provide a manifold for a two-phase cooling system that transfers heat from the return chamber to the supply chamber in operation to improve the heat transfer coefficients in a spray module.

Other objects and advantages of the present invention will become obvious to the reader and it is intended that these objects and advantages are within the scope of the present invention. To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific construction illustrated and described within the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features and attendant advantages of the present invention will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:

FIG. 1 is an upper perspective view of a two-phase cooling system incorporated within a server rack.

FIG. 2 is an upper perspective view of the manifold attached to a rack.

FIG. 3 is an upper perspective view of the manifold.

FIG. 4 is an upper perspective view of an exemplary spray module.

FIG. 5 is a cross sectional view taken along line 5-5 of Figure 3 illustrating the internal structure of the manifold.

FIG. 6 is an end view of a manifold end cap.

FIG. 7 is an upper perspective view of a fluid coupling assembly having male and female portions.

FIG. 8 is a top cross sectional view of an alternative manifold embodiment.

FIG. 9 is a top view of a cable and tube management arm system.

FIG. 10 is a block diagram illustrating the fluid communications of the present invention. FIG. 11 is a cross sectional view taken along line 11-11 of Figure 3 illustrating the supply chamber, the return chamber and the venting chamber.

DETAILED DESCRIPTION OF THE INVENTION

A. Overview. Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, FIGS. 1 through 11 illustrate a manifold for a two-phase cooling system 10, which comprises an extruded manifold having a supply chamber and a return chamber in thermal communication with one another.

B. Rack. Now referring to Figure 1, rack system is comprised of a network rack 12 housing one or more servers 20. As is well known in the art of computer electronics and datacenters, the rack 12 provides incremental mounting positions to the servers 20. The servers 20 can be a wide range of sizes ranging from IU (1.75") to greater than 12U, or blade style. A typical seven foot tall rack 12 can provide 42 rack mounting locations.

C. Thermal Server. In the preferred embodiment of the present invention, at the bottom of rack system 10 is at least one thermal server 30. As shown in Figure 1 of the drawings, the thermal server 30 is preferably located at the bottom of the rack 12 and pumps coolant into a manifold 40. The thermal server 30 thermally conditions the heated return coolant received from the thermal management unit 60.

Thermal server 30 provides the heat exchanger (condenser), pumps, and control systems needed to create the two-phase cooling system. As is generally known in the art, two-phase liquid cooling is a closed loop process wherein a coolant is pumped to a component to be cooled, wherein the coolant absorbs heat causing a phase change of the coolant to at least partially coolant vapor. The coolant vapor is condensed back into a liquid state and re-pumped. The coolant of the present invention is preferably a dielectric fluid, such as FLUORINERT (a trademark of the 3M Corporation), but is not limited to any particular fluid. For example, the present invention is applicable to water based systems.

D. Thermal Management Unit. The thermal management unit 60 is utilized to thermally manage one or more heat producing devices (e.g. microprocessor). The thermal management unit 60 is in thermal communication with the heat producing device either directly (e.g. spraying coolant upon the heat producing device) or indirectly (e.g. in thermal communication via a heat spreader or similar device).

As shown in Figure 4 of the drawings, the thermal management unit 60 has a fluid inlet 62 and a fluid exit 64. The coolant enters the thermal management unit 60 and absorbs heat from heat spreader 66 which is contact with a component being thermally managed as further shown in Figure 4 of the drawings. The spray module may be comprised of any thermal management device capable of thermally managing heat producing devices (e.g. spray modules, cold plates and the like). It is preferable that a two- phase spray module is utilized within the present invention.

The spray module preferably has a separate enclosed structure for retaining and thermally managing the heat producing devices. The spray module may have an integral card cage spray assembly or similar structure for retaining the heat producing devices. More than one spray module may be utilized within the present invention as can be appreciated. The spray module may include one or more spray nozzles for applying atomized coolant upon the heat producing devices. The spray module may be comprised of various well-known spray cooling systems currently available for thermally managing heat producing devices with an atomized coolant.

E. Manifold. The manifold 40 is preferably mounted to the rack 12 in a vertical orientation as illustrated in Figure 2 of the drawings. At each rack spacing, there is preferably a supply port 46 and a return port 44 to provide and receive coolant with respect to a corresponding spray module.

At each port 44, 46 is preferably a male fluid connector 81, which connects to a female connector 80 as illustrated in Figure 7 of the drawings. Each female port 80 delivers coolant to or from a spray module 60 via tubes (not shown).

The manifold 40 is preferably extruded from any of the common aluminum alloys. Figure 5 illustrates a cross sectional view of the extruded manifold 40 illustrating the formed recesses, or pockets, which follow the contour of the manifold.

By extruding down the length of the manifold 40 a supply chamber 72 may coexist in the same structure as a return chamber 73. Supply chamber 72 is in fluid connection with supply ports 46, and conversely, return chamber 73 is in fluid connection with return ports 44. Both chambers 72, 73 preferably reside in the same manifold structure which makes the manifold 40 cost effective to produce, efficient to install, and provides thermal advantages. The return chamber 73 is preferably substantially larger than said supply chamber 72 as shown in Figures 5 and 11 of the drawings. The chambers 72, 73 also preferably extend along a substantial length of the manifold 40 as best illustrated in Figure 11 of the drawings.

For example, according to the preferred embodiment of the present invention, the coolant being transferred in the supply chamber 72 absorbs heat from the coolant being transferred in the return chamber 73. Although each closed loop system will operate at different states of pressure and temperature depending upon its design and boundary conditions, with the preferred embodiment the temperature of the coolant in supply chamber 72 is approximately 37 degrees Celsius, and the temperature of the coolant in the return chamber is approximately 54 degrees Celsius. By transferring some of the heat from the coolant in the return chamber 73 fluid to the coolant in the supply chamber 72, the resulting coolant temperature in thermal management unit 60 can be increased. The resulting increase in coolant temperature within the thermal management unit 60 makes the thermal management unit 60 more effective at reducing electronic component temperatures due to increased heat transfer coefficients.

Another novel feature of the present invention is the creation of insulation chambers 75 within the extruded manifold 40 as further shown in Figure 5 of the drawings. The insulation chambers 75 reduce the amount of heat that can be transferred from the coolant, both the supply and return sides, to externally of the manifold. A significant goal of datacenter level cooling systems is to reduce the air cooling requirements of a rack system. By insulating the coolant chambers 72 and 73 from the ambient air, usually 20 to 25 degrees Celsius, several hundred watts of power can be kept within the coolant and not released into the local air. In addition, certain industry safety specifications require a maximum touch temperature less than 50 degrees Celsius and thus the insulation barrier helps maintain the desired temperature even though coolant within manifold 40 may be greater than 50 degrees Celsius.

The insulation chambers 75 are shown empty, but they could be filled with thermally insulating material for increased thermal performance. In addition, cooling water could flow through the insulation chambers 75 for increased thermal performance.

As illustrated in Figure 3 of the drawings, the manifold 40 preferably has a top cap 51 and a bottom cap 50. Although both caps can be bonded, only bottom cap 50 is shown in Figure 6. Preferably, manifold cap 50 has ridges which protrude .100 inches into the length of manifold 40 and has .010 to .015 inches in clearance between the manifold walls and the cap ridges. Though other joining methods are possible (such as welding or brazing), these protrusion and clearance dimensions provide ample room for the epoxy adhesive, such as DP460, which is commercially available through 3M. Pins (not shown) may be inserted into the outside corners of cap 50 to align the cap with the manifold channels 71. The pins may be a permanent feature or provided by a temporary gluing fixture, and provide the means to accurately align cap 50 to manifold 40 during the gluing or other joining process. It has been found that a hard anodizing, with no sealer, applied to both manifold 40 and cap 50 prior to bonding, creates an acceptable bonding surface that can withstand the rigors the pressure and temperature cycles of the system. Alternatively, cap 50 may be welded to cap 40.

Figure 7 shows the mating pair of fluid connectors, male connector 81 and female connector 80. Ideally, connectors 80 and 81 create low pressure drops, eject little or no fluid when disconnected, and provide a relatively tight seal during operation. A suitable connector is commercially available from FASTER. Another preferable operation of the connector pair is a snap ring 83 which resides co-axially on the female connector 80. To connect the female connector 80 to the male connector 81, the snap ring 83 must be pulled back exposing the internal threads to female connector 80. When the female connector 80 is turned to the correct torque, the snap ring 83 automatically moves forward indicating to the user the connectors 80, 81 have made the proper seal. To separate the connectors 80, 81, the snap ring 83 is pulled back and then twisted. This feature ensures that the mating pair is not easily disconnected by accident. Colors may be applied to the supply and return side so that users can easily distinguish which connector is for the supply and which one is for the return. Optionally, the supply and return connectors can be made different sizes. Because in a two phase system, pressure drops are more detrimental on the return side, it is more desirable to use as large of a connector on the return side as possible. The supply side can be smaller. In the preferred embodiment of the present invention, the supply side is .25 inches and the return side is .375 inches in diameter. With FLUORINERT, the o- ring material is preferably VITON® (a trademark of the DuPont corporation).

F. Venting Chamber. Two-phase liquid cooling systems have several design challenges, one being non- condensable gases. Non-condensable gasses are both needed to a small level, but also decrease thermal performance of the system above a certain level. The need to regulate non-condensable gases within a system is therefore necessary in order to provide the level of uptime that computing systems, especially datacenters, require. The preferred embodiment of the present invention utilizes such a system.

Yet another novel feature of the present invention is the creating of an active venting chamber 74. The purpose of venting chamber 74 is to provide a place for the vertical separation of the liquid coolant, vaporized coolant and non-condensables (e.g. air) as part of the active venting system. A vacuum pump (not shown) is preferably fluidly connected to the venting chamber 74 and draws gases and liquid out of the thermal server 30 and pushes it into venting chamber 74. Liquid coolant falls to the bottom of venting chamber 74 where it can be circulated back into thermal server 30. Coolant vapor within venting chamber 74 falls just above the liquid level within the venting chamber 74. Due to the higher pressures in comparison to the closed loop system, the vapor readily condenses to a liquid as to maintain the venting chamber 74 in equilibrium. Air and other non- condensables rise to the top of the venting chamber 74 wherein they can be removed via the opening of a release valve (e.g. solenoid valve) not shown in the drawings.

G. Coaxial Tube Manifold. Figure 8 illustrates an alternative embodiment of the present invention. A cross sectional view of a coaxial tube manifold 100 is shown in Figure 8. Rather than run a supply and return line, this embodiment uses a single tube with the supply line at least partially surrounded co-axially by the return line (can also be visa-versa). This type of co- axial tube system is described U.S. Patent No. 6,889,515 which is hereby incorporated by reference.

A coaxial fluid connector 103 provides the ability to supply and return coolant within a single connector structure. The coaxial fluid connector 103 is preferably comprised of an inner tube and an outer tube surrounding said inner tube as illustrated in U.S. Patent No. 6,889,515. A return chamber 101 is extruded with supply chamber 102 as shown in Figure 8 of the drawings. The coaxial fluid connector 103 mounts protrudes through supply chamber 102 into return chamber 101. The supply coolant enters the supply port 104 of the coaxial fluid connector 103. The return coolant leaves the coaxial fluid connector 103 through the return port 105 into the return chamber 101. The coaxial fluid connector 103 is preferably sealed via an o-ring (not shown) to the supply chamber 102, but it is not necessary to seal the supply chamber 102 to the return chamber 101.

Other embodiments of the present invention include having multiple manifolds connected to a single thermal server 30 so that two arrays of servers 14 can be cooled with a single thermal server 30. While the manifold 40 is shown with the fluid connectors in an equally spaced apart manner, in practice it may be more cost efficient and practical to place them as needed.

H. Cable Arm System. As shown in Figure 9 of the drawings, another feature of the present invention is a cable arm 90 which provides a controlled bend radius and protection to the tubes (not shown) connecting the manifold 40 and individual servers 14 mounted in the rack 12. An arm end 92 mounts to the manifold holes 48 and server end 94 attaches to the back of a server 14 at a PCI location. A plurality of links 96 are rotatably mounted into a chain structure so that they do not allow vertical translation of the chain, but allow horizontal bending to a desired minimum radius.

What has been described and illustrated herein is a preferred embodiment of the invention along with some of its variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention, which is intended to be defined by the following claims (and their equivalents) in which all terms are meant in their broadest reasonable sense unless otherwise indicated. Any headings utilized within the description are for convenience only and have no legal or limiting effect.

Claims

CLAIMSWe Claim:

1. A manifold for a coolant thermal management system, comprising: a plurality of thermal management units in thermal communication with a plurality of heat producing devices, wherein said thermal management units each include a fluid inlet that receives a supply coolant and a fluid exit that returns a return coolant; a thermal server for thermally conditioning said return coolant; and a manifold including a supply chamber, a plurality of supply ports extending from the manifold, a return chamber, and a plurality of return ports extending from the manifold; wherein said supply ports are in fluid communication with said supply chamber and said fluid inlet of said plurality of thermal management units; wherein said return ports are in fluid communication with said return chamber and said fluid exit of said plurality of thermal management units; wherein said thermal server is in fluid communication with said supply chamber and said return chamber, wherein said supply chamber transfers said supply coolant from said thermal server to said plurality of thermal management units and wherein said return chamber returns said return coolant from said plurality of thermal management units to said thermal server for thermal conditioning.

2. The manifold for a coolant thermal management system of Claim 1, wherein said manifold is comprised of an extruded structure.

3. The manifold for a coolant thermal management system of Claim 1, wherein said manifold is comprised of a unitary extruded aluminum structure.

4. The manifold for a coolant thermal management system of Claim 1, wherein said return chamber is in thermal communication with said supply chamber.

5. The manifold for a coolant thermal management system of Claim 1, wherein said return chamber is parallel to said supply chamber.

6. The manifold for a coolant thermal management system of Claim 1, wherein said return chamber and said supply chamber extend along a substantial length of said manifold.

7. The manifold for a coolant thermal management system of Claim 1, wherein said return chamber is adjacent to said supply chamber.

8. The manifold for a coolant thermal management system of Claim 1, wherein said plurality of supply ports and said plurality of return ports extend from said manifold in pairs.

9. The manifold for a coolant thermal management system of Claim 1, including a top cap attached to an upper end of said manifold and a bottom cap attached to a lower end of said manifold.

10. The manifold for a coolant thermal management system of Claim 1, including a venting chamber within said manifold, wherein said venting chamber is fluidly connected to said thermal server to receive gases within said thermal server.

11. The manifold for a coolant thermal management system of Claim 1, including an insulation chamber within said manifold, wherein said insulation chamber at least partially surrounds said return chamber.

12. The manifold for a coolant thermal management system of Claim 11, including an insulating material positioned within said insulation chamber.

13. The manifold for a coolant thermal management system of Claim 1, wherein said return chamber is substantially larger than said supply chamber.

14. A manifold for a coolant thermal management system, comprising: a plurality of thermal management units in thermal communication with a plurality of heat producing devices, wherein said thermal management units each include a fluid inlet that receives a supply coolant and a fluid exit that returns a return coolant; a thermal server for thermally conditioning said return coolant; a manifold including a supply chamber and a return chamber; and a plurality of coaxial fluid connectors extending into said manifold and in fluid communication with said plurality of thermal management units, wherein said coaxial fluid connectors have an inner tube and an outer tube surrounding said inner tube; wherein said plurality of coaxial fluid connectors each include a supply port in fluid communication with said supply chamber; wherein said plurality of coaxial fluid connectors each include a return port in fluid communication with said return chamber; wherein said thermal server is in fluid communication with said supply chamber and said return chamber, wherein said supply chamber transfers said supply coolant from said thermal server to said plurality of thermal management units and wherein said return chamber returns said return coolant from said plurality of thermal management units to said thermal server for thermal conditioning.

15. The manifold for a coolant thermal management system of Claim 14, wherein said manifold is comprised of an extruded structure.

16. The manifold for a coolant thermal management system of Claim 14, wherein said manifold is comprised of a unitary extruded aluminum structure.

17. The manifold for a coolant thermal management system of Claim 14, wherein said return chamber is in thermal communication with said supply chamber.

18. The manifold for a coolant thermal management system of Claim 14, including a venting chamber within said manifold, wherein said venting chamber is fluidly connected to said thermal server to receive gases within said thermal server.

19. The manifold for a coolant thermal management system of Claim 14, including an insulation chamber within said manifold, wherein said insulation chamber at least partially surrounds said return chamber.

20. A manifold for a coolant thermal management system, comprising: a plurality of thermal management units in thermal communication with a plurality of heat producing devices, wherein said thermal management units each include a fluid inlet that receives a supply coolant and a fluid exit that returns a return coolant; a thermal server for thermally conditioning said return coolant; a manifold including a supply chamber, a plurality of supply ports extending from the manifold, a return chamber, and a plurality of return ports extending from the manifold, wherein said return chamber is substantially larger than said supply chamber; wherein said manifold is comprised of a unitary extruded aluminum structure; wherein said return chamber is parallel to said supply chamber; wherein said return chamber and said supply chamber extend along a substantial length of said manifold; wherein said return chamber is adjacent to and in thermal communication with said supply chamber; wherein said supply ports are in fluid communication with said supply chamber and said fluid inlet of said plurality of thermal management units; wherein said return ports are in fluid communication with said return chamber and said fluid exit of said plurality of thermal management units; wherein said plurality of supply ports and said plurality of return ports extend from said manifold in pairs; wherein said thermal server is in fluid communication with said supply chamber and said return chamber, wherein said supply chamber transfers said supply coolant from said thermal server to said plurality of thermal management units and wherein said return chamber returns said return coolant from said plurality of thermal management units to said thermal server for thermal conditioning; a top cap attached to an upper end of said manifold and a bottom cap attached to a lower end of said manifold; a venting chamber within said manifold, wherein said venting chamber is fluidly connected to said thermal server to receive gases within said thermal server; an insulation chamber within said manifold, wherein said insulation chamber at least partially surrounds said return chamber; and an insulating material positioned within said insulation chamber.