COOLING ASSEMBLY FOR ELECTRONICS DRAWER USING PASSIVE FLUID LOOP AND AIR-COOLED COVER
A cooling apparatus for electronic drawers utilizing a passive fluid cooling loop in conjunction with an air cooled drawer cover. The air cooled cover provides an increased surface area from which to transfer heat to cooling air flowing through the drawer. The increased cooling surface uses available space within the drawer, which may be other than immediately adjacent to a high power device within the drawer. The passive fluid cooling loop provides heat transfer from the high power device to the air cooled cover assembly, allowing placement of the air cooled cover assembly other than immediately adjacent to the high power device. The cooling apparatus is easily disengaged from the electronics drawer, providing access to devices within the drawer.
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The present invention relates in general to cooling electronics systems. In particular, the present invention relates to enhanced cooling of one or more high power electronic components within an air cooled electronics drawer.
BACKGROUND OF THE INVENTIONAs is known, operating electronic devices produce heat. This heat should be removed from the devices in order to maintain device junction temperatures within desirable limits: failure to remove the heat thus produced results in increased device temperatures, potentially leading to thermal runaway conditions. Several trends in the electronics industry have combined to increase the importance of thermal management, including heat removal for electronic devices, including technologies where thermal management has traditionally been less of a concern, such as CMOS. In particular, the need for faster and more densely packed circuits has had a direct impact on the importance of thermal management. First, power dissipation, and therefore heat production, increases as the device operating frequencies increase. Second, increased operating frequencies may be possible at lower device junction temperatures. Finally, as more and more devices are packed onto a single chip, power density (Watts/cm2) increases, resulting in the need to remove more power from a given size chip or module. These trends have combined to create applications where it is no longer desirable to remove the heat from modern devices solely by traditional air cooling methods, such as by using traditional air cooled heat sinks.
While alternatives to air cooling are known, such as chilled water and refrigeration systems, these alternatives tend to increase both manufacturing and operational costs, and therefore tend to be applied primarily in high performance applications. Methods are therefore desirable which augment traditional air cooling methods, thereby overcoming at least some of the limitations of traditional methods, without introducing costly refrigeration or chilled water distribution systems.
In general, enhanced air cooling may be achieved by modifying any of a number of parameters, such as ambient air temperature, airflow rate, heatsink surface area, etc. While an increase in any of these factors tends to improve the efficiency with which heat transfers from heatsink fins to ambient air, design considerations may place practical limitations on the extent to which any parameter may be increased, and interactions between the various parameters may limit the effectiveness of a particular parameter change. For example, ambient air temperatures are typically controlled by customer environmental systems, within established limits. Electronic systems are designed to operate within existing customer installations, and typically do not have the flexibility to require reduced ambient air temperatures. Furthermore, many electronic applications are constrained to occupy a limited volume or footprint (i.e. floor surface area). Increases in fin surface area, therefore, are likely accomplished by decreasing fin thickness and increasing fin density, effectively increasing fin surface area within a constant heatsink volume. As fin density thus increases, however, so does the pressure differential between airflow entering the fins and airflow leaving the fins. Both airflow rates and pressure drops are frequently limited by other design considerations, such as acoustic constraints.
Many modern electronic systems are designed in a rack configuration, such as prior art rack 110 illustrated in
Volume constraints are particularly critical in modern electronic rack systems such as rack 110, having several drawers 120 each containing electronic subsystems. Each drawer 120 is constrained to fit within a relatively small volume. High power components within these drawers, such as processor module 132, typically have a limited volume of space immediately adjacent to the component within which to place a heatsink, such as heatsink 136. The drawer volume constraints therefore place a design limitation on the maximum size heatsink that can be directly attached to a high power device. This places a practical limitation on the extent to which high power devices such as processor 132 may be air cooled within a limited volume drawer.
Electronics drawers typically utilize only a portion of the volume within the drawer, as illustrated in
For the foregoing reasons, therefore, there is a need in the art for an apparatus capable of utilizing the available unused volume within an electronics drawer to provide enhanced air cooling of high power electronic components within the drawer.
SUMMARYThe shortcomings of the prior art are overcome, and further advantages realized, by the provision of a passive liquid cooling loop and air cooled cover assembly for an electronics drawer, per the teachings of the present invention. The air cooled cover assembly provides an increased surface area from which to transfer heat to air flowing through the drawer, by utilizing available space within a drawer. The passive liquid cooling loop provides heat transfer from a high power device to the air cooled cover assembly, allowing placement of the air cooled cover assembly other than immediately adjacent to the high power device.
In one aspect, the present invention involves a cooling apparatus including a high thermal conductivity electronics drawer cover, a plurality of high thermal conductivity cooling fins in thermal contact with an underside of the cover, a fluid cooling loop, and a mechanical biasing component. The fluid cooling loop includes a plurality of high heat transfer fluid channels in thermal contact with the cover underside and located in proximity to the cooling fins, a flexible vapor conduit, one end of which is in fluid flow communication with a first end of the fluid channels, a high heat transfer boiling chamber in fluid flow communication with a second end of the vapor conduit, and at least one flexible condensate return conduit in fluid flow communication with a second end of the fluid channels and further in fluid flow communication with the boiling chamber. The mechanical biasing component is in mechanical contact with the cover underside and an upper side of the boiling chamber.
In another aspect, the present invention involves a cooled electronic drawer, including a drawer frame having a bottom, side components, a front air inlet component, and a rear air outlet component, an electronics board assembly connected to the drawer frame, the board assembly including a plurality of electronic components, at least one of which is a high power component. The drawer further includes at least one air moving device connected to the drawer frame, and a cooling assembly disengagably connected to the drawer frame. The cooling assembly includes a high thermal conductivity drawer cover, a plurality of high thermal conductivity cooling fins in thermal contact with an underside of the cover, a fluid cooling loop, and a mechanical biasing component. The fluid cooling loop includes a plurality of high heat transfer fluid channels in thermal contact with the cover underside and located in proximity to the cooling fins, a flexible vapor conduit, one end of which is in fluid flow communication with a first end of the fluid channels, a high heat transfer boiling chamber in fluid flow communication with a second end of the vapor conduit, and at least one flexible condensate return conduit in fluid flow communication with a second end of the fluid channels and further in fluid flow communication with the boiling chamber. The mechanical biasing component is in mechanical contact with the cover underside and an upper side of the boiling chamber, placing the boiling chamber in thermal contact with the at least one high power component when the cover is in a closed position.
In a further aspect, the present invention involves a cooled electronic rack system including a rack frame, and at least one electronic drawer slidably mounted within the frame. The drawer includes a drawer frame having a bottom, side components, a front air inlet component, and a rear air outlet component, an electronics board assembly connected to the drawer frame, the board assembly including a plurality of electronic components, at least one of which is a high power component. The drawer further includes at least one air moving device connected to the drawer frame, and a cooling assembly disengagably connected to the drawer frame. The cooling assembly includes a high thermal conductivity drawer cover, a plurality of high thermal conductivity cooling fins in thermal contact with an underside of the cover, a fluid cooling loop, and a mechanical biasing component. The fluid cooling loop includes a plurality of high heat transfer fluid channels in thermal contact with the cover underside and located in proximity to the cooling fins, a flexible vapor conduit, one end of which is in fluid flow communication with a first end of the fluid channels, a high heat transfer boiling chamber in fluid flow communication with a second end of the vapor conduit, and at least one flexible condensate return conduit in fluid flow communication with a second end of the fluid channels and further in fluid flow communication with the boiling chamber. The mechanical biasing component is in mechanical contact with the cover underside and an upper side of the boiling chamber, placing the boiling chamber in thermal contact with the at least one high power component when the cover is in a closed position.
It is therefore an object of the present invention to provide enhanced air cooling of high power devices within an electronics drawer, by transferring heat from the high power device to an extended surface area in thermal contact with a high thermal conductivity drawer cover.
It is a further object of the present invention to provide a passive fluid cooling loop to conduct heat from a high power device within an electronics drawer to an extended surface area in thermal contact with a high thermal conductivity drawer cover.
It is a further object of the present invention to provide an electronics drawer cover with extended heat transfer surfaces and a passive fluid cooling loop in a disengagable unit, thereby facilitating access to drawer components for service, repair, replacement, etc., as well as field upgrades of existing electronics drawers.
The recitation herein of a list of desirable objects which are met by various embodiments of the present invention is not meant to imply or suggest that any or all of these objects are present as essential features, either individually or collectively, in the most general embodiment of the present invention or in any of its more specific embodiments.
BRIEF DESCRIPTION OF THE DRAWINGSThe subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of practice, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:
In accordance with preferred embodiments of the present invention, a passive liquid cooling loop and air cooled cover assembly for an electronics drawer is disclosed herein.
As illustrated in
With reference to
In preferred embodiments of the present invention, cover 352 is made from a rigid, high thermal conductivity material such as aluminum. Other materials may be used to construct cover 352 such as copper, nickel, stainless steel, etc., however aluminum provides an additional advantage in providing a relatively light weight cover 352. Fins 354 are preferably formed of a material having high thermal conductivity: in preferred embodiments of the present invention, fins 354 are composed of a material similar to that of cover 352, such as aluminum, copper, nickel, stainless steel, etc. An assembly of cover and fins is formed either by milling or otherwise machining fins 354 from a single structure, or by attaching fins 354 to a separate cover 352 such as by soldering, brazing, or other methods of forming a permanent, high heat transfer bond as known in the art. In preferred embodiments of the present invention, channels 356 are composed of a material having high thermal conductivity, and which is chemically compatible with a cooling fluid selected for use within assembly 350. Preferred embodiments of the present invention employ channels 356 formed of copper or stainless steel, however other materials such as aluminum, nickel, etc. may be used to construct channels 356. Channels 356 are attached to cover 352 by soldering, brazing, welding, or other methods of forming a permanent, high heat transfer bond as known in the art.
As illustrated in
Boiling chamber 360 provides a high heat transfer path between high power component 332 and a cooling fluid within boiling chamber 360. Toward this end, an external lower surface of boiling chamber 360 is in thermal and mechanical contact with an upper surface of component 332 when cover assembly 350 is attached to drawer frame 321 and in a fully closed position, as illustrated in
Flexible conduit 362 provides a hermetic fluid flow path between boiling chamber 360 and fluid/vapor channels 356. In general, conduit 362 is formed of a material that is chemically compatible with a cooling fluid selected for use within assembly 350. Conduit 362 should be sufficiently flexible to maintain fluid connections between boiling chamber 360 and channels 356 when assembly 350 is detached from frame 321, such as illustrated in
To maintain good thermal contact between boiling chamber 360 and high power component 332, assembly 350 provides a compressive force between boiling chamber 360 and high power component 332 when assembly 350 is attached to frame 321 and in a fully closed position, as illustrated in
As previously noted, conduit 362 provides a hermetic fluid path between boiling chamber 360 and channels 356. As illustrated in
Channels 356 direct fluid from conduit 362 to one or more return conduits 364. As illustrated in
Return conduits 364 provide a mechanically flexible path for fluid condensed in channels 356 to return to boiling chamber 360. As previously noted, in order to maintain good thermal contact between high power component 332 and boiling chamber 360, cooling assembly 350 includes a mechanical biasing component in mechanical contact with boiling chamber 360 and cover 352. This biasing component results in a range of deflection between boiling chamber 360 and cover 352 when assembly 350 is engaged with or disengaged from frame 321 (deflection not illustrated in Figures). Return conduits 364 must therefore maintain a hermetic fluid path throughout the range of deflection of boiling chamber 360. In preferred embodiments of the present invention utilizing a cooling fluid at subatmospheric pressure, return conduits 364 must also exhibit sufficient rigidity to resist collapsing under the resulting pressure differential. Return conduits 364 are therefore preferably formed of a material having sufficient flexibility throughout, such as copper, aluminum, nickel, or the like, such as illustrated in
Alternatively, return conduits 764, illustrated in assembly 750 of
While the fluid loop components (channels 356, conduit 362, boiling chamber 360, and return conduits 364) may be formed from a variety of materials, in preferred embodiments of the present invention the same material is used for all components. Alternatively, different materials may be used for various components, provided that the materials are chemically compatible with each other and with a selected cooling fluid, and further provided that the materials enable formation of a hermetic joint when fluid loop components are joined. In preferred embodiments of the present invention, fluid loop components are joined by brazing, welding, or other methods known in the art capable of providing a hermetic seal.
With reference now to the schematic drawing illustrated in
Boiling chamber 760 and a portion of conduit 762 are filled with cooling fluid 766. Cooling fluid 766 should be chemically compatible with the materials selected for the fluid loop components (channels 756, conduit 762, boiling chamber 760, and return conduits 764), in order to avoid corrosion or other undesirable chemical interactions between fluid 766 and fluid loop components. Also, cooling fluid 766 should exhibit a high latent heat of vaporization, and high thermal conductivity. Finally, in preferred embodiments of the present invention using fluid 766 at subatmospheric pressure, fluid 766 should boil within a desired temperature range (such as, for example, 40 C to 60 C) when fluid 766 is at a relatively low vapor pressure. In preferred embodiments of the present invention, cooling fluid 766 is water or brine, however fluid 766 also includes fluids such as refrigerants and fluorocarbons, within the spirit of the present invention. As used herein, a brine is any fluid consisting of a salt in aqueous solution, such as a water-glycol solution, or a solution of water and one or more organic salts, for example. Preferred embodiments of the present invention use a brine suitable for low temperature use, such as a low temperature cooling fluid sold under the tradename DYNALENE HC (sold by the Dynalene Company of Whitehall, Pa., (610) 262-9686). Further, in preferred embodiments of the present invention, fluid 766 boils at a temperature below 100 C, preferably below 60 C, and further preferably within the range of 40 C to 60 C. Where fluid 766 is water or other aqueous solution, an appropriately low boiling point is achieved by first evacuating air from the fluid loop of assembly 750, then partially backfilling with a quantity of fluid 766, keeping fluid 766 at subatmospheric pressure.
Boiling chamber 760 transfers heat from high power component 732 to fluid 766, causing fluid 766 to boil. Fluid 766, now in vapor phase, rises through liquid phase fluid 766 within boiling chamber 760 and conduit 762, then continues to rise through conduit 762 and then enters channels 756. Vapor phase fluid 766 flows along channels 756, transferring heat to channels 756. As previously noted, channels 756 are in thermal contact with cover 752, which in turn is in thermal contact with fins 754. As air flows over fins 754, heat is transferred from fins 754 to the air, which subsequently removes the heat from cooling assembly 750. As heat is thus transferred from vapor phase fluid 766 to the ambient air, fluid 766 condenses from vapor phase to liquid phase, preferably prior to exiting channels 756 and entering return conduits 764. Conduits 764 then collect condensed fluid 766, and return fluid 766 to boiling chamber 760.
As described above, the fluid cooling loop within assembly 750 causes fluid 766 to undergo two phase changes during each fluid circuit: liquid to vapor within boiling chamber 760, and vapor to liquid within channels 756 and/or return conduits 764. By utilizing phase changes, the present invention provides thermal transfer from high power component 732 to ambient air while minimizing the volume flow of fluid 766. Furthermore, waste heat from component 732 provides the motive force to create fluid flow, therefore eliminating the need for a flow-inducing device such as a mechanical pump.
With reference now to
As previously noted, drawer cover cooling assemblies of the present invention, such as assemblies 350 and 750, are designed to transfer heat from a high power component to a set of air cooled fins in thermal contact with drawer cover 352 or 752. For simplicity, the discussion of drawer assembly techniques will refer to drawer 720, however the discussion applies to other embodiments of the present invention such as drawer 320. To maintain good thermal contact between high power component 732 and boiling chamber 760, assembly 750 includes a mechanical biasing component (conduit 762 and/or auxiliary spring 1063), which maintains a compressive force between boiling chamber 760 and high power component 732. Drawer 720 is assembled by securing cover 752 to at least two opposing components of frame 721. Cover 752 is preferably attached to frame 721 using mechanical fasteners as known in the art. Two preferred fastening methods are discussed below, however any mechanical fastening devices and methods may be used, provided two conditions are met. First, cover 752 should be easily disengagable from high power component 732 and all but one component of frame 721, or preferably completely detachable from frame 721, to provide easy access to components within drawer 720 for inspection, repair, replacement, etc. Second, cover 752 must be held in place with sufficient force to compress the mechanical biasing component (conduit 762 and/or spring 1063).
In one embodiment of the present invention, cover 752 is attached to frame 721 using a plurality of bolts (not shown). Assembly using bolts is best illustrated in
In preferred embodiments of the present invention, cover 752 is pivotally mounted to one component of frame 721, and fastened to an opposing component of frame 721 using bolts or other mechanical fasteners as known in the art. One such embodiment is illustrated in
Alternatively, standard hinges can be used to pivotally mount cover 752 to rear frame component 728, however this alternative does not provide easy detachment of cover 752. This alternative provides an assembly 750 that is easily disengaged from high power component 732 and all but one component of frame 721.
While the invention has been described in detail herein in accord with certain preferred embodiments thereof, many modifications and changes therein may be effected by those skilled in the art. Accordingly, it is intended by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.
Claims
1. A cooling apparatus comprising:
- a high thermal conductivity electronics drawer cover;
- a plurality of high thermal conductivity cooling fins in thermal contact with an underside of said cover;
- a fluid cooling loop including: a plurality of high heat transfer fluid channels in thermal contact with said cover underside, said channels located in proximity to said fins; a flexible vapor conduit, a first end of said vapor conduit being in fluid flow communication with a first end of said channels; a high heat transfer boiling chamber in fluid flow communication with a second end of said vapor conduit; at least one flexible condensate return conduit in fluid flow communication with a second end of said fluid channels, said return conduit also in fluid flow communication with said boiling chamber; and
- a mechanical biasing component in mechanical contact with said underside of said cover, and with an upper side of said boiling chamber.
2. The apparatus of claim 1, wherein said flexible vapor conduit is a metallic bellows, and said mechanical biasing component is also said metallic bellows.
3. The apparatus of claim 1, wherein said mechanical biasing component is a spring.
4. The apparatus of claim 1, further comprising a cooling fluid.
5. The apparatus of claim 4, wherein said cooling fluid is at a pressure below atmospheric pressure.
6. The apparatus of claim 5, wherein said cooling fluid boils at a temperature no higher than 60C.
7. The apparatus of claim 4, wherein said cooling fluid is selected from the group consisting of water, brine, refrigerant, and fluorocarbons.
8. The apparatus of claim 1, wherein said boiling chamber is constructed of a material selected from the group consisting of copper, aluminum, stainless steel, and nickel.
9. The apparatus of claim 1, said fluid flow channels further comprising:
- an inlet plenum at said channel first end, said inlet plenum distributing fluid from said vapor conduit to said plurality of channels; and
- an outlet plenum at said channel second end, said outlet plenum collecting fluid from said plurality of channels.
10. The apparatus of claim 1, wherein said flexible return conduit includes at least one inflexible portion and at least one flexible portion.
11. The apparatus of claim 1, wherein said channels and said fins are interdigitated.
12. A cooled electronic drawer apparatus comprising:
- a drawer frame, said drawer frame including a bottom, side components, a front air inlet component, and a rear air outlet component;
- an electronics board assembly connected to said drawer frame, said board assembly including a plurality of electronic components, said plurality of components including at least one high power component;
- at least one air moving device connected to said drawer frame;
- a cooling assembly disengagably connected to said drawer frame, said cooling assembly including: a high thermal conductivity drawer cover; a plurality of high thermal conductivity cooling fins in thermal contact with an underside of said cover; a fluid cooling loop including: a plurality of high heat transfer fluid channels in thermal contact with said cover underside, said channels located in proximity to said fins; a flexible vapor conduit, a first end of said vapor conduit being in fluid flow communication with a first end of said channels; a high heat transfer boiling chamber in fluid flow communication with a second end of said vapor conduit; at least one flexible condensate return conduit in fluid flow communication with a second end of said fluid channels, said return conduit also in fluid flow communication with said boiling chamber; and a mechanical biasing component in mechanical contact with said underside of said cover, and with an upper side of said boiling chamber, and
- wherein said boiling chamber is in thermal contact with said at least one high power component when said cover is in a closed position.
13. The apparatus of claim 12, wherein said mechanical biasing component is compressed when said cover is in a closed position, said mechanical biasing component exerting a compressive force between said boiling chamber and said high power component.
14. The apparatus of claim 12, wherein said flexible vapor conduit is a metallic bellows, and said mechanical biasing component is also said metallic bellows.
15. The apparatus of claim 12, wherein said mechanical biasing component is a spring.
16. The apparatus of claim 12, wherein said electronics board assembly includes a plurality of high power components.
17. The apparatus of claim 12, further comprising a cooling fluid.
18. The apparatus of claim 12, wherein said cover is detachable from said drawer frame.
19. The apparatus of claim 18, wherein said cover is pivotally mounted to one of said frame components.
20. The apparatus of claim 12, wherein said cover is hingably mounted to one of said frame components.
21. A cooled electronic rack system comprising:
- a rack frame;
- at least one electronic drawer slidably mounted within said frame, said drawer including: a drawer frame, said drawer frame including a bottom, side components, a front air inlet component, and a rear air outlet component; an electronics board assembly connected to said drawer frame, said board assembly including a plurality of electronic components, said plurality of components including at least one high power component; at least one air moving device connected to said drawer frame; a cooling assembly disengagably connected to said drawer frame, said cooling assembly including: a high thermal conductivity drawer cover; a plurality of cooling fins in thermal contact with an underside of said cover; a fluid cooling loop including: a plurality of high heat transfer fluid channels in thermal contact with said cover underside, said channels located in proximity to said fins; a flexible vapor conduit, a first end of said vapor conduit being in fluid flow communication with a first end of said channels; a high heat transfer boiling chamber in fluid flow communication with a second end of said vapor conduit; at least one flexible condensate return conduit in fluid flow communication with a second end of said fluid channels, said return conduit also in fluid flow communication with said boiling chamber; a mechanical biasing component in mechanical contact with said underside of said cover, and with an upper side of said boiling chamber, and wherein said boiling chamber is in thermal contact with said at least one high power component when said cover is in a closed position.
22. The system of claim 21, including a plurality of said electronic drawers.
Type: Application
Filed: May 7, 2004
Publication Date: Nov 10, 2005
Applicant: International Business Machines Corporation (Armonk, NY)
Inventors: Richard Chu (Hopewell Junction, NY), Michael Ellsworth (Lagrangeville, NY), Roger Schmidt (Poughkeepsie, NY), Robert Simons (Poughkeepsie, NY)
Application Number: 10/841,748