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  Liquid cooled thermosiphon with flexible coolant tubesUSPTO Application #: 20060162898Title: Liquid cooled thermosiphon with flexible coolant tubes Abstract: A fluid heat exchanger assembly cools an electronic device with a cooling fluid supplied from a heat extractor (R, F) to a plurality of tubes extending between header tanks in an upper portion of a housing. A refrigerant is disposed in the lower portion of the housing for liquid-to-vapor transformation. The tubes are radially flexible to vary the volume of the tubes for modulating the flow of coolant liquid through the tubes in response to heat transferred by an electronic device to the lower portion of the housing. (end of abstract)
Agent: Patrick M. Griffin Delphi Technologies, Inc., Legal Staff - Troy, MI, US Inventors: Ilya Reyzin, Mohinder Singh Bhatti USPTO Applicaton #: 20060162898 - Class: 165080400 (USPTO) Related Patent Categories: Heat Exchange, With Retainer For Removable Article, Electrical Component, Liquid Cooled The Patent Description & Claims data below is from USPTO Patent Application 20060162898. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] The subject invention is related to the inventions disclosed in co-pending applications DP-311409 (H&H 60408-566) and DP-312789 (H&H 60408-597), filed concurrently herewith. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] A fluid heat exchanger assembly for cooling an electronic device. [0004] 2. Description of the Prior Art [0005] Research activities have focused on developing assemblies to efficiently dissipate heat from electronic devices that are highly concentrated heat sources, such as microprocessors and computer chips. These electronic devices typically have power densities in the range of about 5 to 35 W/cm.sup.2 and relatively small available space for placement of fans, heat exchangers, heat sink assemblies and the like. However, these electronic devices are increasingly being miniaturized and designed to achieve increased computing speeds that generate heat up to 200 W/cm.sup.2. [0006] Heat exchangers and heat sink assemblies have been used that apply natural or forced convection cooling methods to cool the electronic devices. These heat exchangers typically use air to directly remove heat from the electronic devices. However, air has a relatively low heat capacity. Such heat sink assemblies are suitable for removing heat from relatively low power heat sources with power density in the range of 5 to 15 W/cm.sup.2. The increased computing speeds result in corresponding increases in the power density of the electronic devices in the order of 20 to 35 W/cm.sup.2 thus requiring more effective heat sink assemblies. [0007] In response to the increased heat to be dissipated, liquid-cooled units called LCUs employing a cold plate in conjunction with high heat capacity fluids, like water and water-glycol solutions, have been used to remove heat from these types of high power density heat sources. One type of LCU circulates the cooling liquid so that the liquid removes heat from the heat source, like a computer chip, affixed to the cold plate, and is then transferred to a remote location where the heat is easily dissipated into a flowing air stream with the use of a liquid-to-air heat exchanger and an air moving device such as a fan or a blower. These types of LCUs are characterized as indirect cooling units since they remove heat from the heat source indirectly by a secondary working fluid, generally a single-phase liquid, which first removes heat from the heat source and then dissipates it into the air stream flowing through the remotely located liquid-to-air heat exchanger. Such LCUs are satisfactory for moderate heat flux less than 35 to 45 W/cm.sup.2 at the cold plate. [0008] In the prior art heat sinks, such as those disclosed in U.S. Pat. Nos. 6,422,307 and 5,304,846, the single-phase working fluid of the liquid cooled unit (LCU) flows directly over the cold plate causing cold plate corrosion and leakage problems. [0009] As computing speeds continue to increase even more dramatically, the corresponding power densities of the devices rise up to 200 W/cm.sup.2. The constraints of the miniaturization coupled with high heat flux generated by such devices call for extremely efficient, compact, and reliable thermosiphon cooling units called TCUs. Such TCUs perform better than LCUs above 45 W/cm.sup.2 heat flux at the cold plate. A typical TCU absorbs heat generated by the electronic device by vaporizing the captive working fluid on a boiler plate of the unit. The boiling of the working fluid constitutes a phase change from liquid-to-vapor state and as such the working fluid of the TCU is considered to be a two-phase fluid. The vapor generated during boiling of the working fluid is then transferred to an air-cooled condenser, in close proximity to the boiler plate, where it is liquefied by the process of film condensation over the condensing surface of the TCU. The heat is rejected into an air stream flowing over a finned external surface of the condenser. The condensed liquid is returned back to the boiler plate by gravity to continue the boiling-condensing cycle. These TCUs require boiling and condensing processes to occur in close proximity to each other thereby imposing conflicting thermal conditions in a relatively small volume. [0010] Examples of cooling systems for electronic devices are disclosed in U.S. Pat. No. 4,704,658 to Yokouchi et al; U.S. Pat. No. 5,529,115 to Paterson and U.S. Pat. No. 5,704,416 to Larson et al. SUMMARY OF THE INVENTION AND ADVANTAGES [0011] In accordance with the subject invention, heat generated by an electronic device is transferred to the lower portion of a housing having a refrigerant therein for liquid-to-vapor transformation as coolant liquid flows through a plurality of flexible tubes in an upper portion of the housing to vary the volume of the tubes for modulating the flow of coolant liquid through the tubes in response to heat transferred by the electronic device to the lower portion of the housing. [0012] The invention employs an array of flexible tubes to separate the secondary two-phase fluid from the single-phase working fluid of the LCU. The flexible tubes perform the useful function of changing the volume of the upper portion or boiling chamber depending on the chip heat flux. As the chip heat flux increases, the flexible tubes contract decreasing the tube volume thereby increasing the coolant flow velocity and the heat transfer. As the chip heat flux decreases, the flexible tubes expand increasing the tube volume thereby decreasing the coolant flow velocity and the heat transfer. Thus the flexible tubes continuously regulate the working fluid flow velocity through the tubes thereby adjusting the heat transfer rate in response to computer cooling demand. [0013] The present invention utilizes a captive secondary fluid capable of undergoing liquid-to-vapor transformation within the boiling chamber to remove heat by ebullition from the cold plate. The resulting vapor surrounds the flexible tubes through which flows the working fluid of the TCU without coming in direct contact with the secondary fluid vapor. The secondary fluid vapor is condensed by the working liquid coolant flowing to the interior of the flexible tubes. Thus the boiling chamber with the secondary two-phase fluid functions as a thermosiphon with superincumbent flexible tubes with working fluid flowing them serving as the condenser tubes. [0014] The heat transfer rate of the two-phase secondary fluid is inherently higher than that of the single-phase working fluid. Therefore, besides enhancing the cooling capacity of the TCU, the invention solves the problem of corrosion and leakage that plagues the LCU with highly aggressive working fluid flowing directly over the cold plate. The captive two-phase secondary fluid in direct contact with the cold plate is not as aggressive as the working fluid of the LCU. BRIEF DESCRIPTION OF THE DRAWINGS [0015] Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: [0016] FIG. 1 is a perspective view of the heat exchanger of the subject invention showing the housing cutaway; [0017] FIG. 2 is a cross sectional view of the heat exchanger shown in FIG. 1; and [0018] FIG. 3 is a schematic of a liquid cooling system in which the heat exchanger of the subject invention may be utilized. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0019] A fluid heat exchanger comprises a housing 20 having an inlet 22 and an outlet 24 and an upper portion 26 and a lower portion 28 extending between the inlet 22 and the outlet 24 for establishing a direction of flow from the inlet 22 to the outlet 24. The assembly is used to cool an electronic device 30 engaging or secured to the lower portion 28 of the housing 20, as by being adhesively held in a recess (not shown) in the bottom of the housing 20. Continue reading... Full patent description for Liquid cooled thermosiphon with flexible coolant tubes Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Liquid cooled thermosiphon with flexible coolant tubes patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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