JP2011220596A - Cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cooling system using a thermosiphon capable of freely setting installation positions of a water cooling jacket, a radiator, and a pipe to connect the both.SOLUTION: The cooling system includes a water cooling jacket 101 that evaporates a liquid refrigerant by heat from a heat generator 109, a radiator 102 that transfers heat of the steam refrigerant transported from the water cooling jacket and condenses the steam, a steam passage 103 through which the refrigerant steam is transported from the water cooling jacket to the radiator, a condensate passage 104 through which condensate is transported from the radiator to the water cooling jacket, permeable membranes 108, 107 that separate the water cooling jacket 101 and the steam passage 103, and the radiator 102 and the condensate passage 104, respectively, and a mixed liquid of solute and refrigerant accommodated within the water cooling jacket 101, wherein the refrigerant is caused to circulate between the water cooling jacket 101 and the radiator 102.

Description

  The present invention relates to a cooling system, and more particularly to an evaporative cooling system using a thermosyphon.

  In recent years, semiconductor devices such as a central processing unit (CPU) mounted on electronic devices such as personal computers and servers have increasingly increased in heat generation due to miniaturization and high integration. The above-mentioned semiconductor devices such as CPUs are usually not only unable to maintain their performance when a predetermined temperature is exceeded, but may be damaged in some cases. Therefore, the temperature management of the semiconductor device is required, and the semiconductor device is cooled.

  Conventionally, cooling of a semiconductor device has generally been realized by attaching a heat sink to a heating element such as a CPU and using a fan that sends cooling air to the heat sink. However, as described above, the heat generation part is localized due to the miniaturization and high integration of the semiconductor device, and cooling using a method using a heat sink and a fan that sends cooling air to the heat sink becomes difficult. In addition, due to the recent demands of environmentally friendly society, reduction of power consumption and noise of electronic devices is required.

  Due to the above-mentioned problem that cooling of semiconductor devices has become difficult and the demand from an environmentally friendly society, for example, a liquid cooling type cooling system using a refrigerant such as water instead of a conventional air cooling type cooling system. Efficient cooling technology such as the above is strongly demanded. Among the liquid cooling type cooling systems, the evaporative cooling system using the phase transition of the refrigerant is attracting attention because of its good cooling efficiency.

  As a conventional technique related to the evaporative cooling system described above, for example, a technique described in Patent Document 1 is known. This prior art evaporates the refrigerant with a water-cooled jacket installed on the surface of the CPU as a semiconductor device, transports the refrigerant vapor to the radiator through metallic and rubber tubes, and releases the heat there. As a result, the above-mentioned refrigerant is condensed, and the liquefied refrigerant is returned to the water-cooled jacket again by a pump.

  The air-cooled cooling system described above must release heat directly above a local heating element such as a CPU by means of a heat sink. However, the evaporative cooling system described above can freely select the position of the radiator that releases heat. Therefore, it is very useful for cooling electronic devices in recent years, in which the heat generation site is localized.

  In contrast to the evaporative cooling system using a pump as described above, there is an evaporative cooling system using a thermosyphon. This thermosiphon evaporative cooling system requires a water-cooling jacket and a radiator, as well as efficiency and locality. It is the same as the evaporative cooling system using the above-mentioned pump because of the advantage for cooling the heat generating part, but since the working fluid operates only by gravity without using the pump, the reliability of the apparatus is higher than that of the evaporative cooling system using the pump. It has the feature of being high. However, in the thermosyphon type evaporative cooling system, since the condensed refrigerant is transported to the water cooling jacket by gravity, the installation position of the water cooling jacket, the radiator, and the pipe connecting the both is limited.

  A cooling system using a heat pipe is known as a cooling system using a heat transport device that recirculates a refrigerant liquid condensed by capillary force instead of gravity. However, since the driving force of the heat pipe is a capillary force obtained by a groove, a wick or the like, the pressure loss of the liquid is large and the working liquid cannot be circulated efficiently. For this reason, the cooling system which performs a heat transport device using capillary force has a smaller heat transport amount than the evaporative cooling system using the thermosyphon described above. As a conventional technique that improves such a defect, for example, a technique described in Patent Document 2 is known. This prior art relates to a cooling system using a heat pipe that can generate a driving pressure for large heat transport by using osmotic pressure.

JP 2006-237188 A JP 63-14087 A

  As described above, there are mainly three types of evaporative cooling systems. The first system is a water cooling system that recirculates the refrigerant liquid condensed from the radiator to the water cooling jacket using a pump. The evaporative cooling system using this pump has the advantage that the amount of heat transport is large, but on the other hand, there is a need for a space for installing a pump, a power source for driving the pump, a reserve tank for storing cooling water, and the like. Has a point. In addition, this system has a problem that the above-described pump consumes electric power, becomes a noise source, and is problematic in terms of reliability.

  The second system is a cooling system that uses heat pipes. The cooling system using the heat pipe is highly reliable and does not require a pump, and therefore has an advantage that there is no concern about the installation space of the power source, the pump, and noise. However, the cooling system using a heat pipe has a problem that the amount of refrigerant that can be transported is small because the recirculation of the condensed refrigerant liquid depends on the capillary force, and therefore the amount of heat transport is small. Yes.

  The third system is a vaporization cooling system using a thermosyphon. The evaporative cooling system using the thermosyphon has a feature that the amount of heat transport is large in addition to the advantage of the cooling system using the heat pipe. However, since the driving force of the refrigerant is gravity, this system has a problem in that there are restrictions on the installation positions of the water cooling jacket, the radiator, and the pipe connecting the two. For this reason, for example, when used for a rack-mount type 1U server, it is necessary to provide a drop in the relative position between the radiator and the water cooling jacket within a height of 1U (about 4.5 cm). In addition, when applied to a blade server in which a 1U or 2U thickness blade case is installed vertically, or a tower type server that is operated both vertically and horizontally, there is a special case design and component layout. Restrictions arise.

  The object of the present invention is to solve the above-mentioned problems of the prior art, have a new driving force for recirculating the condensed refrigerant liquid, and freely set the installation position of the water cooling jacket, the radiator and the pipe connecting the two It is an object of the present invention to provide a cooling system using a thermosyphon that can be used.

  According to the present invention, the object is to provide a water cooling jacket that evaporates the liquid refrigerant by heat from the heating element, a radiator that condenses the vapor by transferring the heat of the vapor refrigerant transported from the water cooling jacket to the outside, and the water cooling A steam passage for transporting refrigerant vapor from a jacket to the radiator; a condensate passage for transporting condensate from the radiator to the water cooling jacket; a space between the water cooling jacket and the steam passage; and the radiator and the condensate passage. And a mixed solution of the solute and the refrigerant accommodated in the water-cooling jacket, and is achieved by circulating the refrigerant between the water-cooling jacket and the radiator. .

  According to the present invention, the refrigerant can be recirculated against the gravity from the lower radiator to the upper water cooling jacket by the osmotic pressure by the osmosis membrane, thereby providing a large heat transport amount, The installation position of the radiator and the pipe connecting the both can be freely set, and a high cooling effect can be obtained.

It is a figure which shows schematic structure of the vaporization cooling system which has the thermosiphon structure by one Embodiment of this invention. It is sectional drawing explaining the detailed structure of a water cooling jacket. It is sectional drawing explaining the detailed structure of a radiator. It is sectional drawing containing the partially expanded view explaining the structure of the radiator tube which comprises a radiator. It is a figure which shows schematic structure of the vaporization cooling system which has the thermosiphon structure by other embodiment of this invention. It is a figure explaining the fine groove structure along the longitudinal direction of piping used as the steam passage in other embodiments. It is the schematic of the rack server accommodated in the rack and a blade server.

  Hereinafter, embodiments of a cooling system according to the present invention will be described in detail with reference to the drawings. The embodiment of the present invention described here is an operation in the top heat mode (the evaporation unit is on the upper side and the condensation unit is on the lower side) which is impossible because the reflux of the condensed cooling liquid is caused by gravity in the conventional system. It is an example of the evaporative cooling system of the thermosiphon structure made possible.

  FIG. 1 is a diagram showing a schematic configuration of an evaporative cooling system having a thermosiphon structure according to an embodiment of the present invention.

  As shown in FIG. 1, a vaporization cooling system having a thermosyphon structure according to an embodiment of the present invention is provided with a water cooling jacket 101 serving as an evaporation unit of water as a refrigerant and a radiator 102 serving as a condensing unit of evaporated water. The two are connected by a vapor passage 103 that is a pipe and a condensate passage 104 to form a loop in which the refrigerant circulates.

  Between the water cooling jacket 101 and the steam passage 103 and between the radiator 102 and the condensate passage 104 are partitioned by permeation membranes 108 and 107, respectively, and a condensate jacket 302 is formed below the radiator 102 to form a solvent. 105 is disposed, and a mixed solution 106 of a solute and a solvent is sealed in the water cooling jacket 101.

  The water-cooling jacket 101 configured as described above is installed such that the bottom surface thereof is in contact with the upper surface of the heating element 109 by a semiconductor device such as a CPU with a small thermal resistance through a sheet having high thermal conductivity, grease, or the like. Used. Although not shown, a fan that generates an air flow is provided in the vicinity of the radiator 102, and the generated air flow promotes cooling of the radiator 102 through a heat-dissipating fin, which will be described later, constituting the radiator 102. .

  In the cooling system according to the above-described embodiment of the present invention, the radiator 102 is connected to the water cooling jacket 101 via the steam passage 103 and the condensate passage 104, and the route between the steam passage 103 and the condensate passage 104 is optional. Can be set to Thereby, the radiator 102 can be installed in an arbitrary position, and in the embodiment of the present invention, the condensate jacket 302 of the radiator 102 can be arranged at a position lower than the water cooling jacket 101.

In the embodiment of the present invention, water is used as the refrigerant, and the inside of the water cooling jacket 101 is decompressed and used as saturated water having a saturated vapor pressure at the environmental temperature. Water as a refrigerant serves as a solvent for a solute used by mixing with water in order to obtain an osmotic pressure, and a benzotriazole (C ₆ H ₅ N ₃ ) -based rust inhibitor is used as the solute. Accordingly, it is possible to expect the effect of suppressing corrosion of copper which is a material of the thermosyphon composed of the loop of the water cooling jacket 101, the radiator 102, the steam passage 103, and the condensate passage 104, which is effective. Further, a cellulose membrane is used as the osmotic membrane.

  FIG. 2 is a cross-sectional view illustrating the detailed structure of the water cooling jacket. As shown in FIG. 2, the water cooling jacket 101 includes a jacket base 202 and a jacket cover 201 that are in contact with a heating element 109 that is a semiconductor device such as a CPU. As the vaporization promoting structure 203 that promotes rapid boiling, the opening size and tunnel pitch are optimized on the upper surface (for example, a large number of 0.2 mm × 0.2 mm square holes in a vertical and horizontal direction with a pitch of 0.5 mm). A refined structure made of porous copper having a groove structure formed) is provided. An osmotic membrane 108 is disposed at the steam passage 103 entrance and at the steam outlet of the water cooling jacket 101, thereby preventing the solute from entering the steam passage 103, and thereby inside the water cooling jacket 101 and the condensate passage 104. It is possible to enclose a mixed solution of a solvent and a solute which is a working solution.

  FIG. 3 is a cross-sectional view illustrating the detailed structure of the radiator. As shown in FIG. 3, the radiator 102 includes a steam jacket 301 provided in the upper part, a condensate jacket 302 provided in the lower part, and one or a plurality of radiators connecting the steam jacket 301 and the condensate jacket 302. The tube 303 and a large number of radiation fins 304 provided around the radiator tube 303 are configured.

  FIG. 4 is a cross-sectional view including a partially enlarged view for explaining the structure of the radiator tube constituting the radiator. The radiator tube 303 has a structure having a cylindrical or flat cylindrical cross section, and as shown in the enlarged view of FIG. 4, a downward fine fin structure (for example, a depth of 0.1 mm) having a knife edge is provided therein. A fin structure 401 having a width of 1 mm, a width of 0.1 mm, and a pitch of 0.3 mm. The fine fin structure 401 also serves as a guide plate that promotes the condensation of the refrigerant vapor and promotes the elimination of the condensed refrigerant liquid from the condensation surface.

  Next, the operation of the evaporative cooling system using the thermosyphon according to the embodiment of the present invention configured as described above will be described.

  When the jacket base 202 is heated by the heating element 109 made of a semiconductor device such as a CPU, the temperature of the working solution in the water cooling jacket 101 rises. The inside of the water cooling jacket 101 is depressurized to a saturated vapor pressure at the environmental temperature, and the solvent of the mixed solution of the solvent and the solute as the working solution has a boiling point at a low temperature of 100 ° C. or lower, for example, 60 ° C. to 50 ° C. Has been adjusted to reach. At this time, the vaporization accelerating structure 203 in the water cooling jacket 101 acts to promote rapid boiling of the solvent liquid.

  In the embodiment of the present invention, water is used as a solvent, and a benzotriazole rust inhibitor is used as a solute. Since water has a lower boiling point than a benzotriazole rust inhibitor, it boils. The steam is water, and the generated water vapor is transported to the radiator 102 through the steam passage 103. Then, the water vapor carried to the radiator 102 is guided from the steam jacket 301 to the radiator tube 303, and is cooled by transferring heat to the radiation fins attached to the radiator tube 303. At this time, rapid condensation of the solvent is promoted by the fine fin structure shown in FIG. 4 provided in the radiator tube 303. Further, the condensed refrigerant liquid is smoothly transported from the radiator tube 303 to the condensate jacket 302. The condensed refrigerant liquid, which is pure water, is stored in the condensate jacket 302 below the radiator, contacts the aqueous solution (including the benzotriazole rust preventive agent) in the condensate passage 104 through the osmotic membrane 107, and the osmotic membrane 107 Due to the osmotic pressure, pure water permeates into the condensate passage 104.

In general, the osmotic pressure P depends only on the molar concentration and temperature of the solute, regardless of the type of solute,
P = MRT
It is represented by the formula shown as Here, M is the molar concentration of the solution [mol / L], R is the gas constant, and T is the absolute temperature. For example, using a solution obtained by dissolving 1 g of 1H-benzotriazole (C ₆ H ₅ N ₃ ) in 100 ml of water as a solution, and considering the conditions of operating at room temperature (300 K), the osmotic pressure is about 2.1 kg / cm 2. ² . This pressure is about 1000 times as large as 0.002 kg / cm ² , which is a driving pressure in a general wick type heat pipe, and 21 m of water is pumped from the bottom of the radiator 102 at the bottom to the water cooling jacket 101 at the top. It means that it is possible. Thereby, the cooling system of the thermosyphon structure which enabled the operation | movement in top heat mode (an evaporation part is an upper part and a condensation part is a lower part) can be comprised.

  When the cooling system according to the above-described embodiment of the present invention is applied to cooling of a general blade server, the condensate jacket 302 of the radiator 102 is provided regardless of the position of the heating element 109 such as a semiconductor device inside the server. It can be arranged so that it is at the lowest position of the server and the steam jacket 301 is at the highest position of the server. In this case, the height of a general blade server is 10 U (about 44.5 cm), and it is only necessary that the permeation membrane 107 can pump water of this height, and benzotriazole is added to 100 ml of water. If only about 21.4 mg (concentration 214 ppm) is added, the necessary permeation pressure can be obtained.

  In addition, the cooling system according to the above-described embodiment of the present invention increases the concentration of the solution when the solution in the water cooling jacket 101 decreases due to a temporary increase in the evaporation amount of water as a solvent. In addition, the osmotic pressure also increases in proportion to the concentration. As a result, the transport of water into the water cooling jacket 101 is promoted, and it is possible to prevent dryout (the working fluid is completely evaporated).

  In addition, the cooling system according to the above-described embodiment of the present invention has a large amount of solvent transport compared to the osmotic heat pipe described as the prior art, and enables efficient cooling by the radiator 102. Has the advantage of being large.

Although the above-described embodiment of the present invention has been described as using copper as the material of the thermosyphon, the present invention can use a metal having high thermal conductivity such as aluminum in addition to copper. As the solute, sucrose (C ₁₂ O ₂₂ H ₁₁ ), an alkali metal borate (for example, Na ₃ BO ₃ ), or the like can be used. As the osmotic membrane, when operating at a low temperature of 90 ° C. or lower, it is appropriate to use an acetyl cellulose membrane, a cellulose-based or nylon-based hollow membrane, and when used at a high temperature of 90 ° C. or higher, it is porous. It is appropriate to use a material such as porous glass or porous ceramics.

  FIG. 5 is a diagram showing a schematic configuration of an evaporative cooling system having a thermosyphon structure according to another embodiment of the present invention, and FIG. 6 shows a fine groove structure along the longitudinal direction of a pipe serving as a steam passage in another embodiment. It is a figure explaining. Another embodiment of the present invention described here is configured by removing the osmotic membrane 108 in the evaporative cooling system shown and described in FIG.

  Other embodiments of the present invention are provided with a water cooling jacket 101 that serves as an evaporating part of water as a refrigerant and a radiator 102 that serves as a condensing part of evaporated water, in the same manner as described with reference to FIG. The two are connected by a vapor passage 103 which is a pipe and a condensate passage 104 to form a loop in which the refrigerant circulates.

  The radiator 102 and the condensate passage 104 are partitioned by a osmotic membrane 107, and a condensate jacket 302 is formed in the lower part of the radiator 102, and a solvent 105 is disposed in the water-cooled jacket 101. And a mixed liquid 106 are enclosed.

  The other embodiment of the present invention as described above is different from that shown in FIG. 1 in that the osmotic membrane 108 that partitions the water cooling jacket 101 and the steam passage 103 is not provided. FIG. 6 illustrates a configuration in which the water cooling jacket 101 side is made to have a uniform gradient and the pipe 103 has a sufficient length, and the inner wall surface of the pipe that becomes the steam passage 103. This is that a fine groove structure 501 is provided along the longitudinal direction of the pipe as shown.

  The permeation membrane 108 shown in FIG. 1 is provided so that the solute in the water-cooled jacket 101 does not evaporate and mix with the solvent in the radiator 102 through the vapor passage 103. Usually, since the evaporation temperature of the solute is higher than that of water as the solvent, the amount of evaporation in the jacket 101 is not so large. Therefore, in another embodiment of the present invention shown in FIG. 6, the osmotic membrane 108 is not installed, and instead, the steam passage 103 is configured by piping having a uniform gradient and a sufficient length as described above. In addition, a fine groove structure 501 as shown in FIG. 6 is provided along the longitudinal direction of the pipe on the inner wall surface of the pipe excluding the vicinity of the steam jacket 103. The fine groove structure 501 provided on the inner wall surface of the above-described pipe has a function of entering the vapor passage 103 by capillary force and transporting the liquefied solute to the water-cooled jacket. It is possible to prevent the solute from being mixed in.

  Other embodiments of the present invention can eliminate the pressure loss caused by the presence of the osmotic membrane 108 as compared with the embodiment of the present invention described in FIG. Can be improved.

  FIG. 7 is a schematic view of a rack server and a blade server housed in a rack. Normally, as shown in FIG. 7A, a plurality of rack mount servers 703 are installed horizontally in a rack 701 including a rack door 702. The rack mount server 701 has a height that is an integral multiple of 1U (about 4.5 cm).

  When the cooling system according to the embodiment of the present invention is provided in such a rack mount server 703, the entire height dimension is used regardless of the arrangement position of a heating element such as a semiconductor device mounted on the substrate. Thus, a cooling system can be configured.

  Further, the blade server 705 is generally configured to have a thickness of 1U or 2U and a height of 10U (about 44.5 cm), and as shown in FIG. A plurality of units are installed vertically in the body 704.

  When providing the cooling system according to the embodiment of the present invention in such a blade server, as in the case of the rack mount server 703, regardless of the arrangement position of a heating element such as a semiconductor device mounted on a substrate, The entire height dimension (10 U) can be used to construct a cooling system.

DESCRIPTION OF SYMBOLS 101 Water cooling jacket 102 Radiator 103 Steam passage 104 Condensate passage 105 Solvent 106 Solution 107, 108 Permeation membrane 109 Heating element 201 Jacket cover 202 Jacket base 203 Evaporation promotion structure 301 Steam jacket 302 Condensate jacket 303 Radiator tube 304 Radiation fin 401 Fine fin Structure 501 Fine groove structure

Claims (7)

  A water cooling jacket that evaporates liquid refrigerant by heat from the heating element, a radiator that condenses the vapor by transferring the heat of the vapor refrigerant transported from the water cooling jacket to the outside, and transports refrigerant vapor from the water cooling jacket to the radiator A steam passage, a condensate passage for transporting condensate from the radiator to the water cooling jacket, a permeation membrane that partitions between the water cooling jacket and the steam passage and between the radiator and the condensate passage. A cooling system comprising a solute contained in the water cooling jacket and a mixed liquid of the refrigerant, and circulating the refrigerant between the water cooling jacket and the radiator. The cooling system according to claim 1,
A cooling system, characterized in that a refined structure made of porous copper in which a groove structure for promoting vaporization of the refrigerant is formed in the water cooling jacket. The cooling system of claim 1, wherein
The radiator is provided with a fine fin structure that promotes the liquefaction of the refrigerant and promotes the elimination of the condensate from the condensation surface of the refrigerant. The cooling system of claim 1, wherein
The cooling system, wherein the solute is a solute having a function of suppressing corrosion of a metal material.   A water cooling jacket that evaporates liquid refrigerant by heat from the heating element, a radiator that condenses the vapor by transferring the heat of the vapor refrigerant transported from the water cooling jacket to the outside, and transports refrigerant vapor from the water cooling jacket to the radiator A steam passage, a condensate passage for transporting condensate from the radiator to the water-cooling jacket, a permeation membrane partitioning the radiator and the condensate passage, a solute contained in the water-cooling jacket, and the refrigerant A cooling system, wherein the refrigerant is circulated between the water cooling jacket and the radiator. The cooling system of claim 5, wherein
The cooling system is characterized in that the steam passage is constituted by a pipe having a uniform gradient and a sufficient length. The cooling system of claim 6.
A cooling system, wherein a fine groove structure is provided along a longitudinal direction of the pipe on an inner wall surface of the pipe serving as the steam passage.

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