JP2011099605A - Micro channel type heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro channel type heat exchanger securing flow of a heat transport medium by separating gas from liquid. <P>SOLUTION: In the micro channel type heat exchanger 1 horizontally formed with a multiplicity of narrow grooves 4 housing the heat transport medium 3 transporting heat by being heated and evaporated, and arranged with heating parts 6 in lower sides of the narrow grooves 4, an affinity layer 4a with high affinity with the heat transport medium 3 is formed in a lower side portion in a vertical direction of an inner face of the narrow groove 4, a non-affinity layer 4b with lower affinity than the affinity layer 4a to the heat transport medium 4 is formed in an upper side portion of the affinity layer 4a, and the affinity layer 4a and non-affinity layer 4b are separately formed in the vertical direction of the narrow groove 4. As a result, when the heat transport medium 3 is vaporized by heat of a heating part 6 and bubbles 7 are generated, the heat transport medium 3 is held in the affinity layer 4a, the bubbles 7 move to the non-affinity layer 4b. Since gas can be separated from liquid, flow of the heat transport medium 3 can be secured. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat exchanger provided with a microchannel.

  A microchannel heat exchanger 101 is known as an example of a heat exchanger that takes heat from a heat source in a small electronic device or the like and cools the heat source. FIG. 3 schematically shows a cross-sectional view of a conventional general microchannel heat exchanger. The microchannel (thin groove) 104 is formed by a thin plate-like fin 105, for example. A heat source 106 is provided below the microchannel heat exchanger 101. When the heat of the heat generation source 106 is transmitted to the microchannel (thin groove) 104 through the casing 102, the heat transport medium 103 may be vaporized by the heat and bubbles 107 may be generated inside the microchannel 104. FIG. 4 schematically shows the internal state when heat from a heat source is transferred to a conventional general microchannel heat exchanger. It is known that bubbles (steam) 107 of the heat transport medium 103 generated by heat input inhibit the flow of the heat transport medium 103 depending on its size. That is, when the bubbles 107 are relatively large, the bubbles 107 block the microchannel 104 through which the heat transport medium 103 flows, and the heat transport medium 103 is difficult to flow. On the other hand, when the bubbles 107 are small, smooth flow of the heat transport medium 103 is hindered. In other words, the presence of the bubbles 107 in the microchannel 104 changes a so-called flow pattern such as the flow rate and flow rate of the heat transport medium 103, which affects the heat transfer efficiency. In addition, since the bubbles 107 act like a so-called air cushion inside the microchannel 104, the pressure inside the microchannel heat exchanger 101 changes, and the flow of the heat transport medium 103 is obstructed as described above. To do.

  Therefore, in the heat exchanger that transports heat by the heat transport medium 103, it has been conventionally studied to make the heat transport medium 103 flow smoothly. An example thereof is described in Patent Document 1. This Patent Document 1 describes an invention in which a hydrophilic part having hydrophilicity is formed on the inner wall surface and a water-repellent water-repellent part is formed on the hydrophilic part in order to improve the performance of the heat pipe. ing.

  Patent Document 2 describes an invention in which a hydrophilic surface is formed at the upper part of the inner wall surface of the heat transfer tube and a water-repellent surface is formed at the lower part.

  Furthermore, as a peripheral technique for forming a hydrophilic or water-repellent surface, Patent Document 3 discloses that fine irregularities are formed by plasma treatment on the surface of a fin that dissipates heat, and the surface is hydrophilic. Alternatively, an invention configured to form a water-repellent coating layer is described. Patent Document 4 describes an invention configured to microscopically disperse both a portion exhibiting hydrophilicity and a portion exhibiting water repellency on the surface of a fin that radiates heat.

JP 2008-39377 A JP-A-6-147784 Japanese Patent Laid-Open No. 2002-90084 JP-A-10-47890

  According to the invention described in Patent Document 1 described above, the heat transfer performance is improved by improving the circulation efficiency of the working fluid in the heat pipe. However, the configuration described in Patent Document 1 increases the evaporation amount of the hydraulic fluid per unit area by improving the so-called wettability of the inner wall surface of the heat pipe. Further, in the heat pipe, when the working fluid heated and vaporized by the heating unit moves to the condensing unit, the flow of the steam is condensed in the condensing unit and returned to the heating unit. Opposite the flow. For this reason, when the amount of evaporation increases, the vaporized hydraulic fluid and the condensed hydraulic fluid are mixed, which may hinder the flow (reflux) of the hydraulic fluid. That is, there is a possibility that gas-liquid separation cannot be performed, and there is room for improvement in this respect.

  Further, according to the invention described in Patent Document 2, the liquid refrigerant is repelled by the lower water-repellent surface and is easily supplied to the upper hydrophilic surface, thereby effective heat transfer when the liquid refrigerant evaporates. The area increases and the heat transfer efficiency can be improved. However, in the configuration described in Patent Document 2, the liquid refrigerant is supplied to the upper portion by the lower water-repellent surface, and tends to be held by the upper hydrophilic surface. For this reason, when the liquid refrigerant is heated and vaporized to generate bubbles, the bubbles and the liquid refrigerant may be mixed to impede the flow of the liquid refrigerant, and there is room for improvement in this respect.

  The present invention has been made paying attention to the above technical problem, and an object of the present invention is to provide a microchannel heat exchanger capable of ensuring the flow of a heat transport medium.

  In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that a plurality of narrow grooves are formed in the horizontal direction for accommodating a heat transport medium for transporting heat by being heated and evaporated, and the lower side of the narrow grooves. In the microchannel heat exchanger in which the heat generating portion is disposed, an affinity layer having a high affinity with the heat transport medium is formed on the lower portion of the inner surface of the narrow groove in the vertical direction, and the affinity A non-affinity layer having a lower affinity with the heat transport medium than the affinity layer is formed in a portion above the layer, and the affinity layer and the non-affinity layer are separated in the vertical direction of the narrow groove. It is characterized by being formed.

  According to a second aspect of the present invention, in the first aspect of the invention, the boundary between the affinity layer and the non-affinity layer is above the center in the vertical direction of the narrow groove and from the upper end of the narrow groove. Is a microchannel heat exchanger characterized by being formed on the lower side.

  According to the first aspect of the present invention, the affinity layer having high affinity with the heat transport medium is formed on the lower portion of the inner surface of the narrow groove. Further, a non-affinity layer having an affinity for the heat transport medium lower than that of the affinity layer is formed on the upper portion of the inner surface of the narrow groove. Therefore, when the heat transport medium is vaporized by heat input from the heat generating portion and bubbles are generated, the liquid phase heat transport medium is held below the narrow groove, and the bubbles move upward. As a result, the gas and liquid can be separated inside the narrow groove, and the flow of the heat transport medium can be ensured. That is, the flow of the heat transport medium in the liquid phase due to the mixture of gas and liquid is not hindered. In other words, since the bubbles are collected on the upper side, they do not act like the air cushion described above, so that changes in so-called flow patterns such as the flow velocity and flow rate of the heat transport medium can be suppressed. Thereby, the fluctuation | variation of an internal pressure can be suppressed compared with the conventional microchannel type heat exchanger. Furthermore, since the lower side of the narrow groove is filled with the liquid phase heat transport medium, the heat transfer efficiency can be improved.

  According to the invention of claim 2, in addition to the same effect as that of the invention of claim 1, the boundary between the affinity layer and the non-affinity layer is above the center in the vertical direction of the narrow groove, and the narrow groove It is formed below the upper end portion. In other words, the affinity layer through which the liquid-phase heat transport medium flows is formed larger than the non-affinity layer. Accordingly, it is possible to ensure a large region in which the liquid phase heat transport medium flows. As a result, a change in the so-called flow pattern of the heat transport medium can be suppressed.

It is a figure which shows typically sectional drawing of the microchannel type heat exchanger which concerns on this invention. It is a figure which shows typically the mode when the heat | fever from a heat-generation source is transmitted to the microchannel type heat exchanger which concerns on this invention. It is a figure which shows typically sectional drawing of the conventional common microchannel type | mold heat exchanger. It is a figure which shows typically the mode when the heat | fever from a heat source is transmitted to the conventional common microchannel type heat exchanger.

  Next, the present invention will be described with reference to specific examples. FIG. 1 schematically shows a cross-sectional view of a microchannel heat exchanger according to the present invention. In the microchannel heat exchanger 1, a plurality of microchannels (narrow grooves) 4 through which the heat transport medium 3 is circulated are accommodated in the hollow interior of the casing 2. The casing 2 is made of an arbitrary material such as metal or resin. In order to reduce the thermal resistance and improve the heat transfer efficiency, it is preferable to use a metallic material such as gold, copper, copper alloy, aluminum, and aluminum alloy. In addition, any refrigerant such as water can be used for the heat transport medium 3.

  The microchannel 4 is formed by, for example, bending a metal fin 5 formed in a thin plate shape into a U-shape. Further, the U-shaped opening 5a is formed to open in opposite directions.

  The microchannel 4 is made of an arbitrary material such as metal or resin. As the metal material, gold, copper, copper alloy, aluminum, aluminum alloy or the like having good thermal conductivity can be applied. When aluminum or an aluminum alloy is applied, these metal materials react with water to generate hydrogen gas. Therefore, it is preferable to coat cupric oxide, lead dioxide, barium peroxide or the like as a so-called hydrogen gas removing agent on the surface of aluminum or aluminum alloy that comes into contact with water.

  The microchannel 4 may be formed by bending the fin 5 formed in a thin plate shape as described above, or may be formed by firing the metal material described above. Further, when the microchannel 4 is made of resin, it can be formed by injection molding.

  A heat source 6 is provided below the microchannel heat exchanger 1 (lower side in FIG. 1), and the heat transport medium 3 in which the heat flows through the microchannel 4 via the casing 2 and the fins 5. Heat is transferred to the. The heat source 6 may be arbitrary, and may be a central processing unit (CPU) of an electronic device, for example.

  In the configuration example shown in FIG. 1, the heat transport medium 3 is configured to flow (flow) through the microchannel 4 in which the heat source 6 side is closed (opened upward in FIG. 1). A plurality of microchannels 4 for circulating the heat transport medium 3 and a plurality of voids of the microchannels 4 opened on the opposite side (lower side in FIG. 1) are arranged alternately. . The hydrophilic layer having a relatively high affinity with the heat transport medium 3 is coated on the inner wall surface 4a below the center of the microchannel 4 in the vertical direction to form an affinity layer 4a. On the contrary, the inner wall surface 4b above the center of the microchannel 4 in the vertical direction is coated with a non-hydrophilic material having a relatively low affinity with the heat transport medium 3, so that the non-affinity layer 4b is formed. Is formed. That is, the boundary between the affinity layer 4a and the non-affinity layer 4b is above the center in the vertical direction of the microchannel 4 and more than the upper end of the microchannel 4 (the portion opening upward in FIG. 1). It is formed on the lower side.

  In addition, the affinity layer 4a should just be formed so that the affinity with respect to the heat transport medium 3 may become relatively higher than the non-affinity layer 4b rather than the non-affinity layer 4b. Similarly, the non-affinity layer 4b may be formed so that the affinity for the heat transport medium 3 is relatively lower than that of the affinity layer 4a.

  More specifically, the affinity layer (hydrophilic layer) 4a described above is formed on the inner wall surface 4a of the microchannel 4 by suspending a hydrophilic material such as titanium oxide or tin oxide in a solvent such as water or alcohol. It is formed by volatilizing the solvent by applying and drying at room temperature and then heating at 100 ° C. or higher for 1 hour or longer. The non-affinity layer 4b is basically the water-repellent layer 4b. The water-repellent layer 4b is formed by suspending a water-repellent material such as hydrophobic silica or a fluorine-based material such as a fluororesin in an organic solvent such as alcohol or toluene. It is formed by volatilizing the solvent by applying to the inner wall surface 4b and naturally drying at normal temperature, and then heating at a temperature of 100 ° C. or higher for 1 hour or longer.

  As a method of forming the above-described two layers on the inner wall surface of the microchannel 4, first, a hydrophilic material is applied to the entire microchannel 4 as described above and sufficiently dried to form the hydrophilic layer 4a. Next, the upper inner wall surface 4b in the vertical direction of the microchannel 4 was immersed in a suspension containing a water repellent material so that the water repellent layer 4b had a predetermined height. Thereafter, the microchannel 4 is taken out of the suspension containing the water-repellent material and dried as described above, whereby the two layers can be accurately configured.

  As another method, first, the entire microchannel 4 is coated with a water repellent material in the same manner as described above, and then the laser beam is subjected to a hydrophilic treatment using a laser processing machine such as an excimer laser. Irradiate the necessary area. In this way, the film of the water repellent material is removed, and the surface of the metal material constituting the microchannel 4 is oxidized, for example, and the surface of the metal oxide may be used as the hydrophilic layer 4a. More specifically, when the microchannel 4 is formed of copper or a copper alloy, the hydrophilic layer 4a may be formed by irradiating a laser beam to form copper oxide on the surface layer of the microchannel 4. That is, copper oxide is an effective hydrophilic material like titanium oxide and tin oxide.

  FIG. 2 schematically shows the internal state when heat from the heat source is transmitted to the microchannel heat exchanger according to the present invention. According to the configuration shown in FIGS. 1 and 2, when heat is input from the heat generation source 6 and the heat transport medium 3 is vaporized by the heat to generate bubbles 7, the bubbles 7 are concentrated on the upper side of the microchannel 4. Is done. That is, since the upper non-affinity layer 4b is a water-repellent layer 4b coated with a water-repellent material, the water as the heat transport medium 3 is concentrated below the microchannel 4 due to the water repellency. Further, the lower affinity layer 4a is a hydrophilic layer 4a coated with a hydrophilic material, and so-called water wettability is good. Therefore, water as the heat transport medium 3 stays below the microchannel 4, and accordingly. The bubbles 7 are collected on the upper side. As a result, the gas phase and the liquid phase can be separated inside the microchannel 4. That is, it is prevented or suppressed that the microchannel 4 is blocked by the bubbles 7 and the bubbles 7 prevent the water that is the heat transport medium 3 from flowing.

  The boundary between the affinity layer 4 a and the non-affinity layer 4 b is formed above the center of the microchannel 4 and below the upper end portion of the microchannel 4. That is, the affinity layer 4a through which the liquid phase heat transport medium flows is formed larger than the non-affinity layer 4b. Therefore, it is possible to ensure a large region in which the liquid-phase heat transport medium 3 flows, and to suppress the so-called flow pattern change and improve the heat transfer efficiency. As a result, since the pressure fluctuation inside the microchannel 4 is suppressed, it is possible to obtain a so-called stable device in which variations in heat transfer efficiency hardly occur.

  DESCRIPTION OF SYMBOLS 1 ... Microchannel type heat exchanger, 3 ... Heat transport medium, 4 ... Microchannel (fine groove), 4a ... Affinity layer (hydrophilic layer), 4b ... Non-affinity layer (water-repellent layer), 5 ... Fin, 6 ... Heat source, 7 ... Bubbles (steam).

Claims (2)

In a microchannel type heat exchanger in which a large number of narrow grooves that accommodate a heat transport medium that transports heat by being heated and evaporated are formed in the horizontal direction, and a heat generating portion is disposed below the narrow grooves.
Of the inner surface of the narrow groove, an affinity layer is formed on the lower portion in the vertical direction, an affinity layer is formed, and an affinity with the heat transport medium is formed on a portion above the affinity layer. A non-affinity layer lower than the affinity layer is formed,
The microchannel heat exchanger, wherein the affinity layer and the non-affinity layer are formed separately in the vertical direction of the narrow groove. The boundary between the affinity layer and the non-affinity layer is formed above the center in the vertical direction of the narrow groove and below the upper end of the narrow groove. Item 2. The microchannel heat exchanger according to Item 1.

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