JP2006207968A - Heat transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve heat transfer performance of a heat transfer device without increasing a pressure loss of a fluid passage carrying a fluid receiving heat exchange. <P>SOLUTION: In the heat transfer device 1 carrying out heat transfer between heat transfer surfaces 3a and 3b, and the fluid, a porous layer 4 is provided in a boundary part of of the heat transfer surfaces 3a and 3b, and the fluid, the porous layer 4 has a multiplicity of pores 5 communicated with at least an area of the fluid, and thermoacoustic self-induced vibration is generated in the fluid in the pore 5. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a heat exchanger for performing heat exchange between two fluids having different temperatures, a heat radiator for a heating element such as an electronic device, and a heat transfer device used as a fluid heater or cooler.

  Conventionally, Patent Document 1 discloses the following technique as a technique for improving the heat transfer performance of a heat transfer device.

  In this prior art, a heat exchanger that performs heat exchange between exhaust gas from an engine and natural gas is used as a heat transfer device. In this heat exchanger, a metal porous member is disposed in a flow path through which exhaust gas passes and in a flow path through which natural gas passes.

With this metal porous member, the area of the heat transfer portion can be increased, and the heat transfer performance can be improved.
JP 2003-240473 A

  However, in the above-described conventional technology, the metal porous member is disposed so as to cross the flow path through which the fluid passes, and thus there arises a problem that the pressure loss of the fluid passage increases.

  An object of this invention is to improve the heat-transfer performance of a heat-transfer apparatus, without increasing the pressure loss of the fluid channel | path through which the fluid which receives heat exchange passes in view of the said point.

  In order to achieve the above object, according to the first aspect of the present invention, in the heat transfer device for transferring heat between the heat transfer surface (3, 3a, 3b, 11) and the fluid, the heat transfer surface (3, 3a) is provided. 3b, 11) and the fluid are provided with a porous layer (4, 4b, 4c), and the porous layer (4, 4b, 4c) has a large number of pores (at least communicating with the fluid region). 5), and is characterized in that thermoacoustic self-excited vibration is generated in the fluid in the pores (5).

  According to this, the fluid in the pores (5) of the porous layer (4, 4b, 4c) generates a thermoacoustic self-excited vibration, thereby generating a vibration flow in the length direction of the pores (5). . With this vibration flow, heat transfer between the heat transfer surfaces (3, 3a, 3b, 11) and the fluid can be efficiently performed, and heat transfer performance can be improved. The porous layer (4, 4b, 4c) is provided at the boundary between the heat transfer surface (3, 3a, 3b, 11) and the fluid and does not need to traverse the fluid passage. There is almost no increase in pressure loss.

  Here, the thermoacoustic self-excited vibration means that in a space formed by the pores (5), when a predetermined temperature gradient in the length direction of the pores (5) is generated in the fluid in the space, As the fluid is heated and cooled, the fluid in the space periodically expands and compresses to generate self-excited vibration in the length direction of the pore (5).

  Proceedings of the Japan Heat Transfer Symposium (Koto, “Heat Transfer Enhancement by Nano / Micro Multi-Porous Porous Layers: In the Case of Air”, 41st Japan Heat Transfer Symposium Proceedings, The Japan Heat Transfer Society, 2003 On May 26, Vol. 2, p.425-426), another technique for improving heat transfer performance is reported.

  According to this report, plate-like copper is used as the heat transfer surface (3, 3a, 3b, 11), and it is transferred with an acid or alkali mixed with carbon nanotubes, copper oxide nanoparticles, or aluminum oxide nanoparticles. The surface of the hot surface (3, 3a, 3b, 11) is chemically etched to form a nanoparticle porous layer (4, 4b, 4c) on the surface of the heat transfer surface (3, 3a, 3b, 11). . The heat transfer device (1) using this heat transfer surface (3, 3a, 3b, 11) is a heat transfer surface (3, 3a, 3b) in which the nanoparticle porous layer (4, 4b, 4c) is not formed. , 11) is reported to have a heat transfer promoting effect than the heat transfer device (1).

  However, this report does not disclose any heat transfer enhancement technology by the generation of thermoacoustic self-excited vibration, which is different from the present invention.

In the invention according to claim 2, in the heat transfer device for transferring heat between the heat transfer surface (3, 3a, 3b, 11) and the fluid, the heat transfer surface (3, 3a, 3b, 11) and the fluid Is provided with a porous layer (4, 4b, 4c), and the porous layer (4, 4b, 4c) has a large number of pores (5) leading to at least the fluid region. The aspect ratio (L / D), which is the ratio of the representative length (L) of the pores (5) to the representative diameter (D) of the pores (5), is L / D ≧ 1774 · L ^0.5 and is porous The layer (4, 4b, 4c) has an equivalent thermal conductivity (λ) of 20 W / (m · K) or less, and generates thermoacoustic self-excited vibration in the fluid in the pore (5). It is characterized by that.

  According to this, thermoacoustic self-excited vibration can be reliably generated in the fluid in the pores (5) of the porous layer (4, 4b, 4c), and in the length direction of the pores (5). An oscillating flow can be generated. With this vibration flow, heat transfer between the heat transfer surfaces (3, 3a, 3b, 11) and the fluid can be efficiently performed, and heat transfer performance can be improved. The porous layer (4, 4b, 4c) is provided at the boundary between the heat transfer surface (3, 3a, 3b, 11) and the fluid and does not need to traverse the fluid passage. There is almost no increase in pressure loss.

By the way, the vibration frequency f (Hz) of the thermoacoustic self-excited vibration is represented by the representative length (L) indicating the average length of the pore (5) and the sound velocity u in the fluid in the pore (5). . Specifically, it is represented by Formula F1.
f = u / (4 · L) (F1)
Further, when the temperature of the fluid in the pores (5) periodically changes, the heat penetration depth σ (m) is used as an index indicating how far the temperature change is transmitted. Specifically, the heat penetration depth σ is an index for determining the distribution of entropy fluctuation in the radial direction of the pore (5) by the thermal diffusion coefficient a (m ² / s) and the angular frequency ω (rad / s). It is represented by Formula F2.
σ = (2 · a / ω) ^0.5 (F2)
Here, the thermal diffusion coefficient a is a value obtained by dividing the thermal conductivity of the fluid in the pores (5) by the specific heat and density of the fluid (JIS29211-1982).

Further, the thermal relaxation time t (s) is used as an index representing how the heat transfer is affected by the fluctuation of the temperature change cycle of the fluid in the pores (5). Specifically, the thermal relaxation time t is expressed by Formula F3 using the representative diameter (D) of the pores (5) and the thermal diffusion coefficient a.
t = (D / 2) ² / 2a (F3)
Here, the representative diameter (D) is represented by (4 · channel cross-sectional area) / (wetting edge length).

From these, when the dimensionless amount ωt is used, the heat exchange inside the pore (5) is defined by Formula F4.
ωt = (D / 2 / σ) ² (F4)
Here, when ωt is 1 or less, the temperature of the fluid in the pore (5) is constant in the radial direction of the pore (5). Therefore, the fluid in the pore (5) changes isothermally in the radial direction of the pore (5) and has a temperature distribution only in the length direction of the pore (5). Desirable conditions can be obtained to generate vibration. That is, when the representative diameter (D) of the pores (5) is set to 2 · σ or less, the range of the aspect ratio (L / D) desirable for generating the thermoacoustic self-excited vibration can be determined.

  FIG. 10 shows the relationship between the representative length (L) of the pores (5), the self-excited vibration frequency f, and the representative diameter (D) when the representative diameter (D) = 2 · σ for air at a temperature of 300K. . FIG. 11 shows the relationship between the representative length (L) and the aspect ratio (L / D).

Thereby, it is understood that the range of the aspect ratio (L / D) in which it is desirable to generate the thermoacoustic self-excited vibration is the range represented by Formula F5. This is the range indicated by the oblique lines in FIG.
L / D ≧ 1774 · L ^0.5 (F5)
Further, as an important parameter for generating thermoacoustic self-excited vibration, there is a temperature gradient dT / dx (K / m) between one end of the pore (5) and the other end. Specifically, the temperature gradient is obtained by dividing the temperature difference between the temperature Th at one end of the pore (5) and the other end Tc by the representative length (L) of the pore (5). And represented by Formula F6.
dT / dx = (Th−Tc) / L (F6)
The temperature gradient dT / dx includes the amount of heat Q (W) transferred from the heat transfer surface (3, 3a, 3b, 11) to the fluid in the pore (5), and the heat transfer area S (m ² ) shown in FIG. And the equivalent thermal conductivity (λ) (W / (m · K)) of the porous layer (4, 4b, 4c).
dT / dx = (Q / S) / λ (F7)
Here, Q / S (W / m ² ) is a heat flux indicating a heat exchange amount per unit area, and an equivalent thermal conductivity (λ) is a member of the porous layer (4, 4b, 4c). The thermal conductivity λa, the thermal conductivity λb of the fluid in the pores (5), the porosity P indicating the ratio of the volume of all the pores (5) to the total volume of the porous layers (4, 4b, 4c), etc. Is the apparent thermal conductivity calculated by

  The temperature gradient required to generate self-excited thermoacoustic vibration in the pores (5) of the porous layer (4, 4b, 4c) is the 6th Stirling Cycle Symposium Proceedings (Correct, “Thermoacoustic Recorder Development ", Stirling Cycle Symposium Proceedings, Japan Society of Mechanical Engineers, October 18, 2002, Vol. 2, p. 127-128), it is reported to be about 9812.5 K / m. Moreover, according to examination of this inventor, it was confirmed that 9333.3 K / m or more is desirable.

Therefore, the temperature gradient necessary for generating the thermoacoustic self-excited vibration is set to 10,000 (K / m) or more, which exceeds the above two numerical values, and the heat flux is as high as 200 (kW / m ² ). In order to promote heat transfer, it is necessary to set the equivalent thermal conductivity λ to 20 (W / m · K) or less.

  According to a third aspect of the present invention, in the heat transfer device according to the first or second aspect, the length direction of the pores (5) is perpendicular to the heat transfer surface (3, 3a, 3b, 11). It is a feature.

  According to this, the direction of the temperature gradient coincides with the length direction of the pores (5), and an oscillating flow having a vertical component is effectively generated on the heat transfer surfaces (3, 3a, 3b, 11). Therefore, heat transfer between the heat transfer surface (3, 3a, 3b, 11) and the fluid can be performed efficiently, and the heat transfer performance can be improved. Here, the term “perpendicular” in claim 3 does not mean that the length direction of the pores (5) is completely perpendicular to the heat transfer surface (3, 3a, 3b, 11). Those having a slight inclination with respect to the vertical direction due to processing errors or the like in the process of forming the pores (5) are also included within the scope of the term vertical.

  According to a fourth aspect of the present invention, in the heat transfer device according to any one of the first to third aspects, the thickness of the porous layer (4, 4b, 4c) is 20% of the representative diameter of the fluid passage. It is characterized by the following.

  By such thickness setting, an increase in pressure loss in the fluid passage can be effectively suppressed.

  As in the invention described in claim 5, in the heat transfer device described in any one of claims 1 to 4, the multiple pores (5) may be independent of each other.

  According to a sixth aspect of the present invention, in the heat transfer device according to any one of the first to fourth aspects, at least some of the large number of pores (5) communicate with each other. Yes.

  According to this, not only the vibration flow in the length direction of the pores (5) is generated, but also a circulation flow is generated through a part of the other pores (5) and the communication holes. Heat transfer between (3, 3a, 3b, 11) and the fluid can be performed efficiently.

  The invention as set forth in claim 7 is characterized in that in the heat transfer device according to any one of claims 1 to 4, all of the large number of pores (5) communicate with each other.

  According to this, not only the vibration flow in the length direction of the pores (5) is generated, but also a circulation flow is generated through the communication holes with all the other pores (5). Heat transfer between (3, 3a, 3b, 11) and the fluid can be performed efficiently.

  As in the invention according to claim 8, in the heat transfer device according to any one of claims 1 to 7, the fluid may be filled in the pores (5).

  In invention of Claim 9, in the heat-transfer apparatus as described in any one of Claim 1 thru | or 7, the fluid is a liquid and the gas (12) exists in the inside of a pore (5). It is characterized by that.

  According to this, a gas having a large amplitude of thermoacoustic self-excited vibration with respect to the liquid generates thermoacoustic self-excited vibration, so that only the liquid exists inside the pore (5). Since the vibration flow with an amplified amplitude can be generated, the heat transfer between the heat transfer surface (3, 3a, 3b, 11) and the fluid can be performed efficiently.

  The invention according to claim 10 is characterized in that, in the heat transfer device according to claim 9, the gas is a gas (12) that is less soluble in the liquid than air.

  According to this, since the gas (12) is hardly dissolved in the liquid, the amplification effect of the thermoacoustic self-excited vibration can be more effectively exhibited.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1A is a front view of a state in which the heat transfer device of the present invention is applied to an air-cooled radiator 1 and the air-cooled radiator 1 is attached to an electronic device 2. FIG. 1B is a side view thereof.

  The air-cooled radiator 1 is composed of a plate-like base material portion 1a and a plate-like fin portion 1b, and the fin portions 1b are arranged at equal intervals perpendicular to the plate-like plane of the base material portion 1a. The material of the air-cooled radiator 1 is a kind of metal having high thermal conductivity, and specifically aluminum. The base material portion 1a and the fin portion 1b are integrally formed.

  The electronic device 2 is, for example, a CPU, a transistor integrated circuit, or the like. The electronic device 2 is fixed on an electronic circuit board (not shown) by soldering or the like, and the air-cooled radiator 1 is fixed to the electronic device 2 by means such as screwing or bonding (not shown). Further, air flows in a direction parallel to the plate surface of the fin portion 1b (in the direction of arrow B in FIG. 1B) by a fan (not shown).

  The outer surfaces of the base material portion 1a and the fin portion 1b of the air-cooled radiator 1 are heat transfer surfaces 3a and 3b, and a porous layer 4 is formed. A broken line in FIG. 1 indicates a range in which the porous layer 4 is formed. Here, it is desirable that the porous layer 4 is not formed on the contact surface between the air-cooled radiator 1 and the electronic device 2. Since heat transfer by solid-solid contact cannot be expected to promote heat transfer due to the generation of thermoacoustic self-excited vibration, it is better to directly contact the solids than to contact via the porous layer 4. Because.

  Next, a method for forming the porous layer 4 on the heat transfer surfaces 3a and 3b will be described. In order to form the porous layer 4, a known anodic oxidation method is used. Specifically, after surface treatment by mechanical polishing of the heat transfer surfaces 3a and 3b → degreasing → washing with water, etc., 3-8% oxalic acid solution is electrolyzed using the air-cooled radiator 1 as an anode. A direct current or an alternating voltage is applied as a liquid, thereby causing an electrochemical reaction on the surface (aluminum surface) of the air-cooled radiator 1. Aluminum dissolved by this electrochemical reaction is combined with oxygen in the electrolytic solution to form a porous aluminum oxide film, that is, a porous layer 4 on the heat transfer surfaces 3a and 3b.

  In the aluminum anodic oxidation method, the shape of the pores 5 of the porous layer 4 can be controlled by performing the texturing process in the pretreatment stage, the electrolytic solution concentration, the electrolytic voltage, the temperature, and the like.

In the present embodiment, since the thickness of the porous layer 4 is 1 μm to 200 μm, the diameter of the pore 5 is 10 nm to 500 nm, and the shape of the pore 5 of the porous layer 4 is controlled,
The relationship of aspect ratio L / D ≧ 1774 · L ^0.5 can be satisfied.

In this embodiment, since the temperature of the aluminum oxide forming the porous layer 4 is about 300 to 350 K, the thermal conductivity λa of the aluminum oxide is about 20 W / (m · K), and the air in the pores 5 The thermal conductivity λb is about 0.25 W / (m · K). Furthermore, since the porosity P of the porous layer 4 by the anodic oxidation method of this embodiment is about 0.163, the equivalent thermal conductivity λ of the porous layer 4 is λ = λa · (1−P) + λb · P.
16.8 W / (m · K).

  From the above, the pores 5 of the porous layer 4 of the present embodiment satisfy the aspect ratio condition described in claim 2, and the equivalent thermal conductivity (λ) of the porous layer 4 also satisfies the condition described in claim 2. Can be satisfied.

  Since the porous layer 4 is formed on the entire surface of the air-cooled radiator 1 in the anodizing method of aluminum, the porous layer 4 is not formed on the contact surface with the electronic device 2 by masking. Alternatively, after the porous layer 4 is formed by the anodic oxidation method, the porous layer 4 is eliminated by polishing the contact surface with the electronic device 2. As a result, the air-cooled radiator 1 and the electronic device 2 can be in direct contact.

  FIG. 2A is an enlarged top view of the porous layer 4 as viewed from the vertical direction of the heat transfer surfaces 3a and 3b, and FIG. 2B is a CC cross section of FIG. The pores 5 of the porous layer 4 formed by the anodic oxidation method are formed in a regular straight tube. The length direction of the pores 5 is formed in a direction perpendicular to the heat transfer surfaces 3a and 3b. In addition, although the bottom face part 4a located in the bottom part of the pore 5 remains in the porous layer 4, even if it is the surface of the aluminum in which the porous layer 4 is not generally formed, the layer of aluminum oxide has generate | occur | produced. Even if the bottom surface portion 4a remains, it does not cause deterioration of the heat transfer performance.

  In the above configuration, when the electronic device 2 is supplied with power through the circuit board and generates heat, the generated heat is transferred to the air-cooled radiator 1 from the contact surface between the electronic device 2 and the air-cooled radiator 1. It is. The amount of heat transferred to the air-cooled radiator 1 is dissipated from the heat transfer surfaces 3a and 3b on which the porous layer 4 of the base portion 1a and the fin portion 1b is formed to the air passing near the surface of the heat transfer surfaces 3a and 3b. Is done. Thereby, the amount of heat generated by the electronic device 2 is radiated to the air, and the temperature rise of the electronic device 2 can be prevented.

  In this embodiment, since the porous layer 4 is formed on the heat transfer surfaces 3a and 3b, it is generated by the aspect ratio of the pores 5 of the porous layer 4 and the temperature difference between the heat transfer surfaces 3a and 3b and air. Due to the temperature gradient of the porous layer 4, the air in the pores 5 generates thermoacoustic self-excited vibration. By this thermoacoustic self-excited vibration, the air in the pore 5 generates a vibration flow in the length direction of the pore 5 (the direction of arrow G in FIG. 2).

  On the other hand, since the main flow of air passing in the vicinity of the heat transfer surfaces 3a and 3b flows in the direction indicated by the arrow B, the vibration flow of the air in the pore 5 is a directional component perpendicular to the main flow direction of the air Have Therefore, the heat transfer between the heat transfer surfaces 3a and 3b and the air can be efficiently performed, and the heat transfer performance can be improved.

  In addition, as a method of forming the porous layer 4, it is also possible to use an etching method, a plating method, a method of sintering nanoparticles, or a combination of an anodic oxidation method and these methods. By using these methods, in addition to the regular straight tubular pores 5 as shown in FIG. 2, at least a part of the pores 5 as shown in FIG. It is also possible to form a porous layer 4 in which all the pores 5 communicate with each other as shown in FIG.

  When at least some of the pores 5 communicate with each other as shown in FIG. 3, not only the vibration flow in the direction of arrow G but also the difference in resistance when fluid enters and exits each pore, A circulating flow in the direction of arrow H in which the fluid moves to the other pore 5 also occurs. By these vibration flow and circulation flow, heat transfer between the heat transfer surfaces 3a and 3b and the air can be performed efficiently.

  Similarly, when all the pores 5 are in communication as shown in FIG. 4, the heat transfer between the heat transfer surfaces 3a and 3b and the air is efficiently performed by the vibration flow in the direction of arrow G and the circulation flow in the direction of arrow H. be able to.

(Second Embodiment)
In the first embodiment, the air-cooled radiator 1 that radiates heat generated by the electronic device 2 to the air has been described. However, the second embodiment illustrates the heat exchanger 6 that performs heat exchange between liquid and air. It demonstrates using 5-6. Specifically, the liquid in the second embodiment is warm water. FIG. 5A is an application of the heat transfer device of the present invention to the heat exchanger 6, and is a schematic view of the side surface of the heat exchanger 6, and FIG. 5B is a cross-sectional view taken along line EE in FIG. It is.

  In the heat exchanger 6, hot water flows in the order of the inlet pipe 7a → the inlet tank 7 → the tube 8 → the outlet tank 9 → the outlet pipe 9a. Fitting support holes 7b for fitting with a plurality of tubes 8 are provided at regular intervals on the side wall of the inlet tank 7, and a similar fitting support hole 9b is also provided on the side surface of the outlet tank 9. . The tube 8 is a tube having a flat cross section, and is arranged such that one end is fitted into the fitting support hole 7b and the other end is fitted into the fitting support hole 9b. The plurality of corrugated fins 10 are thin plates bent in a wave shape so as to fit the interval between the tubes 8, and are arranged between the tubes 8.

  The material of the inlet tank 7, the outlet tank 9, the tube 8, and the corrugated fin 10 is a kind of metal having a high thermal conductivity, and specifically aluminum. The inlet tank 7, the outlet tank 9, the tube 8, and the corrugated fin 10 are temporarily assembled and then brazed together. Further, air flows in a direction parallel to the wave front of the corrugated fin 10 (direction of arrow B in FIG. 5B) by a fan (not shown).

  In the heat exchanger 6, the inner surface of the tube 8 becomes the liquid side heat transfer surface 11 that transfers heat from the hot water to the tube 8, and the surface of the corrugated fin 10 changes to the air side heat transfer surface 3 that transfers heat from the corrugated fin 10 to the air. The porous layers 4b and 4c are formed respectively.

  A two-dot chain line in FIG. 5B indicates a range in which the porous layer 4 b is formed on the inner surface of the tube 8. A broken line indicates a range in which the porous layer 4 c is formed on the surface of the corrugated fin 10. In addition, in the heat transfer from the tube 8 to the corrugated fin 10 as in the first embodiment, it is desirable that the solids are brought into direct contact with each other. Further, since the corrugated fin 10 is extremely thin, it is difficult to remove the porous layer 4c by polishing or the like after the formation of the porous layer 4c.

  Therefore, after the heat exchanger 6 is integrally brazed, the porous layers 4b and 4c are formed by using an anodic oxidation method. Thereby, the porous layers 4b and 4c can be formed simultaneously, and the porous layer 4c can be excluded from the contact surface between the tube 8 and the corrugated fin 10.

  Further, in order to suppress an increase in pressure loss when hot water passes through the tube 8 on the liquid side heat transfer surface 11, the thickness of the porous layer 4 b is 20% or less of the inner diameter of the representative diameter of the hot water passage in the tube 8. Value.

  Further, a gas 12 is allowed to exist in the pores 5 of the porous layer 4 b of the liquid side heat transfer surface 11. As the gas 12, helium 12 is used which is less soluble in water than the air and whose dissolved amount is less affected by the water temperature. Specifically, in the process of forming the porous layer 4b, the inside of the tube 8 is evacuated and replaced with helium 12. At this time, the amount of helium 12 in the pore 5 is adjusted by adjusting the pressure of the helium 12 in the tube 8 at the time of helium replacement. Thereafter, hot water is introduced into the tube 8.

  Although helium 12 in the pores 5 of the porous layer 4b may move in the porous layer 4b, it is difficult for the helium 12 to escape from the porous layer 4b because the pores 5 are extremely small spaces. For this reason, helium 12 can remain in the pores 5 by introducing warm water into the tube 8. At this time, the volume of helium 12 remaining in the pores 5 is desirably 50% or less of the volume of the pores 5 at room temperature.

  In the above configuration, the heat quantity of the hot water is transferred from the liquid side heat transfer surface 11 to the tube 8. The amount of heat transferred to the tube 8 is transferred from the contact surface between the tube 8 and the corrugated fin 10 to the corrugated fin 10, and the amount of heat transferred to the corrugated fin 10 is greater than the air-side heat transfer surface 3 than the air-side heat transfer surface 3. The heat is dissipated to the air passing near the surface.

  In this embodiment, since the porous layer 4b is formed on the liquid side heat transfer surface 11, the aspect ratio of the pores 5 of the porous layer 4b on the liquid side heat transfer surface 11 and the temperature gradient of the porous layer 4b. As a result, the hot water and the helium 12 in the pores 5 generate thermoacoustic self-excited vibrations. At this time, since helium 12 having a large volume change due to temperature change with respect to hot water generates thermoacoustic self-excited vibration, the amplitude is further increased compared to the case where only hot water vibrates in the pore 5. Amplified vibrational flow can be generated. Due to this thermoacoustic self-excited vibration, the hot water and helium 12 in the pores 5 oscillate in the length direction of the pores 5 (the direction of the arrow G in FIG. 6).

  On the other hand, since the main flow of hot water passing through the liquid side heat transfer surface 11 flows in the direction indicated by the arrow B, the oscillating flow of the hot water and the helium 12 in the pores 5 is perpendicular to the main flow direction of the hot water. Will have ingredients. Therefore, the heat transfer between the liquid side heat transfer surface 11 and the hot water can be performed efficiently, and the heat transfer performance can be improved.

  As in the first embodiment, in addition to the regular straight tubular pores 5 as shown in FIG. 6, a porous layer 4b in which at least a part of the pores 5 as shown in FIG. It is also possible to form a porous layer 4b in which all the pores 5 communicate with each other as shown in FIG.

  When at least a part of the pores 5 are in communication as shown in FIG. 7, not only a vibration flow in the direction of arrow G but also a circulation flow in the direction of arrow H occurs. The heat transfer between the hot water and the liquid side heat transfer surface 11 can be efficiently performed by the amplified vibration flow and circulation flow.

  Even when all the pores 5 are in communication as shown in FIG. 8, the heat transfer between the hot water and the liquid-side heat transfer surface 11 is similarly caused by the amplified vibration flow in the arrow G direction and the circulation flow in the arrow H direction. Can be performed efficiently.

  Further, the air in the pores 5 of the porous layer 4c of the air side heat transfer surface 3 that transfers heat from the corrugated fins 10 to the air causes the same thermoacoustic self-excited vibration as in the first embodiment, and the heat transfer is efficiently performed. Can be done.

(Third embodiment)
In the first embodiment, the air-cooled radiator 1 that radiates the heat generated by the electronic device 2 to the gaseous air has been described. The vessel 13 will be described with reference to FIG. Specifically, the liquid in the third embodiment is cooling water. FIG. 9A is a side view of the liquid-cooled radiator 13 attached to the electronic device 2, and FIG. 9B is a cross-sectional view taken along the line II of FIG.

  The liquid-cooled radiator 13 is flat and has a cooling water inflow pipe 14a on one side surface, and a cooling water outflow pipe 14b on the other end surface. The liquid-cooled radiator 13 is provided with a plurality of through holes at regular intervals so as to penetrate the cooling water inflow pipe 14a from the cooling water inflow pipe 14a. This through hole constitutes a cooling water passage 14 serving as a cooling water passage, and the coolant flows in the order of the cooling water inflow pipe 14a → the cooling water passage 14 → the cooling water outflow pipe 14b. The material of the liquid-cooled radiator 13 is a kind of metal having high thermal conductivity, specifically aluminum.

  The electronic device 2 is the same as that of the first embodiment, and the liquid-cooled radiator 13 is fixed to the electronic device 2 by means of a screwing structure or an adhesive (not shown).

  The inner surface of the through hole constituting the cooling water passage 14 of the liquid cooling radiator 13 becomes the liquid side heat transfer surface 11, and the porous layer 4 is formed. A broken line in FIG. 9 indicates a range in which the porous layer 4 is formed. In the porous layer 4, helium 12 is left in the pores 5 of the porous layer 4 in the same manner as in the second embodiment.

  Here, when the porous layer 4 is formed by the anodic oxidation method, the porous layer 4 is formed on the entire outer surface of the liquid-cooled radiator 13. However, as in the first embodiment, in heat transfer from the electronic device 2 to the liquid-cooled radiator 13, it is desirable that the solids are in direct contact with each other. Therefore, the contact surface with the electronic device 2 is subjected to a masking process or a polishing process after the porous layer 4 is formed so that the electronic device 2 and the liquid-cooled radiator 13 can directly contact each other.

  In the configuration as described above, the heat amount of the electronic device 2 is transferred to the liquid-cooled radiator 13, and the heat amount transferred to the liquid-cooled radiator 13 is radiated from the liquid-side heat transfer surface 11 to the cooling water.

  In the present embodiment, since the porous layer 4 is formed on the liquid-side heat transfer surface 11, heat transfer can be efficiently performed by thermoacoustic self-excited vibration of cooling water and helium 12 as in the second embodiment. Can do.

(Other embodiments)
In the first to third embodiments, as an application example of the present invention, a radiator that radiates heat to air or liquid and a radiator that performs heat exchange between hot water and air have been described. The present invention can be widely applied to heat exchangers that perform heat exchange between liquids and gases, and heat exchangers that perform heat exchange between a liquid refrigerant accompanying a phase change and gas or liquid. For example, the present invention can be applied to a warm water heater, an air conditioning condenser, an air conditioning evaporator, and the like.

  In the first to third embodiments, aluminum is used as a kind of metal having high thermal conductivity for the material of the heat transfer device, but the pores 5 of the porous layer 4 are formed in the same manner as in the embodiment. It is also possible to use a material such as copper or stainless steel whose aspect ratio can be controlled.

(A) is a front view of the air-cooling type heat radiator of 1st Embodiment, (b) is a left view. (A) is an enlarged top view showing the schematic structure of the porous layer of 1st Embodiment, (b) is CC sectional drawing of (a). It is an expanded sectional view showing the schematic structure of another porous layer in a 1st embodiment. It is an expanded sectional view showing the schematic structure of another porous layer in a 1st embodiment. (A) is a left view of the heat exchanger of 2nd Embodiment, (b) is EE sectional drawing of (a). It is an expanded sectional view showing the state where gas exists in the pore of the porous layer of a 2nd embodiment. It is an expanded sectional view showing the state where gas exists in the pore of another porous layer in a 2nd embodiment. It is an expanded sectional view showing the state where gas exists in the pore of another porous layer in a 2nd embodiment. (A) is a left view of the liquid cooling type heat radiator of 3rd Embodiment, (b) is II sectional drawing of (a). It is a graph showing the relationship between the representative length L of a pore, the thermoacoustic self-excited vibration frequency f, and the heat penetration depth (sigma). It is a graph showing the relationship between the representative length L of a pore, and the aspect-ratio L / D.

Explanation of symbols

  3, 3a, 3b, 11 ... heat transfer surface, 4, 4b, 4c ... porous layer, 5 ... pore, 12 ... gas.

Claims (10)

In the heat transfer device for transferring heat between the heat transfer surface (3, 3a, 3b, 11) and the fluid,
A porous layer (4, 4b, 4c) is provided at the boundary between the heat transfer surface (3, 3a, 3b, 11) and the fluid,
The porous layer (4, 4b, 4c) has a number of pores (5) leading to at least the region of the fluid;
A heat transfer device characterized in that thermoacoustic self-excited vibration is generated in the fluid in the pores (5). In the heat transfer device for transferring heat between the heat transfer surface (3, 3a, 3b, 11) and the fluid,
A porous layer (4, 4b, 4c) is provided at the boundary between the heat transfer surface (3, 3a, 3b, 11) and the fluid,
The porous layer (4, 4b, 4c) has a number of pores (5) leading to at least the region of the fluid;
The aspect ratio (L / D), which is the ratio of the representative length (L) of the pores (5) and the representative diameter (D) of the pores (5), is L / D ≧ 1774 · L ^0.5
And
The porous layer (4, 4b, 4c) has an equivalent thermal conductivity (λ) of 20 W / (m · K) or less,
A heat transfer device characterized in that thermoacoustic self-excited vibration is generated in the fluid in the pores (5). The heat transfer device according to claim 1 or 2, characterized in that the length direction of the pores (5) is perpendicular to the heat transfer surface (3, 3a, 3b, 11). The heat transfer device according to any one of claims 1 to 3, wherein a thickness of the porous layer (4, 4b, 4c) is 20% or less of a representative diameter of the fluid passage. The heat transfer device according to any one of claims 1 to 4, wherein the plurality of pores (5) are independent of each other. The heat transfer device according to any one of claims 1 to 4, wherein at least some of the plurality of pores (5) communicate with each other. The heat transfer device according to any one of claims 1 to 4, wherein all of the plurality of pores (5) communicate with each other. The heat transfer device according to any one of claims 1 to 7, wherein the fluid is filled in the pores (5). The heat transfer device according to any one of claims 1 to 7, wherein the fluid is a liquid and a gas (12) is present inside the pores (5). The heat transfer device according to claim 9, wherein the gas (12) is a gas that is less soluble in the liquid than air.

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