JP2020020496A - Wick, loop-type heat pipe, cooling device, electronic apparatus, and wick manufacturing method - Google Patents

Abstract

To provide a wick capable of further improving cooling performance of cooling means.SOLUTION: A wick 6 is used in a loop-type heat pipe 1 including an evaporation portion 2 (heat receiving portion 7) changing a phase of a working fluid from a liquid phase to a gas phase, and a condensation portion 3 for changing the phase of the working fluid from the gas phase to the liquid phase, has a plurality of gas phase fluid grooves 10 for transporting the working fluid changed to the gas phase, and is composed of a porous body disposed inside of the evaporation portion 2. The porous body is composed of foam silicone rubber or foam urethane rubber having a plurality of pores of an average pore diameter of 50 [μm] or less, and communicated with each other, and the gas phase fluid grooves 10 satisfy a relationship of La/Lb≥1 when a length of a contact side brought into contact with a housing of the evaporation portion 2 of the gas-phase flow channel cross-section orthogonal to a direction of transporting the working fluid changed to the gas phase is La, and a length of a bottom side opposed to the contact side is Lb, in a state that the wick 6 is disposed inside of the evaporation portion 2.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a wick, a loop heat pipe, a cooling device, an electronic device, and a wick manufacturing method.

  Conventionally, the evaporator that changes the phase of the working fluid from a liquid phase to a gas phase, and a condenser that includes a condenser that changes the phase of the working fluid from a gas phase to a liquid phase, are used for cooling means, and the phase of the working fluid changes to a gas phase. There is known a wick having a plurality of gas-phase fluid grooves for transporting a working fluid and formed of a porous body provided inside the evaporator.

For example, Patent Literature 1 discloses an apparatus in which the following wick is provided inside an evaporator of a loop heat pipe.
A plurality of gas-phase fluid grooves, which are cylindrical hollow members having one end closed and made of porous rubber, and serve as a gas-phase flow path in a direction perpendicular to the circumferential direction of the outer peripheral surface in contact with the casing of the evaporator. The wick has a (steam discharge groove) formed therein, and the wick is provided inside the evaporator.
Specifically, a wick made of foamed silicone rubber or urethane foam, which is larger than the inner diameter of a cylindrical internal space having a casing of the evaporator, is pressed into the casing of the evaporator.
In addition, the specifications (specifications and conditions at the time of manufacture) of the porous cell structure of the porous rubber constituting the wick are such that the average pore diameter is 50 [μm] or less and the porosity is 20 [%] or more. It is considered that the ratio is preferably 80% or less and the open cell ratio is 25% or more and 100% or less.
With these configurations, it is possible to easily secure the adhesion of the wick to the inner surface of the casing of the evaporator and to suppress the local collapse of the pores near the outer peripheral surface of the wick, thereby achieving good cooling performance. It is said that it can be obtained.

  However, in recent years, there has been an increasing demand for cooling means used in electronic devices and the like to further improve the cooling performance.

  In order to solve the above-mentioned problem, an invention according to claim 1 is an evaporator for changing a phase of a working fluid from a liquid phase to a gas phase, and a condenser for changing a phase of a working fluid from a gas phase to a liquid phase. A cooling means having a plurality of gas-phase fluid grooves for transporting a working fluid that has changed into a gas phase, and a wick made of a porous body provided inside the evaporator, The porous body is a foamed silicone rubber or a foamed urethane rubber having a plurality of communicating pores having an average pore diameter of 50 [μm] or less. In the state, the length of the contact side of the flow path cross section orthogonal to the direction in which the working fluid that has changed to the gas phase is transported is La, and the length of the bottom side facing the contact side is La. When the length is Lb, the relationship of La / Lb ≧ 1 is satisfied. And wherein the door.

  ADVANTAGE OF THE INVENTION According to this invention, the wick which can implement | achieve the further improvement of the cooling performance of a cooling means can be provided.

The schematic explanatory drawing showing an example of the loop type heat pipe concerning one embodiment. The figure which shows the virtual cross section when it cut | disconnects by the aa cross section shown by the broken line in FIG. The schematic explanatory drawing of the conventional general loop type heat pipe. FIG. 7 is an explanatory diagram schematically illustrating another example of the loop heat pipe provided in the electronic apparatus according to the embodiment. Explanatory drawing of the groove | channel shape of the gas-phase fluid groove provided in a wick. FIG. 4 is an explanatory diagram of the specifications of samples of Examples and Comparative Examples used for a cooling performance test, and test results.

Hereinafter, an embodiment of a loop heat pipe (hereinafter, referred to as a loop heat pipe 1) as a cooling unit including an evaporator provided with a wick to which the present invention is applied and a condenser will be described as appropriate. This will be described with reference to FIG.
Here, in each of the drawings for describing the present embodiment, components such as members and components having the same function or shape are denoted by the same reference numerals as far as possible. Further, once the components denoted by the same reference numerals are described, the description thereof will be appropriately omitted.
FIG. 1 is a schematic explanatory view showing an example of the loop heat pipe 1 according to the present embodiment, and FIG. 2 shows a virtual cross section taken along a line aa shown by a broken line in FIG. FIG.

  The loop type heat pipe 1 shown in FIG. 1 has a working fluid composed of a condensable fluid such as water, alcohol, acetone, or chlorofluorocarbon sealed therein, and includes the following. An evaporator 2 is provided that absorbs heat from the heat generator to evaporate the working fluid from the liquid phase to the gas phase, and a condenser 3 that condenses the gaseous working fluid guided from the evaporator 2 into the liquid phase. I have. Further, a steam pipe 4 for flowing a gas-phase working fluid from the evaporating section 2 to the condensing section 3 and a liquid pipe 5 for flowing a liquid-phase working fluid from the condensing section 3 to the evaporating section 2 are also provided.

The evaporating section 2 includes a heat receiving section 7 in which a wick 6 is accommodated, and a reservoir section 8 for storing a working fluid in a liquid phase.
One end of the steam pipe 4 is connected to the heat receiving section 7, and one end of the liquid pipe 5 is connected to the reservoir section 8. The other end of each of the vapor pipe 4 and the liquid pipe 5 is connected to the condenser 3. The condensing part 3 is constituted by a stainless steel pipe 31 provided with a large number of thin aluminum fins 32 on the outer peripheral surface.

The wick 6 is a porous body having elasticity. A plurality of gas phase fluid grooves (grooves) 10 are provided on the bottom surface of the wick 6 in FIG. 1 from the end on the steam pipe 4 side to the opposite side.
The plurality of gas-phase fluid grooves 10 are provided at equal intervals on the bottom of the wick 6 as shown in FIG. 2 showing a virtual cross section taken along the aa cross section indicated by a broken line in FIG. Here, in FIG. 2, the dimensions of the gas phase fluid grooves 10 are drawn at a ratio larger than the actual size. The thickness of the wick 6 is set to be slightly larger than the inner size of the housing of the heat receiving section 7 of the evaporating section 2.

  By setting the thickness of the wick 6 as described above, the wick 6 comes into close contact with the inner surface of the heat receiving unit 7 when the wick 6 is housed in the heat receiving unit 7. Further, since the wick 6 is in close contact with the heat receiving unit 7, the heat of the heat generating unit is efficiently transmitted to the wick 6 through the housing of the heat receiving unit 7. On the other hand, in a portion where the gas-phase fluid groove 10 is provided, a space is formed between the heat-receiving unit 7 and the housing.

Since the wick 6 is made of a porous material, that is, a porous material, the liquid-phase working fluid stored in the reservoir 8 permeates into the wick 6 by capillary action. The wick 6 also functions as a pump for sending the liquid-phase working fluid from the condensing section 3 to the evaporating section 2 by the capillary action.
As the working fluid, a condensable fluid such as water, alcohol, acetone, or chlorofluorocarbon is used. The working fluid preferably has good wettability with the wick 6 so that it can easily penetrate into the wick 6. The wettability can be measured by the contact angle between the wick 6 and the working fluid. If the contact angle is 90 [°] or more, the working fluid cannot penetrate into the wick 6, so the contact angle needs to be less than 90 [°].

  In the loop heat pipe 1 according to the present embodiment, when heat from the heat generating unit is transmitted to the liquid-phase working fluid in the wick 6 through the housing of the evaporating unit 2 (heat receiving unit 7), the heat is activated. The fluid evaporates and changes to the gas phase. The working fluid that has been evaporated and changed to the gas phase is sent to the steam pipe 4 through the gas phase fluid groove 10. Then, the gas-phase working fluid is sent to the condenser 3 through the steam pipe 4.

  In the condensing unit 3, the heat of the working fluid passing through the inside (the pipe 31) is released to the outside through the fins 32, so that the temperature of the working fluid is reduced and condensed, and the working fluid is converted from a gas phase to a liquid phase. Change. The working fluid that has changed to the liquid phase moves to the evaporating section 2 through the liquid pipe 5 and permeates again from the reservoir section 8 into the wick 6 provided inside the heat receiving section 7 by capillary action. By performing such circulation of the working fluid, the heat of the heat generating portion is continuously released to the outside, and the cooling target is cooled.

Here, the problem of the conventional loop heat pipe in which the wick is provided inside the evaporator will be described with reference to the drawings.
FIG. 3 is a schematic explanatory view of a conventional general loop type heat pipe 100.
Generally, as shown in FIG. 3, the loop heat pipe 100 includes an evaporating unit 102 that receives heat from the outside and evaporates a working fluid from a liquid phase to a gas phase, and a heat dissipating to the outside to transfer the working fluid from the gas phase. A condensing unit 103 for condensing into a liquid phase is provided. Further, a vapor pipe 104 for flowing a gas-phase working fluid from the evaporating section 102 to the condensing section 103 and a liquid pipe 105 for flowing a liquid-phase working fluid from the condensing section 103 to the evaporating section 102 are also provided.

  The wick 106 made of a porous material (porous material) is accommodated inside the evaporator 102, and the working fluid in the liquid phase sent from the liquid pipe 105 causes the fine pores of the wick 106 to generate capillary action. And penetrates the outer surface of the wick 106. At this time, when the heat from the heat generating portion (cooling target) in contact with the evaporating portion 102 is transmitted to the wick 106 through the housing of the evaporating portion 102, the working fluid evaporates with the heat and changes into a gas phase. Then, the working fluid that has changed to the gas phase moves to the condenser 103 through the steam pipe 104.

In the condensing section 103, the heat of the working fluid is released to the outside, so that the temperature of the working fluid decreases and changes to a liquid phase. Then, the working fluid that has changed to the liquid phase moves to the evaporating section 102 through the liquid pipe 105 and permeates into the wick 106 again. As described above, in the loop heat pipe 100, by utilizing the phase change of the working fluid, the working fluid is circulated, and the heat absorbed by the evaporating unit 102 is transferred to the condensing unit 103, so that the object to be cooled is efficiently placed. Can be cooled.
Here, in order to improve the cooling efficiency, close contact with the evaporator 102 is ensured, the working fluid is circulated by the capillary force of the wick 106, and the wick 106 has a high penetration to minimize the pressure loss. Sex is required.

To solve such a problem, Patent Document 2 discloses that a metal pattern is formed on an outer surface of a wick, and the metal pattern and an inner wall of a casing of the evaporator are diffusion-bonded, so that the wick and the casing are integrated. A loop-type heat pipe is described, which prevents a gap from being formed on a joint surface due to thermal or mechanical stress.
In addition, in order to ensure good adhesion of the wick to the housing, it is common practice to form the wick from a resin material and form the outer diameter of the wick slightly larger than the inner diameter of the housing. . However, if the outer diameter of the wick becomes excessively large due to a manufacturing error, when the wick is housed (press-fitted) in the housing and compressed, the gas-phase fluid groove provided on the outer peripheral portion of the wick is crushed or broken. This may impede the flow of the working fluid and reduce the cooling performance.

On the other hand, Patent Literature 3 discloses the following loop heat pipe.
In addition to the outer groove formed on the outer peripheral surface of the wick, an inner groove extending in the length direction is formed on the inner peripheral surface of the wick. Then, by deforming the wick so that the inner groove is closed when the wick is pressed into the housing of the evaporator and housed therein, even if a manufacturing error occurs in the outer diameter of the wick, the pores near the outer peripheral surface are crushed. Is to suppress.
With these configurations, an evaporator having poor performance is obtained because pores near the outer peripheral surface of the wick are crushed or the outer surface of the wick is not in good contact with the inner surface of the evaporator housing. It is said that wicks that can suppress this can be mass-produced in a stable manner.

  However, in the wick described in Patent Literature 3, the process of forming grooves on both the inner peripheral surface and the outer peripheral surface of the wick becomes complicated, which leads to an increase in cost and specifications of the manufactured wick (specifications and specifications). Depending on the conditions), the desired cooling performance may not be obtained.

Patent Literature 4 describes the following loop heat pipe.
An inner peripheral portion into which a liquid-phase working fluid (working fluid) flows, and an outer peripheral portion in which a plurality of gas-phase fluid grooves (steam discharge grooves) having a depth of 1 mm and a width of 1 mm are formed along the longitudinal direction. Is an oval (oval) resin wick, and the wick is provided inside the evaporator.
Specifically, there is described an example in which the wick, which is larger than the oblong internal space (inner dimension) of the evaporator housing (evaporator case), is pressed into the evaporator housing.
By pressing the wick larger than the internal space of the evaporator into the housing of the evaporator in this way, the adhesion between the inner wall of the evaporator housing and the wick can be increased, and It is said that it promotes a phase change of the working fluid into a gas phase at a contact portion between the wall and the wick.
Further, it is stated that suitable materials for the resin wick include a fluorine resin, a PEEK (polyether ether ketone) resin, a polypropylene resin, a polyacetal resin, and the like.

However, with the resin wick of Patent Document 4, high elasticity cannot be obtained, and when the wick is provided inside the evaporator, local collapse of the gas phase fluid groove, local vicinity of the outer peripheral surface of the wick, or the like occurs. There was a possibility that the desired cooling performance could not be obtained due to the collapse of the pores.
Therefore, with respect to the wick 6 of the present embodiment, the specifications (specifications and conditions at the time of manufacture) of the wick that can further improve the cooling performance of the cooling means are examined.

Next, the wick 6 provided inside the heat receiving section 7 (evaporating section 2) of the loop heat pipe 1 of the present embodiment will be described in detail.
As described above, the wick 6 used in the loop heat pipe 1 according to the present embodiment is made of a porous material such as a porous rubber such as foamed silicone rubber. As described above, since the wick 6 is made of porous rubber, a higher elastic force can be obtained as compared with the porous resin. Therefore, the adhesion of the wick 6 to the housing (heat receiving section 7) of the evaporating section 2 can be obtained. Increase. Thereby, the heat transfer efficiency from the casing of the evaporating section 2 to the wick 6 can be favorably obtained, and the cooling performance of the loop heat pipe 1 is improved.

Further, as described above, it is possible to secure the high adhesion of the wick 6 and suppress the local collapse of the pores only by taking the wick 6 as a porous rubber. For this reason, if post-processing of the gas-phase fluid groove 10 (groove) for transporting the working fluid (evaporated refrigerant) can be omitted, the manufacturing cost can be further reduced.
Various methods can be considered for a method of manufacturing a wick made of such an elastic porous body, that is, a porous elastic body. The porous body in the present embodiment is proposed as, for example, a water-foamed silicone rubber. It can be obtained by applying the technology.
Specifically, using the water-foamed silicone rubber composition, stirring is performed so that bubbles existing in the cross section obtained when the foam formed by sampling are cut are present as follows. The bubbles present in the cross section have a size in the range of 0.1 μm or more and 50 μm or less, and the bubbles having a pore size of 5 μm or more and 10 μm or less are most likely. Stir so that there is more.

More specifically, the above-described porous body is obtained by mixing a catalyst, a surfactant, and a crosslinking agent with a commercially available two-part liquid silicone rubber. There, an additive, a filler, a dispersant, and the like are mixed with water (to which alcohol is added as necessary), and the mixture is stirred with a mixed solution having a viscosity equivalent to that of the liquid silicone rubber to prepare an emulsion composition. The liquid silicone rubber preferably has a specific gravity of 1.00 to 1.05 [g / cm ³ ] in consideration of emulsifiability with water.
Here, the compounding ratio of the liquid silicone rubber and the mixed solution varies depending on the porosity to be obtained.
For example, if the mixing ratio of the liquid silicone rubber and the mixed solution is 1: 1, fine water in the emulsion evaporates to form voids, so that a foam having a porosity of 50% can be obtained.

The emulsion is stirred using a homogenizer or, if necessary, a stirrer with ultrasonic treatment so as to obtain a bubble distribution satisfying the above conditions, stirring time, stirring speed (for example, 300 to 1500 [rpm]). Adjust various stirring conditions such as.
Thereafter, the prepared emulsion composition is filled in a mold and heated to perform primary heating for curing the silicone rubber without evaporating water in the emulsion composition.
Here, the heating temperature is in the range of 80 to 130 ° C., and the heating time is in the range of 30 to 120 minutes. The heating temperature is desirably 90 to 110 [° C], and the heating time is desirably 60 to 90 minutes. Next, secondary heating is performed to remove moisture from the foam after the primary heating. The heating temperature is 150 to 300 [° C.], and the heating time is 1 to 24 hours. Desirably, the heating temperature is 200 to 250 [° C.] and the heating time is 3 to 8 hours. By performing such secondary heating, moisture is removed from the porous body, the cells are made into a continuous cell type, and the final curing of the silicone rubber is completed.

  In addition, there are a method of forming the gas-phase fluid groove 10 in a mold having a groove shape in advance at the time of primary heating, and a method of forming by post-processing using a processing machine such as an end mill after secondary heating. The selection is made in consideration of the shape of the gas-phase fluid groove 10 and the machinability of the porous body.

Next, the specifications of the cross section (specifications, conditions at the time of manufacture) that can be obtained when the water-cured silicone rubber, which is a porous body that has been finally cured, is cut will be described in further detail.
(Pore size peak)
Since the porous body used in the wick 6 has a function of moving the working fluid by the capillary force to drive the loop heat pipe 1, the pore diameter of the porous body is small so that a larger capillary force can be obtained. Is more preferred.
The pore diameter (wick pore radius: rwick) and capillary force (capillary pressure: ΔPcap) of the porous material used in the wick 6 are expressed by the following equation 1.
ΔPcap = 2σcosθ / rwick (Equation 1)
Here, σ is the surface tension of the working fluid, and θ is the contact angle between the wick and the working fluid.

As can be seen from Equation 1 above, the capillary pressure increases as the wick pore radius decreases. Further, in order to operate the loop heat pipe 1, the capillary force (capillary pressure: ΔPcap) and the total pressure loss: ΔPtotal need to satisfy the following expression 2.
ΔPcap ≧ ΔPtotal (Equation 2)
Further, the total pressure loss: ΔPtotal is next calculated using Expression 3.
ΔPtotal = ΔPwick + ΔPgroov + ΔPVL + ΔPcond + ΔPLL + ΔPgrav (Formula 3)
Here, ΔPwick is the pressure loss of the wick, ΔPgroov is the pressure loss of the gas-phase fluid groove 10, ΔPVL is the pressure loss of the steam pipe, ΔPcond is the pressure loss of the condensing section, ΔPLL is the pressure loss of the liquid pipe, and ΔPgrav is the pressure due to gravity. Loss.

As described above, in order to obtain a larger capillary force, the pore diameter peak of the porous body is preferably smaller, specifically, 50 [μm] or less. When the pore diameter peak is larger than 50 [μm], it is difficult to obtain a sufficient capillary force for driving the loop heat pipe. Preferably, the pore diameter peak is 30 [μm] or less, and more preferably, the pore diameter peak is 10 [μm] or less.
More preferably, it is 5 [μm] or less. When the thickness of the wick is extremely thin, it can function at 1 [μm] or less or 0.1 [μm] or less. μm] or more is preferable.
Here, the pore diameter peak can be determined by photographing the cross section of the porous body with a laser microscope and measuring the area of the pores by image processing of the obtained image.

(Cooling performance test)
Next, cooling performance tests performed by setting examples within the main numerical ranges of the conditions of the wick 6 and comparative examples outside the numerical ranges will be described with reference to the drawings as appropriate.
(1) Description of an electronic device (projector) 20 that can suitably include a wick used in a cooling performance test.
FIG. 4 is a schematic explanatory diagram showing another example of the loop heat pipe 1 provided in the electronic device 20 according to the present embodiment.
Further, unlike the example shown in FIG. 1, another example of the loop heat pipe 1 shown in FIG. 4 is a wick slightly larger than the inner diameter of the cylindrical internal space provided in the casing (case) of the evaporator 2. Is pressed into the housing of the evaporator.
However, as the cooling means of the electronic device according to the present embodiment, the loop heat pipe 1 shown in FIG. 1 can be used instead of the loop heat pipe shown in FIG. For the test of the cooling performance of each comparative example, the one shown in FIG. 4 was used.

An electronic device 20 illustrated in FIG. 4 is a projector including an optical unit 21, and the projector is an example of an electronic device to which the present embodiment is applied.
Here, the electronic device to which the loop heat pipe 1 according to the present embodiment can be applied is not limited to a projector. The present invention is not limited to a projector, and is applicable to various electronic apparatuses such as an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction peripheral thereof, a personal computer, a server, an electronic blackboard, a television, a Blu-ray recorder, and a game machine.
In addition, the loop heat pipe 1 and the cooling device according to the present embodiment can be applied to devices other than electronic devices. For example, the loop heat pipe 1 and the cooling device according to the present embodiment may be applied to a cooling device that cools a chemical plant or the like having a reaction furnace or a container or a building attached to an electronic device such as a server rack.

The evaporator 2 (particularly, the heat receiver 7) of the loop heat pipe 1 shown in FIG. 4 is arranged so as to contact the heat generator of the optical unit 21. The evaporating section 2 absorbs heat from the heat generating section and cools a cooling target (heat generating section, optical unit or projector).
The condensing unit 3 is arranged near an exhaust fan 22 provided on a side surface of the housing of the projector main body. When the exhaust fan 22 discharges air to the outside, an airflow is generated around the condensing unit 3, and the condensing unit 3 is cooled by the airflow, and the heat radiation effect in the condensing unit 3 is improved.

  An air supply port 23 is provided on the side opposite to the side of the housing where the exhaust fan 22 is provided, and air taken in from the air supply port 23 passes through the inside of the projector and is exhausted from the exhaust fan 22. Is done. In the example shown in FIG. 4, as the cooling device for cooling the projector, the loop heat pipe 1 and the exhaust fan 22 for enhancing the heat radiation effect of the loop heat pipe 1 are provided. A blower fan for blowing air to the condenser 3 may be provided. Further, a cooling device that does not include a fan but includes only the loop heat pipe 1 may be used.

(2) Detailed Examples and Comparative Examples.
FIG. 5 is an explanatory diagram of the groove shape of the gas-phase fluid groove 10 provided in the wick 6. FIG. 6 is an explanatory diagram of the specifications of the samples used in the cooling performance test and the samples of the comparative example and the test results.
In this test, as shown in FIG. 5, a plurality of wick samples used for the test are the bottom side (length: Lb), the contact side (length: La), and the depth (D) of the groove of the gas-phase fluid groove 10. The samples were prepared by changing the ratio of the lengths of the three sides. All the wick grooves were formed by post-processing.
Then, as an example having the specifications (specifications, manufacturing conditions: material, average pore diameter [μm]) shown in the upper diagram of FIG. 6, a plurality of wick samples were formed using water-foamed silicone rubber and water-foamed urethane rubber. A cooling performance test was performed using a single unit when each sample was prepared and used for the loop heat pipe 1.
For comparison, samples of water-foamed silicone rubber, chemically foamed silicone rubber, SUS, and alumina were also evaluated as comparative examples having the specifications shown in the lower diagram of FIG.

(Examples 1, 2, 3, 4, 5, 6, 7, 8)
The gas-phase fluid grooves 10 of Examples 1, 2, 3, 4, and 5 are trapezoidal grooves having a contact side (La) larger than the base (Lb) (contact side / base = 2), and all of them are grooves. No cooling and good cooling performance.
Here, the gas-phase fluid grooves 10 of the other examples except for the example 4 were manufactured by using water-foamed silicone by molding a silicone rubber and water emulsion. The gas-phase fluid groove 10 of Example 4 was produced using water-foamed urethane rubber by molding the urethane rubber in the same manner as the silicone rubber by molding an emulsion of rubber and water. ] Is the same as Example 1 (5 [μm]), and the cooling performance was also the same. In Examples 2 and 3, since the average pore diameter [μm] was larger than that in Example 1, the capillary force was reduced, and there was a difference in cooling performance. Further, it is considered that the effect of the boiling point cooling was reduced in Example 5 because the groove depth was smaller than 1.

The gas-phase fluid groove 10 of the sixth embodiment has a rectangular shape in which the contact side and the base are the same (contact side / base = 1) and the depth is twice the contact side (contact side / depth). In this result, there was no fall and the cooling performance was good.
However, the gas-phase fluid grooves 10 of Examples 7 and 8 have a shape in which the depth (D) is extremely large with respect to the contact side (La). Cannot be secured, and the cooling performance is degraded.

(Comparative Examples 1, 2, 3)
The gas-phase fluid grooves 10 of Comparative Examples 1, 2, and 3 were produced using water-foamed silicone. Further, the contact side (La) is a half of the base (Lb) and is an inverted trapezoidal groove (contact side / base = 0.5). In Comparative Example 1, the depth (D) is the contact. Since it is the same as the side (La), it does not fall down. However, due to the collapse of the press-fit, the cross section of the gas phase flow path (flow path cross section) cannot be sufficiently secured, and the cooling performance is deteriorated.
Here, the depth (D) of the gas-phase fluid groove 10 of Comparative Example 2 is extremely smaller than the contact side (La) (contact side / depth = 3.5). Since the number of grooves is reduced or the depth (D) is very small, the boiling point cooling effect is reduced, and the cooling performance is deteriorated.
Further, in the gas-phase fluid groove 10 of Comparative Example 3, the cooling performance is further deteriorated due to the collapse of the groove.

(Comparative Example 4)
The gas-phase fluid groove 10 of Comparative Example 4 was made of a chemically foamed silicone rubber, but had a large average pore diameter [μm] and a poor capillary performance, and thus had poor cooling performance.

(Comparative Examples 5 and 6)
In the gas phase fluid grooves 10 of Comparative Examples 5 and 6, SUS was used as the material of the wick 6 in Comparative Example 5 and alumina was used in Comparative Example 6, but the cooling performance tended to be slightly worse than that of Example 1.
Although the average pore diameter [μm] is equivalent to that of water-foamed silicone rubber, it is considered that the cooling efficiency was reduced due to the influence of heat leak because of high thermal conductivity. Further, in order to increase the cooling efficiency, adhesion to the housing is required, and since metal and ceramic are hard, very high precision must be required in order to ensure adhesion. As a result, the problem is that the unit price increases.
From the results of the above-described experiments, it was found that in the configuration of the present embodiment, a very good cooling performance was obtained because the boiling fluid cooling action of the working fluid was ensured and the gas phase fluid groove 10 did not fall down. Was confirmed.

As described above, the present embodiment has been described with reference to the drawings. However, the specific configuration is not limited to the configuration of the loop heat pipe 1 including the wick 6 of the present embodiment described above. The design may be changed without departing from the scope.
For example, the loop heat pipe 1 of the present embodiment described with reference to FIGS. 1, 2, and 4 has been described with respect to a configuration including one evaporating unit 2 and one condensing unit 3 in the present embodiment. The configuration of the loop heat pipe is not limited to such a configuration. The present invention is also applicable to a loop heat pipe including at least two of the evaporator 2 and the condenser 3.
Further, the loop heat pipe 1 of the present embodiment described with reference to FIGS. 1, 2 and 4 has been described with respect to a configuration in which one wick 6 is provided inside the evaporating section 2; May be applied in parallel.

What has been described above is merely an example, and each embodiment has a specific effect.
(Aspect A)
An evaporator such as an evaporator 2 (heat receiving unit 7) for changing a phase of a working fluid such as a condensable fluid from a liquid phase to a gas phase, and a condensing unit 3 for changing a phase of a working fluid from a gas phase to a liquid phase. A cooling means such as a loop-type heat pipe 1 having a condenser, and having a plurality of gas-phase fluid grooves such as a plurality of gas-phase fluid grooves 10 for transporting a working fluid changed to a gas phase; In a wick such as a wick 6 formed of a porous body provided therein, the porous body is made of a foamed silicone rubber or a foamed urethane rubber having a plurality of communicating pores having an average pore diameter of 50 [μm] or less. The gas-phase fluid groove has a flow path cross-section such as a gas-phase flow path cross-section orthogonal to the direction in which the wick is provided inside the evaporator and the working fluid that has changed into a gas phase is transported. Length of the contact side that contacts the casing of the evaporator La, wherein when the length of the base opposite to the contact side was Lb, characterized by satisfying the relation of La / Lb ≧ 1.

According to this, the following effects can be obtained.
Since the porous body constituting the wick is a foamed silicone rubber or a foamed urethane rubber having a plurality of interconnected pores having an average pore diameter of 50 [μm] or less, high elasticity can be obtained. By obtaining such high elasticity, when the wick is provided inside the evaporator, the groove of the gas-phase fluid groove may be collapsed or the local pores near the outer peripheral surface of the wick may be collapsed. Can be suppressed more than a wick composed of a porous body having low elasticity. In addition, since the porous body is an elastic body, the close contact with the casing of the evaporator is improved, and the capillary force necessary for transporting the working fluid can be secured.

Further, the gas phase fluid groove satisfies the relationship of La / Lb ≧ 1 when the length of the contact side is La and the length of the bottom side is Lb in a state where the wick is provided inside the evaporator. In addition, the occurrence of groove collapse of the gas phase fluid groove can be suppressed more than a wick that does not satisfy the relationship of La / Lb ≧ 1.
The above-mentioned specifications do not satisfy the above-mentioned specifications, which cause the deterioration of the cooling performance, the collapse of the gas-phase fluid groove, the local collapse of the pores near the outer peripheral surface of the wick, and the decrease in the adhesion. This can be suppressed more than when a wick is used, and the cooling performance of the cooling means can be further improved.
Therefore, a wick capable of further improving the cooling performance of the cooling means can be provided.

(Aspect B)
In (Aspect A), when the depth in the cross section of the flow path is D in a state in which the wick is provided inside the evaporator, 0.3 ≦ La / D ≦ 3 Is satisfied.
According to this, the balance between the boiling cooling action and the pressure loss can be appropriately maintained, and a decrease in cooling efficiency due to collapse or collapse of the gas-phase fluid groove can be suitably suppressed.

(Aspect C)
(Aspect A) In the aspect A, when the depth of the flow path cross section is D in a state where the wick is provided inside the evaporator and the wick is provided inside the evaporator, 0.5 ≦ La / D ≦ 2 Is satisfied.
According to this, the balance between the boiling cooling action and the pressure loss can be more appropriately maintained, and the cooling efficiency due to the collapse or collapse of the gas-phase fluid groove can be more suitably suppressed.

(Aspect D)
(Aspect A) to (Aspect C), wherein the foamed silicone rubber or urethane rubber is a water-foamed silicone rubber or a water-foamed urethane rubber.
According to this, both the fine pore diameter of the plurality of pores of the wick and the permeability of the working fluid can be achieved.

(Aspect E)
In any of (Aspect A) to (Aspect D), the porous body is a water-foamed silicone rubber or a water-foamed urethane rubber having a plurality of communicating pores having an average pore diameter of 30 [μm] or less. It is characterized by.
According to this, higher elasticity is obtained, the adhesion of the wick to the inner surface of the casing of the evaporator is improved, and the capillary force necessary for transporting the working fluid can be secured.

(Aspect F)
An evaporator such as an evaporator 2 (heat receiving unit 7) for changing a phase of a working fluid such as a condensable fluid from a liquid phase to a gas phase, and a condensing unit 3 for changing a phase of a working fluid from a gas phase to a liquid phase. In a loop heat pipe such as a loop heat pipe 1 including a condenser, a wick such as the wick 6 in any one of (aspect A) to (aspect E) is provided inside the evaporator. .
According to this, it is possible to provide a loop-type heat pipe capable of exhibiting the same effect as the wick of any one of (Aspect A) to (E).

(Aspect G)
An evaporator such as an evaporator 2 (heat receiving unit 7) for changing a phase of a working fluid such as a condensable fluid from a liquid phase to a gas phase, and a condensing unit 3 for changing a phase of a working fluid from a gas phase to a liquid phase. In the cooling device including the condenser, a wick such as the wick 6 in any one of (Embodiment A) to (E) is provided inside the evaporator.
According to this, it is possible to provide a cooling device capable of achieving the same effect as the wick of any one of (Aspect A) to (E).

(Aspect H)
An electronic device such as the electronic device 20 including a cooling unit such as the loop-type heat pipe 1 is characterized by including the cooling device according to (aspect G) as the cooling unit.
According to this, it is possible to provide an electronic device that can achieve the same effect as the cooling device of (Aspect G). That is, an electronic device capable of further improving the cooling performance can be provided.

(Aspect I)
An evaporator such as an evaporator 2 (heat receiving unit 7) for changing a phase of a working fluid such as a condensable fluid from a liquid phase to a gas phase, and a condensing unit 3 for changing a phase of a working fluid from a gas phase to a liquid phase. A cooling means such as a loop-type heat pipe 1 having a condenser, and having a plurality of gas-phase fluid grooves such as a plurality of gas-phase fluid grooves 10 for transporting a working fluid changed to a gas phase; In a wick manufacturing method for manufacturing a wick such as a wick 6 formed of a porous body provided therein, the porous body has a plurality of communicating pores having an average pore diameter of 50 [μm] or less. Rubber or urethane foam, wherein the gas-phase fluid groove is a gas-phase channel cross section orthogonal to a direction in which a working fluid that has changed into a gas phase is transported in a state where the wick is provided inside the evaporator. Such as the cross section of the evaporator When La length of the contact side abuts the body, the length of the base opposite the abutment side was Lb, characterized by satisfying the relation of La / Lb ≧ 1.

According to this, the following effects can be obtained.
In the wick manufactured by the wick manufacturing method of this embodiment, the porous body constituting the wick is a foamed silicone rubber or a urethane foam having a plurality of communicating pores having an average pore diameter of 50 [μm] or less. High elasticity can be obtained. By obtaining such high elasticity, when the wick is provided inside the evaporator, the groove of the gas-phase fluid groove may be collapsed or the local pores near the outer peripheral surface of the wick may be collapsed. Can be suppressed more than a wick composed of a porous body having low elasticity. In addition, since the porous body is an elastic body, the close contact with the casing of the evaporator is improved, and the capillary force necessary for transporting the working fluid can be secured.

Further, the gas phase fluid groove satisfies the relationship of La / Lb ≧ 1 when the length of the contact side is La and the length of the bottom side is Lb in a state where the wick is provided inside the evaporator. In addition, the occurrence of groove collapse of the gas phase fluid groove can be suppressed more than a wick that does not satisfy the relationship of La / Lb ≧ 1.
The above-mentioned specifications do not satisfy the above-mentioned specifications, which cause the deterioration of the cooling performance, the collapse of the gas-phase fluid groove, the local collapse of the pores near the outer peripheral surface of the wick, and the decrease in the adhesion. This can be suppressed more than when a wick is used, and the cooling performance of the cooling means can be further improved.
Therefore, it is possible to provide a wick manufacturing method for manufacturing a wick capable of further improving the cooling performance of the cooling means.

DESCRIPTION OF SYMBOLS 1 Loop type heat pipe 2 Evaporation part 3 Condensing part 4 Steam pipe 5 Liquid pipe 6 Wick 7 Heat receiving part 8 Reservoir part 10 Gas phase fluid groove 20 Electronic equipment

JP 2018-109497 A Japanese Patent No. 5699452 JP 2011-190996 A WO 2012/049752

Claims (9)

An evaporator that changes the phase of the working fluid from a liquid phase to a gaseous phase, and a cooling device that includes a condenser that changes the phase of the working fluid from a gaseous phase to a liquid phase. In a wick having a plurality of gas-phase fluid grooves to be transported and configured by a porous body provided inside the evaporator,
The porous body is a foamed silicone rubber or urethane foam having a plurality of communicating pores having an average pore diameter of 50 [μm] or less,
The gas-phase fluid groove is in contact with a casing of the evaporator having a flow path cross section orthogonal to a direction in which the working fluid transported to the gas phase is transported in a state where the wick is provided inside the evaporator. A wick that satisfies the relationship of La / Lb ≧ 1, where La is the length of the contact side and Lb is the length of the bottom side facing the contact side. The wick according to claim 1,
In the state where the wick is provided inside the evaporator and the depth in the cross section of the flow path is D, the gas phase fluid groove satisfies a relationship of 0.3 ≦ La / D ≦ 3. Wick to feature. The wick according to claim 1,
The gas-phase fluid groove may satisfy a relationship of 0.5 ≦ La / D ≦ 2 when a depth in the cross section of the flow path is D in a state where the wick is provided inside the evaporator. Wick to feature. In the wick according to any one of claims 1 to 3,
A wick, wherein the foamed silicone rubber or urethane foam is water-foamed silicone rubber or water-foamed urethane rubber. In the wick according to any one of claims 1 to 4,
A wick, wherein the porous body is a water-foamed silicone rubber or a water-foamed urethane rubber having a plurality of communicating pores having an average pore diameter of 30 [μm] or less. In a loop heat pipe including an evaporator that changes the phase of the working fluid from a liquid phase to a gas phase, and a condenser that changes the phase of the working fluid from a gas phase to a liquid phase,
A loop heat pipe comprising the wick according to any one of claims 1 to 5 provided inside the evaporator. In a cooling device including an evaporator that changes the phase of the working fluid from a liquid phase to a gas phase, and a condenser that changes the phase of the working fluid from a gas phase to a liquid phase,
A cooling device comprising the wick according to any one of claims 1 to 5 provided inside the evaporator. In an electronic device including a cooling unit,
As the cooling means,
An electronic apparatus comprising the cooling device according to claim 7. An evaporator that changes the phase of the working fluid from a liquid phase to a gaseous phase, and a cooling device that includes a condenser that changes the phase of the working fluid from a gaseous phase to a liquid phase. A wick manufacturing method for manufacturing a wick having a plurality of gas-phase fluid grooves to be transported and formed of a porous body provided inside the evaporator,
The porous body is a foamed silicone rubber or urethane foam having a plurality of communicating pores having an average pore diameter of 50 [μm] or less,
The gas-phase fluid groove is in contact with a casing of the evaporator having a flow path cross section orthogonal to a direction in which the working fluid transported to the gas phase is transported in a state where the wick is provided inside the evaporator. A wick manufacturing method characterized by satisfying a relationship of La / Lb ≧ 1, where La is the length of the contact side and Lb is the length of the bottom side facing the contact side.

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