JP7205741B2 - Wick, loop heat pipe, cooling device, electronic device, and wick manufacturing method - Google Patents

Description

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

Conventionally, it is used for cooling means equipped with an evaporator that changes the phase of the working fluid from the liquid phase to the gas phase, and a condenser that changes the phase of the working fluid from the gas phase to the liquid phase. A wick made of a porous body provided inside the evaporator and having a plurality of gas-phase fluid grooves for transporting the working fluid is known.

For example, Patent Document 1 describes a wick provided inside an evaporator of a loop heat pipe as described below.
A cylindrical hollow member made of porous rubber and closed at one end. A plurality of gas-phase fluid grooves serving as gas-phase flow paths are formed in a direction perpendicular to the circumferential direction of the outer peripheral surface in contact with the housing of the evaporator. It is a wick with (vapor discharge grooves) formed therein, and this wick is provided inside the evaporator.
Specifically, the wick made of foamed silicone rubber or foamed urethane rubber is press-fitted into the housing of the evaporator, the wick being larger than the inner diameter of the cylindrical internal space having the wick in the housing of the evaporator.
In addition, the specifications (specifications, manufacturing conditions) 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 said that 80[%] or less and the open cell ratio is preferably 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 housing of the evaporator and to suppress the local collapse of the pores near the outer peripheral surface of the wick, etc., and to achieve good cooling performance. said to be obtainable.

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

In order to solve the above-mentioned problems, the invention according to claim 1 provides an evaporator that changes the phase of the working fluid from the liquid phase to the gas phase, and a condenser that changes the phase of the working fluid from the gas phase to the liquid phase. A wick composed of a porous body, having a plurality of gas-phase fluid grooves for transporting a working fluid that has undergone a phase change to a gas phase, for use inside the evaporator in a cooling means comprising The porous body is foamed silicone rubber or foamed urethane rubber having a plurality of interconnected pores with an average pore diameter of 50 [μm] or less, and the gas phase fluid groove is formed by the wick being the evaporator The length of the contact side of the flow channel cross section that is perpendicular to the direction of transport of the working fluid that has undergone a phase change to the gas phase and that contacts the housing of the evaporator in the state provided inside the It is characterized by satisfying the relationship La/Lb≧1, where La is the length of the base side opposite to the contact side and Lb is the length of the base side.

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.

A schematic explanatory diagram showing an example of a loop heat pipe according to one embodiment. The figure which shows the virtual cross section when cut|disconnecting by the aa cross section shown by the broken line in FIG. Schematic explanatory drawing of the conventional general loop heat pipe. FIG. 4 is a schematic explanatory diagram showing another example of the loop heat pipe provided in the electronic device according to one embodiment; FIG. 4 is an explanatory diagram of a groove shape of gas-phase fluid grooves provided in the wick; FIG. 4 is an explanatory diagram of specifications of samples of an example and a comparative example used in 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 means having an evaporator provided with a wick to which the present invention is applied and a condenser will be described as appropriate in the figure. will be used to explain.
Here, in each drawing for explaining the present embodiment, constituent elements such as members and component parts having the same function or shape are denoted by the same reference numerals as much as possible. In addition, once the components denoted by the same reference numerals have been described once, the description thereof will be omitted as appropriate.
FIG. 1 is a schematic explanatory diagram showing an example of a loop heat pipe 1 according to the present embodiment, and FIG. 2 shows a virtual cross section taken along the aa cross section indicated by the dashed line in FIG. It is a diagram.

A loop-type heat pipe 1 shown in FIG. 1 is filled with a working fluid made of condensable fluid such as water, alcohol, acetone, or CFC substitute, and has the following components. It has an evaporator 2 that absorbs heat from the heat generating part and evaporates the working fluid from the liquid phase to the gas phase, and a condensation part 3 that condenses the gas phase working fluid introduced from the evaporator 2 into the liquid phase. there is Also provided are a vapor pipe 4 for circulating a vapor-phase working fluid from the evaporator 2 to the condenser 3 and a liquid pipe 5 for circulating a liquid-phase working fluid from the condenser 3 to the evaporator 2 .

The evaporating portion 2 is composed of a heat receiving portion 7 in which a wick 6 is accommodated, and a reservoir portion 8 that stores a liquid-phase working fluid.
One end of the steam pipe 4 is connected to the heat receiving portion 7 , and one end of the liquid pipe 5 is connected to the reservoir portion 8 . The other ends of the steam pipe 4 and the liquid pipe 5 are connected to the condensation section 3 . The condenser section 3 is composed of a stainless steel pipe 31 having a large number of aluminum thin plate-like fins 32 on its outer peripheral surface.

The wick 6 is an elastic porous body. Further, a plurality of gas-phase fluid grooves 10 are provided on the bottom surface of the wick 6 in FIG.
A plurality of gas-phase fluid grooves 10 are provided at equal intervals on the bottom of the wick 6, as shown in FIG. Here, in FIG. 2, the dimensions of the gas-phase fluid grooves 10 are drawn in proportions larger than the actual dimensions. Moreover, the thickness of the wick 6 is set to be slightly larger than the inner dimension of the housing of the heat receiving portion 7 of the evaporating portion 2 .

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

Since the wick 6 is made of a porous body, that is, a porous material, the liquid-phase working fluid stored in the reservoir portion 8 permeates into the wick 6 by capillary action. Due to this capillary action, the wick 6 also serves as a pump for sending the liquid-phase working fluid from the condensation section 3 to the evaporation section 2 .
Condensable fluids such as water, alcohol, acetone, CFC alternatives, etc. are used as working fluids. Moreover, the working fluid preferably has good wettability with the wick 6 so that the working fluid can easily permeate 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 permeate 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 the heat from the heat generating portion is transmitted to the liquid-phase working fluid in the wick 6 through the housing of the evaporating portion 2 (heat receiving portion 7), the heat causes operation. The fluid evaporates and changes to the gas phase. The working fluid that has evaporated and changed to a vapor phase is sent to the vapor pipe 4 through the vapor phase fluid groove 10 . Then, the vapor-phase working fluid is sent to the condensation section 3 through the vapor pipe 4 .

In the condensing section 3, the heat of the working fluid passing through the interior (pipe 31) is released to the outside through the fins 32, so that the temperature of the working fluid is lowered and condensed, and the gas phase changes to the liquid phase. Change. The working fluid that has changed to a liquid phase moves to the evaporator 2 through the liquid pipe 5 and permeates again from the reservoir 8 into the wick 6 provided inside the heat receiving part 7 by capillary action. By circulating the working fluid in this manner, the heat of the heat generating portion is continuously released to the outside, and the object to be cooled is cooled.

Here, the problem of the conventional loop-type heat pipe in which the wick is provided inside the evaporator will be described with reference to the drawings.
FIG. 3 is a schematic illustration of a conventional general loop heat pipe 100. As shown in FIG.
In general, as shown in FIG. 3, the loop heat pipe 100 includes an evaporator 102 that receives heat from the outside and evaporates the working fluid from the liquid phase to the gas phase, and an evaporator 102 that radiates heat to the outside and evaporates the working fluid from the gas phase. A condensing section 103 for condensing into a liquid phase is provided. Also provided are a vapor pipe 104 for circulating the vapor-phase working fluid from the evaporator 102 to the condenser 103 and a liquid pipe 105 for circulate the liquid-phase working fluid from the condenser 103 to the evaporator 102 .

A wick 106 made of a porous body (porous material) is accommodated inside the evaporator 102, and the liquid-phase working fluid sent from the liquid pipe 105 moves through the fine pores of the wick 106 by capillary action. permeates and seeps out to the outer surface of the wick 106 . At this time, the heat from the heat-generating portion (to be cooled) in contact with the evaporating portion 102 is transmitted to the wick 106 through the housing of the evaporating portion 102, and the heat causes the working fluid to evaporate and change to the gas phase. Then, the working fluid that has changed to the vapor phase moves to the condensation section 103 through the vapor pipe 104 .

In the condensation section 103, the heat of the working fluid is released to the outside, so that the temperature of the working fluid drops and changes to the liquid phase. The working fluid that has changed to the liquid phase moves through the liquid pipe 105 to the evaporator 102 and permeates the wick 106 again. As described above, in the loop heat pipe 100, the phase change of the working fluid is utilized to circulate the working fluid and transfer the heat absorbed in the evaporating section 102 to the condensing section 103, thereby efficiently cooling the object to be cooled. Allow to cool.
Here, in order to improve the cooling efficiency, the adhesiveness with the evaporator 102 is ensured, the working fluid is circulated by the capillary force of the wick 106, and the wick 106 is highly permeable to minimize the pressure loss. need sex.

In order to solve such problems, Patent Document 2 discloses that the wick and the housing are integrated by forming a metal pattern on the outer surface of the wick and diffusion bonding the metal pattern to the inner wall of the housing of the evaporator. A loop-type heat pipe is described that reduces gaps between mating surfaces 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 to 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 manufacturing errors, the gas-phase fluid grooves provided on the outer periphery of the wick will collapse or break when the wick is accommodated (press-fitted) in the housing and compressed. As a result, the flow of the working fluid may be obstructed and the cooling performance may be degraded.

On the other hand, Patent Document 3 describes a loop heat pipe as follows.
In addition to outer grooves formed on the outer peripheral surface of the wick, inner grooves extending in the longitudinal direction are formed on the inner peripheral surface of the wick. When the wick is press-fitted into the housing of the evaporator, it deforms so that the inner groove is closed, so that even if there is a manufacturing error in the outer diameter of the wick, the holes near the outer peripheral surface are crushed. is to suppress
In addition, due to these configurations, the 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 housing of the evaporator, resulting in an evaporator with poor performance. It is said that wicks that can suppress this can be mass-produced in a stable manner.

However, in the wick described in Patent Document 3, the process of forming grooves on both the inner and outer peripheral surfaces of the wick is complicated, which leads to an increase in cost and the specifications of the manufactured wick (specifications, manufacturing, etc.). Depending on the time conditions, there is a possibility that the desired cooling performance cannot be obtained.

Patent document 4 describes the following loop heat pipe.
An inner peripheral portion into which a liquid-phase working fluid (working liquid) flows and an outer peripheral portion in which a plurality of gas-phase fluid grooves (vapor discharge grooves) with a depth of 1 [mm] and a width of 1 [mm] are formed along the longitudinal direction. is a resin wick having an elliptical cross section (oval shape), and this wick is provided inside the evaporator.
Specifically, it describes an example in which the wick, which is larger than the elliptical inner space (inner dimension) of the evaporator housing (evaporator case), is press-fitted into the evaporator housing.
By press-fitting the wick, which is larger than the internal space of the evaporator, into the housing of the evaporator, the adhesion between the wick and the inner wall of the housing of the evaporator can be improved. It is said to promote the phase change of the working fluid to the vapor phase at the contact between the wall and the wick.
Suitable materials for the resin wick are said to include fluorine resin, PEEK (polyetheretherketone) resin, polypropylene resin, polyacetal resin, and the like.

However, with the resin wick of Patent Document 4, high elasticity cannot be obtained. There is a fear that the desired cooling performance cannot be obtained due to the crushing of the pores.
Therefore, with regard to the wick 6 of the present embodiment, the specifications (specifications, manufacturing conditions) of the wick that can further improve the cooling performance of the cooling means were examined.

Next, the wick 6 provided inside the heat receiving portion 7 (the evaporating portion 2) of the loop heat pipe 1 of this 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 porous rubber such as foamed silicone rubber. By configuring the wick 6 with porous rubber in this way, it is possible to obtain a higher elastic force than with porous resin, so that the adhesion of the wick 6 to the housing (heat receiving section 7) of the evaporating section 2 is improved. increases. As a result, good heat transfer efficiency from the housing of the evaporator 2 to the wick 6 can be obtained, and the cooling performance of the loop heat pipe 1 is improved.

In addition, as described above, it is possible to ensure high adhesion of the wick 6 and suppress local crushing of pores by simply making the wick 6 of porous rubber. Therefore, if the post-processing of the gas-phase fluid grooves 10 (grooves) for transporting the working fluid (evaporated refrigerant) can be omitted, the manufacturing cost can be further reduced.
Various methods are conceivable for manufacturing a wick composed of such an elastic porous body, that is, a porous elastic body. It can be obtained by applying the technology.
Specifically, a water-foamed silicone rubber composition is used, and agitation is carried out so that the air bubbles present in the cross section obtained by cutting the foam formed in a sampling manner are 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 pore diameter is 5 [μm] or more and 10 [μm] or less. Agitation is carried out so that there are many.

More specifically, the porous material described above is obtained by mixing a commercially available two-liquid type liquid silicone rubber with a catalyst, a surfactant, and a cross-linking agent. Additives, fillers, dispersants, etc., are mixed with water (where necessary alcohol is added), and a mixed solution having a viscosity equivalent to that of liquid silicone rubber is added and stirred to prepare an emulsion composition. Considering emulsifiability with water, the liquid silicone rubber preferably has a specific gravity of 1.00 to 1.05 [g/cm ³ ].
Here, the compounding ratio of the liquid silicone rubber and the mixed solution varies depending on the desired porosity.
For example, if the mixing ratio of the liquid silicone rubber and the mixed solution is 1:1, fine particles of moisture in the emulsion evaporate and form voids, so that a foam with a porosity of 50% can be obtained.

The emulsion is stirred using a homogenizer or, if necessary, a stirrer with ultrasonic treatment, and stirring means, stirring time, and stirring speed (for example, 300 to 1500 [rpm]) so as to obtain a bubble distribution that satisfies the above conditions. Adjust various stirring conditions such as
After that, the prepared emulsion composition is filled in a mold and heated to perform primary heating to cure 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. Desirably, the heating temperature is 90 to 110 [° C.] and the heating time is 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 in the range of 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 open-cell type, and the final curing of the silicone rubber is completed.

Further, the gas-phase fluid grooves 10 can be formed in a mold having a groove shape in advance during primary heating, or formed by post-processing using a processing machine such as an end mill after secondary heating. Selection is made in consideration of the shape of the gas-phase fluid groove 10 and the machinability of the porous body.

Next, the cross-sectional specifications (specifications, manufacturing conditions) obtained by cutting the water-foamed silicone rubber, which is a porous material that has been finally cured, will be described in more detail.
(pore diameter peak)
Since the porous body used for the wick 6 has the function of moving the working fluid by its capillary force and driving the loop heat pipe 1, the pore diameter of the porous body is small so as to obtain a greater capillary force. is preferred.
The pore diameter (wick pore radius: rwick) and capillary force (capillary pressure: ΔPcap) of the porous body used for the wick 6 are expressed using the following equation 1.
ΔPcap=2σ cos θ/rwick (Formula 1)
where 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 smaller the pore radius of the wick, the greater the capillary pressure. In order to operate the loop heat pipe 1, the capillary force (capillary pressure: ΔPcap) and the total pressure loss: ΔPtotal must satisfy Equation 2 below.
ΔPcap≧ΔPtotal (Formula 2)
Furthermore, the total pressure loss: ΔPtotal is then determined using Equation 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 condensation section, ΔPLL is the pressure loss of the liquid pipe, and ΔPgrav is the pressure due to gravity. is a loss.

As described above, in order to obtain a greater capillary force, it is preferable that the pore diameter peak of the porous body is small, specifically 50 [μm] or less. This is because when the pore diameter peak is larger than 50 [μm], it becomes difficult to obtain sufficient capillary force to drive the loop heat pipe. The pore diameter peak is preferably 30 [μm] or less, and more preferably 10 [μm] or less.
More preferably, it is 5 [μm] or less, and if the wick is extremely thin, it can function even at 1 [μm] or less or 0.1 [μm] or less, but the lower limit value is 0.1 [μm]. μm] or more.
Here, the pore diameter peak can be obtained by photographing a cross section of the porous body with a laser microscope and measuring the area of the pores by image processing the obtained image.

(Cooling performance test)
Next, cooling performance tests conducted by setting examples within the main numerical ranges of the conditions of the wick 6 described above and comparative examples outside the numerical ranges will be described as appropriate with reference to the drawings.
(1) Description of the electronic device (projector) 20 that can be suitably provided with the wick used in the 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 this embodiment.
4 is different from the example shown in FIG. is press-fitted into the housing of the evaporator.
However, as the cooling means for the electronic device according to the present embodiment, the loop heat pipe 1 shown in FIG. 1 can be used in place of the loop heat pipe shown in FIG. And for the cooling performance test of each comparative example, the one shown in FIG. 4 is used.

An electronic device 20 shown in FIG. 4 is a projector including an optical unit 21, and this projector is an example of an electronic device to which this embodiment is applied.
Here, the electronic device to which the loop heat pipe 1 according to this embodiment can be applied is not limited to the projector. The present invention can be applied not only to projectors but also to various electronic devices such as image forming apparatuses such as printers, copiers, facsimiles, and multifunction machines thereof, personal computers, servers, electronic blackboards, televisions, Blu-ray recorders, and game machines.
Also, the loop heat pipe 1 and the cooling device according to this 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 for cooling a chemical plant or the like having a reactor, or to a container or building associated with electronic equipment such as a server rack.

The evaporator 2 (especially the heat receiver 7) of the loop heat pipe 1 shown in FIG. The evaporator 2 cools an object to be cooled (a heat generator, an optical unit, or a projector) by absorbing heat from the heat generator.
The condensation unit 3 is arranged near an exhaust fan 22 provided on the side surface of the housing of the projector main body. As the exhaust fan 22 discharges air to the outside, an airflow is generated around the condenser section 3 , the condenser section 3 is cooled by the airflow, and the heat radiation effect in the condenser section 3 is improved.

An air supply port 23 is provided on the side surface opposite to the side surface of the housing where the exhaust fan 22 is provided, and the air sucked from the air supply port 23 passes through the interior of the projector and is discharged from the exhaust fan 22. be done. In the example shown in FIG. 4, as a 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 condensation section 3 may be provided at the end. Alternatively, the cooling device may include only the loop heat pipe 1 without the fan.

(2) Description of 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. As shown in FIG. FIG. 6 is an explanatory diagram of the specifications of the samples of the example and the comparative example used in the cooling performance test, and the test results.
In this test, as shown in FIG. 5, a plurality of wick samples used for the test were measured at the base (length: Lb), the contact side (length: La), and the depth (D) of the gas-phase fluid groove 10. Samples were prepared by changing the ratio of the lengths of the three sides of . Further, all grooves of the wick were formed by post-processing.
Then, as an example having the specifications (specifications, manufacturing conditions: materials, average pore size [μm]) shown in the upper diagram of FIG. Each sample was used for the loop heat pipe 1, and a cooling performance test was conducted with a single machine.
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 in which the contact side (La) is larger than the base (Lb) (contact side/base = 2). There was no collapse of the cooling performance, and the cooling performance was also good.
Here, the gas-phase fluid grooves 10 of other examples except Example 4 were produced using water-foamed silicone by molding an emulsion of silicone rubber and water. The gas-phase fluid grooves 10 of Example 4 were produced using water-foamed urethane rubber by molding an emulsion of urethane rubber and water in the same manner as silicone rubber. ] is the same as in Example 1 (5 [μm]), the cooling performance is also the same. Further, Examples 2 and 3 had an average pore diameter [μm] larger than that of Example 1, and thus the capillary force decreased, resulting in a difference in cooling performance. In addition, it is considered that Example 5 has a smaller groove depth than that of Example 1, so that the effect of boiling point cooling is reduced.

The gas-phase fluid groove 10 of Example 6 has a rectangular shape with the same contact side and base (contact side/base=1) and a depth twice as large as the contact side (contact side/depth). (height = 0.5), and there was no collapse in this result, which also showed good cooling performance.
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 deteriorates.

(Comparative Examples 1, 2, 3)
The gas-phase fluid grooves 10 of Comparative Examples 1, 2, and 3 were made using water-foamed silicone. The contact side (La) is 1/2 the base (Lb) and the groove is an inverted trapezoid (contact side/base = 0.5). Since it is the same as the side (La), there is no collapse. However, due to the collapse due to the press-fitting, a sufficient cross section of the gas phase flow path (flow path cross section) cannot be ensured, and the cooling performance is degraded.
Here, since the gas-phase fluid groove 10 of Comparative Example 2 has an extremely small depth (D) with respect to the contact side (La) (contact side/depth=3.5), Since the number of grooves is reduced or the depth (D) is extremely small, the boiling point cooling effect is reduced and the cooling performance is deteriorated.
Further, the gas-phase fluid groove 10 of Comparative Example 3 has a tilted groove, so the cooling performance is further deteriorated.

(Comparative Example 4)
Although chemically foamed silicone rubber was used for the gas-phase fluid groove 10 of Comparative Example 4, the average pore size [μm] was large and the capillary force did not work sufficiently, resulting in poor cooling performance.

(Comparative Examples 5 and 6)
In the gas-phase fluid grooves 10 of Comparative Examples 5 and 6, the material of the wick 6 was SUS in Comparative Example 5 and alumina in Comparative Example 6, but the cooling performance tended to be slightly worse than in Example 1.
Although the average pore diameter [μm] is equivalent to that of water-foamed silicone rubber, it is considered that the cooling efficiency is reduced due to the influence of heat leakage due to the high thermal conductivity. In addition, in order to increase the cooling efficiency, it is necessary to have good adhesion to the housing. Since metals and ceramics are hard, extremely high precision must be required 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, the boiling cooling action of the working fluid is ensured and the gas-phase fluid grooves 10 do not collapse, so that very good cooling performance can be obtained. was confirmed.

The present embodiment has been described above with reference to the drawings, but the specific configuration is not limited to the configuration of the loop heat pipe 1 provided with the wick 6 of the present embodiment described above. Design changes, etc. may be made within a range that does not deviate.
For example, the loop heat pipe 1 of the present embodiment explained with reference to FIGS. The configuration of the loop heat pipe is not limited to such a configuration. It can also be applied to a loop heat pipe including at least one of the evaporating section 2 and the condensing section 3 .
In addition, although the loop heat pipe 1 of the present embodiment described with reference to FIGS. It is also applicable to a configuration in which are provided in parallel.

What has been described above is only an example, and each of the following aspects has a unique effect.
(Aspect A)
An evaporator such as an evaporator 2 (heat receiving unit 7) that changes the phase of a working fluid such as a condensable fluid from a liquid phase to a gas phase, and a condensation unit 3 that changes the phase of a working fluid from the gas phase to the liquid phase. It is used for cooling means such as a loop-type heat pipe 1 equipped with a condenser, and has gas-phase fluid grooves such as a plurality of gas-phase fluid grooves 10 that transport the working fluid that has undergone a phase change to a gas phase, and the evaporator. In a wick such as the wick 6 which is provided inside and which is composed of a porous material, the porous material is foamed silicone rubber or foamed urethane rubber having a plurality of interconnected pores with an average pore diameter of 50 [μm] or less. The gas-phase fluid groove has a cross-section of a gas-phase flow channel, such as a cross-section of a gas-phase flow channel, perpendicular to the direction in which the working fluid that has undergone a phase change to the gas phase is transported in a state in which the wick is provided inside the evaporator. A relationship of La/Lb≧1 is satisfied, where La is the length of the contact side that contacts the housing of the evaporator, and Lb is the length of the base side that faces the contact side.

According to this, the following effects can be obtained.
Since the porous material constituting the wick is foamed silicone rubber or foamed urethane rubber having a plurality of interconnected pores with an average pore size of 50 [μm] or less, high elasticity can be obtained. Due to such high elasticity, when a wick is provided inside the evaporator, the gas-phase fluid groove collapses, and local collapse of pores near the outer peripheral surface of the wick does not occur. can be suppressed more than a wick composed of a porous body with low elasticity. In addition, since the porous body is an elastic body, the adhesion to the housing of the evaporator can be improved, and the capillary force necessary for transporting the working fluid can be ensured.

Further, when the wick is provided inside the evaporator, the gas-phase fluid groove satisfies the relationship La/Lb≧1, where La is the length of the contact side and Lb is the length of the base. , the occurrence of groove collapse of gas-phase fluid grooves can be suppressed more than with a wick that does not satisfy the relationship La/Lb≧1.
If the above-mentioned specifications are not satisfied, groove collapsing of gas-phase fluid grooves, local crushing of holes in the vicinity of the outer peripheral surface of the wick, and deterioration of adhesion, which lead to deterioration of these cooling performances, will occur. It can be suppressed more than when using a wick, and further improvement of the cooling performance of the cooling means can be realized.
Therefore, it is possible to provide a wick capable of further improving the cooling performance of the cooling means.

(Aspect B)
In (Aspect A), when the wick is provided inside the evaporator, the gas-phase fluid groove has a depth of 0.3≦La/D≦3, where D is the depth in the cross section of the flow path. It is characterized by satisfying the relationship of
According to this, it is possible to suitably maintain the balance between the boiling cooling action and the pressure loss, and to suitably suppress the deterioration of the cooling efficiency due to the collapse or crushing of the gas-phase fluid grooves.

(Aspect C)
In (Aspect A), when the wick is provided inside the evaporator, the gas-phase fluid groove has a depth of 0.5≦La/D≦2, where D is the depth in the cross section of the flow path. It is characterized by satisfying the relationship of
According to this, it is possible to more preferably maintain the balance between the boiling cooling action and the pressure loss, and to more preferably suppress the deterioration of the cooling efficiency due to the collapse or crushing of the gas-phase fluid grooves.

(Aspect D)
In any one of (Aspect A) to (Aspect C), the foamed silicone rubber or foamed urethane rubber is water-foamed silicone rubber or water-foamed urethane rubber.
According to this, it is possible to achieve both the fine pore size of the plurality of pores of the wick and the permeability of the working fluid.

(Aspect E)
In any one of (Aspect A) to (Aspect D), the porous body is water-foamed silicone rubber or water-foamed urethane rubber having a plurality of interconnected pores with an average pore size of 30 [μm] or less. characterized by
According to this, higher elasticity can be obtained, the adhesion of the wick to the inner surface of the housing of the evaporator can be 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) that changes the phase of a working fluid such as a condensable fluid from a liquid phase to a gas phase, and a condensation unit 3 that changes the phase of a working fluid from the gas phase to the liquid phase. A loop heat pipe such as a loop heat pipe 1 including a condenser, wherein a wick such as the wick 6 according to 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 that can achieve the same effect as the wick of any one of (Aspect A) to (Aspect E).

(Aspect G)
An evaporator such as an evaporator 2 (heat receiving unit 7) that changes the phase of a working fluid such as a condensable fluid from a liquid phase to a gas phase, and a condensation unit 3 that changes the phase of a working fluid from the gas phase to the liquid phase. and a condenser, wherein a wick such as the wick 6 according to any one of (Aspect A) to (Aspect E) is provided inside the evaporator.
According to this, it is possible to provide a cooling device that can achieve the same effect as the wick of any one of (Aspect A) to (Aspect E).

(Aspect H)
An electronic device such as the electronic device 20 including cooling means such as the loop heat pipe 1 is characterized by including the cooling device of (Aspect G) as the cooling means.
According to this, it is possible to provide an electronic device that can achieve the same effect as the cooling device of (Aspect G). In other words, it is possible to provide an electronic device capable of further improving the cooling performance.

(Aspect I)
An evaporator such as an evaporator 2 (heat receiving unit 7) that changes the phase of a working fluid such as a condensable fluid from a liquid phase to a gas phase, and a condensation unit 3 that changes the phase of a working fluid from the gas phase to the liquid phase. It is used for cooling means such as a loop-type heat pipe 1 equipped with a condenser, and has gas-phase fluid grooves such as a plurality of gas-phase fluid grooves 10 that transport the working fluid that has undergone a phase change to a gas phase, and the evaporator. In the wick manufacturing method for manufacturing a wick, such as the wick 6 that is provided inside and is composed of a porous material, the porous material is foamed silicone having a plurality of interconnected pores with an average pore diameter of 50 [μm] or less. It is made of rubber or foamed urethane rubber, and the gas-phase fluid groove has a gas-phase flow channel cross section perpendicular to the direction in which the working fluid that has undergone phase change to the gas phase is transported in a state where the wick is provided inside the evaporator. The relationship La/Lb≧1 is satisfied, where La is the length of the contact side of the cross section of the flow path that contacts the housing of the evaporator, and Lb is the length of the base that faces the contact side. It is characterized by

According to this, the following effects can be obtained.
In the wick manufactured by the wick manufacturing method of this embodiment, the porous material constituting the wick is foamed silicone rubber or foamed urethane rubber having a plurality of interconnected pores with an average pore size of 50 [μm] or less. High elasticity is obtained. Due to such high elasticity, when a wick is provided inside the evaporator, the gas-phase fluid groove collapses, and local collapse of pores near the outer peripheral surface of the wick does not occur. can be suppressed more than a wick composed of a porous body with low elasticity. In addition, since the porous body is an elastic body, the adhesion to the housing of the evaporator can be improved, and the capillary force necessary for transporting the working fluid can be ensured.

Further, when the wick is provided inside the evaporator, the gas-phase fluid groove satisfies the relationship La/Lb≧1, where La is the length of the contact side and Lb is the length of the base. , the occurrence of groove collapse of gas-phase fluid grooves can be suppressed more than with a wick that does not satisfy the relationship La/Lb≧1.
If the above-mentioned specifications are not satisfied, groove collapsing of gas-phase fluid grooves, local crushing of holes in the vicinity of the outer peripheral surface of the wick, and deterioration of adhesion, which lead to deterioration of these cooling performances, will occur. It can be suppressed more than when using a wick, and further improvement of the cooling performance of the cooling means can be realized.
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.

REFERENCE SIGNS LIST 1 loop heat pipe 2 evaporator 3 condenser 4 vapor tube 5 liquid tube 6 wick 7 heat receiving section 8 reservoir section 10 gas phase fluid groove 20 electronic device

JP 2018-109497 A Japanese Patent No. 5699452 JP 2011-190996 A WO2012/049752

Claims (9)

For use inside the evaporator in a cooling means comprising an evaporator for changing the phase of a working fluid from a liquid phase to a gas phase, and a condenser for changing the phase of a working fluid from a gas phase to a liquid phase, A wick having a plurality of gas-phase fluid grooves for transporting a working fluid that has undergone a phase change to a gas phase and made of a porous material,
The porous body is foamed silicone rubber or foamed urethane rubber having a plurality of interconnected pores with an average pore size of 50 [μm] or less,
The vapor-phase fluid groove is a housing of the evaporator having a flow passage cross section orthogonal to a direction in which the working fluid that has undergone a phase change to the vapor phase is transported in a state in which the wick is provided inside the evaporator. A wick that satisfies the relationship La/Lb≧1, where La is the length of a contact side that abuts against the contact side, and Lb is the length of a base side that faces the contact side. The wick of claim 1, wherein
The gas-phase fluid groove satisfies the relationship 0.3≦La/D≦3, where D is the depth in the cross section of the flow path, with the wick provided inside the evaporator. Wick characterized. The wick of claim 1, wherein
The gas-phase fluid groove satisfies the relationship of 0.5≦La/D≦2, where D is the depth in the cross section of the flow path, with the wick provided inside the evaporator. Wick characterized. The wick according to any one of claims 1 to 3,
The wick, wherein the foamed silicone rubber or foamed urethane rubber is water-foamed silicone rubber or water-foamed urethane rubber. A wick according to any one of claims 1 to 4,
The wick, wherein the porous material is water-foamed silicone rubber or water-foamed urethane rubber having a plurality of interconnected pores with an average pore size of 30 [μm] or less. A loop heat pipe comprising an evaporator that changes the phase of a working fluid from a liquid phase to a gas phase, and a condenser that changes the phase of a working fluid from the gas phase to a liquid phase,
A loop heat pipe, wherein the wick according to any one of claims 1 to 5 is provided inside the evaporator. In a cooling device comprising an evaporator that changes the phase of a working fluid from a liquid phase to a gas phase, and a condenser that changes the phase of a working fluid from the gas phase to a liquid phase,
A cooling device, wherein the wick according to any one of claims 1 to 5 is provided inside the evaporator. In an electronic device with cooling means,
As the cooling means,
An electronic device comprising the cooling device according to claim 7 . For use inside the evaporator in a cooling means comprising an evaporator for changing the phase of a working fluid from a liquid phase to a gas phase, and a condenser for changing the phase of a working fluid from a gas phase to a liquid phase, In a wick manufacturing method for manufacturing a wick having a plurality of gas-phase fluid grooves for transporting a working fluid that has undergone a phase change to a gas phase and made of a porous material,
The porous body is foamed silicone rubber or foamed urethane rubber having a plurality of interconnected pores with an average pore size of 50 [μm] or less,
The vapor-phase fluid groove is a housing of the evaporator having a flow passage cross section orthogonal to a direction in which the working fluid that has undergone a phase change to the vapor phase is transported in a state in which the wick is provided inside the evaporator. A method of manufacturing a wick, wherein a relationship of La/Lb≧1 is satisfied, where La is a length of a contacting side that contacts the contacting side, and Lb is a length of a base side facing the contacting side.

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