WO2016051569A1 - Evaporator, cooling device, and electronic device - Google Patents

Abstract

An evaporator (2) is provided with: a porous body (6) having a plurality of cylindrical protruding sections (6A); a vapor chamber (7) and a liquid chamber (8), which are separated from each other by means of the porous body; a case (9) that has a first portion (9A) having a vapor tube (4) connected thereto, said first portion defining the vapor chamber, a second portion (9B) having a liquid tube (5) connected thereto, said second portion defining the liquid chamber, and a plurality of protruding sections (9C), which are provided to the first portion, and which protrude toward the second portion side, said protruding sections being fitted in the cylindrical protruding sections of the porous body; and a plurality of masks (10) that cover the surfaces of the cylindrical protruding sections such that the area of the liquid contact surfaces of the cylindrical protruding sections of the porous body is small, said liquid contact surfaces being in contact with a liquid-phase working fluid (11).

Description

Evaporator, cooling device and electronic device

The present invention relates to an evaporator, a cooling device, and an electronic device.

For example, as a cooling device for cooling a heating element such as an electronic component provided in an electronic device such as a computer, high cooling performance is obtained by utilizing latent heat of vaporization when a liquid-phase working fluid evaporates to become a gas-phase working fluid. There is a cooling device that uses a gas-liquid two-phase flow.
As such a cooling device, for example, an evaporator including a porous body (wick) and a condenser are provided, and an outlet of the evaporator and an inlet of the condenser are connected by a vapor pipe, and the outlet of the condenser and the evaporator There is a loop heat pipe (LHP) in which a working fluid is sealed inside.

In such a loop heat pipe, for example, it is possible to circulate the working fluid by the capillary force of the porous body without using a liquid transport pump or the like to transport heat.
In the evaporator provided in the loop heat pipe as described above, if a flat porous body is used, the evaporation area is small and sufficient cooling performance cannot be obtained. For this reason, in order to increase the evaporation area and improve the cooling performance, some porous bodies and the heating surface are provided with projections and recesses so as to be fitted to each other. In some cases, a plurality of protrusions are provided on a case serving as a heat transfer portion, and a porous body is fitted into each of the plurality of protrusions.

US Pat. No. 4,765,396 JP 2007-247931 A JP 2009-115396 A JP 2013-257129 A JP 2003-185370 A

However, when the porous body and the heating surface are provided with irregularities, and the porous body is provided so that the concave portions between the convex portions of the heating surface and the convex portions are embedded, For example, when the heat generation amount of the heating element increases and the evaporation amount increases, it becomes difficult to supply the liquid-phase working fluid to the end portion on the heating surface side of the porous body. As a result, dryout occurs, the evaporation area decreases, and the cooling performance decreases.

In order to prevent this, a plurality of protrusions are provided on the case serving as the heat transfer part, and a porous body is fitted into each of the plurality of protrusions, and around each protrusion where the porous body is fitted. It is conceivable to create a space in which a liquid-phase working fluid flows.
However, if a space in which the liquid-phase working fluid flows is formed around each projection portion in which the porous body is fitted, the area of the wetted surface with which the liquid-phase working fluid of the porous body comes into contact increases. When the area of the liquid contact surface with which the liquid-phase working fluid of the porous body comes into contact increases, heat leak from the porous body to the liquid-phase working fluid increases, and the cooling performance decreases.

Therefore, it is desired to reduce heat leak from the porous body to the liquid-phase working fluid, to suppress a decrease in cooling performance, and to obtain a stable cooling performance.

The evaporator includes a porous body having a plurality of cylindrical convex portions, a vapor chamber and a liquid chamber separated by the porous body, a first portion to which a vapor pipe is connected and defining the vapor chamber, and a liquid pipe Are connected to each other, a second part defining the liquid chamber, and a plurality of protrusions provided in the first part, projecting toward the second part, and fitted into each of the plurality of cylindrical convex parts of the porous body And a plurality of masks covering the respective surfaces of the plurality of cylindrical protrusions so that the area of the liquid contact surface with which the liquid-phase working fluid of the plurality of cylindrical protrusions of the porous body comes into contact is reduced. With.

The cooling device includes an evaporator in which a liquid-phase working fluid evaporates, a condenser in which a gas-phase working fluid condenses, a vapor pipe that connects the evaporator and the condenser and through which the gas-phase working fluid flows, The condenser and the evaporator are connected, and a liquid pipe through which a liquid-phase working fluid flows is provided. The evaporator includes a porous body having a plurality of cylindrical protrusions, a vapor chamber separated by the porous body, and A liquid chamber, a steam pipe is connected, a first part that defines the steam chamber, a liquid pipe is connected, a second part that defines the liquid chamber, and the first part are provided toward the second part. And a liquid contact surface where the liquid-phase working fluid of the plurality of cylindrical projections of the porous body comes into contact with the case having a plurality of projections that are respectively projected into the plurality of cylindrical projections of the porous body And a plurality of masks covering respective surfaces of the plurality of cylindrical convex portions so that the area of the plurality of cylindrical convex portions is reduced.

The electronic device includes an electronic component provided on a wiring board and a cooling device that cools the electronic component. The cooling device includes an evaporator that evaporates a liquid-phase working fluid and a vapor-phase working fluid that is condensed. A vapor pipe that connects the condenser and the evaporator and the vapor phase working fluid flows, and a liquid pipe that connects the condenser and the evaporator and flows the liquid phase working fluid. The vessel is composed of a porous body having a plurality of cylindrical protrusions, a vapor chamber and a liquid chamber separated by the porous body, a vapor pipe connected, and a first portion defining the vapor chamber, and the liquid pipe connected. A second portion that defines the liquid chamber, and a plurality of protrusions that are provided in the first portion, protrude toward the second portion, and are respectively fitted into the plurality of cylindrical protrusions of the porous body. And the area of the wetted surface where the liquid-phase working fluid of the plurality of cylindrical projections of the porous body comes into contact with each other is reduced And a plurality of mask covering the surface of each of the plurality of tubular projections on.

Therefore, according to the evaporator, the cooling device, and the electronic device, heat leak from the porous body to the liquid-phase working fluid can be reduced, and the deterioration of the cooling performance can be suppressed, and the stable cooling performance can be obtained. There is an advantage.

It is typical sectional drawing which shows the structure of the evaporator with which the cooling device concerning this embodiment is equipped. It is a disassembled perspective view which shows the structure (those provided with the mask of the 1st specific example of a specific structural example) of the evaporator with which the cooling device concerning this embodiment is equipped. It is a typical perspective view showing composition of a cooling device concerning this embodiment and an electronic device provided with the same. 4A and 4B are schematic views for explaining the problem of the present invention, and FIG. 4A is a cross-sectional view along the height direction of the protrusion provided in the case. FIG. 4B is a cross-sectional view along the radial direction of the protrusion provided on the case. 5A and 5B are schematic cross-sectional views for explaining the operation and effect of the mask provided in the evaporator provided in the cooling device according to the present embodiment. ) Shows a case where a mask is not provided, and FIG. 5B shows a case where a mask is provided. 6A and 6B show the results of a cooling experiment in the case where the mask of the first specific example is used in the cooling device of the specific configuration example of the present embodiment, and FIG. Indicates the result of measuring the evaporator bottom surface temperature, and FIG. 6B shows the result of measuring the evaporator top surface temperature. It is a typical perspective view which shows the structure of the modification (mask of the 2nd specific example of a specific structural example) of the mask provided in the evaporator with which the cooling device concerning this embodiment is provided. FIG. 8A and FIG. 8B show the results of a cooling experiment when the mask of the second specific example is used in the cooling device of the specific configuration example of the present embodiment, and FIG. Indicates the result of measuring the evaporator bottom surface temperature, and FIG. 8B shows the result of measuring the evaporator top surface temperature. It is a typical perspective view which shows the structure of the modification (mask of the 3rd specific example of a specific structural example) of the mask provided in the evaporator with which the cooling device concerning this embodiment is provided. FIG. 10A and FIG. 10B show the results of a cooling experiment when the mask of the third specific example is used in the cooling device of the specific configuration example of the present embodiment. Indicates the result of measuring the evaporator bottom surface temperature, and FIG. 10B shows the result of measuring the evaporator top surface temperature. It is a typical perspective view which shows the structure of the modification of the mask provided in the evaporator with which the cooling device concerning this embodiment is provided. It is a typical perspective view which shows the structure of the modification of the mask provided in the evaporator with which the cooling device concerning this embodiment is provided. It is a typical perspective view which shows the structure of the modification of the mask provided in the evaporator with which the cooling device concerning this embodiment is provided. It is a typical top view which shows the state which provided the mask of the modification in the cylindrical convex part of the porous body provided in the evaporator with which the cooling device concerning this embodiment is provided. It is typical sectional drawing which shows the structure of the modification of the evaporator with which the cooling device concerning this embodiment is equipped. FIG. 16A and FIG. 16B are schematic views showing the configuration of a modification of the mask provided in the evaporator provided in the cooling device according to the present embodiment, and FIG. 16A is a perspective view. FIG. 16B is a cross-sectional view. It is a typical perspective view which shows the structure of the modification of the mask provided in the evaporator with which the cooling device concerning this embodiment is provided.

Hereinafter, an evaporator, a cooling device, and an electronic device according to an embodiment of the present invention will be described with reference to FIGS.
The cooling device according to the present embodiment is a cooling device that cools a heating element such as an electronic component provided in an electronic device such as a computer (for example, a server or a personal computer). Note that the electronic device is also referred to as an electronic device. The electronic component is, for example, a CPU or an LSI chip.

First, as shown in FIG. 3, for example, the electronic apparatus according to the present embodiment includes a wiring board 52 (for example, a printed wiring board) in which a plurality of electronic components 51 are mounted in a housing 50, and a wiring board 52. A blower fan 53 for air-cooling the electronic component 51, a power source 54, and an HDD (Hard Disk Drive) 55 that is an auxiliary storage device.
And in the some electronic component 51, the electronic component which is a heat generating body, ie, the heat-emitting component 51X, is contained. Here, a CPU (Central Processing Unit) 51X is included as a heat generating component. Since the CPU 51X as the heat generating component cannot be sufficiently cooled only by the air blowing by the blower fan 53, the cooling device 1 (here, a loop heat pipe) is mounted to cool the CPU 51X.

In the present embodiment, the cooling device 1 realizes high cooling performance by using latent heat of evaporation when the liquid-phase (liquid state) working fluid evaporates to become a gas-phase (gas state) working fluid. A cooling device using a liquid two-phase flow.
That is, the cooling device 1 connects the evaporator 2 in which the liquid-phase working fluid evaporates, the condenser 3 in which the gas-phase working fluid condenses, the evaporator 2 and the condenser 3, and operates in the gas-phase operation. A vapor pipe 4 through which a fluid flows, a condenser 3 and an evaporator 2 are connected, and a liquid pipe 5 through which a liquid-phase working fluid flows is connected, and these are connected in a loop shape. ) Is a loop heat pipe.

In this loop heat pipe 1, as shown in FIG. 1, the evaporator 2 is provided with a porous body 6, and the working fluid is circulated by the capillary force of the porous body 6 to transport heat. Is possible.
That is, here, the evaporator 2 is thermally connected to the CPU 51X as a heat generating component. For example, the evaporator 2 is brought into close contact with the CPU 51X provided on the wiring board 52 via the thermal grease 56 so that the heat from the CPU 51X is transmitted to the evaporator 2.

Thereby, a part of the liquid-phase working fluid supplied to the evaporator 2 oozes out from the surface of the porous body 6 provided in the evaporator 2, and the liquid oozed out from the surface of the porous body 6. The phase working fluid is evaporated (vaporized) by the heat transmitted from the CPU 51X as the heat generating component, and becomes a gas phase working fluid.
This gaseous working fluid flows into the condenser 3 through the steam pipe 4 as shown in FIG. Thereby, the heat absorbed by the evaporator 2 is transported to the condenser 3.

The gas-phase working fluid flowing into the condenser 3 is condensed (liquefied) by being cooled by the condenser 3 and becomes a liquid-phase working fluid. Thereby, the heat transported to the condenser 3 is radiated. Here, the condenser 3 is provided in the vicinity of the blower fan 53, and the heat radiating fins 57 are provided in the condenser 3. Then, the heat transported to the condenser 3 is radiated through the radiation fins 57 and released to the outside of the housing 50 by the blast from the blower fan 53.

Note that another heat radiating member such as a heat radiating plate may be provided in place of the heat radiating fins 57. Moreover, you may make it cool by blowing air directly with respect to a pipe, without providing a heat radiating member. In addition, here, the air cooling type cooling means is used for cooling, but the water cooling type cooling means may be used for cooling.
This liquid-phase working fluid flows into the evaporator 2 through the liquid pipe 5.

In this way, the working fluid recirculates in the circulation path constituted by the evaporator 2, the steam pipe 4, the condenser 3, and the liquid pipe 5.
In particular, in the present embodiment, the evaporator 2 is configured as follows.
Here, a thin plate evaporator suitable for efficiently cooling a flat plate heating element (here, the CPU 51X as a heat generating component) will be described as an example of the evaporator 2. The thin plate evaporator is also referred to as a thin plate evaporator or a flat plate evaporator.

As shown in FIGS. 1 and 2, the evaporator 2 of the present embodiment includes a porous body (wick made of a porous material) 6, a vapor chamber 7 and a liquid chamber 8 separated by the porous body 6, A case 9 and a mask 10 are provided.
Here, the porous body 6 is a porous body with low thermal conductivity. Specifically, it is a porous PTFE (polytetrafluoroethylene) resin molded body (resin porous body).

In particular, in the present embodiment, the porous body 6 has a plurality of cylindrical convex portions 6A. That is, the porous body 6 includes a flat plate portion 6B and a plurality of cylindrical convex portions 6A provided on the flat plate portion 6B. Here, each of the plurality of cylindrical convex portions 6A is provided so as to protrude toward the liquid chamber 8 side (that is, the upper portion 9B side of the case 9) with respect to the flat plate-like portion 6B. An insertion hole 6C into which a protrusion 9C provided on the lower portion 9A of the case 9 is inserted (that is, on the lower portion 9A side of the case 9 described later). A plurality of grooves 6D extending in the depth direction are provided on the side surface of the insertion hole 6C.

The case 9 includes a lower part (first part) 9A that is connected to the steam pipe 4 and defines the steam chamber 7, and an upper part (second part) 9B that is connected to the liquid pipe 5 and defines the liquid chamber 8. Is provided.
That is, the lower portion 9A of the case 9 is provided with a steam pipe connection opening 9D (an outlet of the evaporator 2), and the steam pipe 4 is connected to the steam pipe connection opening 9D. In this way, the steam pipe 4 is connected to the steam chamber 7 defined by the lower portion 9A of the case 9 constituting the evaporator 2. Here, the lower portion 9A of the case 9 is composed of a bottom plate 9AX having a recess 9AY, and the steam pipe 4 is connected to a steam pipe connection opening 9D provided in the bottom plate 9AX.

Further, a liquid pipe connection opening 9E (an inlet of the evaporator 2) is provided in the upper portion 9B of the case 9, and the liquid pipe 5 is connected to the liquid pipe connection opening 9E. In this way, the liquid pipe 5 is connected to the liquid chamber 8 defined by the upper portion 9B of the case 9 constituting the evaporator 2. Here, the upper portion 9B of the case 9 includes a frame body 9BX and a cover 9BY, and the liquid pipe 5 is connected to a liquid pipe connection opening 9E provided in the frame body 9BX.

Here, the steam pipe 4 and the liquid pipe 5 are connected to one side of the case 9, but the present invention is not limited to this, for example, the liquid pipe 5 is connected to one side of the case 9, The steam pipe 4 may be connected to the other side.
The lower portion 9A of the case 9 is thermally connected to the CPU 51X as a heat generating component. Thus, the vapor chamber 7 defined by the lower portion 9A of the case 9 is provided at a position close to the CPU 51X, and the liquid chamber 8 defined by the upper portion 9B of the case 9 is provided at a position far from the CPU 51X. Yes. Further, the thermal conductivity of the upper portion 9B of the case 9 is made lower than that of the lower portion 9A. For example, as will be described later, the upper portion 9B of the case 9 is made of stainless steel, and the lower portion 9A of the case 9 is made of copper, so that the thermal conductivity of the upper portion 9B of the case 9 is lower than that of the lower portion 9A. Just do it. This makes it difficult for the heat of the CPU 51X as the heat generating component to be transmitted to the liquid-phase working fluid, and makes it difficult for the temperature of the liquid-phase working fluid to rise.

The case 9 has a plurality of protrusions 9C provided on the lower portion 9A, projecting toward the upper portion 9B, and fitted into the plurality of cylindrical protrusions 6A of the porous body 6, respectively. That is, the lower portion 9A of the case 9 is provided with a plurality of protrusions 9C that protrude toward the upper portion 9B, and the plurality of protrusions 9C are formed of a plurality of tubes of the porous body 6. It fits in the insertion hole 6C provided in each of the convex portions 6A. Here, a plurality of protrusions 9C are integrally formed on the surface of the recess 9AY of the bottom plate 9AX constituting the lower portion 9A of the case 9. Then, the plurality of protrusions 9C have a plurality of protrusions 9C so that the center axis of the protrusion 9C coincides with the center axis of the cylindrical protrusion 6A of the porous body 6 (that is, the center axis of the insertion hole 6C). It fits in the insertion hole 6C provided in each cylindrical convex part 6A.

In this way, the porous body 6 is accommodated in the case 9. In particular, a plurality of tubes of the porous body 6 are formed so that a space is formed between the back surface (the lower surface in FIG. 1) of the porous body 6 and the surface (the upper surface in FIG. 1) of the lower portion 9A of the case 9. A plurality of protrusions 9C are fitted into each of the convex portions 6A. Thereby, the space formed between the back surface of the porous body 6 and the surface of the lower portion 9 </ b> A of the case 9 becomes the vapor chamber 7. Here, a plurality of grooves 6D are formed on the side surfaces of the insertion holes 6C provided in each of the plurality of cylindrical protrusions 6A of the porous body 6, and a space formed between these grooves 6D, that is, The space between the bottom surface of the groove 6D formed in the insertion hole 6C and the side surface of the projection 9C also constitutes a part of the steam chamber 7. On the other hand, a space formed between the surface of the porous body 6 (upper surface in FIG. 1) and the surface of the upper portion 9B of the case 9 (lower surface in FIG. 1) becomes the liquid chamber 8. The liquid chamber 8 also serves as a liquid storage tank for storing a liquid-phase working fluid.

Then, the liquid-phase working fluid flowing into and stored in the liquid chamber 8 permeates from the periphery of each of the plurality of cylindrical convex portions 6A of the porous body 6 and oozes out to the vapor chamber 7 side by a capillary phenomenon. . On the other hand, when the CPU 51X as the heat generating component generates heat, the heat is transmitted to the lower portion 9A of the case 9 and further to each of the plurality of protrusions 9C. The liquid-phase working fluid that oozes out to the vapor chamber 7 side is evaporated (vaporized) by the heat transmitted to each of the plurality of protrusions 9C, and becomes a gas-phase working fluid. In particular, by providing the porous body 6 with a plurality of cylindrical protrusions 6A, the evaporation area is increased and the cooling performance is improved. Further, the protrusion 9C is provided on the lower portion 9A of the case 9, and the cylindrical protrusion 6A is fitted into the protrusion 9C, so that the permeation distance of the liquid-phase working fluid is made uniform. Accordingly, even when the heat generation amount of the heating element increases and the evaporation amount increases, for example, when the CPU 51X which is a heat generating component becomes large and the heat generation amount increases and the evaporation amount increases, the vapor of the porous body 6 increases. This prevents the liquid-phase working fluid from becoming difficult to be supplied to the surface on the chamber 7 side (that is, the end portion on the heating surface side), causes dryout, reduces the evaporation area, and significantly reduces the cooling performance. Is prevented. In this way, in the porous body 6 in which the cylindrical protrusion 6A is provided and the evaporation area is enlarged, the thickness is made uniform, the wet state of the porous body 6 in contact with the protrusion 9C is made uniform, and the evaporation area is enlarged. The liquid-phase working fluid is efficiently evaporated from the porous body 6 so that stable cooling performance can be obtained.

By the way, as described above, the protruding portion 9C is provided on the lower portion 9A of the case 9, and the cylindrical convex portion 6A is fitted into the protruding portion 9C, and around each protruding portion 9C in which the cylindrical convex portion 6A is fitted. When a space where the liquid-phase working fluid flows is created, the area of the liquid contact surface 6X with which the liquid-phase working fluid 11 of the porous body 6 contacts as shown in FIGS. 4 (A) and 4 (B). Becomes larger. When the area of the liquid contact surface 6X with which the liquid-phase working fluid 11 of the porous body 6 comes into contact increases, heat leak from the porous body 6 to the liquid-phase working fluid 11 increases, and the cooling performance decreases. End up. 4A and 4B, an arrow indicated by a symbol X indicates a heat flow, and an arrow indicated by a symbol Y indicates a flow of a liquid-phase working fluid.

That is, in the loop heat pipe 1 described above, in order to improve the cooling performance, the protruding portion 9C is provided on the lower portion 9A of the case 9 that is thermally connected to the CPU 51X as the heat generating component, and the porous body is provided thereon. The evaporating area is expanded by fitting the 6 cylindrical convex portions 6A. In this case, the evaporation surface 6Y that comes into contact with the protruding portion 9C of the cylindrical body 6A of the porous body 6 that contacts the high temperature and the low-temperature liquid-phase working fluid 11 of the cylindrical protrusion 6A of the porous body 6 come into contact. Since the liquid contact surface 6X is integrated with the front and back, if the area of the evaporation surface 6Y of the porous body 6 is increased as described above, the area of the liquid contact surface 6X is further increased.

Here, heat transfer from the porous body 6 to the liquid-phase working fluid 11 is according to the following equation.

Here, Q is the heat leak heat quantity from the porous body 6 to the liquid-phase working fluid 11, h is the heat transfer coefficient, A is the contact area (wetted area) of the porous body 6 and the liquid-phase working fluid 11, _TW is the surface temperature of the porous body 6, and _TL is the temperature of the liquid-phase working fluid 11.
For this reason, the heat leak heat quantity Q from the porous body 6 to the liquid-phase working fluid 11 increases as the liquid contact area A increases.

Also, wetted area A is by expanding the surface temperature T _W of the porous body 6 is increased. This is because the flow rate of the liquid-phase working fluid 11 flowing into the liquid contact surface 6X of the porous body 6 decreases as the liquid contact area A of the porous body 6 increases [FIG. 5A]. reference]. Here, the flow velocity of the liquid-phase working fluid 11 flowing into the porous body 6 is approximately several tens of μm / sec to several hundreds of μm / sec depending on the type of the working fluid and the heat generation amount. It greatly affects the heat conduction inside. When the inflow speed of the porous body 6 to the liquid contact surface 6X is fast, the amount of heat (heat leak) traveling through the porous body 6 is pushed back, but when the inflow speed is slow, the heat travels through the porous body 6 by heat conduction. The amount of heat increases and heat leak to the liquid-phase working fluid 11 side increases. As described above, when the wetted area of the porous body 6 is increased, not only the heat exchange area (A) is increased, but also the temperature (T _W ) of the heat exchange surface is increased, so that the heat leak becomes very large. .

The working fluid inside the loop heat pipe 1 is maintained in a saturated state, and the fluid is operated by a vapor pressure difference caused by a temperature difference between the vapor side and the liquid side separated by the porous body 6 in the evaporator 2. For this reason, when the amount of heat leak heat transferred from the vapor side of the evaporator 2 to the liquid side through the porous body 6 is large, the loop heat pipe 1 causes a significant performance deterioration.
For this reason, it is desired to eliminate the cause of the performance degradation of the loop heat pipe 1 and to realize the loop heat pipe 1 having high cooling performance and an electronic device including the same.

Therefore, in the present embodiment, as shown in FIGS. 1 and 2, the area of the liquid contact surface 6 </ b> X with which the liquid-phase working fluid 11 of the plurality of cylindrical protrusions 6 </ b> A of the porous body 6 contacts is reduced. A plurality of masks 10 that cover the respective surfaces of the plurality of cylindrical protrusions 6A are provided. By providing the mask 10 in this manner, the liquid-phase working fluid 11 flows into the liquid contact surface 6X where the liquid-phase working fluid 11 on the surface of the cylindrical convex portion 6A of the porous body 6 contacts. The area (passage area) is narrowed down. Thus, by providing the mask 10 so that the liquid contact surface 6X of the cylindrical convex portion 6A of the porous body 6 becomes small, the area where the liquid-phase working fluid 11 and the porous body 6 are in direct contact is reduced. In addition, the flow velocity of the liquid-phase working fluid 11 flowing into the porous body 6 can be increased. By these synergistic effects, the amount of heat transfer from the porous body 6 to the liquid-phase working fluid 11 can be reduced, and heat leak from the porous body 6 to the liquid-phase working fluid 11 can be reduced. It is possible to increase the cooling efficiency of the loop type heat pipe 1 and further increase the cooling capacity of the loop heat pipe 1.

For example, the mask 10 may have an opening 10A through which the liquid-phase working fluid 11 flows in a portion covering the side surface of the cylindrical convex portion 6A. In this case, the surface of the cylindrical convex portion 6A of the porous body 6 is covered with the mask 10, and only the portion where the opening 10A of the mask 10 is located on the side surface of the cylindrical convex portion 6A of the porous body 6 is the wetted surface. 6X, and the area of the liquid contact surface 6X of the cylindrical convex portion 6A of the porous body 6 is reduced.

Here, the opening 10A may be a plurality of holes 10B.
These holes 10B are preferably provided uniformly over the entire surface of the portion of the mask 10 that covers the side surface of the cylindrical projection 6A.
Further, as shown in FIG. 7, it is preferable that these holes 10 </ b> B are larger on the flat plate-like portion 6 </ b> B side than the tip side of the cylindrical convex portion 6 </ b> A of the porous body 6. That is, it is preferable that these holes 10B are larger on the lower portion (first portion) 9A side than on the upper portion (second portion) 9B side of the case 9. This is because the vapor chamber 7 side defined by the lower portion 9A is hotter than the liquid chamber 8 side defined by the upper portion 9B of the case 9, and the amount of evaporation is larger. In this way, the distribution of the size of the holes 10B reduces the area (liquid contact area) where the porous body 6 and the liquid-phase working fluid 11 are in direct contact, and flows into the porous body 6. The flow rate of the liquid-phase working fluid 11 can be increased uniformly, and heat leak from the porous body 6 to the liquid-phase working fluid 11 can be reduced uniformly.

In addition, although the shape of the hole 10B is circular here, it is not restricted to this, For example, it can be set as various shapes, such as a triangular shape and a square shape.
Further, the opening 10A may be a plurality of slits 10C as shown in FIG.
These slits 10C are preferably provided uniformly over the entire surface of the portion of the mask 10 covering the side surface of the cylindrical projection 6A.

Further, it is preferable that these slits 10C have a wider width on the flat plate portion 6B side than on the tip side of the cylindrical convex portion 6A of the porous body 6. That is, it is preferable that these slits 10 </ b> C have a wider width on the lower portion (first portion) 9 </ b> A side than on the upper portion (second portion) 9 </ b> B side of the case 9. This is because the vapor chamber 7 side defined by the lower portion 9A is hotter than the liquid chamber 8 side defined by the upper portion 9B of the case 9, and the amount of evaporation is larger. In this way, by changing the width of the slit 10C, the area (liquid contact area) in which the porous body 6 and the liquid-phase working fluid 11 are in direct contact is reduced, and the operation of the liquid phase flowing into the porous body 6 is performed. The flow rate of the fluid 11 can be increased uniformly, and heat leak from the porous body 6 to the liquid phase working fluid 11 can be reduced uniformly.

Here, the slit 10C extends in the height direction of the cylindrical convex portion 6A, but is not limited thereto, and may extend in the circumferential direction of the cylindrical convex portion 6A, for example. Further, when the slit 10C extending in the height direction of the cylindrical convex portion 6A is used, the slit 10C can be manufactured with a mold in consideration of mass production and cost reduction, as shown in FIG. Is preferably extended to the lower end so as to form a slit extending from the lower end.

In these cases, the mask 10 is provided with the opening 10A so that the area of the liquid contact surface 6X on the side surface of the cylindrical convex portion 6A is 50% or less of the area of the side surface of the cylindrical convex portion 6A. It is preferable to do this. In this case, the area (opening area) of the opening 10A of the mask 10 is 50% or less of the area of the portion of the mask 10 that covers the side surface of the cylindrical protrusion 6A. That is, the portion covering the side surface of the cylindrical convex portion 6A of the mask 10 includes the opening 10A (the portion where the porous body 6 and the liquid-phase working fluid 11 are in contact) and the portion other than the opening 10A (the porous body 6). The area of the opening 10A is equal to or smaller than the area of the part other than the opening 10A. Thus, the ratio of the opening 10A in the portion covering the side surface of the cylindrical convex portion 6A of the mask 10, that is, the opening ratio of the mask 10 is preferably 50% or less. Thus, it is preferable that the area of the liquid contact surface 6X on the side surface of the cylindrical convex portion 6A of the porous body 6 is 50% or less as compared with the case where the mask 10 is not provided. Thereby, the area where the liquid-phase working fluid 11 (working fluid) and the porous body 6 are in direct contact with each other can be reduced to ½ or less, and the liquid-phase working fluid 11 flows into the porous body 6. The flow rate to be increased can be doubled or more.

In addition, it is preferable to lower the aperture ratio of the mask 10 as the area of the liquid contact surface 6X of the cylindrical convex portion 6A increases, and in the case of a specific configuration example described below, for example, the aperture ratio of the mask 10 is increased. It is preferably about 35% or less.
Further, the sizes of the plurality of holes 10B and the slits 10C as the opening 10A are set so that the upper portion (second portion) 9B side of the case 9 (the tip side of the cylindrical convex portion 6A; the liquid chamber 8 side; the projection 9C). If the lower part (first part) 9A side (the base side of the cylindrical projection 6A; the steam chamber 7 side; the high temperature side of the projection 9C) is larger than the lower part (first part) 9A, the mask 10 The opening ratio of the lower portion (first portion) 9A is higher than that of the upper portion (second portion) 9B of the case 9. In this case, the average aperture ratio of the mask 10 may be 50% or less. For example, the opening ratio of the mask 10 is 55% on the upper portion (first portion) 9B side of the case 9, and the opening ratio of the mask 10 is 35% near the center. The lower portion (second portion) of the case 9 The aperture ratio of the mask 10 is 15% on the 9A side, and the aperture ratio of the mask 10 may be distributed so that the average aperture ratio of the mask 10 is 50% or less.

Here, the mask 10 is a cylindrical mask having an opening 10A and is covered with the cylindrical convex portion 6A of the porous body 6, but is not limited thereto.
For example, as shown in FIGS. 13 and 14, the mask 10 includes a first portion 101 that partially covers the side surface of the first cylindrical convex portion 61 </ b> A included in the four adjacent cylindrical convex portions 6 </ b> A, and four The second portion 102 partially covering the side surface of the second cylindrical convex portion 62A included in the cylindrical convex portion 6A and the side surface of the third cylindrical convex portion 63A included in the four cylindrical convex portions 6A are partially And a fourth portion 104 partially covering the side surface of the fourth cylindrical convex portion 64A included in the four cylindrical convex portions 6A, and four adjacent masks 10-1˜ The side surface of one cylindrical convex portion 61A is covered with four portions 101-1 to 101-4 provided one for each of 10-4, and between these four portions 101-1 to 101-4 Alternatively, a slit 10D through which the liquid-phase working fluid 11 flows may be formed.

In this case, the mask 10 includes a first portion 101 to a fourth portion 104 and a plate-like portion 105 that supports them, and the first portion 101 to the fourth portion 104 are adjacent to four cylindrical convex portions 6A. It is inserted into the area surrounded by (61A to 64A).
With this configuration, the mask 10 can be installed even if the gap between the cylindrical convex portions 6A is narrow.

The evaporator 2 provided with the mask 10 configured as described above is as shown in FIG.
In FIGS. 13 and 14, it is assumed that the portions 101 to 104 of the mask 10 are integrated, and a flow path 10E through which the liquid-phase working fluid 11 flows is provided at the center. However, the present invention is not limited to this, and it is assumed that the portions 101 to 104 of the mask 10 are separated from each other and independent, and the central region surrounded by these portions 101 to 104 is a liquid-phase working fluid. 11 may be used as a flow path.

Also in this case, similarly to the slit 10C as the opening 10A described above, the slit 10D is preferably provided uniformly over the entire surface of the portion of the mask 10 covering the side surface of the cylindrical convex portion 6A. In addition, it is preferable that the slit 10D has a wider width on the lower portion (first portion) 9A side than on the upper portion (second portion) 9B side of the case 9. The mask 10 is provided with slits 10D so that the area of the liquid contact surface 6X on the side surface of the cylindrical convex portion 6A is 50% or less of the area of the side surface of the cylindrical convex portion 6A. preferable.

Further, for example, as shown in FIGS. 16A and 16B, the mask 10 may have a groove 10F through which the liquid-phase working fluid 11 flows in a portion covering the side surface of the cylindrical convex portion 6A. good. In this case, a plurality of grooves 10F may be provided. And like the hole 10B and the slit 10C as the opening 10A described above, these grooves 10F are preferably provided uniformly over the entire surface of the portion covering the side surface of the cylindrical convex portion 6A of the mask 10. . Further, it is preferable that these grooves 10F have a wider width on the lower portion (first portion) 9A side than on the upper portion (second portion) 9B side of the case 9. The mask 10 is provided with grooves 10F so that the area of the liquid contact surface 6X on the side surface of the cylindrical convex portion 6A is 50% or less of the area of the side surface of the cylindrical convex portion 6A. preferable.

In addition, here, the mask 10 is provided with a projection 10G on its end face, and the mask 10 is inserted into a region surrounded by the four adjacent cylindrical projections 6A so that the projection 10G is positioned downward. A gap is formed between the material 6 and the flat plate-like portion 6B. This is because the plate-like portion 6B side of the porous body 6 becomes hot and the amount of evaporation increases, so that the liquid-phase working fluid 11 is easily supplied thereto.

In FIGS. 16A and 16B, the mask 10 is inserted into a region surrounded by four adjacent cylindrical convex portions 6A. However, the present invention is not limited to this. A cylindrical mask having a groove 10 </ b> F through which the liquid-phase working fluid 11 flows on the outer peripheral surface may be covered with the cylindrical convex portion 6 </ b> A.
In addition, as described above, the holes 10B, the slits 10C, 10D, and the grooves 10F are provided uniformly over the entire surface of the portion of the mask 10 that covers the side surface of the cylindrical convex portion 6A, so that the inside of the porous body 6 is in a liquid phase The distance traveled by the working fluid 11 can be shortened, and the pressure loss can be reduced.

Further, as shown in FIG. 9, the mask 10 may be a porous body mask 10H having holes (pores) through which the liquid-phase working fluid 11 flows. In this case, the porous body mask 10H preferably has a porosity of 50% or less. In addition, it is preferable to use a material having a lower porosity as the area of the liquid contact surface 6X of the cylindrical convex portion 6A increases. In the case of a specific configuration example described later, for example, the porosity is 35%. It is preferable to use one having a degree or less. Moreover, it is preferable to use a porous body mask 10H having a large hole diameter in order to reduce pressure loss. For example, the porous body mask 10H preferably has a pore diameter (porous diameter; pore diameter) larger than that of the porous body 6 (wick). This is because the porous body 6 as a wick is preferably one having a small diameter in order to obtain a capillary force, whereas the porous body mask 10H has low flow resistance and low fluidity. This is because it is preferable to use a material having a large hole diameter for improvement. For example, when a porous PTFE resin molded body (resin porous body) is used for the porous body 6, the porous body mask 10H has a porous PTFE resin molded body (resin made of resin) having a larger porous diameter. A porous body) may be used. Specifically, the porous body mask 10H preferably has a hole diameter of 50 μm or more.

Moreover, it is preferable that the several mask 10 is integrated as shown, for example in FIG. As a result, the number of parts can be reduced and the cost can be kept low. Here, an example in which the mask 10 shown in FIG. 13 is integrated is shown as an example, but the present invention is not limited to this, and the other mask 10 described above may be integrated.
The material of the mask 10 is a material having low thermal conductivity. For example, when PTFE resin is used, the thermal conductivity is about 0.2 to about 0.3 W / mK. That is, the material of the mask 10 is a material (resin material) having a thermal conductivity of 0.5 W / mK or less. For example, the material of the mask 10 is preferably a material having a lower thermal conductivity than the liquid-phase working fluid 11. Here, when the liquid-phase working fluid 11 is water, its thermal conductivity is about 0.6 W / mK. Therefore, the material of the mask 10 is a material having a thermal conductivity lower than 0.6 W / mK. It is preferable to do this. For example, when the liquid-phase working fluid 11 is ethanol or acetone, its thermal conductivity is about 0.2 W / mK, so that the material of the mask 10 has a thermal conductivity lower than about 0.2 W / mK. It is preferable to use a material having

Therefore, according to the evaporator, the cooling device, and the electronic device according to the present embodiment, heat leak from the porous body 6 to the liquid-phase working fluid 11 can be reduced, and a decrease in cooling performance can be suppressed. There is an advantage that the cooling performance can be obtained. In other words, the cooling performance of the loop heat pipe 1 is greatly improved, the heat generating components provided in the electronic device can be stably cooled, the electronic device can be improved in performance, and the reliability can be improved. is there.

Hereinafter, a specific configuration example of a loop heat pipe as the cooling device 1 according to the present embodiment will be described.
First, the evaporator 2 has an outer size of about 75 mm × about 75 mm and a height of about 25 mm. Since the lower portion 9A of the case 9 of the evaporator 2 is thermally connected to the heating element 51X, the upper portion 9B of the case 9 is made of stainless steel having a relatively low thermal conductivity. It shall be made. This makes it difficult for heat from the heating element 51X to be transmitted to the liquid-phase working fluid via the lower portion 9A of the case 9. Further, here, non-porous PTFE (polytetrafluoroethylene) is attached to the inner wall surface of the upper portion 9B of the case 9, that is, the wall surface of the liquid chamber 8 that is in direct contact with the liquid-phase working fluid. Heat leakage from the upper portion 9B to the liquid-phase working fluid is blocked.

Then, in order to attach the porous body 6, a total of 36 protrusions (6 in the vertical direction, 6 in the horizontal direction and 6 in the grid are arranged on the bottom surface (copper base) of the lower portion 9 </ b> A of the case 9. (Cylinder; convex portion; copper pin) 9C is provided (see FIG. 2), and the dimensions of each protrusion 9C are about 5 mm in diameter (outer diameter) and about 15 mm in height.
The porous body 6 is a molded article using a mold. Here, a porous PTFE (polytetrafluoroethylene) resin molded body having a porosity of about 40% and an average porous diameter of about 10 μm ( Resin porous body). A total of 36 cylindrical convex portions (cylindrical convex portions) 6 </ b> A are provided on the porous body 6 in a lattice shape with six in the vertical direction and six in the horizontal direction. These cylindrical convex portions 6A have an outer diameter of about 9 mm and an inner diameter of about 7 mm. The central axis of these cylindrical convex portions 6A, that is, the central axis of the insertion hole 6C provided on the back surface side of the cylindrical convex portion 6A is respectively a projection 9C provided on the lower portion 9A of the case 9. It matches with the central axis of. And each protrusion part 9C provided in the bottom face of 9 A of lower parts of the case 9 is inserted in the insertion hole 6C provided in the back surface side of these cylindrical convex parts 6A, respectively, and the porous body 6 is attached. It is attached to the lower part of the case 9 (see FIGS. 1 and 2).

Here, the depth of the insertion hole 6C provided on the back side of the cylindrical convex portion 6A is about 13 mm. As a result, the protrusions 9C provided on the bottom surface of the lower portion 9A of the case 9 are inserted into the insertion holes 6C provided on the back surface side of the cylindrical convex portions 6A, respectively, so that the porous body 6 Is attached to the lower portion 9A of the case 9, the bottom surface of the case 9 (that is, the bottom surface of the lower portion 9A of the case 9) and the back surface of the porous body 6 (that is, the flat plate portion 6B of the porous body 6). 2 mm), and a steam chamber 7 is formed (see FIG. 1).

Further, the diameter of the insertion hole 6C provided on the back surface side of the cylindrical convex portion 6A is made to be smaller by about 50 μm to about 200 μm than the outer diameter size of the protruding portion 9C of the case 9. Thereby, when the porous body 6 is attached to the lower portion 9A of the case 9, sufficient adhesion can be obtained.
Further, a groove (groove) 6D having a width of about 1 mm, a depth of about 1 mm, and a pitch of about 2 mm extending in the depth direction (vertical direction) is uniformly provided on the side surface (inner wall) of the insertion hole 6C (see FIGS. 1 and 2). ). Thereby, the space formed between the grooves 6D, that is, the space between the bottom surface of the groove 6D formed on the side surface of the insertion hole 6C and the side surface of the projection 9C of the case 9 is also one of the steam chambers 7. To function as a part. Thus, the side surface of the insertion hole 6 </ b> C has a fin structure, and the tip of the fin is in close contact with the side surface of the protrusion 9 </ b> C of the case 9. Then, the liquid-phase working fluid 11 supplied from above the porous body 6 passes through the inside of the cylindrical convex portion 6A of the porous body 6 and is provided on the side surface of the insertion hole 6C. Evaporated and vaporized at the tip of the fin contacting the projection 9C, the vapor generated at the tip of the fin flows downward through the groove between the fins and passes through the space between the back surface of the porous body 6 and the bottom surface of the case 9. However, it reaches the steam pipe 4.

Then, by connecting the upper portion 9B of the case 9 to the lower portion 9A of the case 9 to which the porous body 6 is attached, the porous body 6 is accommodated in the case 9, That is, an internal space having a height of about 5 mm is formed between the upper surface of the cylindrical convex portion 6A of the porous body 6 and the lower surface of the upper portion 9B of the case 9, and this internal space and a plurality of porous bodies 6 are formed. A space between the cylindrical convex portions 6A is defined as a liquid chamber 8 also serving as a liquid reservoir tank (see FIG. 1).

The vapor chamber 7 of the evaporator 2 thus manufactured (that is, the lower portion 9A of the case 9 defining the vapor chamber 7 of the evaporator 2) and the inlet of the condenser 3 are connected by the vapor pipe 4 (see FIG. 3). Further, the liquid chamber 8 of the evaporator 2 (that is, the upper portion 9B of the case 9 that defines the liquid chamber 8 of the evaporator 2) and the outlet of the condenser 3 are connected by a liquid pipe 5 (see FIG. 3).
Here, the steam pipe 4 is a copper pipe having an outer diameter of about 6 mm and an inner diameter of about 5 mm, and its length is about 300 mm. The liquid pipe 5 is a copper pipe having an outer diameter of about 4 mm and an inner diameter of about 3 mm, and its length is about 200 mm. The condenser 3 has a width of about 150 mm, a height of about 50 mm, and a length of about 45 mm. Here, aluminum plate fins (radiating fins 57) are caulked and attached to a condenser tube provided in the condenser 3 (see FIG. 3). As this condensing tube, a copper groove tube having an outer diameter of about 6.35 mm is used, and the aluminum plate fins 57 have a thickness of about 0.2 mm and a pitch of about 1.5 mm.

The working fluid is ethanol, and the inside of the loop heat pipe 1 is evacuated by a vacuum pump to be in a vacuum state, and then a predetermined amount of saturated ethanol degassed by vacuum is sealed and hermetically sealed.
Incidentally, in the case of the evaporator 2 having the above-described structure, in order to improve the cooling performance, as shown in FIG. 5A, a protrusion 9C (pin structure) is provided on the bottom surface of the lower portion 9A of the case 9. Since the evaporation area is increased by fitting the cylindrical convex portion 6A of the porous body 6 into this, the area of the liquid contact surface 6X integrated with the evaporation surface 6Y is also increased. Therefore, the heat exchange area between the porous body 6 and the liquid-phase working fluid 11 is large, and the liquid-phase working fluid 11 flowing into the porous body 6 has a large flow velocity. The heat leak to the working fluid 11 is very large. Due to this influence, the temperature (liquid temperature) of the liquid working fluid 11 above the porous body 6 rises, the temperature of the liquid working fluid 11 supplied to the porous body 6 increases, and the liquid phase The temperature of the gas-phase working fluid in which the working fluid 11 is evaporated and vaporized also increases. For this reason, the temperature of the case 9 provided with the protruding portion 9C is also high, and the CPU 51X as the heat generating component cannot be sufficiently cooled.

Therefore, as a first specific example, in order to prevent heat flow from the porous body 6 to the liquid-phase working fluid 11, the opening ratio is about 35% in each cylindrical protrusion 6 </ b> C of the porous body 6 described above. Thus, a mask 10 (wick mask; heat insulating mask) in which holes 10B having a diameter of about 1 mm were uniformly provided on the side surface was installed [see FIGS. 1, 2, and 5B].
Here, the mask 10 uses a PTFE resin (non-porous body) having a low thermal conductivity (about 0.23 W / mK here) and excellent heat resistance as its material, and its thickness is about 0.8 mm. To do. By providing this mask 10, the area where the porous body 6 and the liquid working fluid 11 are in direct contact (liquid contact area) is reduced to about 35%, and the operation of the liquid phase flowing into the porous body 6 is performed. The flow rate of the fluid 11 can be increased about three times.

And the experiment which cools the heater imitating the heat-emitting component 51X in an electronic device using the loop type heat pipe 1 provided with the evaporator 2 which installed such a mask 10 was conducted. For comparison, a cooling experiment using a loop heat pipe provided with an evaporator without a mask was also performed.
Here, FIG. 6A shows the result of performing these cooling experiments and measuring the heater temperature, that is, the evaporator bottom surface temperature (case bottom surface temperature).

In FIG. 6A, a solid line A indicates the bottom surface temperature of the evaporator 2 in contact with the heater when the heater is cooled using the loop heat pipe 1 including the evaporator 2 provided with the mask 10 as described above. Is shown. In FIG. 6A, a solid line B indicates the bottom surface temperature of the evaporator in contact with the heater when the heater is cooled using a loop heat pipe including an evaporator without a mask.

As shown in FIG. 6A, when the loop type heat pipe 1 including the evaporator 2 provided with the mask 10 as described above is used, an evaporator having no mask is provided for all the calorific values. Compared with the case of using a loop heat pipe, the bottom temperature of the evaporator, that is, the heater temperature, was reduced by about 10 ° C.
Further, since the upper surface temperature of the evaporator 2 which also serves as a liquid storage tank is considered to reflect the temperature of the liquid-phase working fluid 11, the upper surface temperature (case upper surface temperature) of the evaporator 2 was also measured. A measurement result as shown in FIG. 6 (B) was obtained.

In FIG. 6B, a solid line A indicates the upper surface temperature of the evaporator 2 when the heater is cooled using the loop heat pipe 1 including the evaporator 2 provided with the mask 10 as described above. Yes. In FIG. 6B, a solid line B indicates the upper surface temperature of the evaporator when the heater is cooled using a loop heat pipe including an evaporator without a mask.
As shown in FIG. 6B, when the loop type heat pipe 1 including the evaporator 2 provided with the mask 10 as described above is used, an evaporator having no mask is provided for all the calorific values. Compared with the case where a loop heat pipe is used, the upper surface temperature of the evaporator is lower by about 5 to about 8 ° C., which means that the temperature of the liquid-phase working fluid 11 is reduced.

As described above, by using the loop heat pipe 1 including the evaporator 2 provided with the mask 10 as described above, the temperature of the liquid-phase working fluid 11 can be reduced, and the liquid-phase working fluid can be reduced from the porous body 6. It was confirmed that the heat leak to 11 could be reduced. In addition, it was confirmed that the heater temperature can be reduced, a decrease in cooling performance can be suppressed, and a stable cooling performance can be obtained.

Further, as a second specific example, in order to prevent heat flow from the porous body 6 to the liquid-phase working fluid 11, the average opening ratio of each cylindrical protrusion 6 </ b> A of the porous body 6 is about 35%. A mask 10 provided with holes 10B having a diameter of about 0.5 mm to about 1.5 mm on the side surface, that is, a mask 10 (wick mask; heat insulating mask) having a distribution in the aperture ratio is installed (see FIG. 7).
Here, the mask 10 uses a PTFE resin (non-porous body) having a low thermal conductivity (about 0.23 W / mK here) and excellent heat resistance as its material, and its thickness is about 0.8 mm. To do. Further, since the temperature of the protrusion 9C (copper pin) of the case 9 is high at the root portion and low at the tip portion, the evaporation amount is estimated to be large at the root portion of the protrusion 9C and small at the tip portion. Therefore, the opening ratio of the mask 10 is 55% (opening diameter: about 1.5 mm) near the base of the protrusion 9C of the case 9, and the opening ratio of the mask 10 is 35% (opening diameter: 1.0 mm) near the center. ), And the aperture ratio of the mask 10 is 15% (the aperture diameter is about 0.5 mm) on the tip side of the projection 9C of the case 9, and the average aperture ratio of the mask 10 is about 35%. The aperture ratio of the mask 10 was distributed in the height direction of the portion 9C. By providing this mask, the area where the porous body 6 and the liquid-phase working fluid 1 are in direct contact (wetted area) is reduced to about 35% as a whole, and the liquid phase flowing into the porous body 6 is reduced. The flow rate of the working fluid 11 can be increased uniformly about three times. In this way, the flow velocity of the liquid-phase working fluid 11 flowing into the liquid contact surface 6X of the cylindrical convex portion 6A of the porous body 6 can be made substantially uniform in the height direction, and from the surface of the porous body 6 It is possible to uniformly reduce heat leak to the liquid-phase working fluid 11 in the height direction.

And the experiment which cools the heater imitating the heat-emitting component 51X in an electronic device using the loop type heat pipe 1 provided with the evaporator 2 which installed such a mask 10 was conducted. For comparison, a cooling experiment using a loop heat pipe provided with an evaporator without a mask was also performed.
Here, FIG. 8A shows the results of performing these cooling experiments and measuring the heater temperature, that is, the evaporator bottom surface temperature (case bottom surface temperature). In FIG. 8A, a solid line A indicates the bottom surface temperature of the evaporator in contact with the heater when the heater is cooled using the loop heat pipe 1 including the evaporator 2 provided with the mask 10 as described above. Show. Further, in FIG. 8A, a solid line B indicates the bottom surface temperature of the evaporator in contact with the heater when the heater is cooled using a loop heat pipe including an evaporator without a mask.

As shown in FIG. 8A, when the loop heat pipe 1 including the evaporator 2 having the mask 10 as described above is used, an evaporator having no mask is provided for all the calorific values. Compared with the case where a loop heat pipe was used, the evaporator bottom surface temperature, that is, the heater temperature, could be reduced by about 12 ° C.
Further, since the upper surface temperature of the evaporator 2 which also serves as a liquid storage tank is considered to reflect the temperature of the liquid-phase working fluid 11, the upper surface temperature (case upper surface temperature) of the evaporator 2 was also measured. Measurement results as shown in FIG. 8 (B) were obtained. In FIG. 8B, a solid line A indicates the upper surface temperature of the evaporator when the heater is cooled using the loop heat pipe 1 including the evaporator 2 provided with the mask 10 as described above. . Further, in FIG. 8B, a solid line B indicates the upper surface temperature of the evaporator when the heater is cooled using a loop heat pipe including an evaporator without a mask.

As shown in FIG. 8B, when the loop type heat pipe 1 including the evaporator 2 provided with the mask 10 as described above is used, an evaporator having no mask is provided for all the heat generation amounts. Compared with the case where a loop heat pipe is used, the upper surface temperature of the evaporator is lower by about 6 to about 9 ° C., which means that the temperature of the liquid-phase working fluid 11 is reduced.

As described above, by using the loop heat pipe 1 including the evaporator 2 provided with the mask 10 as described above, the temperature of the liquid-phase working fluid 11 can be reduced, and the liquid-phase working fluid can be reduced from the porous body 6. It was confirmed that the heat leak to 11 could be reduced. In addition, it was confirmed that the heater temperature can be reduced, a decrease in cooling performance can be suppressed, and a stable cooling performance can be obtained.

Further, as a third specific example, in order to prevent heat flow from the porous body 6 to the liquid-phase working fluid 11, each cylindrical protrusion 6 </ b> A of the porous body 6 has a porosity of about 10 as a mask 10. A 35% porous body mask 10H (wick mask; heat insulating mask) was installed (see FIG. 9). Here, the porous body mask 10H uses PTFE resin (porous body) having a low thermal conductivity (about 0.23 W / mK here) and excellent heat resistance as its material, and its thickness is about 0.00. 8 mm. Here, in order for the porous body 6 as the wick to flow the working fluid, it is necessary to generate a large capillary force with a fine porous diameter, whereas the porous body of the mask 10 needs to generate a capillary force. The smaller the pressure loss when the liquid-phase working fluid 11 passes through the mask 10, the more advantageous for stable operation. Therefore, it is preferable that the porous diameter is as large as possible. Therefore, here, the porous diameter of the porous body mask 10H is about 100 μm. By providing this porous body mask 10H, the area where the porous body 6 and the liquid-phase working fluid 11 are in direct contact (wetted area) is reduced to about 35%, and the liquid flowing into the porous body 6 is provided. The flow rate of the phase working fluid 11 can be increased about three times.

And the experiment which cools the heater imitating the heat-emitting component 51X in an electronic device using the loop type heat pipe 1 provided with the evaporator 2 which installed such a mask 10H was conducted. For comparison, a cooling experiment using a loop heat pipe provided with an evaporator without a mask was also performed.
Here, FIG. 10A shows the result of performing these cooling experiments and measuring the heater temperature, that is, the evaporator bottom surface temperature (case bottom surface temperature). In FIG. 10A, the solid line A indicates the bottom surface temperature of the evaporator 2 in contact with the heater when the heater is cooled using the loop heat pipe 1 including the evaporator 2 provided with the mask 10H as described above. Is shown. In FIG. 10A, a solid line B indicates the bottom surface temperature of the evaporator in contact with the heater when the heater is cooled using a loop heat pipe including an evaporator without a mask.

As shown in FIG. 10 (A), when the loop heat pipe 1 including the evaporator 2 provided with the mask 10H as described above is used, an evaporator having no mask is provided for all the heat generation amounts. Compared with the case of using a loop heat pipe, the bottom temperature of the evaporator, that is, the heater temperature, was reduced by about 10 ° C.
Further, since the upper surface temperature (case upper surface temperature) of the evaporator 2 also serving as a liquid reservoir tank is considered to reflect the temperature of the liquid-phase working fluid 11, the upper surface temperature of the evaporator 2 was also measured. Measurement results as shown in FIG. 10 (B) were obtained. In FIG. 10B, a solid line A indicates the upper surface temperature of the evaporator 2 when the heater is cooled using the loop heat pipe 1 including the evaporator 2 provided with the mask 10H as described above. Yes. Further, in FIG. 10B, a solid line B indicates the upper surface temperature of the evaporator when the heater is cooled using a loop heat pipe including an evaporator without a mask.

As shown in FIG. 10B, when the loop heat pipe 1 including the evaporator 2 provided with the mask 10H as described above is used, an evaporator without a mask is provided for all the heat generation amounts. Compared with the case where a loop heat pipe is used, the upper surface temperature of the evaporator is lower by about 5 to about 8 ° C., which means that the temperature of the liquid-phase working fluid 11 is reduced.

Thus, by using the loop heat pipe 1 including the evaporator 2 provided with the mask 10H as described above, the temperature of the liquid-phase working fluid 11 can be reduced, and the liquid-phase working fluid from the porous body 6 can be reduced. It was confirmed that the heat leak to 11 could be reduced. In addition, it was confirmed that the heater temperature can be reduced, a decrease in cooling performance can be suppressed, and a stable cooling performance can be obtained.

The present invention is not limited to the configuration described in the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 Cooling device (loop heat pipe)
DESCRIPTION OF SYMBOLS 2 Evaporator 3 Condenser 4 Steam pipe 5 Liquid pipe 6 Porous body 6A Cylindrical convex part 6B Flat plate part 6C Insertion hole 6D Groove 6X Liquid contact surface 6Y Evaporating surface 61A 1st cylindrical convex part 62A 2nd cylindrical convex part Part 63A Third cylindrical convex part 64A Fourth cylindrical convex part 7 Vapor chamber 8 Liquid chamber 9 Case 9A Lower part 9AX Bottom plate 9AY Recessed part 9B Upper part 9BX Frame body 9BY Cover 9C Protrusion part 9D Steam pipe connection opening 9E Liquid pipe connection opening 10 Mask 10A Opening 10B Hole 10C Slit 10D Slit 10E Flow path 10F Groove 10G Projection 10H Porous mask 101 First part 102 Second part 103 Third part 104 Fourth part 105 Plate-like part 10 -1 to 10-4 Four adjacent masks 101-1 to 101-4 Four parts, one for each of the four adjacent masks 11 Liquid-phase working fluid (working fluid)
50 housing 51 electronic component 51X CPU (heating element; heating component; electronic component)
52 Wiring board 53 Blower fan 54 Power supply 55 HDD
56 Thermal grease 57 Heat dissipation fin

Claims (20)

A porous body having a plurality of cylindrical protrusions;
A vapor chamber and a liquid chamber separated by the porous body;
A steam pipe is connected, the first part defining the steam chamber, a liquid pipe is connected, the second part defining the liquid chamber, and provided in the first part, toward the second part side A case having a plurality of protrusions fitted into each of the plurality of cylindrical protrusions of the porous body,
A plurality of masks covering respective surfaces of the plurality of cylindrical protrusions so as to reduce an area of a liquid contact surface with which a liquid-phase working fluid of the plurality of cylindrical protrusions of the porous body comes into contact. An evaporator characterized by that. The evaporator according to claim 1, wherein the mask has an opening through which the liquid-phase working fluid flows in a portion covering a side surface of the cylindrical convex portion. The evaporator according to claim 2, wherein the opening is a plurality of holes. The evaporator according to claim 3, wherein the hole is larger on the first part side than on the second part side of the case. The evaporator according to claim 2, wherein the opening is a plurality of slits. The mask includes a first portion that partially covers a side surface of the first cylindrical convex portion included in the four adjacent cylindrical convex portions, and a second cylindrical convex portion included in the four cylindrical convex portions. A second portion partially covering the side surface of the first cylindrical portion, a third portion partially covering the side surface of the third cylindrical convex portion included in the four cylindrical convex portions, and the four cylindrical convex portions. A fourth portion partially covering the side surface of the fourth cylindrical convex portion,
The side surfaces of one cylindrical convex portion are covered with four portions, one for each of the four adjacent masks, and a slit through which a liquid-phase working fluid flows is formed between the four portions. The evaporator according to claim 1, wherein The evaporator according to claim 5 or 6, wherein the slit has a width wider on the first portion side than on the second portion side of the case. The mask is characterized in that the opening is provided so that the area of the liquid contact surface of the side surface of the cylindrical convex portion is 50% or less of the area of the side surface of the cylindrical convex portion. The evaporator according to any one of claims 2 to 5 and 7. The slit is provided so that an area of the liquid contact surface of the side surface of the cylindrical convex portion is 50% or less of an area of the side surface of the cylindrical convex portion. 8. The evaporator according to 7. The evaporator according to claim 1, wherein the mask has a groove through which the liquid-phase working fluid flows in a portion covering a side surface of the cylindrical convex portion. The evaporator according to claim 10, wherein the groove has a width wider on the first part side than on the second part side of the case. The groove is provided in the mask so that an area of the liquid contact surface on a side surface of the cylindrical convex portion is 50% or less of an area of a side surface of the cylindrical convex portion. Item 12. The evaporator according to Item 10 or 11. The evaporator according to claim 1, wherein the mask is a porous body mask having holes through which the liquid-phase working fluid flows. The evaporator according to claim 13, wherein the porous body mask has a porosity of 50% or less. The evaporator according to claim 13 or 14, wherein the porous body mask has a diameter of the pores larger than that of the porous body. The evaporator according to any one of claims 13 to 15, wherein the porous body mask has a diameter of the hole of 50 µm or more. The evaporator according to any one of claims 1 to 16, wherein the material of the mask is a material having a thermal conductivity of 0.5 W / mK or less. The evaporator according to any one of claims 1 to 17, wherein the plurality of masks are integrated. An evaporator for evaporating the liquid-phase working fluid;
A condenser that condenses the gas-phase working fluid;
A vapor pipe connecting the evaporator and the condenser and through which a gas-phase working fluid flows;
Connecting the condenser and the evaporator, and a liquid pipe through which a liquid-phase working fluid flows,
The evaporator is
A porous body having a plurality of cylindrical protrusions;
A vapor chamber and a liquid chamber separated by the porous body;
A steam pipe is connected, the first part defining the steam chamber, a liquid pipe is connected, the second part defining the liquid chamber, and provided in the first part, toward the second part side A case having a plurality of protrusions fitted into each of the plurality of cylindrical protrusions of the porous body,
A plurality of masks covering respective surfaces of the plurality of cylindrical protrusions so as to reduce an area of a liquid contact surface with which a liquid-phase working fluid of the plurality of cylindrical protrusions of the porous body comes into contact. A cooling device characterized by that. Electronic components provided on the wiring board;
A cooling device for cooling the electronic component,
The cooling device is
An evaporator for evaporating the liquid-phase working fluid;
A condenser that condenses the gas-phase working fluid;
A vapor pipe connecting the evaporator and the condenser and through which a gas-phase working fluid flows;
Connecting the condenser and the evaporator, and a liquid pipe through which a liquid-phase working fluid flows,
The evaporator is
A porous body having a plurality of cylindrical protrusions;
A vapor chamber and a liquid chamber separated by the porous body;
A steam pipe is connected, the first part defining the steam chamber, a liquid pipe is connected, the second part defining the liquid chamber, and provided in the first part, toward the second part side A case having a plurality of protrusions fitted into each of the plurality of cylindrical protrusions of the porous body,
A plurality of masks covering respective surfaces of the plurality of cylindrical protrusions so as to reduce an area of a liquid contact surface with which a liquid-phase working fluid of the plurality of cylindrical protrusions of the porous body comes into contact. An electronic device characterized by that.

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