Patent Application
20150034288
The present invention relates to cooling devices for semiconductor devices and electronic equipment and, in particular, to a flat plate cooling device and a method for using the same employing an ebullient cooling system in which heat transport and heat radiation are performed by a cycle of vaporization and condensation of a refrigerant.
In recent years, with the progress of high performance and high functionality in semiconductor devices, electronic equipment and the like, the amount of heat generation from them has also been increasing. On the other hand, the miniaturization of semiconductor devices and electronic equipment has been advancing due to the popularization of portable devices. Because of such background, a cooling device with high efficiency and a small size has been required. The cooling device using an ebullient cooling system in which heat transport and heat radiation are performed by a cycle of vaporization and condensation of a refrigerant does not require any driving unit such as a pump. It is therefore suitable for miniaturization, and accordingly it has been expected as a cooling device for semiconductor devices, electronic equipment and the like.
An example of the cooling device using the ebullient cooling system (hereinafter, also denoted as an ebullient cooling device) is described in patent literature 1.
The heat dissipation unit 520 is composed of a plurality of heat radiation tubes connecting two headers and heat radiation fins interposed between respective heat radiation tubes. The two headers are respectively attached to one side of the coolant tub 510 almost perpendicularly to the heat radiation surface 512, and are formed connected to the internal space of the coolant tub 510.
The coolant tub 510 is provided with a tank 513 as a water level regulation unit. The tank 513 is disposed at the other side of the coolant tub 510 protruding to the same side as the heat dissipation unit 520. A given amount of refrigerant is enclosed in the internal space of the coolant tub 510. Here, as shown in
It is said that employing the above-described configuration in the related ebullient cooling device 500 enables the heat of the heating elements 530 and 531 surely to be transferred to the refrigerant and to be cooled, even if the arrangement attitude (the vertical direction attitude or the horizontal direction attitude) of the coolant tub 510 is changed. Patent Literature 1: Japanese Patent Application Laid-Open Publication No. 2004-349652 (paragraphs [0017] to [0027])
As described above, the related ebullient cooling device 500 is configured to dispose the tank 513 as the water level regulation unit for the coolant tub 510 with it protruding in order to increase a degree of freedom of the arrangement in installing it in electronic equipment. Accordingly, there has been a problem that the cooling device becomes larger. When the related ebullient cooling device 500 is disposed turning it upside down in the vertical direction attitude, the heat dissipation unit 520 becomes located below the ebullient cooling device 500 in the vertical. Since the reflux of the refrigerant is not accelerated in that case, the cooling performance is remarkably degraded. Therefore, there has been a problem that it is impossible to use the ebullient cooling device 500 as a cooling device in the arrangement.
Thus, the related ebullient cooling device has a problem that the cooling device becomes larger when a degree of freedom of the arrangement in installing it in electronic equipment is increased, and that it is impossible to obtain a sufficient degree of freedom of the arrangement.
The object of the present invention is to provide a flat plate cooling device and a method for using the same which solve the problem mentioned above that in a cooling device using an ebullient cooling system, a cooling device becomes larger when a degree of freedom of the arrangement in installing it in electronic equipment is increased, and that it is impossible to obtain a sufficient degree of freedom of the arrangement.
A flat plate cooling device according to an exemplary aspect of the invention includes a plate-like container including a first flat plate and a second flat plate opposite to the first flat plate; a refrigerant enclosed in the plate-like container; and a guiding wall unit connecting the first flat plate to the second flat plate and controlling a flow of the refrigerant in the plate-like container; wherein the plate-like container includes a heat receiving area which is thermally connected to a heating element disposed on at least one of the first flat plate and the second flat plate; and the guiding wall unit includes a pair of guiding walls, and the guiding walls are disposed on opposite sides of the heat receiving area.
A method for using a flat plate cooling device according to an exemplary aspect of the invention includes the steps of: using a flat plate cooling device according to an exemplary aspect of the invention switching between a first arrangement state where a straight line parallel to one side in a longitudinal direction of the plate-like container is parallel to the vertical direction and a second arrangement state where to be disposed upside down in the vertical direction inversely with the first arrangement state.
According to the flat plate cooling device of the present invention, it is possible to obtain a small flat plate cooling device employing an ebullient cooling system with an improved degree of freedom of the arrangement in installing it in electronic equipment.
The exemplary embodiments of the present invention will be described with reference to drawings below.
The flat plate cooling device 100 is used with a heating element 300 such as a semiconductor device thermally connected to the outer surface of the plate-like container composing the flat plate cooling device 100. The heat from the heating element 300 is transmitted to the refrigerant through the plate-like container, and the refrigerant vaporizes. Since the refrigerant draws heat as vaporization heat from the heating element 300 at that time, the increase in temperature of the heating element 300 is suppressed. The vaporized refrigerant radiates heat in the plate-like container and condenses and liquefies. Thus, the flat plate cooling device 100 is configured employing an ebullient cooling system in which heat transport and heat radiation are performed by a cycle of vaporization and condensation of a refrigerant.
The configuration of the flat plate cooling device 100 will be described in more detail using
The plate-like container 110 includes a heat receiving area 140 which is thermally connected to a heating element 300 disposed on at least one of the first flat plate and the second flat plate. The guiding wall unit 130 is composed of a pair of guiding walls 131 and 132, and the guiding walls 131 and 132 are disposed on opposite sides of the heat receiving area 140.
In
Since a flow path of the refrigerant is restricted by the guiding wall unit 130 regardless of the arrangement state, it is possible to obtain a small flat plate cooling device employing an ebullient cooling system with an improved degree of freedom of the arrangement in installing it in electronic equipment according to the flat plate cooling device 100 of the present exemplary embodiment.
Next, a description will be given of a method for making the flat plate cooling device 100 in accordance with the present exemplary embodiment. As shown in
The joining process is not limited to the above-described process, but it is also accepted that the side frame unit 113 is fixed to the first flat plate 111 and the second flat plate 112 by screws and the like using a sealing member such as an O-ring. It is also possible to produce a part of the first flat plate 111 or the second flat plate 112 and the side frame unit 113 as a unit by means of a cutting process, a press process and the like.
After producing the plate-like container 110 and the guiding wall unit 130, the refrigerant 120 is injected into the plate-like container 110.
At that time, for example, by forming an inlet in the side frame unit 113, injecting the refrigerant 120, and sealing the inlet after evacuating the plate-like container through the inlet, it is possible to keep the internal pressure in the plate-like container 110 at the saturated vapor pressure of the refrigerant.
Next, the operation of the flat plate cooling device 100 in accordance with the present exemplary embodiment will be described. Arrowed lines in
According to the flat plate cooling device 100 of the present exemplary embodiment, a pair of guiding walls 131 and 132 composing the guiding wall unit 130 is disposed on opposite sides of the heat receiving area 140. In the present exemplary embodiment, as shown in
That is to say, if the interval between a pair of guiding walls 131 and 132 is narrower or less than the width of the heat receiving area 140, the bubble refrigerant 121 also arises on the outside of the guiding walls 131 and 132, which does not contribute to generating the vapor-liquid two-phase flow because such a bubble refrigerant diffuses within the refrigerant in liquid state. In contrast, if the interval between a pair of guiding walls 131 and 132 is wider than the width of the heat receiving area 140, the generation of the vapor-liquid two-phase flow is suppressed because the vapor-phase refrigerant flows out through all boundaries of the outer perimeter of the heat receiving area 140 and the liquid-phase refrigerant flows into there. It is desirable, therefore, that the interval between the guiding walls 131 and 132 should be set equal to or smaller than the outer perimeter of the heat receiving area 140.
Thus, the flat plate cooling device 100 of the present exemplary embodiment is configured to transport and diffuse heat by changing the liquid refrigerant into the vapor-phase refrigerant through the phase transition. In that case, the larger the space occupied by the vapor refrigerant in the plate-like container 110 is, the more widely heat diffuses, and accordingly, it is possible to improve the cooling performance. On the other hand, it is necessary for the liquid refrigerant to be thermally in contact with the heat receiving area 140 in order to receive heat from the heating element 300. It is considered, therefore, to increase the amount of the liquid refrigerant, which causes the volume occupied by the vapor refrigerant within the plate-like container 110 to decrease. In that case, it becomes difficult to improve the cooling performance because the vapor refrigerant is capable of transporting large amounts of heat.
It is possible, however, to prevent the problem because the flat plate cooling device 100 of the present exemplary embodiment is configured to dispose a pair of guiding walls 131 and 132 composing the guiding wall unit 130 on opposite sides of the heat receiving area 140. The reason is as follows. The bubble refrigerant 121 arisen from the phase transition caused by receiving heat of the heating element 300 is prevented from diffusing by the guiding walls 131 and 132, and moves in clusters upward in the vertical direction in the guiding wall unit 130 by buoyancy. At that time, the refrigerant becomes a vapor-liquid two-phase flow and rises with the vapor refrigerant taking in the liquid refrigerant. It becomes possible, therefore, for the liquid refrigerant to reach the heat receiving area 140 located above the vapor-liquid interface of the refrigerant in the vertical direction. Accordingly, it is only necessary for the vapor-liquid interface of the refrigerant to be located higher than the lower limit of the heat receiving area 140 in the vertical direction. As a result, it becomes possible to reduce the amount of the liquid refrigerant and to increase the volume of a space occupied by the vapor refrigerant. Which enhances the diffusion and the heat radiation of the vapor refrigerant, and so it is possible to improve the cooling performance of the flat plate cooling device 100.
When the bubble refrigerant 121 escapes from the heat receiving area 140, liquid refrigerant flows into the heat receiving area 140. At that time, the liquid refrigerant flows round the outside of the guiding wall unit 130 into the heat receiving area 140. That is to say the flow path of the liquid refrigerant increases in length due to the guiding wall unit 130. By which the heat radiation of the liquid refrigerant is also enhanced, and so it becomes possible to further improve the cooling performance of the flat plate cooling device 100.
As described above, according to the flat plate cooling device 100 of the present exemplary embodiment, since the flow path of the refrigerant is restricted by the guiding wall unit 130, it is possible to use the flat plate cooling device 100 even in the arrangement state where it is disposed upside down in the vertical direction. That is to say, it becomes possible to use the flat plate cooling device 100 switching between a first arrangement state where the straight line parallel to one side in a longitudinal direction of the plate-like container 110 is parallel to the vertical direction and a second arrangement state where the flat plate cooling device 100 is disposed upside down in the vertical direction inversely with the first arrangement state. Here, by adopting the configuration where the heat receiving area 140 is disposed near the center of one side in a longitudinal direction of the plate-like container 110, it is possible to minimize the amount of liquid refrigerant in a case where the flat plate cooling device 100 is used in two upside-down arrangement states.
It is also accepted that a roughened surface area is formed on the inner surface of the plate-like container 110. The roughened surface area has a concavo-convex structure, which functions as a generating nucleus of a bubble refrigerant in the heat receiving area 140 and functions as a condensing nucleus of the vapor-phase refrigerant in the area where the vapor-phase refrigerant lies. As a result, it is possible to activate the phase transition of the refrigerant and to further increase the cooling performance.
The optimum value of the size of the concavo-convex structure is determined by considering physical properties such as surface tension of the refrigerant and the amount of heat generation of the heating element. For example, if hydrofluorocarbon, hydrofluoroether, and the like, which are insulating and inactive materials, are used as the refrigerant, the optimum size of the bubble nucleus is in the range of sub-micron to about a hundred micrometers in center line average roughness. It is possible, therefore, to form the concavo-convex structure comparable in size to it by a mechanical processing using abrasive grains, a sandblast, and the like, or by a chemical processing such as a plating.
It is also accepted to use the flat plate cooling device 100 thermally connecting a heat radiating unit 400 composed of heat radiation fins and the like to the outer surface of the plate-like container 110 composing the flat plate cooling device 100, as shown in
Next, the second exemplary embodiment of the present invention will be described.
The flat plate cooling device 200 in accordance with the present exemplary embodiment differs from the flat plate cooling device 100 of the first exemplary embodiment in the configuration of the guiding wall unit 230. That is to say, as shown in
According to the flat plate cooling device 200 of the present exemplary embodiment, since a flow path of the refrigerant is restricted by the guiding wall unit 230 regardless of the arrangement state, it is possible to obtain a small flat plate cooling device employing an ebullient cooling system with an improved degree of freedom of the arrangement in installing it in electronic equipment. That is to say, as shown in
In addition, as is the case with the first exemplary embodiment, it is possible to use the flat plate cooling device 200 even in the arrangement state where it is disposed upside down in the vertical direction. That is to say, as shown in
The present invention is not limited to the above-mentioned exemplary embodiments and can be variously modified within the scope of the invention described in the claims. It goes without saying that these modifications are also included in the scope of the present invention.
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2011-219887, filed on Oct. 4, 2011, the disclosure of which is incorporated herein in its entirety by reference.
100, 200 flat plate cooling device
110 plate-like container
111 first flat plate
112 second flat plate
113 side frame unit
120 refrigerant
121, 221 bubble refrigerant
130, 230 guiding wall unit
131, 132, 231, 232 guiding wall
140 heat receiving area
300 heating element
400 heat radiating unit
500 related ebullient cooling device
510 coolant tub
511 heat receiving surface
512 heat radiation surface
513 tank
520 heat dissipation unit
530, 531 heating element
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-219887 | Oct 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2012/075575 | 9/26/2012 | WO | 00 |
