US20040134641A1

US20040134641A1 - Cooling device boiling and condensing refrigerant

Info

Publication number: US20040134641A1
Application number: US10/744,642
Authority: US
Inventors: Hiroshi Tanaka
Original assignee: Individual
Current assignee: Denso Corp
Priority date: 2002-12-26
Filing date: 2003-12-22
Publication date: 2004-07-15
Also published as: JP2004207643A

Abstract

A cooling device includes a first refrigerant container having a side wall to which a heat-generating member is attached, a second refrigerant container, and plural tubes communicated with both of the containers. The first refrigerant container has therein a flow control unit for controlling a refrigerant flow in the first refrigerant container. The flow control unit is provided such that refrigerant introduced from the second refrigerant container into the first refrigerant container flows along an inner surface of the side wall of the first refrigerant container at least from a height position corresponding to a top end of the heat-generating member. Therefore, a height level of liquid refrigerant stored in the first refrigerant container can be decreased while heat radiation area can be widened. Thus, cooling performance is improved in the cooling device used in a side-heat condition.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2002-377657 filed on Dec. 26, 2002, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a cooling device for cooling a heat-generating member such as a semiconductor or the like, by movement of latent heat due to boiling and condensation of the refrigerant.

2. Description of Related Art

JP-A-2003-130561 proposes a

cooling device

100 that is constructed with a refrigerant container 101 for storing refrigerant, plural tubes 130 and a header tank 160, as shown in FIG. 10. A heat-generating member 10 is attached to a heat reception surface 110 a placed under the refrigerant container 101.

The

tubes

130 are substantially vertically arranged with respect to a heat radiation surface 110 b of the refrigerant container 101, so that the refrigerant container 101 and the header tank 101 are communicated with each other. A boiling area is defined in a place where the surface area of the heat-generating member 10 is projected to the heat radiation surface 110 b. Tubes 130 (i.e., tubes 130C) arranged in the boiling area and the tubes 130 (i.e., tubes 130D) arranged away from the boiling area respectively have refrigerant passages. The refrigerant passage area of each tube 130C is set larger than the refrigerant passage area of each tube 130D, at the lower end opening connected to the refrigerant container 101.

Refrigerant is boiled and evaporated by the heat received from the heat-generating

member

10, and is preferentially introduced into the tubes 130C comparing with the tubes 130D. As a result, refrigerant from the tubes 130C is introduced into the header tank 160, and is diffused in the header tank 160. The refrigerant introduced into the tubes 130D is cooled so as to be condensed, and the condensed refrigerant is returned to the refrigerant container 101.

Recently, heat radiation amount of such the heat-generating

member

10 tends to be increased, so cooling performance of the cooling device 100 strongly needs to be improved. Furthermore, as shown in FIG. 11, the cooling device 100 is apt to be used in a side-heat condition for improving packing density of the heat-generating member 10. The heat-generating member 10 is positioned in the side surface of the refrigerant container 101 in the side-heat condition. Generally, the heat-generating member 10 is mounted in the substantially center of the refrigerant container 101 for convenience of various wiring. Therefore, the refrigerant needs to be filled in the refrigerant container 101 up to the vicinity of the top end of the heat-generating member 10, in this side-heat condition. As a result, a heat radiation section, where the evaporated refrigerant is condensed, is narrowed. That is, because the number of the tubes 130, where the evaporated refrigerant passes, is decreased, sufficient cooling performance cannot be obtained.

SUMMARY OF THE INVENTION

In view of the foregoing problems, it is an object of the present invention to provide a cooling device that improves cooling performance by widening heat radiation section. The heat radiation section can be effectively widened by lowering a liquid refrigerant level stored in the cooling device when the cooling device is used in the side-heat condition.

According to the present invention, a cooling device for cooling a heat-generating member includes a first refrigerant container having a side wall to which the heat-generating member is attached, a second refrigerant container that is disposed on an opposite side of the heat-generating member with respect to the first refrigerant container, a plurality of tubes through which refrigerant evaporated in the first refrigerant container by heat from the heat-generating member flows into the second refrigerant container and refrigerant in the second refrigerant container returns to the first refrigerant container while being cooled and condensed, and a refrigerant flow control unit provided in the first refrigerant container for controlling a refrigerant flow. In the cooling device, the refrigerant flow control unit is provided in such a manner that the refrigerant introduced into the first refrigerant container from the second refrigerant container flows along an inner wall surface of the side wall of the first refrigerant container at least from a position corresponding to a top end of the heat-generating member. Thus, the liquid refrigerant flowing on the inner wall surface of the side wall of the first refrigerant container can be directly boiled and evaporated by the heat of the heat-generating member in the first refrigerant container. Accordingly, the height level of the liquid refrigerant stored in the first refrigerant container can be set lower, and heat radiation area of the tubes can be relatively increased. Therefore, the first refrigerant container can be effectively downsized. As a result, cooling performance of the cooling device can be improved in the side-heat condition.

Preferably, the refrigerant flow control unit includes a partition section that is placed in the vicinity of the top end of the heat-generating member so as to partition the inner section of the first refrigerant container into an upper section and a lower section, and a passage section that is provided adjacent to the partition section for communicating the upper section and the lower section on a side of the inner wall surface of the side wall. Therefore, the refrigerant flow control unit can be readily constructed in the first refrigerant container.

More preferably, the passage section has an opening area that is smaller than a total passage sectional area of the tubes in which refrigerant flows from the first refrigerant container toward the second refrigerant container. Therefore, a refrigerant circulation in the cooling device can be facilitated, and the cooling capacity of the cooling device can be further improved.

The tubes are horizontally arranged in addition to the vertically stacked arrangement, to which an external fluid is generally horizontally supplied. In this case, the tubes, through which the refrigerant passes from the first refrigerant container to the second refrigerant container, have a refrigerant flow area that increases in a flow direction of the external fluid from an upstream position toward a downstream position. Further, the tubes, through which the refrigerant passes from the second refrigerant container to the first refrigerant container; have a refrigerant flow area that increases in a flow direction of the external fluid from the downstream position toward the upstream position. Accordingly, the refrigerant circulation in the cooling device can be further facilitated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: [0014]
FIG. 1 is a schematic perspective view showing a cooling device according to a first embodiment of the present invention; [0015]
FIG. 2 is a cross-sectional view of the cooling device taken along line II-II in FIG. 1; [0016]
FIG. 3A is a schematic plan view showing a heat radiation plate for constructing a first refrigerant container of the cooling device, FIGS. 3B and 3C are schematic plan views showing intermediate plates for constructing the first refrigerant container of the cooling device, and FIG. 3D is a schematic plan view showing a heat reception plate for constructing the first refrigerant container of the cooling device, according to the first embodiment; [0017]
FIG. 4 is a cross-sectional view of the cooling device taken along line IV-IV in FIG. 2; [0018]
FIG. 5 is a partial plan view showing stacked intermediate plates according to the first embodiment; [0019]
FIG. 6 is a cross-sectional view showing tubes of a cooling device according to a second embodiment of the present invention; [0020]
FIG. 7 is a cross-sectional view showing a cooling device according to a third embodiment of the present invention; [0021]
FIGS. 8A and 8B are schematic sectional views showing cooling devices according to a fourth embodiment of the present invention; [0022]
FIG. 9 is a schematic perspective view showing a cooling device according to a fifth embodiment of the present invention; [0023]
FIG. 10 is a perspective view showing a cooling device according to a related art; and [0024]
FIG. 11 is a schematic sectional view showing a cooling device in a side-heat condition in a related art.[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

The first embodiment of the present invention will be now described with reference to FIGS. [0026] 1-5. As shown in FIG. 1, a cooling device 100 according to the first embodiment is constructed with a first refrigerant container 110, a second refrigerant container 120, plural tubes 130 and heat radiation fins 150. The cooling device 100 is used for cooling a heat-generating member 10 such as a semiconductor device or the like. Members of the cooling device 100 described as follows are made of aluminum or an aluminum alloy. The members of the cooling device 100 are joined with each other, and are integrally brazed by using brazing material at joining sections between the members.
The first [0027] refrigerant container 110 is constructed with a heat reception plate 111, a heat radiation plate 112 and plural intermediate plates 113, 114. The heat reception plate 111 is used as a sidewall of the cooling device 100. The intermediate plates 113, 114 are stacked between the heat reception plate 111 and the heat radiation plate 112. The heat radiation plate 112 is arranged on the opposite side of the heat reception plate 111 with respect to the intermediate plates 113, 114. The whole structure of the first refrigerant container is integrally brazed.
As shown in FIG. 3D, the [0028] heat reception plate 111 is a substantially square plate-shaped member. The heat-generating member 10 is attached onto the heat reception plate 111. As shown in FIG. 3A the heat radiation plate 112 is a substantially square plate-shaped member as well as the heat reception plate 111 as described above. Plural tube insertion holes 112 a are formed in the heat radiation plate 112, so that one side ends of the tubes 130 are respectively inserted into the tube insertion holes 112 a.
As shown in FIG. 3B, each [0029] intermediate plate 113 is a substantially square plate-shaped member. The intermediate plate 113 has plural openings 113 a extending vertically and horizontally. Thick wall sections 113 b are formed between adjacent openings 113 a. For example, three intermediate plates 113 are used in the cooling device 100 of the first embodiment. As shown in FIG. 3C, the intermediate plate 114 has openings 114 a, similarly to the intermediate plate 113 as described above. Each intermediate plate 114 has slit-shaped plural openings 114 b that vertically extends in a place corresponding to the heat-generating area of the heat-generating member 10. Thick wall sections 114 c are formed between the openings 114 a and the openings 114 b. The openings 113 a, 114 a and 114 b of the intermediate plates 113, 114 are formed by cutting, pressing, etching or the like.
As shown in FIG. 2, the [0030] intermediate plates 113 and 114 are stacked and inserted between the heat reception plate 111 and the heat radiation plate 112, so that the first refrigerant container 110 is constructed. The openings 113 a, 114 a and 114 b are overlapped with each other so as to communicate each other, so that inner sections are formed in the first refrigerant container 110. Predetermined amount of refrigerant is sealed in the inner sections of the first refrigerant container 110. Freon (HFC134a) is used as the refrigerant in this invention. However, other fluid such as water, alcohol, fluorocarbon can be used as the refrigerant.
The [0031] openings 113 a, 114 a, 114 b and the thick wall sections 113 b, 114 c are suitably combined, so that a refrigerant flow control unit 140 is formed in the first refrigerant container 110. The refrigerant flow control unit 140 is a characterizing portion in this invention.
The [0032] heat reception plate 111 of the first refrigerant container 110 has a heat reception surface 110 a on its outer side. The heat-generating member 10 is attached to the central section of the heat reception surface 110 a and is fixed using bolts or the like (not shown). Thermal conductive grease can be inserted between the heat reception surface 110a and the heat-generating member 10 for reducing thermal resistance on the contact surfaces. The heat-generating member 10 is mounted on the heat reception plate (side wall) 111 of the first refrigerant container 110, so that the cooling device 100 is used in a side-heat condition.
Plural plates [0033] 121-124 are stacked, so that the second refrigerant container 120 is constructed similarly to the first refrigerant container 110 as described above. The second refrigerant container 120 is arranged on the opposite side of the heat-generating member 10 with respect to the first refrigerant container 110. Intermediate plates 122, 123 are inserted in the second refrigerant container 120. The intermediate plate 122 has an opening 122 a, and the intermediate plate 123 has an opening 123 a respectively. The opening 122 a and the opening 123 a are overlapped with each other, so that an inner section is formed in the second refrigerant container 120. Besides, tube insertion holes 121 a are formed in the plate 121.
As shown in FIG. 4, each [0034] tube 130 has a flat cross-sectional shape, and plural flow passages 131 are formed in each tube 130. The plural tubes 130 are arranged in the vertical direction (e.g., seven levels in this embodiment), and are arranged in the horizontal direction (e.g., three rows in this embodiment). The tubes 130 are formed by extrusion.
The [0035] tubes 130 are inserted into the tube insertion holes 112 a of the heat radiation plate 112 at one ends, and brazed. The tubes 130 are inserted into the tube insertion holes 121 a of the plate 121 at the other ends, and brazed. Thus, the tubes 130 communicate with the inner section (inner space) of the first refrigerant container 110 and the inner section (inner space) of the second refrigerant container 120.
The ends of the [0036] tubes 130 are positioned so as not to protrude to the inner spaces of both of the refrigerant containers 110, 120. Thus, both of the refrigerant containers 110, 120 are downsized, and refrigerant flow is not disturbed around the ends of the tubes 130 in the refrigerant containers 110, 120.
Plural [0037] heat radiation fins 150 are provided to be connected to the tubes 130. The tubes 130 penetrate through the heat radiation fins 150, so that the heat radiation fins 150 are attached to the tubes 130. The heat radiation fins 150 are generally classified in a plate fin type.
Cooling air is supplied so as to pass through the [0038] tubes 130 and the heat radiation fins 150 using a blower or the like (not shown), when the cooling device 100 is activated. The cooling air is substantially horizontally (specifically, in the arrangement direction of the tubes 130) supplied as an external fluid for enhancing heat exchange.
Next, the characterizing portion will be described. The refrigerant [0039] flow control unit 140 is provided in the first refrigerant container 110. The intermediate plates 113, 114 are constructed to form a partition section 141 and a gap section (passage section) 142, so that the refrigerant flow control unit 140 is constructed.
The [0040] thick wall sections 113 b of the intermediate plates 113 have stacking portions corresponding to the vicinity of the upper end section of the heat radiation member 10. The stacking portions of the thick wall sections 113 b are stacked so that the partition section 141 extending horizontally are formed. As shown in FIG. 5, the openings 113 a of the intermediate plates 113 and the openings 114 of the intermediate plate 114 respectively have communication portions corresponding to the vicinity of the upper end section of the heat radiation member 10. The communication portions of the openings 113 a, 114 b are slightly overlapped, so that the gap section 142 is formed.
The [0041] thick wall section 114 c in the vicinity of the gap section 142 and the partition section 141 partition the inner section of the first refrigerant container 110 into the upper section and the lower section approximately at the vicinity of the upper end of the heat-generating member 10. The upper section and the lower section of the first refrigerant container 110 are communicated with each other through the gap section 142 on a side of an inner wall surface 111 a of the heat reception plate 111.
Here, the [0042] tubes 130 positioned between a liquid surface 149 of the liquid refrigerant and the bottom surface of the partition section 141 are defined as tubes 130A. Refrigerant is boiled and evaporated in the first refrigerant container 110 by the heat of the heat-generating member 10 as described below. The evaporated gas refrigerant passes through the tubes 130A. Furthermore, the opening area of the gap section 142 is set smaller than the total opening area of the flow passages 131 of the tubes 130A opened in the first refrigerant container 110.
The refrigerant is boiled and evaporated by the heat of the heat-generating [0043] member 10 in the cooling device 100. Most flow of the evaporated gas refrigerant is restricted by the partition section 141, so that the evaporated refrigerant is introduced to the second refrigerant container 120 through the tubes 130A. Subsequently, the refrigerant introduced into the second refrigerant container 120 flows into the tubes 130 (i.e., tubes 130B) placed over the tubes 130A, and returns to the first refrigerant container 110. The evaporated refrigerant is cooled and condensed by the cooling air while passing through the tubes 130A, 130B, and is introduced into the upper section of the first refrigerant container 110. Heat of the evaporated refrigerant is radiated as condensation latent heat to the cooling air, so that the heat-generating member 10 is cooled. The radiation of the condensation latent heat is enhanced by the heat radiation fins 150. The refrigerant is cooled and condensed while passing through the tubes 130A, and accumulated in the lower area of the second refrigerant container 120.
Gas refrigerant in the second [0044] refrigerant container 120 is further condensed while passing through the tubes 130B, and introduced into the upper section of the first refrigerant container 110. The condensed refrigerant flows down through the gap 142 while forming thin liquid film along the inner wall surface 111 a.
Because the refrigerant [0045] flow control unit 140 is provided in the first refrigerant container 110, condensed liquid refrigerant is supplied in an arrangement area of the inner wall surface 111 a corresponding to the heat-generating area of the heat-generating member 10 in the first refrigerant container 110. Thus, the liquid refrigerant flowing along the inner wall surface 111 a can be readily boiled and evaporated by the heat directly transmitted from the heat-generating member 10. Thus, refrigerant liquid level 149 contained in the first refrigerant container 110 can be set lower. Accordingly, heat radiation area of the tubes 130 can be enlarged due to the decreased refrigerant liquid level, and cooling performance can be enhanced in the cooling device 100 used in the side-heat condition.
Furthermore, the refrigerant [0046] flow control unit 140 is constructed with the partition section 141 and the gap section 142. Therefore, the refrigerant flow control unit 140 can be formed easily.
The opening area of the [0047] gap section 142 is set smaller than the total opening area of the tubes 130A opened into the first refrigerant container 110, so that the evaporated refrigerant can readily flow into the tubes 130A. Therefore, the refrigerant flowing into the tubes 130A is readily recycled toward the gap section 142 through the second refrigerant container 120. The recycle is enhanced and the cooling performance is improved, because the liquid refrigerant flow is restricted at the gap section 142.
The plural plates [0048] 111-114, 121-124 are stacked, so that the refrigerant containers 110, 120 are constructed. Therefore, the refrigerant containers 110, 120 can be manufactured easily. Especially, the refrigerant flow control unit 140 can be easily formed using the stack structure.

Second Embodiment

As shown in FIG. 6, in this second embodiment, the total flow areas of the [0049] tubes 130A and the tubes 130B are respectively varied with respect to the flow direction of the cooling air, comparing with the first embodiment. That is, the refrigerant flow control unit 140 is set at a middle height portion of the heat-generating member 10 in the vertical direction, at an upstream position of the cooling air in the cooling device 100. The refrigerant flow control unit 140 is set at a position upper than the top end of the heat-generating member 10, at a downstream position of the cooling air in the cooling device 100. Therefore, the number of the tubes 130A is increased from the upstream position of the cooling air toward the downstream position of the cooling air. That is, total flow area of the tubes 130A increases downstream with respect to the cooling air flow direction. On the other hand, the total flow area of the tubes 130B is increased from the downstream position of the cooling air toward the upstream position of the cooling air.
Temperature of the cooling air is increased in the [0050] cooling device 100 toward its downstream position while performing heat-exchange with the refrigerant. Here, the total flow area of the tubes 130A is reduced in the cooling device in the upstream position of the cooling air comparing with the downstream position of the cooling air. Therefore, the heated evaporated refrigerant readily flows from the first refrigerant container 110 toward the second refrigerant container 120 through the tubes 130A. Accordingly, the evaporated refrigerant does not stay in the upstream position of the cooling air in the cooling device 100. Therefore, condensation of the evaporated refrigerant is restricted in the tubes 130A, so that flow does not become stagnant in the tubes 130A. On the contrary, the evaporated refrigerant in the tubes 130B is largely condensed by the cooling air at the upstream air side. Therefore, the refrigerant flow from the second refrigerant container 120 toward the first refrigerant container 110 can be facilitated. Thus, the recycle of the refrigerant between the first refrigerant container 110 and the second refrigerant container 120 is enhanced, so that cooling performance can be improved. In the second embodiment, the other parts are similar to those of the above-described first embodiment.

Third Embodiment

The third embodiment of the present invention will be now described with reference to FIG. 7. [0051]
The [0052] refrigerant containers 110, 120 are not limited to the stacked structure formed with plural plates, and can be formed with flat containers. In the third embodiment, as shown in FIG. 7, the partition section 141 is formed in the first container 110 to form a gap section 142 on the side of the inner wall surface 111 a, so that the refrigerant flow control unit 140 can be constructed. That is, in the third embodiment, the partition section is formed in the first refrigerant container 110 to form the gap section 142, so that condensed liquid refrigerant from the gap section 142 flows along the inner surface 111 a at least from the top position of the heat generating member 10.

Fourth Embodiment

The fourth embodiment of the present invention will be now described with reference to FIGS. 8A and 8B. [0053]
As shown in FIG. 8A, a first [0054] refrigerant container 110 of the fourth embodiment is constructed with plural plates 111-114. The second refrigerant container 120 is constructed with the plural plates 121-124. Intermediate plates 113, 114 respectively have the plural openings 113 a, 114 a, and intermediate plates 122, 123 respectively have the plural openings 122 a, 123 a in the same manner as the first embodiment. The refrigerant flow control unit, 140 is constructed with a communication passage 143 and an opening section (passage section) 144. Refrigerant is introduced from the tubes 130B toward the arrangement area of the inner wall surfaces 111 a through the opening section 144 and the communication passages 143. The opening section 144 is provided, so that the flow of the condensed liquid refrigerant is regulated. The arrangement area of the inner wall surfaces 111 a corresponds to the heat radiation area of the heat-generating member 10. The flow area of the opening section 144 can be set smaller than the total opening area of the tubes 130A opened in the first header tank 110.
FIG. 8B shows [0055] refrigerant containers 110, 120 constructed with flat containers. The refrigerant flow control unit 140 is formed with a tube-shaped member. The tube-shaped member has a communication passage 143 communicated with the tubes 130B, and an opening section 144. The opening section 144 is substantially vertically opened, so that the condensed liquid refrigerant flows along the inner wall surface 111 a downwardly at least from the top end portion of the heat-generating member 10.
Accordingly, in the fourth embodiment, advantages described in the first embodiment can be obtained. [0056]

Fifth Embodiment

The [0057] heat radiation fins 150 are not limited to the plate fin type. As shown in FIG. 9, corrugated fins 151 or the like can be used for increasing heat radiation, for example. The corrugated fins 151 are formed in a wave-shape, and provided (integrally brazed) between the tubes 130. Other structures of the refrigerant containers 110, 120 are substantially equivalent to the first embodiment. Accordingly, in the fourth embodiment, advantages described in the first embodiment can be obtained.

Other Embodiments

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. [0058]
For Example, the number of each [0059] intermediate plate 114, 122, 123 is not limited to one, and the number of the intermediate plates 113 are not limited to three for the refrigerant containers 110, 120. Combinations of the intermediate plates 113, 114, 122, 123 can be performed freely.
The cooling device described in the above-embodiments can be used in a bottom heat condition. In this case, the [0060] tubes 130 are arranged in the vertical direction, and the first refrigerant container 110 is placed below the tubes 130 in the bottom heat condition. Further, the heat-generating member 10 is placed below the first refrigerant container 110.
Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims. [0061]

Claims

What is claimed is:

1. A cooling device for cooling a heat-generating member, comprising:

a first refrigerant container for storing therein at least liquid refrigerant, the first refrigerant container having a side wall to which the heat-generating member is attached;

a second refrigerant container that is disposed on an opposite side of the heat-generating member with respect to the first refrigerant container;

a plurality of tubes through which refrigerant evaporated in the first refrigerant container by heat from the heat-generating member flows into the second refrigerant container and refrigerant in the second refrigerant container returns to the first refrigerant container while being cooled and condensed, wherein the tubes are stacked substantially in a vertical direction and connected to the first refrigerant container and the second refrigerant container to be communicated with both of the first refrigerant container and the second refrigerant container; and

a refrigerant flow control unit provided in the first refrigerant container in such a manner that the refrigerant introduced into the first refrigerant container from the second refrigerant container flows along an inner wall surface of the side wall of the first refrigerant container at least from a position corresponding to a top end of the heat-generating member.

2. The cooling device according to claim 1, wherein the refrigerant flow control unit including:

a partition section that is placed in the vicinity of the top end of the heat-generating member so as to partition the inner section of the first refrigerant container into an upper section and a lower section; and

a passage section that is provided adjacent to the partition section, for communicating the upper section and the lower section on a side of the inner wall surface.

3. The cooling device according to claim 2, wherein the passage section has an opening area which is smaller than a total passage sectional area of the tubes in which refrigerant flows from the first refrigerant container toward the second refrigerant container.

4. The cooling device according to claim 1, wherein

the tubes are horizontally arranged in addition to the vertically stacked arrangement, to which an external fluid is generally horizontally supplied, wherein

the tubes, through which the refrigerant passes from the first refrigerant container to the second refrigerant container, have a refrigerant flow area that increases in a flow direction of the external fluid from an upstream position toward a downstream position, and

the tubes, through which the refrigerant passes from the second refrigerant container to the first refrigerant container, have a refrigerant flow area that increases in a flow direction of the external fluid from the downstream position toward the upstream position.

5. The cooling device according to claim 1, wherein

the first refrigerant container and the refrigerant flow control unit are constructed with a plurality of plates stacked with each other in a stacked direction,

the second refrigerant container is constructed with a plurality of plates stacked with each other in the stacked direction, and

at least one plate arranged in an intermediate section in the stacked direction has a plurality of openings.

6. The cooling device according to claim 1, wherein at least one of the first refrigerant container and the second refrigerant container is a flat container.

7. The cooling device according to claim 1, further comprising a plurality of fins disposed between the first and second container to contact the tubes.