COOLING DEVICE

A cooling device includes a cooling tank, a liquid storage tank, and a connector. The cooling tank stores refrigerant liquid for immersing and cooling a heating element. The liquid storage tank stores the refrigerant liquid outside the cooling tank and has an atmosphere opening portion. The connector connects the two tanks and allows the refrigerant liquid to pass through the connector. One end of the connector has a cooling-tank opening portion located in a gravity direction at a position lower than or same as a liquid level of the refrigerant liquid. An upper portion of the cooling tank stores a gas generated in the cooling tank. The refrigerant liquid flows between the two tanks via the connector in accordance with a change in volume of the gas. The liquid storage tank is provided upward of the cooling tank. The two tanks are connected only by the connector.

TECHNICAL FIELD

The present disclosure relates to a cooling device.

BACKGROUND

A cooling device for cooling a heating element immerses the heating element in refrigerant liquid.

SUMMARY

According to at least one embodiment, a cooling device includes a cooling tank, a liquid storage tank, and a connector. The cooling tank stores refrigerant liquid for immersing and cooling a heating element. The liquid storage tank stores the refrigerant liquid outside the cooling tank and has an atmosphere opening portion opening to an atmosphere. The connector connects the liquid storage tank and the cooling tank and allows the refrigerant liquid to pass through the connector.

One end of the connector facing the cooling tank has a cooling-tank opening portion located in a gravity direction at a position lower than or same as a liquid level of the refrigerant liquid in the cooling tank. An upper portion of the cooling tank stores a gas generated in the cooling tank.

The refrigerant liquid flows between the cooling tank and the liquid storage tank via the connector in accordance with a change in volume of the gas in the upper portion of the cooling tank. The liquid storage tank is provided upward of the cooling tank in the gravity direction. The cooling tank and the liquid storage tank are connected only by the connector.

DETAILED DESCRIPTION

In a cooling device for cooling a heating element such as an electronic device by immersing the heating element in refrigerant liquid, the refrigerant liquid can be reduced due to vaporization of the refrigerant liquid by heat generation of the heating element, and insufficient cooling of the heating element may be caused.

Contrary to this, a comparative example in which a sealing tank that accommodates a sealing material is provided outside a cooling tank in which a heating element is immersed in a refrigerant liquid, and the sealing tank functions as a trap or a seal, thereby reducing discharge of refrigerant vapor generated in the cooling tank to the outside.

However, since temperature of the cooling tank becomes higher than that of the sealing tank due to the heat generation of the heating element, if the refrigerant liquid evaporated in the cooling tank continues to condense in the sealing tank, the sealing tank may eventually be filled with the refrigerant liquid, and the refrigerant liquid or the sealing material may overflow from the sealing tank to the outside.

According to one aspect of the present disclosure, a cooling device includes a cooling tank, a liquid storage tank, and a connector. The cooling tank stores refrigerant liquid for immersing and cooling a heating element. The liquid storage tank stores the refrigerant liquid outside the cooling tank and has an atmosphere opening portion opening to an atmosphere. The connector connects the liquid storage tank and the cooling tank and allows the refrigerant liquid to pass through the connector.

One end of the connector facing the cooling tank has a cooling-tank opening portion located in a gravity direction at a position lower than or same as a liquid level of the refrigerant liquid in the cooling tank. An upper portion of the cooling tank stores a gas generated in the cooling tank.

The refrigerant liquid flows between the cooling tank and the liquid storage tank via the connector in accordance with a change in volume of the gas in the upper portion of the cooling tank. The liquid storage tank is provided upward of the cooling tank in the gravity direction. The cooling tank and the liquid storage tank are connected only by the connector.

Thus, an outflow of the gas-phase refrigerant from the atmosphere opening portion of the liquid storage tank to the outside via the connector can be reduced. As a result, a decrease in the refrigerant liquid in the cooling tank can be reduced.

Hereinafter, embodiments for implementing the present disclosure is described referring to drawings. In each embodiment, the same reference numerals may be given to parts corresponding to matters described in a preceding embodiment, and overlapping explanations may be omitted. When only a part of the configuration is described in each embodiment, the previously described other embodiments can be applied to other parts of the configuration. The present disclosure is not limited to combinations of embodiments which combine parts that are explicitly described as being combinable. As long as no problems are present, the various embodiments may be partially combined with each other even if not explicitly described.

First Embodiment

A first embodiment of the present disclosure will be described with reference to the drawings. InFIG.1, an up-down direction of the drawing is a gravity direction.

As shown inFIG.1, a cooling device1of the first embodiment includes a cooling tank10, a liquid storage tank20, and a connector30. The cooling tank10, the liquid storage tank20, and the connector30are made of, for example, a resin material or a metal material.

The cooling tank10is a container in which an electronic device2to be cooled is accommodated. The electronic device2is a heating element that generates heat with operation and requires cooling. The electronic device2is, for example, an electronic substrate on which a heating element is mounted, an inverter, or the like. The electronic device2of the present embodiment is a plate-like member, and is disposed such that a plate surface of the electronic device is parallel to the gravity direction. The electronic device2corresponds to a heating element of the present disclosure.

Refrigerant liquid11for cooling the electronic device2is stored in the cooling tank10. The electronic device2is immersed in the refrigerant liquid11. In the present embodiment, a fluorine-based inert liquid is used as the refrigerant liquid11. The fluorine-based inert liquid is a refrigerant liquid having excellent insulating properties, heat transfer characteristics, and stability. In the present embodiment, the refrigerant liquid11having a low boiling point lower than about 120° C. is used. The fluorine-based inert liquid is, for example, Novec (trade name of 3M) having a hydro fluoro ether (HFE) structure or Fluorinert (trade name of 3M) having a perfluorocarbon (PFC) structure.

The boiling point of the refrigerant liquid11is lower than a heat generation temperature of the electronic device2. In the present embodiment, the refrigerant liquid11having a boiling point about 10 to 20° C. lower than the heat generation temperature of the electronic device2is used. Therefore, the refrigerant liquid11can be boiled by heat generation of the electronic device2, and boiling cooling in which the refrigerant liquid11boils and absorbs heat from the electronic device2is performed in the cooling tank10. In the present embodiment, subcool boiling is performed in which the refrigerant liquid11in contact with the electronic device2boils and the refrigerant liquid11in the cooling tank10boils in a state of being a subcool liquid having a temperature lower than the boiling point.

The gas-phase refrigerant generated by the boiling of the refrigerant liquid11is condensed and reduced by the subcool liquid, but bubbles that cannot be condensed move upward inside the refrigerant liquid11. The gas generated in the cooling tank10is stored in an upper portion of the cooling tank10to form a gas portion12. The gas portion12contains the gas-phase refrigerant, dissolved gas discharged from the refrigerant liquid11, air present in the cooling tank10from the beginning, and the like. A volume of the gas portion12is variable and may become 0 volume.

The gas-phase refrigerant contained in the gas portion12is generated by vaporization of the refrigerant liquid11inside the cooling tank10. The vaporization of the refrigerant liquid11includes boiling and evaporation of the refrigerant liquid11. The gas-phase refrigerant contained in the gas portion12is condensed to become the refrigerant liquid11of liquid-phase.

A dissolved gas mainly composed of an atmosphere is dissolved in the refrigerant liquid11. The dissolved gas contained in the gas portion12is generated by the dissolved gas dissolved in the refrigerant liquid11being discharged from the refrigerant liquid11. Solubility of the dissolved gas dissolved in the refrigerant liquid11varies depending on a temperature of the refrigerant liquid11and the like. The solubility of the dissolved gas decreases, and the dissolved gas is released from the refrigerant liquid11when the temperature of the refrigerant liquid11increases. The dissolved gas released from the refrigerant liquid11forms the gas portion12together with the gas-phase refrigerant. The dissolved gas contained in the gas portion12can be dissolved again in the refrigerant liquid11by the temperature decrease of the refrigerant liquid11.

The liquid storage tank20is a container capable of storing the refrigerant liquid11therein. The liquid storage tank20is provided outside the cooling tank10. In the present embodiment, the liquid storage tank20is provided to face an upper surface of the cooling tank10.

An atmosphere opening21is provided in an upper portion of the liquid storage tank20. An inside of the liquid storage tank20communicates with the atmosphere via the atmosphere opening21at the upper portion. The liquid storage tank20is open to the atmosphere, and the atmosphere is present upward of the refrigerant liquid11inside the liquid storage tank20.

The liquid storage tank20is connected to the cooling tank10by the connector30. The connector30is a cylindrical member, and the refrigerant liquid11is capable of passing through the inside thereof. The connector30has one end connected to the cooling tank10and the other end connected to the liquid storage tank20. The connector30of the present embodiment is provided so as to penetrate the upper surface of the cooling tank10.

The inside of the liquid storage tank20communicates with the cooling tank10through the connector30on a lower portion. Since the inside of the liquid storage tank20is open to the atmosphere through the atmosphere opening21, the inside of the liquid storage tank20and the inside of the cooling tank10are maintained at atmospheric pressure. That is, the cooling device1of the present embodiment is of an open air type.

A cooling-tank opening31is provided at a position near the cooling tank10and at the one end of the connector30. In the present embodiment, the cooling-tank opening31is provided at a lower portion of the connector30in the gravity direction, and the cooling-tank opening31opens downward in the gravity direction.

A liquid level of the refrigerant liquid11in the cooling tank10is normally located above the cooling-tank opening31, and can be lowered to the cooling-tank opening31when the volume of the gas portion12increases. Therefore, the cooling-tank opening31is located below or at the same height as the liquid level of the refrigerant liquid11in the cooling tank10in the gravity direction. That is, a height H2in the gravity direction of the cooling-tank opening31is at a position lower than or equal to a height H1of the liquid level of the refrigerant liquid11.

The inside of the liquid storage tank20communicates with the inside of the cooling tank10via the connector30. Therefore, the refrigerant liquid11is capable of flowing between the cooling tank10and the liquid storage tank20via the connector30. The refrigerant liquid11flows between the cooling tank10and the liquid storage tank20according to volume variation of the gas portion12.

Since the refrigerant liquid11flows between the cooling tank10and the liquid storage tank20, the volume of the refrigerant liquid11in the cooling tank10and the volume of the refrigerant liquid11in the liquid storage tank20vary in conjunction with each other. More specifically, the volume of the refrigerant liquid11in the liquid storage tank20increases when the volume of the refrigerant liquid11in the cooling tank10decreases, and the volume of the refrigerant liquid11in the liquid storage tank20decreases when the volume of the refrigerant liquid11in the cooling tank10increases.

In the present embodiment, the cooling tank10and the liquid storage tank20are not in contact with each other, and a gap is formed between the cooling tank10and the liquid storage tank20. An air layer, which is a gap formed between the cooling tank10and the liquid storage tank20, functions as a heat insulating portion40. The heat insulating portion40suppresses heat transfer between the cooling tank10and the liquid storage tank20.

A circulation circuit50for circulating the refrigerant liquid11in the cooling tank10is connected to the cooling tank10. A circulation pump51and a heat exchanger52are provided in the circulation circuit50.

The circulation pump51pumps and circulates the refrigerant liquid11in the circulation circuit50. The heat exchanger52dissipates heat of the refrigerant liquid11to cool the refrigerant liquid. The heat exchanger52is, for example, a radiator that cools the refrigerant liquid11by exchanging heat with an outside air, a chiller that cools the refrigerant liquid11by exchanging heat with a low-temperature refrigerant of a refrigeration cycle, or the like. Since the heat exchanger52cools the refrigerant liquid11, a temperature rise of the refrigerant liquid11can be suppressed, and the subcooled state of the refrigerant liquid11can be maintained.

The circulation circuit50is connected to the cooling tank10at an inlet portion53and an outlet portion54. The refrigerant liquid11in the cooling tank10flows into the circulation circuit50through the inlet portion53. The refrigerant liquid11circulated through the circulation circuit50flows out to the cooling tank10through the outlet portion54.

A flow of the refrigerant liquid11from the outlet portion54toward the inlet portion53is formed in the cooling tank10. In an example shown inFIG.1, the outlet portion54is provided on a left of the cooling tank10, and the inlet portion53is provided on a right of the cooling tank10. Therefore, a flow of the refrigerant liquid11from the left to the right is formed inside the cooling tank10.

The gas-phase refrigerant generated by the refrigerant liquid11boiling due to the heat generation of the electronic device2becomes bubbles, and the bubbles rise inside the cooling tank10while moving downward in a flow direction of the refrigerant liquid11. The cooling-tank opening31of the connector30is provided at a position where it is difficult for the gas-phase refrigerant to flow in. More specifically, the cooling-tank opening31is provided upstream in the flow direction of the refrigerant liquid11in the cooling tank10. That is, the cooling-tank opening31is provided near the outlet portion54than the inlet portion53in the flow direction of the refrigerant liquid11.

Next, a description will be given on operation of the cooling device1of the present embodiment having the above configuration.

In the cooling tank10, the refrigerant liquid11in the vicinity of the electronic device2boils due to the heat generation of the electronic device2, and a gas-phase refrigerant is generated. The gas-phase refrigerant rises inside the cooling tank10as bubbles and forms the gas portion12. The dissolved gas released from the refrigerant liquid11due to the temperature rise of the refrigerant liquid11also forms the gas portion12together with the gas-phase refrigerant. The gas-phase refrigerant obtained by vaporizing the refrigerant liquid11and the dissolved gas discharged from the refrigerant liquid11are stored in the cooling tank10.

The gas-phase refrigerant generated by boiling rises in the refrigerant liquid11as bubbles. Since the refrigerant liquid11in the cooling tank10is a subcool liquid, the air bubbles formed of the gas-phase refrigerant are cooled by the refrigerant liquid11when moving up inside the refrigerant liquid11, and the gas-phase refrigerant condenses. As a result, the bubbles formed of the gas-phase refrigerant are reduced in a middle of rising inside the refrigerant liquid11, and the bubbles disappear when a subcool degree of the refrigerant liquid11is large.

The refrigerant liquid11in the cooling tank10is supplied to the heat exchanger52through the circulation circuit50and is cooled by the heat exchanger52. By the cooling by the heat exchanger52, the refrigerant liquid11can be actively maintained in the subcooled state.

The gas-phase refrigerant generated by boiling of the refrigerant liquid11in the vicinity of the electronic device2rises while moving downward in the flow direction of the refrigerant liquid11. Since the cooling-tank opening31of the connector is provided upstream in the flow direction of the refrigerant liquid11in the cooling tank10, the gas portion12can be formed inside the cooling tank10without the gas-phase refrigerant flowing into the cooling-tank opening31.

In the cooling tank10, the volume of the gas portion12increases due to the vaporization of the refrigerant liquid11and the release of the dissolved gas from the refrigerant liquid11. As the volume of the gas portion12increases, the volume of the refrigerant liquid11in the cooling tank10decreases. As the volume of the refrigerant liquid11in the cooling tank10decreases, the refrigerant liquid11flows from the cooling tank10to the liquid storage tank20, and the volume of the refrigerant liquid11in the liquid storage tank20increases.

The temperature of the refrigerant liquid11decreases, in the cooling tank due to a decrease in an amount of heat generation of the electronic device2, or an increase in cooling capacity of the heat exchanger52. By decreasing the temperature of the refrigerant liquid11, condensation of the gas-phase refrigerant contained in the gas portion12is promoted, and dissolution of the dissolved gas contained in the gas portion12into the refrigerant liquid11is promoted.

In the cooling tank10, the volume of the gas portion12decreases and the volume of the refrigerant liquid11increases due to condensation of the gas-phase refrigerant contained in the gas portion12and dissolution of the dissolved gas contained in the gas portion12into the refrigerant liquid11. The refrigerant liquid11flows from the liquid storage tank20to the cooling tank10, and the volume of the refrigerant liquid11decreases inside the liquid storage tank20when the volume of the refrigerant liquid11increases.

In the present embodiment described above, the cooling-tank opening31of the connector30is located below or at the same height as the liquid level of the refrigerant liquid11of the cooling tank10in the gravity direction. Further, the gas generated in the cooling tank10is stored in the upper portion of the cooling tank10to form the gas portion12, and the refrigerant liquid11flows between the cooling tank10and the liquid storage tank20via the connector30according to the volume variation of the gas portion12. Thus, an outflow of the gas-phase refrigerant from the atmosphere opening21of the liquid storage tank20to the outside via the connector30can be reduced. As a result, in the cooling device1, a decrease in the refrigerant liquid11in the cooling tank10can be reduced even when the cooling device1is used for a long period of time.

Further, in the present embodiment, the cooling device1of the open air type having the atmosphere opening21communicating with the atmosphere is used. Accordingly, a decrease in the refrigerant liquid11in the cooling tank10can be reduced without using a pressure resistant container for sealing the refrigerant liquid11. Therefore, the cooling device1can be downsized.

In addition, in the cooling device1of the present embodiment, the boiling cooling in which the refrigerant liquid11boils due to the heat generation of the electronic device2is performed. In the boiling cooling, the electronic device2can be efficiently cooled, but on the other hand, a generation amount of the gas-phase refrigerant increases, and the gas-phase refrigerant easily flows out to the outside. According to the present embodiment, also in the cooling device1that performs the boiling cooling for boiling the refrigerant liquid11, a decrease in the refrigerant liquid11can be effectively reduced.

In the present embodiment, the refrigerant liquid11in the cooling tank10is a subcool liquid, and subcool boiling is performed. Therefore, the gas-phase refrigerant generated by boiling of the refrigerant liquid11due to the heat generation of the electronic device2is cooled and condensed by the refrigerant liquid11formed of the subcool liquid. Accordingly, the gas-phase refrigerant from flowing to the circulation pump51and the heat exchanger52via the circulation circuit50can be reduced, and the performance of the circulation pump51and the heat exchanger52can be maintained to stably use them.

In the present embodiment, the refrigerant liquid11in the cooling tank10is circulated by the circulation circuit50, and the refrigerant liquid11is cooled by the heat exchanger52. Accordingly, the temperature rise of the refrigerant liquid11can be reduced, and the gas-phase refrigerant can be effectively cooled by the refrigerant liquid11in the subcooled state. As a result, an increase in the volume of the gas portion12can be reduced, and a decrease in the liquid level of the refrigerant liquid11in the cooling tank10and an increase in the liquid level of the refrigerant liquid11in the liquid storage tank20can be reduced.

Further, in the present embodiment, the cooling-tank opening31of the connector30is provided upstream in the flow direction of the cooling tank10. Since bubbles formed of the gas-phase refrigerant rise while moving downstream in the flow direction of the refrigerant liquid11, the bubbles rise while moving away from the cooling-tank opening31. Therefore, the gas-phase refrigerant from flowing into the cooling-tank opening31provided upstream in the flow direction of the cooling tank10can be reduced. Accordingly, an outflow of the gas-phase refrigerant generated inside the cooling tank10to the outside from the atmosphere opening21of the liquid storage tank20through the cooling-tank opening31can be reduced, and a decrease in the refrigerant liquid11can be reduced.

In the present embodiment, the heat insulating portion40is provided between the cooling tank10and the liquid storage tank20. Thus, heat transfer from the cooling tank10to the liquid storage tank20can be reduced, and the refrigerant liquid11can be reduced from evaporating in the liquid storage tank20and flowing out to the outside.

In the present embodiment, the cooling tank10, the liquid storage tank20, and the connector30are made of a resin material. Thus, a size and weight of the cooling tank10and the like can be reduced, manufacturing costs of the cooling tank10and the like can be reduced, and a degree of freedom of the shape of the cooling tank10and the like can be increased. Furthermore, since the cooling tank10, the liquid storage tank20, and the connector30are made of a resin material, heat transfer from the cooling tank10to the liquid storage tank20can be reduced, and the refrigerant liquid11can be suppressed from evaporating in the liquid storage tank20and flowing out to the outside.

Second Embodiment

The following describes a second embodiment of the present disclosure. Hereinafter, only portions different from the first embodiment will be described.

As shown inFIG.2, a wire2ais connected to the electronic device2of the second embodiment. The wire2afunctions as a power supply and a transmission path of an electric signal. The wire2ais provided so as to extend from a cooling tank10to a connector30and a liquid storage tank20. The wire2ais extended to an outside from an atmosphere opening21of the liquid storage tank20.

As described above, in the second embodiment, the wire2aof the electronic device2is taken out to the outside by using the atmosphere opening21opened to the atmosphere. Therefore, the wire2aof the electronic device2can be taken out to the outside without providing a seal structure for preventing the refrigerant liquid11from flowing out to the outside.

Third Embodiment

The following describes a third embodiment of the present disclosure. Hereinafter, only portions different from the above embodiments will be described.

As shown inFIG.3, in the third embodiment, a cooling-tank opening31of a connector30is located above an electronic device2in a gravity direction. That is, a height H2in the gravity direction of the cooling-tank opening31of the connector30is higher than a height H3in the gravity direction of the electronic device2. The height H3in the gravity direction of the electronic device2is a height of an upper end portion of the electronic device2.

According to the third embodiment described above, even when a volume of a gas portion12increases, a liquid level of the refrigerant liquid11falls only to the cooling-tank opening31of the connector30. Therefore, the liquid level of the refrigerant liquid11is always maintained at a position higher than that of the electronic device2. Thus, the electronic device2can be always immersed in the refrigerant liquid11without being exposed from the refrigerant liquid11, and cooling capacity of the cooling device1can be maintained. An excess gas of the gas portion12is discharged to the outside from the atmosphere opening21of the liquid storage tank20through the cooling-tank opening31when the gas portion12reaches the cooling-tank opening31.

Fourth Embodiment

Next, a fourth embodiment of the present disclosure is described. Hereinafter, only portions different from the above embodiments will be described.

As shown inFIG.4, a heat transfer portion13is provided at the cooling tank10of the fourth embodiment. The heat transfer portion13is disposed so as to straddle a refrigerant liquid11and a gas portion12inside a cooling tank10, and promotes heat transfer between the refrigerant liquid11and the gas portion12. The heat transfer portion13is fixed to an inner wall of an upper surface of the cooling tank10. In an example illustrated inFIG.4, three heat transfer portions13are provided, but a number of heat transfer portions13can be arbitrarily set and may be one or more.

A material having an excellent heat transfer coefficient is used for the heat transfer portion13. For example, a metal plate made of aluminum or copper can be used as the heat transfer portion13.

According to the fourth embodiment described above, the gas portion12is cooled by the refrigerant liquid11through the heat transfer portion13. Thus, condensation of the gas-phase refrigerant contained in the gas portion12can be promoted, and an increase in the volume of the gas portion12can be reduced. As a result, a liquid level of the refrigerant liquid11in the cooling tank10can be prevented from falling, and the liquid level of the refrigerant liquid11in the liquid storage tank20can be prevented from rising.

Fifth Embodiment

Next, a fifth embodiment of the present disclosure is described. Hereinafter, only portions different from the above embodiments will be described.

As shown inFIG.5, in the fifth embodiment, an electronic device2having a plate shape is horizontally disposed inside a cooling tank10. That is, in the cooling tank10, a plate surface of the plate-shaped electronic device2is disposed so as to intersect a gravity direction.

Also, in the configuration of the fifth embodiment, the cooling tank10and a liquid storage tank20are connected to each other by a connector30, and a height H2in the gravity direction of a cooling-tank opening31of the connector30is lower than a liquid level H1of the refrigerant liquid11of the cooling tank10. As a result, similarly to the first embodiment, an outflow of the gas-phase refrigerant from the atmosphere opening21of the liquid storage tank20to the outside via the connector30can be reduced.

Sixth Embodiment

Next, a sixth embodiment of the present disclosure is described. Hereinafter, only portions different from the above embodiments will be described.

As shown inFIG.6, in the sixth embodiment, a liquid storage tank20is provided to face a side surface of a cooling tank10. A connector30of the sixth embodiment is provided so as to penetrate the side surface of the cooling tank10, and a cooling-tank opening31is opened in a horizontal direction. A liquid level of the refrigerant liquid11in the liquid storage tank20is higher than the liquid level of the refrigerant liquid11in the cooling tank10. A gap is provided between the side surface of the cooling tank10and the liquid storage tank20, and this gap functions as a heat insulating portion40.

Also, in the configuration of the sixth embodiment, the cooling tank10and a liquid storage tank20are connected to each other by a connector30, and a height H2in the gravity direction of a cooling-tank opening31of the connector30is lower than a liquid level H1of the refrigerant liquid11of the cooling tank10. As a result, similarly to the first embodiment, an outflow of the gas-phase refrigerant from the atmosphere opening21of the liquid storage tank20to the outside via the connector can be reduced.

In addition, in the sixth embodiment, the cooling-tank opening31of the connector30is opened in the horizontal direction, and air bubbles made of the gas-phase refrigerant are less likely to flow into the cooling-tank opening31than when the cooling-tank opening31is opened downward in the gravity direction. Accordingly, an outflow of the gas-phase refrigerant generated inside the cooling tank10to the outside from the atmosphere opening21of the liquid storage tank20through the cooling-tank opening31can be reduced, and a decrease in the refrigerant liquid11can be reduced.

The present disclosure is not limited to the embodiments described above, and can be variously modified as follows without departing from the gist of the present disclosure. The means disclosed in the individual embodiments may be appropriately combined as long as the combination is feasible.

For example, in each of the above embodiments, the electronic device2is immersed in the refrigerant liquid11and cooled in the cooling tank10, but a heating element other than the electronic device2may be immersed in the refrigerant liquid11and cooled. The heating element to be cooled may be an object that generates heat and can be cooled by being immersed in the refrigerant liquid11.

In the configuration of each of the above embodiments, an evaporation inhibitor may be provided on an upper surface of the refrigerant liquid11in the liquid storage tank20. The upper surface of the refrigerant liquid11in the liquid storage tank is a contact surface with the atmosphere. The evaporation inhibitor only needs to reduce evaporation of the refrigerant liquid11, and for example, oil for oil film covering the upper surface of the refrigerant liquid11in the liquid storage tank20, particles covering the upper surface of the refrigerant liquid11in the liquid storage tank20, or the like can be used.

In addition, in the fourth embodiment, the heat transfer portion13that promotes heat transfer between the refrigerant liquid11and the gas portion12is provided, but the heat transfer portion13may have a different configuration. For example, a heat transfer portion13may be provided across the atmosphere and the gas portion12, and the heat transfer between the atmosphere and the gas portion12may be promoted by the heat transfer portion13to cool the gas portion12. In this case, the heat transfer portion13may be exposed to the outside of the cooling tank10, and the heat transfer portion13may be provided so as to straddle the outside and the inside of the cooling tank10.

Further, the cooling-tank opening31of the connector30is opened downward in the gravity direction in the first to fifth embodiments and is opened in the horizontal direction in the sixth embodiment, but a cooling-tank opening31may be opened upward in the gravity direction. Accordingly, air bubbles formed of the gas-phase refrigerant is difficult to flow into the cooling-tank opening31, the gas-phase refrigerant from flowing out from the atmosphere opening21of the liquid storage tank20to the outside through the cooling-tank opening31can be reduced, and a decrease in the refrigerant liquid11can be reduced.

In each of the above embodiments, the heat insulating portion40is the air layer in the gap between the cooling tank10and the liquid storage tank20. However, the configuration is not limited to this, and a heat insulating portion40may include a heat insulating member between the cooling tank10and the liquid storage tank20to form a heat insulating portion40.

While the present disclosure has been described with reference to embodiments thereof, it is to be understood that the disclosure is not limited to the embodiments and constructions. To the contrary, the present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various elements are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.