TW201408980A - Boiling cooling device - Google Patents

Abstract

The present invention provides an ebullient cooling device which achieves a high critical heat flux and is operable at a high pressure and a low temperature. Provided is an ebullient cooling device that comprises a closed chamber (10) which is provided with, at the bottom thereof, a heating part (11) to which heat from a heat source (3) is transmitted, and in which a refrigerant is sealed, and that cools the heat source (3) by transmitting the heat from the heating part (11) to the refrigerant. In the closed chamber (10), a first refrigerant and a second refrigerant that is insoluble in the first refrigerant are sealed, and in a state before the heat source (3) generates heat, the first refrigerant (21) in a liquid state, the second refrigerant (22) in a liquid state, and mixed vapor (23) containing the first refrigerant in a gas state and the second refrigerant in a gas state are present in the closed chamber (10).

Description

Boiling cooling device

The present invention relates to a boiling cooling device for cooling a machine by boiling.

With the development of semiconductor technology in recent years, the heat density of semiconductor elements has dramatically increased. Therefore, a cooling device having a high cooling performance is sought. For example, a boiling cooling device that uses a boiling phenomenon to transfer heat by boiling a refrigerant is known, for example, from Patent Document 1. The boiling cooling device has high cooling performance due to the evaporation heat transfer caused by the phase change of the refrigerant.

[Previous Technical Literature]

[Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2011-21789

If the heat source supplies an excessive heat flux to the heating portion of the boiling cooling device as described above, the film of the refrigerant is boiled, causing the heating portion to burn. The heat flux at which this burnout occurs is referred to as the critical heat flux. The boiling cooling device is used in an environment where the heat flux below the critical heat flux is transmitted to the heating portion.

In general, although an attempt to increase the critical heat flux has been carried out in a boiling cooling device, the change over time due to long-term use is still a problem, and it is a lack of reliability. Therefore, it is difficult to use for cooling of a heat source that generates a large amount of heat.

Further, in the case where pure water is used as the refrigerant of the boiling cooling device, the boiling point of the pure water is 100 ° C at atmospheric pressure, and the boiling cooling device is operated at least above atmospheric pressure in order to prevent the heat of the cooling system from being impeded by the incorporation of air. Therefore, the boiling cooling device is cooled by the boiling phenomenon of the heating portion at a temperature of 100 ° C or higher. Thus, a boiling cooling device having an operating temperature of 100 ° C or higher cannot be used, for example, for cooling of a semiconductor element having a heat resistant temperature of less than 100 ° C. Therefore, in order to cool the heat source having a low heat-resistant temperature, it is possible to maintain the boiling cooling device capable of exhibiting the original cooling performance at a lower temperature while maintaining the pressure at or above atmospheric pressure.

It is an object of the present invention to provide a boiling cooling device which has a high critical heat flux and can operate at high pressure or low temperature.

According to the present invention, there is provided a boiling cooling device which is provided with a heating portion for transmitting heat from a heat source at a lower portion, and has a sealed chamber in which a refrigerant is sealed inside, and transfers heat to the refrigerant from the heating portion. a boiling cooling device for cooling the heat source; wherein the sealed chamber is sealed with a first refrigerant and a second refrigerant that is insoluble with the first refrigerant; and in the state before the heat source generates heat, the sealed chamber exists The second refrigerant having a liquid, the second refrigerant of the liquid, and the mixed vapor of the first refrigerant containing the gas and the second refrigerant of the gas.

The boiling cooling device of the present invention, wherein the second refrigerant has a higher boiling point and a lower density than the first refrigerant; and the volume of the first refrigerant of the liquid can be compared in a state before the heat source generates heat. The volume of the second refrigerant of the liquid is small.

In the above-described boiling cooling device of the present invention, the liquid level of the first refrigerant of the heating portion to the liquid may be 10 mm in a state before the heat is generated by the heat source. under.

In the above-described boiling cooling device of the present invention, the sealed chamber may have a partition wall that maintains a certain amount above the heating portion in a state where the temperature in the sealed chamber is lower than the boiling point of the first refrigerant. The first refrigerant of the liquid described above.

In the above-described boiling cooling device of the present invention, the second refrigerant may have a higher boiling point and a higher density than the first refrigerant.

In the above-described boiling cooling device of the present invention, the second refrigerant may be water.

In the above-described boiling cooling device according to the present invention, the sealed chamber may have a condensing portion that is thermally connected to the heat radiating portion, and condenses the first refrigerant of the gas and the second refrigerant of the gas back to the liquid.

In the above-described boiling cooling device of the present invention, the sealed chamber may have a gas transport path that transports the first refrigerant and the second refrigerant heated by the heating portion to a gas to the condensation portion. And a liquid return path for returning the first refrigerant and the second refrigerant, which are condensed by the gas to the liquid in the condensation portion, back to the heating portion.

The boiling cooling device according to the present invention may further include: a cooling unit that is connected to the sealed chamber via a transport path, and that dissipates heat of the first refrigerant and the second refrigerant to the outside; and a pump The cooled first refrigerant and the second refrigerant are returned to the sealed chamber.

In the above-described boiling cooling device of the present invention, the sealed chamber may have a bubble trap which is open toward the lower side and maintains a certain amount of gas in the first refrigerant and gas before and after heating of the heating element. The above second refrigerant.

In the above-described boiling cooling device according to the present invention, the first refrigerant and the second refrigerant cooled by the cooling unit can be sent to the pump without passing through the gas-liquid separator.

A boiling cooling device according to the present invention, wherein the upper surface of the heating portion is It is inclined so as to become higher toward the opposite side to the acceleration direction of the heat source.

In the boiling cooling device of the present invention, since the first refrigerant and the second refrigerant do not dissolve each other, the pressure of the mixed vapor of the first refrigerant containing the gas and the second refrigerant of the gas acts on the first refrigerant of the liquid and the second of the liquid. Refrigerant. That is, if one of the first refrigerant or the second refrigerant is focused on, the saturated vapor pressure of the other refrigerant acts in addition to the saturated vapor pressure of the refrigerant which is one of the temperatures in the closed chamber. Therefore, under the pressure in the sealed chamber which is the sum of the saturated vapor pressures of the first refrigerant and the second refrigerant, the first refrigerant and the second refrigerant are below the respective saturation temperatures at the equilibrium temperature inside the sealed chamber. And the first refrigerant and the second refrigerant are both in a supercooled state. Since the degree of supercooling is higher, the critical heat flux becomes higher, so that a boiling cooling device having a higher critical heat flux can be obtained.

Moreover, since the pressure of the first refrigerant and the second refrigerant are equal to or higher than the respective saturated vapor pressures, the partial pressure of the first refrigerant and the partial pressure of the second refrigerant are both lower than the total pressure of the sealed chamber, and the After the equal pressure is added, it is equal to the total pressure. Therefore, the first refrigerant or the second refrigerant can boil at a lower temperature than when the sealed chamber is filled with only one of the first refrigerant or the second refrigerant, and if the pressure in the chamber is considered to be fixed. Thereby, the refrigerant or the heat generating portion can activate the boiling cooling device at the original cooling performance at a lower temperature. Further, since the temperature of the refrigerant is fixed at the same time, the operation can be performed at a higher pressure, so that the steam generated by the incorporation of air does not hinder the condensation, and the reliability of the long-term operation of the cooling system can be improved.

1‧‧‧Boiling cooling device

2‧‧‧ circuit board

3‧‧‧heat source

4‧‧‧ radiator

10‧‧‧Closed chamber

11‧‧‧ heating department

12‧‧‧Condensation

13‧‧‧ side wall

14‧‧‧ gas transport path

15‧‧‧ Liquid return path

16‧‧‧ bubble trap

17‧‧‧ partition wall

21‧‧‧ The first refrigerant of liquid

22‧‧‧Second refrigerant of liquid

23‧‧‧ gas phase

24‧‧‧The first refrigerant bubble

25‧‧‧second refrigerant bubble

26‧‧‧The first refrigerant droplet

30‧‧‧ radiator

40‧‧‧ gas-liquid separation device

50‧‧‧ pump

60‧‧‧ catheter

P1‧‧‧saturated vapor pressure

P2‧‧‧saturated vapor pressure

Pt‧‧‧ total pressure

q‧‧‧Heat flux

S‧‧‧Confined space

T1‧‧‧ temperature

T2‧‧‧ temperature

Tt‧‧‧ temperature

Tw‧‧‧temperature

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a boiling cooling device according to an embodiment of the present invention.

Figure 2 is a diagram illustrating the refrigerant in a compressed state.

Fig. 3 is a view showing the state in which the refrigerant is in a supercooled state.

4(a) to 4(d) are diagrams showing changes in behavior of the first refrigerant and the second refrigerant when the temperature of the heating portion is increased in the boiling cooling device shown in Fig. 1.

Fig. 5 is a schematic view showing the relationship between the temperature Tw of the heat source and the heat flux q.

Fig. 6 is a schematic view showing the overshoot phenomenon.

Fig. 7 is a graph showing the relationship between the temperature difference ΔTb between the heating portion and the medium and the heat flux q.

Fig. 8 shows the relationship between the temperature Tw of the heat source and the heat flux q.

Fig. 9 is a schematic view showing an example in which the boiling cooling device of the embodiment is applied to a steam chamber.

Fig. 10 is a schematic view showing an example in which the boiling cooling device of the embodiment is applied to a heat pipe.

Fig. 11 is a schematic view showing an example in which the boiling cooling device of the embodiment is applied to a heat source to which acceleration is applied.

Figure 12 is a schematic view showing a boiling cooling device including a pump.

Fig. 13 is a schematic view showing a variation of the boiling cooling device shown in Fig. 12.

Fig. 14 is a schematic view showing a variation of the boiling cooling device shown in Fig. 12.

Hereinafter, an embodiment of the boiling cooling device of the present invention will be described with reference to the drawings.

<Configuration of boiling cooling device>

Fig. 1 is a cross-sectional view showing a boiling cooling device 1 of the present embodiment. The boiling cooling device 1 is mounted on the heat source 3. In the illustrated example, the heat source 3 is a semiconductor element mounted on the circuit board 2. The boiling cooling device 1 cools the heat source 3 by taking heat from the heat source 3 and finally efficiently dissipating heat to the atmosphere.

The boiling cooling device 1 comprises a closed chamber 10. The hermetic chamber 10 may be formed of a metal material such as stainless steel or aluminum. The sealed chamber 10 includes a heating portion 11 that is disposed on the bottom surface, a condensation portion 12 that is disposed on the upper surface, and a side wall 13 that connects the heating portion 11 and the condensation portion 12.

The heating portion 11 is provided in connection with the heat source 3, and transfers heat from the heat source 3 to the lower portion of the sealed chamber 10. The condensation portion 12 and the heat dissipation disposed on the upper portion of the sealed chamber 10 The device 4 is connected and thermally connected to the heat sink 4. As the heat sink 4, in addition to the heat sink shown, an air cooling fan or a water-cooled type may be used.

A sealed space S is provided inside the sealed chamber 10. The first refrigerant and the second refrigerant are sealed in the sealed space S. In a state before the heat source 3 is heated, in the sealed space S, there is a first liquid layer 21 containing a liquid first refrigerant, a second liquid layer 22 containing a liquid second refrigerant, and a gas layer 23 It comprises a mixed vapor of a first refrigerant containing a gas and a second refrigerant of a gas. The first refrigerant and the second refrigerant are appropriately selected from substances which are insoluble in each other within the operating temperature range of the boiling cooling device 1. In the following description, especially when the first refrigerant and the second refrigerant are not referred to separately, the first refrigerant and the second refrigerant are also referred to as refrigerant.

In the present embodiment, as the first refrigerant, a perfluorocarbon FLUORINERT FC72 (boiling point: 56 [° C.], density: 1.68 [g/mm ³ ]) of a low boiling point high density medium is used, and as a second refrigerant. Pure water of high boiling point low density medium (boiling point: 100 [° C], density: 1.00 [g/mm ³ ]). Further, the amount of the first refrigerant to be sealed is such that the distance from the bottom surface of the sealed space S to the liquid surface of the first liquid layer 21 (the layer thickness of the first liquid layer 21) is 5 mm in the sealed space S having a height of 100 mm. Set it up. The amount of the second refrigerant to be sealed is set such that the distance from the liquid surface of the first liquid layer 21 to the liquid surface of the second liquid layer 22 (the thickness of the second liquid layer 22) is 95 mm.

<Self-compressed and super-cooled state>

In order to facilitate understanding of the principle of operation of the boiling cooling device 1 constructed as described above, the concept of self-compression and undercooling is first described. Fig. 2 is a view showing the first refrigerant and the second refrigerant in a compressed state. Fig. 3 is a view showing the first refrigerant and the second refrigerant in a supercooled state. In Figs. 2 and 3, the horizontal axis represents the temperature in the sealed space S, and the vertical axis represents the pressure in the sealed space S. Further, in Figs. 2 and 3, A represents a saturated vapor pressure curve of the first refrigerant, and B represents a saturated vapor pressure curve of the second refrigerant. Further, the black circles in the figure indicate the pressure and temperature in a certain state in the sealed space S.

In a state before the heat source 3 generates heat, the inside of the sealed chamber 10 is formed at substantially the same constant temperature (equilibrium temperature). In this state, one of the first refrigerant and one of the second refrigerant partially evaporate, and a gas layer 23 is formed above the first liquid layer 21 and the second liquid layer 22. Inside the sealed space S, a state of thermal equilibrium is established between the first liquid layer 21, the second liquid layer 22, and the gas layer 23. That is, as shown in Fig. 2, at this temperature (equilibrium temperature) Tt, the sum of the saturated vapor pressure P1 of the first refrigerant and the saturated vapor pressure P2 of the second refrigerant is the total pressure Pt = P1 + P2 in the sealed space S. Further, the sum of the partial pressures P1 and P2 of the first refrigerant and the second refrigerant becomes the total pressure Pt in the sealed space S.

This means that in the case of focusing on the first refrigerant, the first refrigerant in the sealed space S acts on the saturated vapor pressure P2 of the second refrigerant in addition to the saturated vapor pressure P1 of the first refrigerant. Similarly, if attention is paid to the second refrigerant, the second refrigerant in the sealed space S acts on the saturated vapor pressure P1 of the first refrigerant in addition to the saturated vapor pressure P2 of the second refrigerant. That is, both the first refrigerant and the second refrigerant in the sealed space S have a higher pressure Pt than the saturated vapor pressures P1 and P2 of the equilibrium temperature Tt, and it can be said that the first refrigerant and the second refrigerant are in a compressed state. Such a situation in which the two refrigerants which are insoluble in each other are sealed in the sealed space S, and the refrigerant having a higher pressure than the saturated vapor pressure corresponding to the temperature of the sealed space S acts as a self-compression.

Further, according to different opinions, as shown in FIG. 3, the temperature Tt of the first refrigerant in the sealed space S becomes larger than the saturation temperature T1 of the first refrigerant corresponding to the total pressure Pt in the sealed space S. low. Similarly, the temperature Tt of the second refrigerant in the sealed space S becomes lower than the saturation temperature T2 of the second refrigerant corresponding to the total pressure Pt in the sealed space S. Thus, the first refrigerant and the second refrigerant are in a subcooling state (Subcool).

The difference (T1-Tt) between the temperature T1 of the first refrigerant corresponding to the total pressure Pt and the temperature Tt in the sealed space S, and the temperature T2 of the second refrigerant corresponding to the total pressure Pt here and the sealed space S The difference in temperature Tt (T2-Tt) is called undercooling [K]. The degree of subcooling indicates an indicator of the degree of the supercooled state of the refrigerant. As shown in FIG. 3, the boiling point is higher than the boiling point of the first refrigerant. The second refrigerant in the point is set to have a large degree of subcooling.

<Action of boiling cooling device>

Next, the operation of the boiling cooling device 1 shown in Fig. 1 will be described with reference to Figs. 4 and 5 .

The boiling cooling device 1 cools the heat source 3 by transferring the heat generated by the heat source 3 to the side of the radiator 4 via the first refrigerant and the second refrigerant. More specifically, as shown in Figs. 4(a) to (d), the heat transfer mode changes depending on the heat flux.

Fig. 4 is a view showing changes in behavior of the first refrigerant and the second refrigerant when the heat flux from the heat source 3 rises in the boiling cooling device 1 shown in Fig. 1.

Fig. 5 is a schematic view showing the relationship between the temperature Tw [K] of the heat source 3 and the transfer heat flux q [W/mm ² ] of the boiling cooling device. Further, Fig. 5A shows the relationship between the heat flux q of the boiling cooling device 1 of the present embodiment and the temperature Tw of the heat source. B of Fig. 5 shows the relationship between the heat flux q of the boiling cooling device in which only the FC 72 is sealed in the closed space and the temperature Tw of the heat source. C of Fig. 5 shows the relationship between the heat flux q of the boiling cooling device in which only pure water is sealed in the closed space and the temperature Tw of the heat source.

(The temperature of the heating section does not reach the boiling point of the first refrigerant)

Fig. 4(a) shows a state in which the heat flux is small and the temperature of the heating portion 11 does not reach the boiling point of the first refrigerant.

The heat from the heat source 3 is transferred to the first liquid layer 21 of the first refrigerant via the heating portion 11. Convection is generated inside the first liquid layer 21, and heat is transferred to the second liquid layer 22. Further, by the convection generated by the second liquid layer 22, heat is transferred to the gas layer 23, and heat is transferred from the condensation portion 12 to the heat sink 4. Further, when the density of the first refrigerant and the second refrigerant are close to each other, convection occurs while the first refrigerant and the second refrigerant are mixed.

Thus, as shown in FIG. 4(a), convection is generated by the first refrigerant and the second refrigerant, and the boiling cooling device 1 cools the heat source 3. The section (a) of Fig. 5 corresponds to the state shown in (a) of Fig. 4 .

(The heat flux starts above the boiling flux of the first refrigerant, but does not reach the critical heat flux of the first refrigerant)

(b) of FIG. 4 shows a state in which the temperature of the heating portion 11 is above the boiling point of the first refrigerant, but does not reach the film boiling temperature of the first refrigerant.

In this state, boiling occurs in the first liquid layer 21 by the heat from the heating portion 11. The first refrigerant 24, which is boiled and vaporized as a gas, passes through the second liquid layer 22 to reach the gas layer 23, and is then cooled to the droplets 26 at the condensation portion 12 and returned to the liquid phase. The liquid droplet 26 of the first refrigerant condensed into a liquid in the condensing portion 12 is dropped toward the heating portion 11, or is transmitted from the side wall 13 to the heating portion 11 side, and is introduced into the first liquid layer 21.

Thus, in the state shown in FIG. 4(b), the first cooling agent circulates in the sealed space S with the phase change of the liquid and the gas, and the boiling cooling device 1 cools the heat source 3. The section (b) of Fig. 5 corresponds to the state shown in Fig. 4(b).

As described above, in the boiling cooling device 1 of the present embodiment, when the first refrigerant 24 heated and vaporized in the lower portion of the sealed chamber 10 is moved upward, the condensation portion 12 provided on the upper portion of the sealed chamber 10 is reached. Then, the first refrigerant liquefied by the condensation portion 12 is again moved by gravity to the heating portion 11 below. Therefore, it is not necessary to provide a device such as a pump that allows the refrigerant to flow.

(The heat flux is above the critical heat flux of the first refrigerant, but does not reach the boiling capacity of the second refrigerant to start the heat flux)

Fig. 4(c) shows a state in which the heat flux is above the critical heat flux of the first refrigerant, but does not reach the boiling heat of the second refrigerant.

When the film of the first refrigerant is boiled by the heat from the heating unit 11, the first liquid layer 21 disappears. Then, the second liquid layer 22 containing the second refrigerant drops to the space occupied by the first liquid layer 21, and the second liquid layer 22 contacts the heating portion 11. Convection occurs in the second liquid layer 22 by the heat from the heating portion 11. Heat is transferred from the second liquid layer 22 to the gas layer 23, which transfers heat to the condensation portion 12 by convective heat transfer.

Thus, in the state shown in FIG. 4(c), the convective heat transfer and gas by the second liquid layer 22 The convection of the layer 23 and the heat transfer of the condensation cause the boiling cooling device 1 to cool the heat source 3. Further, the first refrigerant is in a gas state and is stored in the gas layer 23, but is condensed to become the droplets 26 and is lowered into the second refrigerant. The section (c) of Fig. 5 corresponds to the state shown in Fig. 4(c). Moreover, the state in which only the first refrigerant is burned is referred to as intermediate burnout.

In addition, when the thickness of the layer of the first liquid layer 21 is not more than 10 mm, the second liquid layer 22 can be surely brought into contact with the heating portion when the first liquid layer 21 is burned, which is preferable. More preferably, the layer thickness of the first liquid layer 21 is set to be about 5 mm or less.

(The heat flux is above the boiling rate of the second refrigerant, but the critical heat flux of the second refrigerant is not reached)

(d) of Fig. 4 shows a state in which the heat flux is above the boiling start heat flux of the second refrigerant but not to the critical heat flux of the second refrigerant.

In this state, boiling occurs in the second liquid layer 22 by the heat from the heating portion 11. The second refrigerant 25 that has boiled and vaporized rises and is cooled by the condensation portion 12 and recondensed back to the liquid. The second refrigerant which is liquid in the condensing portion 12 is dropped onto the heating portion 11, or is transferred from the condensing portion 12 to the heating portion 11 via the side wall 13.

Thus, in the state shown in FIG. 4(d), the boiling cooling device 1 cools the heat source 3 by circulating the second refrigerant along with the phase change. The first refrigerant is in the state of a gas and is present in the gas layer 23. The section (d) of Fig. 5 corresponds to the state shown in Fig. 4(d).

If the heat flux is equal to or higher than the critical heat flux of the second refrigerant, the film is boiled by the second refrigerant, so that the heat source 3 cannot be stably cooled. Therefore, the boiling cooling device 1 of the present embodiment can stably cool the heat source 3 until the heat flux of the film boiling occurs in the second refrigerant.

<critical heat flux>

In general, the upper limit of the heat flux to which the boiling cooling device can be applied is determined by the critical heat flux. The critical heat flux is a heat flux that causes the film to boil and the heat is burned in the heating portion. Thus, the critical heat flux is also referred to as the burnt heat flux.

In the boiling cooling device 1 shown in FIG. 1, the first cold is used in the manner described using FIG. Both the medium and the second refrigerant boil in a subcooled state (also known as subcooled boiling). Therefore, the upper limit of the heat flux to which the boiling cooling device 1 can be applied is determined by the critical heat flux at the time of subcooled boiling. In general, the critical heat flux at the time of supercooled boiling is the critical heat flux at the time of saturated boiling, and is expressed by the following formula (1).

q _sub =(1+C△T _sub )q _sat formula (1)

Here, q _sub is the critical heat flux [W/m ² ] at the time of supercooled boiling, C is a constant [1/K], ΔT _sub is the degree of supercooling [K], and q _sat is the critical value at the time of saturated boiling. Heat flux [W/m ² ].

The critical heat flux when it is too cold and boiling is greater as the degree of subcooling of the refrigerant increases. As shown in FIG. 3, since both the first refrigerant and the second refrigerant have a degree of subcooling, the critical heat flux of the first refrigerant becomes larger than the case where the sealed space S is filled only by the first refrigerant. Further, the critical heat flux of the second refrigerant becomes larger than the case where the sealed space S is filled only by the second refrigerant.

Therefore, the boiling cooling device 1 of the present embodiment can stably operate even when applied to a heat source having a large heat flux.

First, the boiling cooling device 1 of the present embodiment can continue to operate with a lower heat flux than the second refrigerant generating film boiling heat. Since the heat flux in this state is larger than the critical heat flux of the first refrigerant, the boiling cooling device of the present embodiment can be applied to generate a larger one than the boiling cooling device in which only the first refrigerant is sealed in the sealed space S. Heat source of heat flux.

Further, as described above, the second refrigerant is in a supercooled state, and the low-boiling refrigerant, that is, the high vapor pressure generated by the first refrigerant acts on the second refrigerant, thereby increasing the degree of subcooling of the second refrigerant. Therefore, the critical heat flux is larger than that of the boiling cooling device in which only the second refrigerant is sealed in the sealed space S, and the boiling cooling device of the present embodiment can be applied to a heat source that generates a large heat flux.

<Pressure and temperature in a confined space>

As described above, the first refrigerant and the second refrigerant which are not dissolved in each other are sealed in the sealed chamber 10, and both of them are in a compressed state. However, since the vapor pressure of the high-boiling refrigerant, that is, the second refrigerant, is low, the subcooling degree of the low-boiling refrigerant, that is, the first refrigerant, is kept to a small value. Therefore, the first refrigerant contacts the heat source at a higher density than the second refrigerant in a state before the boiling starts, and a state in which only the first refrigerant is sealed in the sealed chamber (that is, a state in which the first refrigerant is saturated). Compared to almost unchanged.

For example, when only the pure water is sealed in the sealed space, the pure water is boiled at 100 ° C when the pressure of the closed space is set to atmospheric pressure. Therefore, the operating temperature of such a boiling cooling device is around 100 ° C, and the temperature of the heat source is above it.

On the other hand, when a boiling cooling device is used for cooling of a semiconductor element or the like having a heat-resistant temperature of less than 100 ° C, it is necessary to set the pressure of the sealed space of the boiling cooling device to be equal to or lower than atmospheric pressure.

However, if the pressure in the confined space does not reach atmospheric pressure, there is a concern that the atmosphere invades the confined space with the passage of time. When the atmosphere intrudes into the sealed space, since the atmosphere acts as a non-condensable gas, the partial pressure of the first refrigerant and the second refrigerant rapidly decreases in the vicinity of the condensing portion 12, and the equilibrium temperature rapidly drops. Then, since the temperature difference between the temperature of the refrigerant and the final cooling medium outside the sealed chamber 10, that is, the atmosphere, etc., is lowered, significant condensation inhibition is caused. As a result, the temperature in the sealed chamber 10 rises, and the difference between the temperature of the heating portion 10 and the refrigerant becomes small, so that cooling cannot be achieved. That is, the pressure in the closed space is increased, and the operating temperature of the boiling cooling device becomes high.

When only one type of refrigerant such as pure water is sealed in a sealed space, it is difficult to simultaneously prevent deterioration over time and to reduce the operating temperature.

On the other hand, according to the boiling cooling device of the present embodiment in which the first refrigerant (for example, FC72) and the second refrigerant (for example, pure water) which are insoluble in each other are sealed in the sealed chamber 10, even inside the sealed chamber 10 When the pressure is set to atmospheric pressure, as also illustrated in Fig. 2, the partial pressure of pure water does not reach atmospheric pressure. Therefore, in the case of a high heat flux, it may not be reached. The temperature of 100 ° C causes the pure water to boil, and the operating temperature of the boiling cooling device 1 can be set to 100 ° C or less.

In fact, since the boiling cooling device 1 is operated since the temperature at which the FC 72 is boiling, and the boiling point of the FC 72 is also less than 56 ° C, the operating temperature becomes about 52 ° C. Therefore, even if the inside of the sealed chamber 10 is set to be higher than atmospheric pressure, the operating temperature of the boiling cooling device 1 or the temperature of the heat source 3 can be suppressed to less than 100 ° C in a wide range of heat flux.

As described above, according to the boiling cooling device 1 of the present embodiment, the pressure of the sealed space S can be set to be higher than the atmospheric pressure, and the operating temperature of the boiling cooling device 1 can be lowered while preventing deterioration over time, thereby cooling the heat source of the fear heat. A boiling cooling device 1 is applied.

In the above description, an example in which pure water is used as the second refrigerant is exemplified. However, when an organic solvent or an alcohol is used as the refrigerant, the pressure of the sealed space S may be set to atmospheric pressure. As described above, the operating temperature of the boiling cooling device 1 is set to be low. In addition, in the cooling of semiconductors such as GaN or SiC which have been proposed to have heat resistance in recent years, the pressure setting can be further increased, and the operating temperature of the boiling cooling device 1 can be set to a temperature of 100 ° C or higher.

<Overshoot of heat source temperature>

Figure 6 is a schematic diagram showing the relationship between the temperature of a general heat source and the heat flux. Generally, before and after boiling, there is a hysteresis between the temperature of the heat source and the heat flux as shown in FIG.

When the heat flux from the heat source is increased, boiling does not occur even if the boiling point of the refrigerant exceeds several tens of degrees (a of Fig. 6). For example, in the case where the refrigerant is in a supercooled state, the case where the heating portion is extremely smooth, the case where the boiling is under a low pressure, and the case where the surface of the heat source is transferred is small, the refrigerant is hard to boil. As described above, when the refrigerant does not boil, the heat is transferred to the refrigerant by the heat source due to the convection having a low cooling capacity, so that the temperature of the heat source is temporarily increased.

On the contrary, in the case of reducing the heat flux of the heat source to the refrigerant, the boiling bubbles are eliminated in order, and the state of boiling heat transfer rapidly proceeds to the convective heat transfer. state. Therefore, the temperature continuity of the heat source is lowered (b of Fig. 6).

Thus, there is a hysteresis between the heat source temperature and the heat flux when the heat flux is increased and reduced. The temporary increase in the temperature of the heat source when the heat flux is increased is called the overshoot of the heat source temperature.

Such overshoot is often observed in high boiling media such as pure water of the second refrigerant. On the other hand, the low-boiling medium such as FLORINERT or Freon of FC72 of the first refrigerant is liable to boil because the evaporation heat of one bubble is small, and it is difficult to cause an overshoot phenomenon.

In the boiling cooling device 1 of the present embodiment, when the density of the first refrigerant is high as shown in FIG. 4(b) and the heat source 3 is directly contacted to start boiling, the first refrigerant is a low-boiling medium such as FC72. The rush phenomenon is alleviated.

Further, as shown in (d) of FIG. 4, when the second refrigerant is boiled, the heat flux is also high, so that the bubbles of the first refrigerant stored in the second refrigerant tend to cause the second refrigerant to start boiling. Therefore, no overshoot occurs when the boiling of the second refrigerant starts.

As described above, in the boiling cooling device 1 of the present embodiment, it is difficult to cause an overshoot phenomenon. For example, when a power supply semiconductor (inverter) that supplies electric power such as a motor of an electric vehicle or a battery is used, when the boiling cooling device of the present embodiment is applied to cooling of a heat source having a large amount of heat fluctuation during sudden start, the power semiconductor is not temporary. It is at a high temperature, so that it can continue to operate stably. Since the inverter of the automobile repeatedly generates a sudden increase in the amount of heat generated from the heat source when the vehicle is started, the boiling cooling device 1 is also suitable for the cooling of the inverter of the automobile.

<Layer thickness of the first refrigerant>

Next, the boiling cooling device 1 of the embodiment of the present embodiment and the boiling cooling device of Comparative Examples 1 and 2 were produced, and the characteristics thereof were evaluated. In the sealed chamber 10 having a height of about 200 mm in the sealed space S, the refrigerant is sealed in the following ratio. The height of the enclosed space is not an important value.

(Example)

The sealing chamber 10 was sealed so that the layer thickness of the FC72 as the first refrigerant was 5 mm and the layer thickness of the pure water as the second refrigerant was 95 mm.

(Comparative Example 1)

Only pure water having a layer thickness of 100 mm was enclosed in the closed chamber 10.

(Comparative Example 2)

Only the FC 72 having a layer thickness of 100 mm was enclosed in the sealed chamber 10.

Fig. 7 shows the relationship between the temperature difference ΔTb [K] between the heating portion 11 and the sealed space S and the heat flux q [W/m ² ] of the boiling cooling device 1. Fig. 8 shows the relationship between the temperature Tw [K] of the heat source 3 and the heat flux q [W/m ² ] of the boiling cooling device 1.

The horizontal dashed line in Figure 7 represents the critical heat flux value. As shown in Fig. 7, the critical heat flux of Comparative Example 2 in which only FC72 was sealed was about 1/4 of the critical heat flux of Comparative Example 1 in which only pure water was sealed. When the first refrigerant, that is, the layer thickness before the FC72 was heated, was 5 mm, the critical heat flux of the example also became higher than the critical heat flux of Comparative Example 1. Further, limited to the experimental apparatus, the heat flux cannot be set to a value of 1.8 × 10 ⁶ [W/m ² ] or more as shown, but the critical heat flux of the boiling cooling device of the embodiment is indeed 2 × 10 ⁶ [W/m ² ] The above values. That is, according to the boiling cooling device of the present embodiment, it was confirmed that a high critical heat flux can be obtained. What is important here is that in the case where the layer thickness before heating is 5 mm, the first refrigerant boils after the start of boiling to a low heat flux, and automatically changes to the second refrigerant boiling at a high heat flux.

That is, in the boiling start phase, it is difficult for the first refrigerant which has an overshoot of the heat source temperature to boil.

Furthermore, since the critical heat flux of the first refrigerant is low, if the first refrigerant is mostly evaporated, it is automatically switched to convective heat transfer using the second refrigerant. This switching is based on the burning of the first refrigerant with a lower critical heat flux and is named intermediate burning. In addition, even if such intermediate burnout occurs, the cooling effect of the boiling cooling device is not adversely affected.

In this case, in order to automatically switch from the boiling of the first refrigerant to the second refrigerant Boiling, it is preferred to set the layer thickness of the first refrigerant to be small. In addition, the heat flux during intermediate burning was slightly lower than that of Comparative Example 2. If the heat flux becomes large, the second refrigerant boils. Since the second refrigerant has a large degree of subcooling, the critical heat flux is greatly improved as compared with Comparative Example 1.

When the density of the first refrigerant layer is higher than that of the second refrigerant, if the thickness of the first liquid layer 21 is too large, the switching from the boiling of the first refrigerant to the boiling of the second refrigerant may not proceed smoothly. . For example, when the thickness of the liquid layer of the first refrigerant, that is, FC72, is 10 mm before heating, the critical heat flux is 4 × 10 ⁵ [W/m ² ], which is comparable to the critical heat flux of Comparative Example 1. Much smaller. In this system, the thickness of the layer of FC72 before heating is excessively large, and the FC72 of the first refrigerant having a lower critical heat flux is mixed in a large amount in the pure water of the second refrigerant.

The layer thickness of the first preferred refrigerant is related to the physical properties or boiling characteristics of the refrigerant, and the conclusion that the thickness of the first liquid layer 21 is set to 5 mm is preferably determined by a combination of various liquids thereafter. Regardless of the combination of the refrigerants, when the first refrigerant is in a high density, the thickness of the first liquid layer 21 is preferably set to be 10 mm or less.

As shown in Fig. 8, the temperature Tw of the heat source after the middle burnout in the embodiment became lower than the temperature Tw of Comparative Example 1. In other words, when the heat source generates a high heat flux, it is confirmed that the heat source can be maintained at a lower temperature by the boiling cooling device of the present embodiment.

<Changes in refrigerants>

In the above description, an example in which a refrigerant having a higher boiling point and a lower density than the first refrigerant is used as the second refrigerant will be described, but the present invention is not limited thereto. For example, as the second refrigerant, a refrigerant having a higher boiling point and a higher density than the first refrigerant may be used.

In this case, since the second refrigerant is located below the first refrigerant before heating, when the heat source is disposed below, the second refrigerant contacts the heating unit 11. Therefore, the intermediate burnout as shown in Fig. 4(c) is not produced. However, since the first refrigerant and the second refrigerant are self-compressing, According to the high vapor pressure of the first refrigerant, the degree of subcooling of the second refrigerant is set to be large, so that it is possible to operate at a low temperature even if the critical heat flux is large and the pressure in the closed space is high. Boiling cooling device.

Further, in the above example, an example in which FC72 is used as the first refrigerant and pure water is used as the second refrigerant is described, but the present invention is not limited thereto. For example, Novec 7100 (registered trademark) (boiling point 61 ° C, density 1.52 [g/mm ³ ]) is used as the first refrigerant, and pure water is used as the second refrigerant, or Novec 649 (registered trademark) (boiling point 49 ° C, density 1.60) is used. [g/mm ³ ]) may be used as the first refrigerant, and pure water may be used as the second refrigerant. Alternatively, FC72 may be used as the first refrigerant, and alcohol may be used as the second refrigerant.

The substance which can be used for the first refrigerant and the second refrigerant is not particularly limited as long as it does not dissolve in the range of the operating temperature of the boiling cooling device. Among them, the first refrigerant has a low boiling point component and the second refrigerant has a high boiling point component. However, if the second refrigerant uses pure water, it is preferable because the boiling cooling device can be realized at a low cost, and a high critical heat flux (heat removal capacity) can be expected.

Further, although an example in which two kinds of refrigerants are sealed in the sealed chamber 10 will be described, three or more kinds of refrigerants may be enclosed. In this case, if at least two types of refrigerants are not dissolved, the same effect as described above can be obtained. possibility.

<The amount of refrigerant enclosed>

Further, in order to allow the refrigerant enclosed in the sealed chamber 10 to be in a self-compressed state and a supercooled state, it is necessary to form a gas by at least two kinds of refrigerants which are insoluble in each other in a state in which heat is generated before the heat source 3 generates heat. Layer 23. Although this is usually achieved when the refrigerant is sealed, it will be achieved at the beginning of boiling, so there is no difficulty in achieving it. In the state in which the gas layer 23 is formed, the following formula (2) holds.

v”=h _fg /(T _sat ×(dP/dT))+v' formula (2)

Here, v" is the specific volume of the evaporated refrigerant [m ³ /kg], v' is the specific volume of the refrigerant in the liquid state [m ³ /kg], h _fg is the latent heat of vaporization [J/kg], and T _sat is The saturation temperature [K] and dP/dT are gradients of the vapor pressure curve [N/m ² K].

Since the specific volume of the liquid refrigerant is much smaller than the specific volume of the evaporated refrigerant, the formula (2) can be regarded as the following formula (3).

v”≒h _fg /(T _sat ×(dP/dT)) Formula (3)

Formula (2) and Formula (3) can be applied to the first refrigerant or the second refrigerant by using the physical properties of each of the equilibrium temperatures.

On the other hand, the specific volume v ₁ of the first refrigerant is obtained by the following formula (4).

v ₁ =(V ₁ +V ₀ )/m ₁ Formula (4)

Here, m ₁ is the sealing weight [kg] of the first refrigerant, V ₁ is the volume of the first refrigerant [m ³ ] of the liquid at the temperature before the heat source 3 is heated, and the temperature of the V ₀ heat source 3 before the heat is generated. The volume of the first refrigerant of the gas and the second refrigerant of the gas [m ³ ].

Thus, using the formula (3) and the formula (4), the encapsulation weight m _{1 of the} first refrigerant satisfies the following formula (5), which is the maximum subcooling degree given to the second refrigerant to increase the critical heat flux. . However, even if it is not satisfied, the boiling heat transfer characteristics of the present embodiment are qualitatively the same. According to v ₁ <v ₁ ”, m ₁ >(V ₁ +V ₀ )×T _sat,1 ×(dP/dT) ₁ /h _fg,1 formula (5)

The word 1 indicates the first refrigerant.

Here, the first refrigerant is treated as a low-boiling point component, and the second refrigerant is treated as a high-boiling point component. However, it is effective to increase the critical heat flux to a large degree of subcooling of the second refrigerant.

When there is no large difference between the critical heat flux of the single component of the first refrigerant and the second refrigerant, and the density of the first refrigerant is higher than the density of the second refrigerant, the first refrigerant will be given a larger The method of cooling, thereby increasing the critical heat flux, is also effective. In this case, It is desirable to satisfy the formula (6) instead of the formula (5).

m ₂ >(V ₂ +V ₀ )×T _sat,2 ×(dP/dT) ₂ /h _fg,2Formula (6)

Word 2 indicates the second refrigerant.

Here, m ₂ is the enclosed weight [kg] of the second refrigerant, V ₂ is the volume of the second refrigerant [m ³ ] of the liquid at the temperature before the heat source 3 is heated, and the temperature of the V ₀ -based heat source 3 before the heat is generated. The volume of the first refrigerant of the gas and the second refrigerant of the gas [m ³ ].

In the method, the thickness of the liquid layer of the first refrigerant must be sufficiently large, and the layer thickness of the second refrigerant is desirably to be supercooled to the maximum amount of the first refrigerant in a manner not to be extremely small in order to satisfy the relationship of the formula (5). degree.

<Specific application>

The boiling cooling device described above can be applied to, for example, the steam chamber shown in FIG.

(steam room)

The steam chamber shown in Fig. 9 is a suitable device for cooling a small heat source having a large amount of heat. The upper surface and the bottom surface of the sealed chamber 10 of the steam chamber are formed to be larger than the upper surface of the heat source 3. The steam chamber can expand the heat source by transferring heat to the heat sink 4 which is larger for the smaller heat source 3, thereby effectively cooling the heat source.

The sealed chamber 10 of the steam chamber has a gas transport path 14 and a liquid return path 15.

The gas transport path provided inside the sealed space S is formed to extend in the left-right direction from directly above the heat source. The refrigerant vaporized by the heating portion 11 passes through the gas delivery path 14 and moves to the upper surface of the sealed chamber 10. At this time, since the gas transport path 14 is formed outside the heating unit 11 in the left-right direction, the vaporized refrigerant can be moved to the upper surface of the sealed chamber 10 which is not located directly above the heat source 3.

When moving hot in the steam chamber, it is not necessary to have a temperature difference in the gas transport path 14 as one of the characteristics of the steam chamber. Set to the same temperature inside the steam chamber, and with this Unlike the invention, when a single-component or co-soluble mixed refrigerant is filled into a steam chamber, the inside of the steam chamber becomes a saturation temperature. However, since the non-co-soluble mixed refrigerant is used in the present embodiment, the inside of the steam chamber becomes an equilibrium temperature, and each of the refrigerants is in a supercooled state, thereby obtaining a plurality of excellent heat transfer characteristics as described.

The liquid return path 15 is disposed over the entire area of the bottom surface of the sealed space S. The liquid return path 15 is a path for returning the refrigerant liquefied by a portion not located directly above the heat source 3 to the heating unit 11. The liquid return path 15 can be, for example, a capillary structure core (capillary structure).

With this configuration, the steam chamber can effectively cool the smaller heat source by transferring heat from the smaller heat source 3 to the large-area heat sink 4.

(Heat pipe)

Fig. 10 is a schematic view showing an example of a heat pipe to which the present invention is applied. The heat pipe transfers heat from the lower portion of the heat source 3 to the upper portion of the heat sink 4. The heat pipe also has a tubular closed chamber 10, a gas recovery path 14 extending in the longitudinal direction to a central portion of the closed chamber, and a liquid return path 15 disposed along the inner wall of the closed chamber 10 between.

According to this configuration, the refrigerant vaporized by the heat source 3 is moved upward via the gas return path 14. The refrigerant reaching the upper portion of the sealed chamber 10 is condensed by the radiator 4 and turned into a liquid. The liquefied refrigerant is moved to the lower side by the liquid return path 15. As such, the heat pipe can efficiently transfer heat from the heat source 3 to the heat sink 4.

(cooling device acting on the heat source with acceleration)

The boiling cooling device of the present invention can be used for cooling of an inverter constituted by, for example, a large semiconductor that controls electric power supplied to a motor or a battery of an electric vehicle. The inverter supplies a large amount of electric power during acceleration, and also frequently changes the amount of electric power supplied during traveling. It is also preferable to use the boiling cooling device of the present invention which is difficult to generate an overshoot phenomenon of the operating temperature as described above for the cooling of the inverter having a large change in the amount of heat generation.

In addition, in this case, the amount of heat generation is maximized when the electric vehicle is accelerated. because Therefore, the heating portion 11 may be formed on the surface inclined with respect to the horizontal plane so as to increase the rearward direction with respect to the traveling direction of the vehicle as shown in FIG. Fig. 11 is a schematic view showing an example in which the boiling cooling device of the embodiment is applied to a heat source to which acceleration is applied. As shown in the figure, the upper surface of the heating portion 11 is preferably inclined such that the opposite side to the direction of acceleration becomes higher. Thereby, as shown in FIG. 11, the refrigerant can be continuously brought into contact with the heating portion 11 even when the vehicle is accelerating.

<Application to boiling cooling device with forced flow>

Further, in the above embodiment, the device in which the refrigerant is not actively flown is described. However, the present invention is also applicable to a cooling device that forcibly flows the refrigerant. Fig. 12 is a schematic view showing an example in which the present invention is applied to a cooling device including a pump for flowing a refrigerant.

The boiling cooling device shown in Fig. 12 includes a sealed chamber 10 mounted on a heat source 3, a radiator 30, a gas-liquid separation device 40, a pump 50, and a conduit 60 connected thereto. The refrigerant is driven by the pump 50 and circulated in the sealed chamber 10, the radiator 30, the gas-liquid separation device 40, and the pump 50.

An outlet is provided above the sealed chamber 10, and the outlet is connected to the heat sink 30 via a conduit 60. The radiator 30 cools the refrigerant conveyed through the duct 60. The gas-liquid separation device 40 separates the refrigerant cooled by the radiator 30 into a gas and a liquid, and sends only the liquid to the pump 50.

In the boiling cooling device of such a configuration, the first refrigerant and the second refrigerant which are not dissolved in the same manner as described above are sealed inside the sealed chamber 10. In the following description, an example in which FC72 is used as the first refrigerant and pure water is used as the second refrigerant is used in the same manner as in the above embodiment.

If heat is transferred from the heat source 3, the FC72 boils together with the pure water. At this time, the super-cooling degree of the high-boiling medium, that is, pure water is large, and the sub-cooling degree of the low-boiling medium, that is, FC72 is small. Therefore, the boiled and vaporized pure water is rapidly liquefied by the pure water having a large degree of supercooling around, but the FC 72 is moved to the radiator 30 via the outlet provided at the upper portion of the sealed chamber 10 in a gaseous state. Scatter The heater 30 cools the FC 72.

The FC 72 liquefied by the radiator 30 and the FC 72 not liquefied flow into the gas-liquid separation device 40 together. The FC72 is separated into a gas and a liquid by the gas-liquid separation device 40. The liquid-only FC 72 is then fed again into the closed chamber 10 via the pump 50.

By circulating the FC 72 in this manner, the boiling cooling device cools the heat source 3.

By thus flowing the refrigerant by the pump 50 as described above, the heat sink 30 can be disposed at a position away from the sealed chamber 10, and the present invention can be applied even when the heat sink 30 is not directly disposed on the upper portion of the sealed chamber 10. . Further, since the refrigerant flows through the pump 50, bubbles are less likely to accumulate on the heating portion 11, and film boiling can be suppressed, and the critical heat flux can be further increased.

Further, since the second refrigerant is set to have a large degree of subcooling, it is easy to immediately condense and disappear in the first liquid layer 21 or the second liquid layer 22 after the bubble 25 (steam) is generated. In contrast to this, since the first refrigerant subcooling is set to be small, the bubble 24 (steam) is reduced by a few volumes due to condensation, and is transported downstream, and is again condensed in the radiator 30.

However, depending on the selection of the first refrigerant and the second refrigerant, the two refrigerants can be simultaneously set to a specific degree of subcooling. In this case, the steam 24, 25 generated by the two kinds of refrigerants can be condensed inside the sealed chamber 10. In this case, if the bubble trap 16 shown in Fig. 13 is provided, it is easy to ensure the degree of subcooling of the two refrigerants by self-compression.

FIG. 13 shows an example in which the bubble trap 16 is provided in the sealed chamber 10 in order to maintain the compressed state in the sealed chamber 10. The bubble trap 16 is formed in a space in the sealed space S to open downward.

By the bubble trap 16, the steam 24, 25 generated in the sealed chamber 10 is immediately condensed, thereby avoiding an increase in pressure in the closed chamber 10 or a decrease in the degree of subcooling of the refrigerant, resulting in an increase in critical heat flux. The big effect is reduced. The separator of the bubble trap 16 is desirably heat-insulating, and it is preferred that the steam 24, 25 is not easily condensed in the bubble trap 16.

Thus, if it is saturated under the operating pressure of the boiling cooling device of the present embodiment When the first refrigerant and the second refrigerant in the vicinity of the saturation temperature indicated by the vapor pressure curve, the two kinds of refrigerant bubbles 24 and 25 generated in the vicinity of the heating portion 11 are cooled together by the surrounding refrigerant to be liquefied again. Thereby, the first refrigerant and the second refrigerant having the liquid are simultaneously introduced into the radiator 30. Since the radiator 30 constantly flows out of the liquid first refrigerant and the liquid second refrigerant, it is not necessary to provide the gas-liquid separator 40 on the upstream side of the pump 50, and the gas-liquid separator 40 shown in Fig. 13 can be omitted.

If the first refrigerant and the second refrigerant are selected in this way, and the specific supercooling degree is applied to the two cooling liquids, the bubbles (steam) of the two kinds of refrigerant generated by the heating portion 11 immediately condense and stay in the closed chamber 10 Internally, the gas-liquid separator 40 can also be disposed of, and the loop of the refrigerant circulation shown in Fig. 12 can be applied in the same manner as the liquid cooling which is widely used now, except for the internal structure of the sealed chamber 10.

However, the cooling device shown in Fig. 13 is constructed using a forced convection cooling device of the existing single-phase refrigerant. That is, if the selection of the first refrigerant and the second refrigerant is sought, the existing forced convection cooling device can be used. This makes it possible to significantly facilitate the application of boiling cooling using a forced flow system, and to divert the existing device, and to improve the cooling performance drastically at a low cost. Further, since the reduction in the pumping flow rate is accompanied by a decrease in the circulating flow rate, it is extremely useful to promote energy saving.

Further, the conduit connecting the pump 50 and the sealed chamber 10 is preferably attached to the lower portion of the sealed chamber 10 so that the refrigerant faces the heating portion 11. Thereby, since the occurrence of bubbles can be forcibly excluded, film boiling can be suppressed, and the critical heat flux can be further increased.

Further, in the case where the sealed chamber is not a vertically long person as shown in Fig. 12 or Fig. 13, but is a horizontally long person, the flow of the first refrigerant from the end of the heating portion 11 is prevented in order to prevent the flow due to the pump 50. Alternatively, as shown in FIG. 14, the partition wall 17 is provided in the vertical direction from the bottom surface of the sealed chamber 10. Fig. 14 is a schematic view showing a boiling cooling device having a horizontally long sealed chamber 10. A certain amount of the first liquid layer is held directly above the heating portion 11 by the partition wall 17.

Hereinabove, the present invention has been described in detail with reference to specific embodiments, but It is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

The present application is based on U.S. Provisional Patent Application Serial No. 61/668, filed on Jul.

[Industrial Applicability]

According to an aspect of the present invention, a boiling cooling device which has a high critical heat flux and can operate at a high pressure and a low temperature is provided.

1‧‧‧Boiling cooling device

2‧‧‧ circuit board

3‧‧‧heat source

4‧‧‧ radiator

10‧‧‧Closed chamber

11‧‧‧ heating department

12‧‧‧Condensation

13‧‧‧ side wall

21‧‧‧ Liquid first refrigerant

22‧‧‧Liquid second refrigerant

23‧‧‧ gas phase

S‧‧‧Confined space

Claims (12)

A boiling cooling device is provided in a lower portion including a heating portion that transfers heat from a heat source, and has a sealed chamber in which a refrigerant is sealed inside, and cools the heat source by transferring heat from the heating portion to the refrigerant; a first refrigerant and a second refrigerant that is insoluble with the first refrigerant are sealed in the sealed chamber; and the first refrigerant and the liquid are present in the sealed chamber in a state before the heat is generated by the heat source. The second refrigerant and the mixed vapor of the first refrigerant containing the gas and the second refrigerant of the gas. The boiling cooling device of claim 1, wherein the second refrigerant has a higher boiling point and a lower density than the first refrigerant; and the volume of the first refrigerant of the liquid is smaller than the liquid in a state before the heat source generates heat. The volume of the above second refrigerant. The boiling cooling device according to claim 2, wherein a thickness of the liquid surface of the first refrigerant from the heating portion to the liquid is 10 mm or less in a state before heat is generated by the heat source. The boiling cooling device according to any one of claims 1 to 3, wherein the sealed chamber comprises a partition wall in a state in which the temperature in the sealed chamber is lower than a boiling point of the first refrigerant, in the heating portion The first refrigerant is maintained above a certain amount of liquid. The boiling cooling device of claim 1, wherein the second refrigerant has a higher boiling point and a higher density than the first refrigerant. The boiling cooling device according to any one of claims 1 to 5, wherein the second refrigerant is water. A boiling cooling device according to any one of claims 1 to 6, wherein said sealed chamber package The condensed portion is thermally connected to the heat dissipating portion, and the second refrigerant of the gas and the second refrigerant of the gas are condensed back to the liquid. The boiling cooling device of claim 7, wherein the sealed chamber comprises: a gas transport path, wherein the first refrigerant and the second refrigerant heated by the heating portion to be vaporized by the liquid are transported to the condensation portion; And a liquid returning path for returning the first refrigerant and the second refrigerant, which are condensed by the gas to the liquid in the condensing unit, to the heating unit. The boiling cooling device according to any one of claims 1 to 6, further comprising: a cooling portion connected to the sealed chamber via a conveying path, and dissipating heat of the first refrigerant and the second refrigerant to the outside And a pump for returning the cooled first refrigerant and the second refrigerant to the sealed chamber. The boiling cooling device of claim 9, wherein the sealed chamber comprises a bubble trap which is open toward the lower side and maintains a certain amount of gas of the first refrigerant and gas inside and outside the heating element before and after heating of the heating element The second refrigerant described above. The boiling cooling device according to claim 10, wherein the first refrigerant and the second refrigerant cooled by the cooling unit are not sent to the pump via the gas-liquid separator. The boiling cooling device according to any one of claims 1 to 11, wherein the upper surface of the heating portion is inclined so as to become higher toward the opposite side of the acceleration direction acting on the heat source.