JPH0632408B2 - Boiling cooler - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiling cooling device, and more particularly to a boiling cooling device suitable for a heat absorbing device for electronic components and transformers.

[Background of the Invention]

At present, the degree of integration of electronic components such as electronic elements mounted on a computer is increasing. For this reason, the heat generation density of the electronic element also rapidly increases, and what has been cooled by air cooling or indirect liquid cooling until now is directly liquid cooled or the electronic element is directly immersed in the liquid and the latent heat of vaporization of the liquid is used. It is necessary to cool to boiling. Further, boiling cooling is being applied to other fields with high heat generation density such as transformers and rectifiers.

The liquid used for this boiling cooling is called a refrigerant, and since boiling cooling is usually performed at atmospheric pressure, the standard boiling point is an important factor in selecting a refrigerant. That is, if the operating temperature of the heating element such as an electronic element is determined, the refrigerant can be selected based on the standard boiling point of the refrigerant. Since compounds having a standard boiling point within a certain range are limited, as a countermeasure against this, as shown in JP-A-54-7657 and JP-A-54-7658, a refrigerant is mixed to adjust the standard boiling point. Although the method is adopted, the components having a small difference in standard boiling point were mixed.

In addition to the refrigerant selection requirements, the refrigerant's electrical properties, nonflammability, low toxicity, and chemical stability are taken into consideration. Among them, chemical stability is an important factor that requires high reliability, such as computers, and in general, the chemistry of perfluoro compounds in which all the hydrogen atoms in a hydrocarbon compound are replaced by fluorine atoms. It is known that it has excellent stability. If a substance satisfying the above selection requirements is selected from the perfluoro compounds, it is further limited.

Further, since the boiling cooling uses the latent heat of vaporization of the refrigerant for cooling, it can be said that the refrigerant having a large latent heat of vaporization has excellent cooling performance. Therefore, since the coolant for boiling cooling of the electronic device using the chemically stable perfluoro compound is extremely limited, the cooling capacity is also within a limited range.

[Object of the Invention]

An object of the present invention is to provide a refrigerant with improved boiling cooling performance to realize a more reliable boiling cooling device for electronic devices, transformers and the like.

[Outline of Invention]

The present inventor, in boiling cooling using a perfluoro compound,
In contrast to the present situation where the cooling performance is limited, it was found that when the refrigerants with different standard boiling points are mixed and the mixture is a non-azeotropic mixed refrigerant, the latent heat of vaporization that governs the cooling performance of the refrigerant can be significantly improved. The present invention has been achieved. The term "non-azeotropic mixed refrigerant" as used herein means that the composition of the liquid phase and the composition of the vapor phase of the mixed refrigerant are different when the vapor and the liquid of the mixed refrigerant are in thermal equilibrium at a certain temperature and pressure. The non-azeotropic mixed refrigerant referred to in the invention means that the liquid phase composition and the vapor phase composition are different at least under the temperature and pressure for operating as a boiling cooling device.

That is, the feature of the boiling cooling apparatus of the present invention is an apparatus for cooling an object to be cooled by immersing it in a liquid, and the liquid is composed of two or more kinds of components having a large boiling point difference, a low boiling point component and a high boiling point component. It is a non-azeotropic mixed refrigerant. It is desirable that the difference in boiling points between the constituents be 70 ° C. or higher. For example, the low boiling point component is octafluorocyclbutane, and the high boiling point component in this case has a boiling point of 70 ° C. or higher. Examples of high-boiling components include trifluoromethyl-undecafluorocyclohexane, 1,2-bis (trifluorothymer) -decafluorocyclohexane, octadecafluoro (4.4.
0] decane, 2-nonafluorobutyl-heptafluorooxolane. The device of the present invention using the refrigerant composed of these components is suitable for the heat absorbing device of electronic parts and transformers.

Example of Invention

FIG. 1 shows a schematic sectional view of an embodiment of the device to which the present invention is applied. This example is a direct heat exchange type in which a heating element is directly immersed in a refrigerant.

The heating element 1 is installed at the bottom of the container 2. The non-azeotropic mixed refrigerant 3 is injected so that the liquid phase portion covers the heating element 1.
4 is a cooling fin.

The liquid-phase non-azeotropic mixed refrigerant 3 becomes heat-exchanged with the heat generated from the heating element 1 such as a semiconductor element, and becomes the gas-phase refrigerant 5 that rises as bubbles. The cooling fins 4 condense and liquefy the vapor phase refrigerant 5.

FIG. 2 is a schematic sectional view of an indirect type natural circulation device. 6
Is a tube, and 7 is a heat dissipation fin provided outside the tube 6.
The heating element 1 is directly or indirectly arranged on the outer surface of the tube 6.

When the liquid phase non-azeotropic mixed refrigerant 3 in the pipe 6 is heated by the heating element 1 and the boiling temperature of the low boiling point component is exceeded, bubbles 8 of the low boiling point component are generated. The generation of bubbles causes a large density difference between the tube near the heating element 1 and the tube on the opposite side in the closed circuit.
The refrigerant 3 rises in the portion of the pipe 6 near the heating element 1 and descends in the opposite pipe portion to complete a closed circuit. The two-phase flow of the non-azeotropic mixed refrigerant 3 containing the bubbles 8 is cooled by the radiating fins 7 to reduce the bubbles 8, and becomes a single-phase flow to reach the corresponding portion of the heating element 1 again.
The inner diameter of the tube 6 is preferably larger than the maximum diameter of the bubble 8.

The vapor pressure and vapor density of the refrigerant were measured, and the latent heat of vaporization of the refrigerant was determined using the Clapeyron-Clausius equation shown in equation (1).

Here, p: vapor pressure of refrigerant, T: absolute temperature, ΔH: latent heat of vaporization, ΔV: difference in specific volume of liquid of vapor (approximated by vapor specific volume) is schematically shown in FIG. A stainless steel container 9 containing a refrigerant having a known composition ratio is immersed in a constant temperature oil tank 10,
The temperature and the pressure are measured by the sensors 11 and 12. A hollow glass 13 is hung in the container by a quartz spring 14, and its expansion and contraction is observed through a pressure resistant glass window of the container. With this, the temperature of the refrigerant, the vapor pressure, and the vapor specific volume can be measured, and the latent heat of vaporization can be obtained according to the equation (1). Incidentally, 16 is a heat medium of the oil tank.

The table shows the temperatures at which the vapor pressure of the refrigerant reaches 1 atm (standard boiling point and the latent heat of vaporization at that time. In the case of mixed refrigerants, the boiling point difference of the components is shown.

A vapor sampling pipe 15 was attached to the sample container, and after the vapor was collected, the refrigerant composition ratio of the vapor was measured by a gas chromatograph. It was found that the mixed refrigerants in Examples 1 to 8 in the table are all non-azeotropic.

In the table, Comparative Example 1 shows that the boiling point of tetradecafluorohexane is 57 ° C. and the latent heat of vaporization is 20.6 kcal / kg. Further, as shown in Comparative Examples 2 and 3, the latent heat of vaporization of other pure perfluoro refrigerants (NHO, BUdH) is 19.8 to 21 kcal /
It is kg. On the other hand, as shown in Examples 1 to 8, it was shown that the latent heat of vaporization can obtain 22.8 to 26.6 kcal / kg by a combination of pure components having a boiling point difference of 73.2 ° C or more.

(1) Comparison at the same boiling point level: Comparison between Comparative Example 1 and Examples 2 and 8 (boiling point 57 ° C.) Comparative Example 1 is 20.6 kcal / kg, while Example 2 is
25.8 kcal / kg, Example 8 is 22.8 kcal / kg. That is, according to the present invention, the latent heat of vaporization is improved by 11% to 25%.

(2) Overall tendency: Comparing Comparative Example 1 with the present invention having a boiling range of 50 to 65 ° C., Comparative Example 1 has 20.6 kcal / kg, whereas the present invention has a latent heat of vaporization of 22.8 to 26.6 kcal / kg. Can be obtained. That is, the latent heat of vaporization is improved by 11 to 29%.

Further, as shown in Comparative Examples 1 to 3, the latent heat of vaporization of the pure perfluoro-based refrigerant is about 20 to 21 kcal / kg. On the other hand, in the present invention, the latent heat of vaporization is 22.8 to 26.6 kcal / kg as described above. Therefore, the latent heat of vaporization of at least 9% can be improved.

As shown in this example, the improvement of the latent heat of vaporization is remarkable when the boiling point difference becomes large. As described above, according to the present invention, the boiling cooling performance can be significantly improved. The smaller the boiling point difference between the components is, the lower the latent heat of vaporization tends to be, but if the boiling point difference is 70 ° C. or higher, the effect of improving the latent heat of vaporization is obvious.

〔The invention's effect〕

As described above, according to the present invention, since the latent heat of vaporization of the refrigerant is large, there is an effect that a boiling cooling device having excellent cooling performance can be obtained.

[Brief description of drawings]

1 and 2 are schematic cross-sectional views of the apparatus of the embodiment of the present invention, and FIG. 3 is a schematic cross-sectional view of the apparatus for measuring latent heat of vaporization of a refrigerant applied to the present invention. 1 ... Heating element, 2 ... Container, 3 ... Non-azeotropic mixed refrigerant, 6 ... Tube,
8 ... bubbles.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Honma ▲ Yoshi ▼ Oji, 1-1, Saiwaicho, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Fumio Nakano Sachimachi, Hitachi City, Ibaraki Prefecture 3-1, 1-1, Hitachi Research Laboratory, Hitachi Ltd. (56) References JP-A-49-85567 (JP, A) JP-A-54-7658 (JP, A) JP-A-54-7657 (JP, A)

Claims (7)

[Claims] 1. An apparatus for cooling an object to be cooled by immersing it in a liquid, which is a non-azeotropic mixed refrigerant composed of two or more components in which the liquid is compatible. 2. The boiling cooling apparatus according to claim 1, wherein the components constituting the non-azeotropic mixed refrigerant have a boiling point difference of 70 ° C. or more. 3. The boiling cooling apparatus according to claim 2, wherein the low boiling point component of the components is octafluorocyclobutane. 4. The boiling cooling apparatus according to claim 2, wherein the high boiling point component of the components has a boiling point of 70 ° C. or higher. 5. The high-boiling component is trifluoromethyl-undecafluorocyclohexane, 1,2-bis (trifluorothymer) -decafluorocyclohexane, octadecafluoro [4.4.0] decane, 2-nonafluoro. The boiling cooling device according to claim 1 or 3, which is selected from butyl-heptafluorooxolane. 6. The boiling cooling device according to claim 1, wherein the object to be cooled is an electronic component. 7. The boiling cooling apparatus according to claim 1, wherein the object to be cooled is a transformer.