Heat exchanger unit

Abstract

According to the present invention, there is provided a heat exchanger unit having, over a base, a surface-modified portion composed of a metal, the surface-modified portion being brought into contact with a flow path provided for a liquid refrigerant, wherein the liquid refrigerant is a liquid having a surface tension smaller than that of water, and the surface-modified portion has a porous structure, in which a plurality of recesses are provided on the flow path side thereof, each recess has an introduction path having a cross-section area gradually reduced from the inlet of the recess, and a cavity communicated with the introduction path while placing an inflection portion in between, and the shortest distance between the inflection portion and the flow path is larger than the shortest distance between the cavity and the flow path.

Description

TECHNICAL FIELD[0001]The present invention relates to a semiconductor heat exchanger unit, and in particular to a semiconductor heat exchanger unit making use of phenomenon of boiling.BACKGROUND ART[0002]For the purpose of conducting a large energy of heat generated by semiconductor devices, there has been developed a method of obtaining a high level of cooling effect based on latent heat of vaporization of a refrigerant capable of boiling at a temperature not higher than the upper limit temperature of operation of the semiconductor devices. In recent years, investigations have been focused on influences of surface conditions of a boiling surface and thermo-physical properties of refrigerant, which govern the size and density of generated vapor bubbles, aiming at stabilizing and optimizing the heat conduction effect obtainable by boiling of the refrigerant.[0003]It has been known that the heat conduction characteristics may be improved in pool boiling on a flat plate, by forming an ...

AI Technical Summary

Benefits of technology

[0024]It may not always be necessary that the actual micro-structure is completely identical to that illustrated in FIG. 2, wherein a state of allowing stable residence of bubbles by virtue of the double-inlet structure, and uniform provision of the structure over the entire heat conduction surface may contribute to improvement and optimization of the heat conduction effect, based on boiling as a macroscopic consequence. The vapor bubbles of a refrigerant having a small surface tension may further downsize themselves in the process of dissociation, so that micronization of the recess structure to as small as several micrometers or around may be effective in view of promoting the downsizing. As a consequence, the boiling may be expected to start at a temperature more closer to the boiling point.

Problems solved by technology

As explained in Non-Patent Document 1, any conventional efforts for assimilating such ideal geometry have resulted in thickening over the entire surface geometry (100 μm to 1 mm or thicker), and any efforts have failed in obtaining the ideal geometry of the recesses.

The thickness and the recesses of several hundred micrometers to 1 mm or around may result in higher thermal resistance as compared with smaller structures, and may raise a problem in retention property of the vapor nuclei, when a refrigerant having a surface tension smaller than that of water is used.

Furthermore, while the geometry shown in Non-Patent Document 1 is not given with a scale, the size and so forth of the opening in an actual structure may vary, so that it may be very easy to presume that this raises negative effects, depending on physical properties of the refrigerant.

Although various micro-structures have been experimented, no invention has been successful to provide a surface geometry obtained by optimizing an ideal double-inlet structure with respect to an actual refrigerant.

Various trails have been made on the surface conditions, only to fail in achieving the ideal geometry, because thermal resistance may increase as the thickness of the surface increases.

Most of the surfaces at present are not structurally idealized, and is therefore far from being optimized for the nuclei, with some exceptions exhibiting the effect of heat conduction by virtue of the micro-structure.

It may therefore be understood from the above that the radius of curvature of the gas-liquid interface is determined by the angle of contact point of three phases, that are gas, liquid and solid phases (reference numerals 20 and 21 in FIG. 9 and FIG. 10, representing the angles on the liquid side), and that use of the V-shape structure for a refrigerant having a small surface tension may result in only a poor effect of retention of vapor nuclei.

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