JPH0760875B2 - Heat transfer body for boiling cooling - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat transfer body for boiling cooling, and specifically, when cooling a heat generation body having a high heat generation density by utilizing vapor deposition latent heat of a refrigerant liquid. In order to efficiently perform heat transfer between the refrigerant liquid and the heating element, the present invention relates to one that is thermally engaged with the heating element and immersed in a boiling refrigerant liquid for use.

[Conventional technology]

A fin-shaped heat transfer body having porosity as shown in FIG. 6 is attached to a heating element having a high heat generation density such as a semiconductor element, and the fin-shaped heat transfer body is immersed in a boiling refrigerant liquid to form a refrigerant liquid. Japanese Patent Laid-Open No. 229353/1985 discloses a method of effectively removing the heat of a substance having a high heat generation density by boiling water.

That is, as shown in FIG. 1A, the heat transfer body 3 is thermally coupled to the top surface of the heat generating body 2 attached to the substrate 1. The heat transfer body 3 is made of a base material having good thermal conductivity, and extends in the tangential direction of the joint surface with the heating element 2 to form a large number of vertical tunnels 4 and horizontal tunnels 5 as shown in FIG. It is formed, and is further formed by laminating in a multilayer shape in the direction normal to the joint surface. The vertical tunnel 4 and the horizontal tunnel 5 of each layer are communicated with each other through a communication hole 6. Therefore, according to the heat transfer body 3 shown in FIG. 6, when the heat generation density is lower than a certain value, the boiling nuclei in the vertical and horizontal tunnels 4 and 5 can be well secured, so that high nucleate boiling is achieved. The heat transfer coefficient is obtained.

[Problems to be solved by the invention]

However, in the above-mentioned conventional technique, in the case of a high heat density object in which the heating value of the heating element 2 is high, boiling on the heat transfer surface of the heat transfer element 3 becomes active, and finally the heat transfer surface is covered with boiling bubbles. This may lead to so-called burnout, which causes a transition from nucleate boiling to film boiling. In such a state, the heat transfer surface of the heat transfer body 3 is covered with the vapor film, so that heat transfer is hindered and the cooling efficiency is extremely lowered.

That is, according to the above-mentioned conventional technique, in order to maintain the nucleate boiling state in which stable and good heat transfer is performed, the heat flux must be suppressed to a certain limit heat flux or less, and a heat generating element having a high heat generation density is obtained. There was a problem that could not be applied.

An object of the present invention is to break the vapor film generated at the interface between the heat transfer element and the refrigerant liquid to increase the critical heat flux for burnout, thereby stably cooling the heating element having a high heat generation density. It is to provide a heat transfer body for boiling cooling which can be performed.

[Means for solving problems]

The present invention is, in order to achieve the above object, a boiling cooling heat transfer body which is thermally coupled to a heating element and is used by being immersed in a boiling refrigerant liquid, wherein the heat transfer body has a fin. The finned perforated plate is a flat plate made of a solid base material or a porous base material, and a large number of vertical grooves and horizontal grooves are formed on the back surface and the front surface at right angles to each other. In addition, a large number of fin-shaped projections are formed on the outer peripheral edge portion thereof.

[Action]

With such a configuration, when heat of a heat flux equal to or higher than the heat flux at which boiling starts from the heating element is input to the heat transfer element, the refrigerant liquid evaporates on the inner surface and the outer surface of the flow passage of the heat transfer element. Boiling occurs, and the latent heat of vaporization cools the heating element via the heat transfer element. As the amount of heat input to the heat transfer body increases, the number of bubbles generated from the surface of the heat transfer body increases, and finally the nucleate boiling reaches the film boiling state, and the vapor film covers the surface of the heat transfer body. However, this vapor film is ruptured by the effect of the geometrical shape of the protrusions on the outer surface of the heat transfer body, and nucleate boiling heat transfer is secured.

That is, when the film boiling causes the vapor film to cover the entire surface of the heat transfer body, the heat transfer at the interface between the heat transfer body and the refrigerant liquid is extremely reduced. However, in general, the vapor film thickness
Since it is a thin film of about 10 to several tens of μm, even if the vapor film tries to wrap around the protrusions present on the surface of the heat transfer member, the interface between the vapor film and the refrigerant liquid undulates due to disturbance, and FIG. As shown in, when the protrusion 10 having a height higher than this wave is present, the vapor film 11 is broken. Note that the disturbance includes generation of bubbles due to boiling, flow of gas and liquid, and the like.

Also, in the vapor film formed at the corners of the projection, the curvature of the interface between the vapor film and the refrigerant liquid becomes smaller according to the curvature of the corners, and the surface tension of the liquid and the pressure of both vapor and refrigerant liquid parts. Due to the difference, the vapor film cannot exist stably, and the vapor film is broken.

In other words, the vapor film is less likely to be generated at the tip of the protrusion, and the interface between the vapor film and the refrigerant liquid located on the side surface of the protrusion can be expected to move toward the base of the protrusion due to the surface tension of the liquid. Membranes cannot exist in a stable manner.

In this way, when a part of the vapor film is broken, the refrigerant liquid comes into direct contact with the surface of the heat transfer body from there, so that burnout can be suppressed and the nucleate boiling state can be maintained. Become.

Further, if the projection is made porous, the refrigerant liquid directly contacting the projection will be supplied to the entire projection and thus the entire heat transfer body by the capillary force of the porous body. Since the heat flux density in the portion is reduced, the film boiling transition, that is, burnout can be further suppressed.

〔Example〕

 Hereinafter, the present invention will be described based on examples.

FIG. 1 shows a partial perspective sectional view of an embodiment of the present invention. As shown in the figure, the heat transfer body 20 is formed by laminating a large number of finned perforated plates 21 as shown in FIG. The perforated plate with fins 21 has a large number of vertical grooves 22 and horizontal grooves 23 formed on the front and back of a flat plate made of a solid base material or a porous base material so as to be orthogonal to each other, and has a large number of fin-like shapes on the outer peripheral end of the flat plate. It is supposed to have a protrusion 24. The heat transfer body 20 is formed by stacking the finned porous plates 21 formed in this manner and bonding the adjacent finned porous plates 21 to each other by, for example, a diffusion bonding method. Then, the vertical groove 22 becomes the vertical tunnel 26 of the heat transfer body 20, and the horizontal groove 23 is the horizontal tunnel.
27.

The heat transfer body 20 configured in this way can be used for vertical and horizontal tunnels.
26 and 27 are thermally coupled to a heating element (not shown) so as to form a layer in the heat flow direction Q, and are immersed in a boiling refrigerant for use. As a result, the heat generated by the heating element is transferred into the heat transfer body 20 along the heat flow direction Q, and the inner surfaces of the tunnels 26 and 27 as the flow holes of the heat transfer body 20 and the heat transfer body 20. Evaporation and boiling of the refrigerant liquid occur on the outer surface, the heat of the heat transfer body 20 is transferred to the refrigerant liquid, and the heating element is cooled.

When the amount of heat generated by the heating element becomes extremely high and reaches a high heat flux region where film boiling occurs, a vapor film is usually formed at the interface between the heat transfer element 20 and the refrigerant liquid. According to the example, as will be described below, the action of the fin-shaped projections 24 or the actions of the tunnels 26, 27 prevent the formation of a vapor film, and maintain a high heat transfer coefficient by nucleate boiling cooling. That is, the fin-shaped projection 24 protruding into the refrigerant liquid is the third
As described in the figure, the stable penetration is prevented by breaking through the vapor film, whereby heat transfer is performed in the state where the surface of the fin-shaped projection 24 is in direct contact with the refrigerant liquid.

Since the refrigerant liquid enters the space formed between the fin-shaped projections 24 by the above action, the capillary liquid guides the refrigerant liquid to the tunnels 26 and 27 formed in the heat transfer body 20, and further tunnels. The capillary forces of 26 and 27 act so as to spread the refrigerant liquid over the entire inside of the heat transfer body 20, so that the stable existence of the vapor film is further prevented.

The refrigerant liquid drawn into the tunnels 26, 27 by the capillary force evaporates in the tunnels, and the vapor is tunnels 26, 27.
Since it spouts out into the refrigerant liquid from the outlet, it disturbs the evaporation film that tries to wrap the outer surface of the heat transfer body 20, and acts to prevent the stable existence of the vapor film.

By providing the fin-shaped projections 24, the heat transfer area of the heat transfer body 20 is substantially expanded, and the cooling effect is improved.

According to the present embodiment, the nucleate boiling state can be maintained even in a high heat flux region where normally the film boiling state is transitioned to by the synergistic action of these, particularly the synergistic combined action of. The effect is that you can do it.

The size of the tunnels 26 and 27 and the fin-shaped projection 24
The interval between and is determined in consideration of the physical properties of the refrigerant liquid, the liquid permeation action due to the capillary force, the pressure loss of the vapor, etc.
For example, 1 mm or less is desirable.

In addition, in the present embodiment, the fin-attached porous plate 21 provided with the fin-shaped projections 24 in advance is shown as being laminated and joined, but after the porous plates without the fin-like protrusions 24 are laminated and joined, For example, by using a wire cut, etc.
It goes without saying that the same effect can be obtained even if the outer surface of 20 is finned. Also, in this embodiment, 4
Although the case of layers is shown, the optimum number of layers may be selected according to the amount of heat generated by the heating element and the size of the allowable occupied space of the heat transfer element.

FIG. 4 shows another embodiment of the present invention. The difference from the embodiment of FIG. 1 is that the surface of the fin-shaped projection 24 has a vertical groove 24a and a horizontal groove 24b.
Has been established. By doing so, a larger capillary force than that in the embodiment of FIG. 1 can be obtained,
Since the spreading action of the refrigerant liquid (the above action) is promoted,
In addition to the effect of the first embodiment, there is an effect that the nucleate boiling state can be maintained even at a higher heat flux.

Since the present embodiment is mainly intended to promote the capillarity of the space formed by the fin-shaped projections 24, the grooves 24a and 24b can be used as long as the action can be achieved. However, the same action and effect can be obtained even if the fin-shaped protrusions 24 are formed by using sintered particles or needle-shaped fibers by a crystal precipitation method.

FIG. 5 shows still another embodiment of the present invention. The difference from the embodiment of FIG. 1 is that the solid portion 28 having no tunnel as a through hole is formed inside the heat transfer body 20. With this structure, the heat conduction inside the heat transfer body 20 is improved, so that the temperature of the outer surface portion of the heat transfer body 20 is almost equal to that of the heat transfer body 20 as compared with the case of the embodiment of FIGS. It has the same effect as the temperature of, and the thermal conductivity is improved.

〔The invention's effect〕

As described above, according to the present invention, since a large number of protrusions are formed on the outer surface of the heat transfer body having a large number of through holes opened on the outer surface, heat transfer is hindered. It is possible to prevent the stable existence of the film boiling that occurs, thereby increasing the critical heat flux and being able to stably cool the heating element having a high heating density.

[Brief description of drawings]

1 is a partial sectional perspective view of an embodiment of the present invention, FIG. 2 is a perspective view of a perforated plate with fins constituting the embodiment of FIG. 1, and FIG.
FIG. 4 is a diagram for explaining the vapor film rupture action of the present invention, and FIGS. 4 and 5 are partial cross-sectional perspective views of another embodiment of the present invention, respectively.
6 (A) and 6 (B) are perspective views of a conventional example. 2 ... Heating element, 20 ... Heat transfer element, 21 ... Finned perforated plate, 24 ... Fin-shaped projection, 24a ... Vertical groove, 24b ... Horizontal groove, 26 ... Vertical tunnel, 27 ... Horizontal tunnel.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeo Ohashi, 502 Jinritsucho, Tsuchiura City, Ibaraki Prefecture, Hiritsu Seisakusho Co., Ltd. (72) Motohiro Sato, 502, Jinritsucho, Tsuchiura City, Ibaraki Prefecture, Hiritsu Co., Ltd. (56) Reference JP 60-136353 (JP, A) JP 60-229353 (JP, A) JP 61-168790 (JP, A)

Claims (1)

[Claims] 1. A heat transfer body for boiling cooling, which is thermally coupled to a heating element and immersed in a boiling refrigerant liquid to be used, wherein the heat transfer element is formed by laminating finned perforated plates in multiple layers. The finned perforated plate is a flat plate made of a solid base material or a porous base material, and a large number of vertical grooves and horizontal grooves are formed on the back surface and the front surface at right angles to each other, and at the outer peripheral edge portion thereof. A heat transfer body for boiling cooling, comprising a large number of fin-shaped projections.