JP2636980B2 - High performance heat transfer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance heat exchanger for a heat exchanger used in a large temperature difference region such as a low-temperature etching apparatus and a vaporizer of an LPG.

[0002]

2. Description of the Related Art A heat exchanger transfers two fluids having different temperatures to reduce a temperature difference between the two fluids, and there is a problem of surface heat transfer at a heat exchanger wall separating the two fluids. In this case, if the boiling point of one fluid is lower than the heat transfer surface temperature,
The fluid boils, and the heat transfer varies greatly depending on nucleate boiling or film boiling, which is different from the normal form of heat transfer. Nucleate boiling is when liquid is in contact with the heat transfer surface and vapor bubbles come out from the heat transfer surface, and film boiling is a vapor layer on the heat transfer surface, and the liquid and heat transfer surface are in contact with each other. Does not mean that the vapor bubbles come out of the liquid surface in contact with the vapor layer.

[0003] In the heat transfer in the case of boiling, in which the temperature difference between the fluids is relatively small, there is a nucleate boiling-promoting high-performance heat transfer surface, which is provided with micro holes in the heat transfer surface to promote nucleate boiling. When the same amount of heat is transferred as a result, the difference between the heat transfer surface temperature and the fluid temperature is reduced.

When the temperature difference between fluids is relatively large,
One of the liquids causes film boiling, and heat transfer is transferred from the heat transfer surface to the vapor layer to the liquid surface.
The surface heat transfer coefficient decreases.

Conventionally, various ingenuity has been devised and a patent application has been filed for a reliable high-performance heat transfer material having high heat transfer performance in a small temperature difference region and stable heat transfer performance. ing. For example, a porous heat transfer surface described in Japanese Patent Publication No. 2-53717 is one of them. On the other hand, what is described in the publication is that, on a heat transfer surface constituted by a porous layer, a plurality of grooves in which one porosity of the surface of the porous layer is regularly changed are formed in a part of the surface of the porous layer. And the porosity of the groove portion is formed smaller than that of the portion without the groove.

[0006]

SUMMARY OF THE INVENTION The above-mentioned conventional heat transfer bodies are:
In the small temperature difference region, high heat transfer performance is exhibited to promote nucleate boiling, but when used in the large temperature difference region, film boiling occurs between the heat transfer surface and the fluid, and the heat transfer surface has It becomes a vapor layer and the liquid and the heat transfer surface are not in contact with each other, and heat transfer is conducted to the heat transfer surface, the vapor layer, and the liquid surface, so that the surface heat transfer coefficient decreases.

In view of the above problems, the present invention does not cause film boiling even when the temperature difference is large, and can maintain the nucleate boiling state. Even when the temperature difference is small, nucleate boiling is promoted. It is another object of the present invention to provide a high-performance heat transfer surface even in a small temperature difference region.

[0008]

SUMMARY OF THE INVENTION The present invention is a high-performance heat transfer element characterized in that a fine particle bonding layer and a coarse particle bonding layer of a heat conductive material are sequentially provided on the surface of a heat transfer substrate. . The fine particle bonding layer is made of, for example, bronze particles having good heat conductivity,
It is appropriate that the particle size is 130 μm or less and the layer thickness is 200 to 300 μm. The coarse particle bonding layer may be made of a material having good heat conductivity such as bronze particles, or may be made of a material having low heat conductivity such as ceramics and stainless steel. The particle size is 400μm or more and 600μm
Below, the layer thickness is preferably twice or less the particle size.

FIG. 1 schematically shows the structure of the present invention. About three layers of fine particles 2 are laminated on the surface of a heat transfer substrate 1 to form a fine particle bonding layer 4. As it is, it becomes a nucleate-boiling-promoting high-performance heat transfer surface.
And the liquid temperature difference is 5K or less. However, in order to cause film boiling, the temperature difference cannot be reduced to 20K. Conversely, when the coarse particles are directly attached to the heat transfer substrate 1, the difference between the heat transfer substrate and the liquid temperature can be increased, but the heat transfer when the temperature difference is small also decreases. Therefore, when the coarse particle bonding layer 5 is formed by laminating about two coarse particles 3 on the fine particle bonding layer 4, the nucleate boiling state can be maintained without film boiling even when the temperature difference is large, and the temperature difference can be maintained. Nucleate boiling is promoted even when is small, and as a result, a high-performance heat transfer surface can be obtained in both a high heat flux region and a low heat flux region.

[0010]

EXAMPLES Examples will be described together with comparative examples.

[0011] Bronze fine particles are formed on the surface of a heat transfer substrate made of copper.
Using a 130 μm grain, a fine particle bonding layer having a thickness of 250 μm was formed by sintering, and a coarse particle bonding layer having a thickness of 500 μm was formed thereon by sintering using 400 μm grains of bronze coarse particles thereon to obtain a sample A. . In addition, as a comparative example, an untreated sample (sample B), a sample in which only the fine particle bonding layer was formed on the heat transfer base material surface (sample C), and only the coarse particle bonding layer formed on the heat transfer base material surface (Sample D) was prepared.

When a heat transfer characteristic test was performed using liquid nitrogen, the results shown in FIG. 2 were obtained. In the figure, the arrow indicates that the film boiling occurs due to the heat flux above that point, and the temperature difference increases rapidly. Sample B shows a temperature difference of 6K at 10 ⁵ w / m ² , above which film boiling occurs. Nucleate boiling occurs in a relatively narrow temperature range of 5 × 10 ³ w / m ² and a temperature difference of 2K. Sample C is 1.3 × 10 ⁵ w /
shows the temperature difference 4.5K m ^2, and the more in cause film boiling, 5 × 10 ³ in w / m ² results in nucleate boiling at the temperature difference 0.2K or less and small temperature difference, so-called nucleate boiling-promoting high Shows the characteristics of the performance heat transfer surface. Sample D has a temperature difference of 14K at 1.5 × 10 ⁵ w / m ²
Above that, film boiling occurs, and a temperature difference of 0.3 K or less at 5 × 10 ³ w / m ² shows a nucleate boiling promoting effect in a low heat flux region.

On the other hand, sample A had a temperature difference of 50K at 1.8 × 10 ⁵ w / m ² , but it was difficult to cause film boiling. At 5 × 10 ³ w / m ² , the temperature difference was 0.15K and the nucleate boiling promoting effect was obtained. Is shown.

Table 1 shows the heat transfer coefficient (= heat flux / temperature difference).

[0015]

[Table 1] Heat flux (w / m ² ) ABCD 1.8 × 10 ⁵ 3600 w / m ² K Film boiling Same left Same as left (250 w / m ² K) 1.0 × 10 ⁵ 6250 16700 28500 10500 5 × 10 ³ 33000 2500 25000 17000 Sample A is hard to boil even in a high heat flux region and shows 3600 w / m ² K even at 1.8 × 10 ⁵ w / m ² , but B, C and D are film boiling and this heat transfer coefficient is 250 w 10 times more effective performance than / m ² K.

Next, an application example of the present invention will be described.

A low-temperature etching apparatus used for processing an VLSI has a structure as shown in FIG. 3, for example, in order to cool a processing surface to about -130.degree. In FIG. 3, reference numeral 6 denotes a processing surface, on which a liquid nitrogen tank 7 is mounted, and a heat transfer control rod 8 hanging from the processing surface 6 is immersed in liquid nitrogen for cooling. Liquid nitrogen enters through a liquid nitrogen inlet 9 and is discharged as a gas through a nitrogen gas outlet 10. The heat transfer control is performed by adjusting the liquid level of the liquid nitrogen and changing the liquid immersion depth of the heat transfer control rod 8 in balance with the cooling control and the heating control by the heater 11 built in the processing surface 6. The problem with this method is that the working surface is -130 ° C and the boiling point of liquid nitrogen is -196 ° C.
The temperature difference between the two is a large temperature difference of 66 ° C. And the surface of the heat transfer rod is boiling heat transfer. In order to improve the response of heat transfer control, it is necessary that the processed surface and the heat transfer control rod have good thermal conductivity, and in order to reduce the size of the heat transfer section, the heat transfer of the heat transfer control rod must be good. is required. However, good heat conduction means that a large temperature difference between the heat transfer control rod and the liquid causes film boiling on the heat transfer control rod surface, resulting in poor heat transfer. Therefore, the surface of the heat transfer control rod is required to have a property that film boiling is difficult. Therefore, the present invention is applied to the heat transfer control rod surface. According to the calculation, by applying the present invention to the surface of the heat transfer control rod, the length of the heat transfer control rod can be shortened, and the entire apparatus can be downsized. In addition, the fact that the length of the heat transfer control rod is short and that the amount of heat transfer is large due to the difficulty of film boiling makes the temperature response quick and easy to control.

FIG. 4 shows another example of application to a low-temperature etching apparatus, in which a high-performance heat transfer body of the present invention is formed on the inner wall surface of a liquid nitrogen tank 7. This device has a feature that it is easier to process than the device of FIG.

[0019]

According to the present invention, the film boiling does not occur even when the temperature difference between the heat transfer surface and the fluid is large, the nucleate boiling state can be maintained, and the nucleate boiling is promoted even when the temperature difference is small. A high-performance heat transfer surface can be obtained even in the difference region and the small temperature difference region, and is useful when applied to a low-temperature etching device, a vaporizer of LPG, and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of the present invention.

FIG. 2 is a graph showing a relationship between a temperature difference and a heat flux in Examples and Comparative Examples.

FIG. 3 is an explanatory diagram of an application example of the present invention.

FIG. 4 is an explanatory diagram of another application example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat transfer base material 2 Fine particle 3 Coarse particle 4 Fine particle bonding layer 5 Coarse particle bonding layer 6 Processing surface 7 Liquid nitrogen tank 8 Heat transfer control rod 9 Liquid nitrogen inlet 10 Nitrogen gas outlet 11 Heater 12 High-performance heat transfer element

Claims (2)

(57) [Claims] 1. A high-performance heat transfer material comprising a heat transfer base material and a fine particle bond layer and a coarse particle bond layer of a heat conductive material sequentially provided on the surface of the heat transfer base material. 2. The fine particles have a particle size of 130 μm or less, the fine particle bonding layer has a thickness of 200 to 300 μm, and the coarse particles have a particle size of
2. The high-performance heat transfer body according to claim 1, wherein the thickness of the coarse particle bonding layer is 400 μm or more and twice or less the particle size of the coarse particles.