JPS5993190A - Heat exchange wall - Google Patents

Abstract

PURPOSE:To maintain a high heat transfer efficiency in a wide range of thermal load by a method wherein an upper tunnel and a lower tunnel each having an opening are provided among fins, while a boiling liquid is flowed through the upper tunnel and the upper tunnel is made to communicate with the lower tunnel. CONSTITUTION:Thin wires 21 each provided with a fine groove 22 are wound around grooves among an array of fins so that a gap 23 formed between each of the thin wires 21 and each of the fins 19 forms the lower tunnel and the fine groove 22 in the thin wire 21 forms the opening of the lower tunnel. Then the array of the fins 19 is laid down and the adjoining fins are bonded together by a roll processing to thereby form cavities 11'.

Description

[Detailed description of the invention] The present invention relates to improvements in heat exchange walls.

[Prior art]

The heat shown in Figure 1 is an attempt to efficiently transfer heat from the surface of a pipe or plate to a liquid that comes into contact with it, such as water, fluorocarbon liquid, liquid crab, liquid helium, etc., which undergoes a phase change and boils. A replacement wall is proposed.

The heat exchange wall 1 in FIG. The heat exchange wall 1 is formed by a large number of minute openings 3 with limited
communicates with the outside.

If the heat exchange wall has such a configuration, when the heat exchange wall is heated to a higher temperature than the liquid in contact with it, vapor bubbles 8 will form in the cavity 2, as shown in the boiling state. and grow. As the heating continues, the natural gas pressure within the cavity 2 becomes higher than the pressure of the external liquid, and some of the vapor bubbles 8 are released through the restricted opening 3 and separate as bubbles 9. Since the perforated plate 5 prevents the release of steam within the cavity 2, a portion of the steam is retained within the cavity 2 as residual steam. As the bubbles 9 leave, a pressure change occurs within the cavity 2. At that time, steam 9
An external liquid (not shown) enters the cavity 2 as shown by arrow 10 from an opening 3 different from the opening 3 from which the liquid was released. Since residual vapor exists in the cavity 2, the infiltrated liquid is pushed to the wall of the cavity 2 by the residual vapor bubbles, spreads along the wall and into the cavity 2. The expanded liquid immediately evaporates due to the overheating of the heat exchange wall 1, causing vapor bubbles 8 to grow. In this way, the cycle of evaporation of the infiltrating liquid, growth of vapor bubbles, separation of the bubbles, and infiltration of the liquid is repeated one after another.

During this cycle, in particular, the liquid that has entered the interior of the cavity 2 spreads out on the cavity wall in the form of a thin liquid film, which can quickly evaporate with a small degree of superheating.

For this reason, the heat exchange wall of FIG. 1 has a high heat transfer performance.

However, even when using the heat exchange wall, the heat transfer performance of the heat exchange wall is maintained over a wide range of heat loads (the amount of heat transferred per unit time and unit area), as shown in the experiment below. Can not do it.

Figure 3 shows the heat exchange wall in Figure 1 with fluorocarbon refrigerant R1 under atmospheric pressure.
1 () Cuchloro-monofluoro-methane cpcz3) The results of a boiling heat transfer experiment were performed by immersing the sample in a liquid. The horizontal axis is the heat flux q (W/m”) based on the projected area of the heat exchange wall,
The vertical axis is the heat transfer coefficient α (W/n?・) based on the above projected area.
K) is shown in logarithmic coordinates.

The heat exchange walls of 2(I) are made of copper and have a cavity pitch of 0.
．． 55 mm, the width of the cavity cross section is 0.25 mm, the height is 0.4 mm, the thickness of the perforated plate is 0.05 mm, the opening pitch is 0.7 mm, etc., but the diameter of the opening of heat transfer wall A is 0. .2 mm%
The heat transfer wall B is 0.1 mm. The heat transfer wall A decreases significantly when the heat load is low compared to when the heat load is high. On the other hand, heat transfer Q1
g Bu: Compared to A, the performance is improved under low heat loads, but the performance is decreased under high heat loads. Heat transfer wall A.

All eight surfaces cannot achieve high performance over a wide range of heat loads. This means that when applied to various heat exchangers, the operating range in which high performance can be obtained is narrow. In order to optimally supply the amount of liquid in the cavity for each heat load, the heat exchange wall skin layer (C) has a large number of elongated groove-shaped cavities forming multiple layers, and is limited to be smaller than the maximum cross-sectional area of the cavities in each layer, It is characterized by a plurality of openings that communicate with each other between the multilayer cavities and between the outside of the heat exchange wall and the upper layer cavity.As shown in FIG. A shallow groove 18 is made by knurling in the tube.
It is assumed to be in the ° direction. Next, in the second step, the fins are carved in a direction almost perpendicular to the tube axis.
make it higher. By this method, 190 rows of fins having unevenness 20 as shown in FIG. 5 are formed. In the third step, as shown in FIG. 6, a thin wire 21 having small tracing grooves 22 is wound around the grooves between the fin rows as shown in FIG. A gap 23 formed between the thin wire 21 and the fin gap 19 forms a lower tunnel,
The minute grooves 22 provided in the first line of glaze form the openings of the lower tunnel.

Furthermore, even if a thin wire without microgrooves is wound, a gap may be formed at the portion where the thin wire and the fin come into contact, but providing microgrooves provides more stable opening. In the fourth step, as shown in FIG. 8, the fins 19 are laid down by rolling or plastic processing. A cavity 11' is formed by joining adjacent fins. The shallow groove 18 in the first step constitutes the opening 12.

As another embodiment, the tunnel of the present invention is not limited to two stages, but may have a fin row having a tapered cross section as shown in FIG. 9, and the thin wire 21 may be wound in multiple stages.

In this case, such a heat transfer wall can be easily obtained by making the thin wire of the lower stage 4111 very thin. However, if the fine grooves provided in the thin wire 21' on the lower stage side are made smaller, the size of the openings provided in the lower tunnel will be disadvantageous in terms of heat transfer performance. The diameter of the opening in the uppermost tunnel can be increased by increasing the depth of the groove in the knurling process in the first step.

On the other hand, even if the knurling in the first step and the fin-laying process in the fourth step are eliminated, a multi-stage tunnel structure can be easily obtained by forming multiple stages of thin wire windings as shown in Figure 10. [Effects of the Invention] In a heat transfer surface having apertures and tunnels, the type of heat transfer within the tunnel may change depending on the size of the apertures or the heat load, leading to a decrease in performance. The optimum value of the aperture size that can maintain high heat transfer performance is within a narrow range depending on the value of the heat load.

In the present invention, the tunnel has a double structure, each tunnel is provided with an opening, and the boiling liquid and the upper tunnel, and the upper tunnel and the lower tunnel, are communicated through the opening. Therefore, depending on the heat load, each tunnel is effectively operated to maintain high heat transfer performance over a wide heat load range.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the conventional technology, Figures 2 and 3 are explanatory diagrams showing phenomena and characteristics of the prior art, Figures 4 to 8 are explanatory diagrams showing the manufacturing process of the present invention, and Figures 9 to 10 are illustrations of the present invention. FIG. 7 is a diagram showing another embodiment of the invention. 1...Tunnel, 2...Open hole, 3...Liquid film, 5 River liquid, 1'...Upper tunnel, 1"...Lower tunnel, 6...Dry surface, 8...・Knurled groove, 9...Minute fin, 1o...Concavity, 11...Thin wire, 12...
- Micro groove, 13... void. Leg / 'fJ 2 Figure No. 3 Figure Encounter 4 Figure Hama g Figure 'FJ Otsu Figure Area 7 Figure 1 11' % q Figure No. /θ Figure

Claims (1)

[Scope of Claims] 1. A large number of elongated tunnels arranged in parallel to each other under the skin of the heat transfer surface in two or more stages in the vertical direction, and the maximum cross-sectional area of the tunnels located in each stage is limited to be smaller than the maximum cross-sectional area of the tunnels, A heat exchange wall characterized by being composed of a large number of openings that communicate between the tunnels of each stage and between the tunnels of the uppermost stage.2. The heat exchange wall is characterized in that the size of the limited openings gradually decreases from the heat transfer wall surface toward the bottom. 3. In the above item 1, the fins have a tapered cross section due to the perforation process. When forming a row of fine wires and winding them in multiple stages between the fin rows, the thin wire forming the lower tunnel is made thinner, and the fine wire forming the upper tunnel is made thicker to form two or more stages. A heat exchange wall characterized by forming an elongated tunnel. 4. In the above item 1, micro knurling grooves running in parallel are provided on a smooth surface by knurling, and then micro fins are formed by plowing. , forming a row of fins with uneven tips, then winding a thin wire with micro grooves between the rows of fins, creating a tunnel between the thin wire and the fins, forming a tunnel, and then brushing or A heat exchange wall characterized by removing the tip of the fin by roll processing and joining adjacent fins to form an uppermost tunnel communicating with the boiling liquid. 5. In the above item 2, the lower stage l. A heat exchange wall characterized in that the micro grooves provided in the thin wire forming the tunnel are made smaller, and the micro grooves provided in the thin wire forming the upper tunnel are made larger.