JPH0113039B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a heat exchanger tube, such as a heat exchanger for an air conditioner or refrigerator, which allows a phase-change refrigerant to flow inside the tube to exchange heat with a fluid outside the tube. .

Conventional Structure and Problems Conventionally, as shown in FIG. 1, this type of heat exchanger tube uses an internal helical grooved tube 2 having a plurality of helical grooves 1 on the inner wall of the tube at an angle of β to the tube axis. ing.

This internal spiral grooved tube 2 has an angle β with respect to the tube axis.
By providing narrow grooves with a diameter of 4 to 15 degrees, in the case of condensation heat transfer, the condensate gathers at the bottom of the groove due to the action of surface tension, and the average thickness of the condensate film formed on the tube wall becomes thinner, resulting in boiling. In the case of heat transfer, the liquid refrigerant at the bottom of the tube rises through the narrow grooves due to capillarity, and the average thickness of the refrigerant liquid film formed on the tube wall becomes thinner, which is said to improve heat transfer performance. Ta.

However, according to our experience, for example, in the case of condensation heat transfer, the condensate collects at the bottom of the narrow groove and flows inside the groove, forming a thin condensate film at the top of the groove because the refrigerant is very dry. , that is, only at the beginning of the condensation process. As the condensation process progresses and the degree of dryness decreases, a large amount of condensate that is generated easily fills the narrow grooves and flows over the narrow grooves, so that the heat transfer performance does not improve much. In addition, in the case of boiling heat transfer, as the boiling process progresses and reaches a high dryness region, the liquid refrigerant flowing along the pipe wall collides with the narrow grooves and becomes droplets, which separate from the pipe wall and float in the steam. Therefore, the heat transfer performance does not improve much.

Purpose of the Invention The present invention eliminates the above-mentioned drawbacks of the conventional technology by adding a heat transfer surface that is not easily buried in condensate and capable of capturing suspended liquid refrigerant, and furthermore, a thin temperature boundary layer is provided on the heat transfer surface. The purpose of this is to significantly improve heat transfer performance.

Structure of the Invention The heat transfer tube of the present invention has an annular shape in which a plurality of cut-out portions having openings at both ends in the tube axis direction and a plurality of small holes are provided in an outer tube having a plurality of spiral thin grooves on the inner wall. A thin-walled member is inserted and brought into thermal contact with the outer tube.

With this structure, in the case of condensation heat transfer, the plurality of cut-out portions of the annular thin-walled member function as fins, that is, heat transfer surfaces, and even if the spiral narrow groove is filled with condensate, it will not be cut. The riser is located in the steam and forms a thin thermal boundary layer, causing the steam to condense due to the boundary layer leading edge effect. Furthermore, even if the cut-out portion is buried in condensate, the condensate film has a laminar flow, so it is highly effective in forming a thin temperature boundary layer. Next, in the case of boiling heat transfer, the multiple cut-outs of the annular thin-walled member are in the liquid refrigerant at the beginning of the boiling process, and function as fins to form a thin temperature boundary layer, resulting in the boundary layer leading edge effect. The liquid refrigerant is evaporated by In addition, in high dryness regions, the cut and raised portion collides with the narrow grooves, captures and evaporates droplets that have separated from the tube wall.

Furthermore, the plurality of small holes in the annular thin-walled member actively facilitate the inflow of refrigerant vapor into the spiral groove in condensation heat transfer, and the inflow of liquid refrigerant into the spiral groove and the outflow of evaporated refrigerant vapor in boiling heat transfer. Make it.

In addition, since both ends of the cut and raised portion of the annular thin-walled member are open in the tube axis direction, shape resistance is small and pressure loss hardly increases.

From the above, the present invention can achieve a significant improvement in heat transfer performance.

Description of examples An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall view of the heat exchanger tube, FIG. 3 is a developed view of the annular thin-walled member, and FIG. 4 is a perspective view of the annular thin-walled member.

As shown in the figure, a thin annular member 7 having a plurality of cut-out portions 5 and a plurality of small holes 6 is inserted into an outer tube 4 having a plurality of spiral thin grooves 3 on the inner wall to obtain thermal contact with the outer tube 4. For this reason, the heat exchanger tube is configured by being brought into close contact with the top of the spiral narrow groove 3. The plurality of cut-and-raised portions 5 provided in the annular thin-walled member 7 have openings 5a and 5b that are open at both ends in the tube axis direction, that is, the flow direction of the refrigerant, and the plurality of small holes 6 are cut and raised. An annular thin member 7 other than the portion 5 is provided on the substrate. As shown in FIG. 3, the annular thin member 7 has a thin inner plate 8 provided with a plurality of cut-out portions 5 and a plurality of small holes 6.
As shown in FIG. 4, the tube is formed into an annular shape with a curvature commensurate with the inner diameter of the outer tube 4, and both ends in the tube axis direction are joined.

In addition, in order to make good line contact with the top of the spiral thin groove 3 when the annular thin-walled member 7 is inserted into the outer tube 4, the annular thin-walled member 7 is coated with brazing material in advance and then inserted into the outer tube 4.
It may also be heated and soldered after being inserted into.

In addition, although the cut-and-raised portions 5 are arranged in a base arrangement, they may be arranged in a staggered manner.Furthermore, the top of the cut-and-raised portions 5 is made parallel to the tube axis because it is easy to form into an annular shape, but the velocity component perpendicular to the tube axis is In order to promote the flow of refrigerant into the spiral narrow groove 3, the openings 5a and 5b may be cut and tilted with respect to the tube axis, that is, the heights of the openings 5a and 5b may be changed.

Next, the action and effects will be explained.

First, in the case of condensation heat transfer, the plurality of cut-out portions 5 of the annular thin-walled member 7 function as fins, that is, heat transfer surfaces, and because they exist intermittently at certain intervals in the flowing refrigerant, the temperature boundary layer is thin and the heat transfer surface is The so-called boundary layer leading edge effect with high transmission rate can be utilized. Even if the spiral narrow groove 3 is filled with condensate, the cut-out portion 5
exists in the steam and forms a thin thermal boundary layer, causing the steam to condense. Furthermore, even when the cut-out portion 5 is buried in condensate, the condensate film is a laminar flow, so the effect of forming a thin temperature boundary layer is significant.

Next, in the case of boiling heat transfer, the plurality of cut-out portions 5 of the annular thin-walled member 7 are in the liquid refrigerant at the beginning of the boiling process, and function as fins to form a thin temperature boundary layer and transfer the liquid refrigerant. Evaporate. In addition, in a high dryness region, the cut-and-raised portion 5 traps liquid refrigerant, which is attracted by the evaporated vapor flow and whose speed increases, collides with the narrow groove, separates from the pipe wall, and tries to float in the vapor flow. evaporate.

Furthermore, the plurality of small holes 6 in the annular thin-walled member 7 are in close contact with the inner wall of the outer tube 4, and the refrigerant vapor flows into the spiral pores 3 during condensation heat transfer, and into the spiral narrow grooves 3 during boiling heat transfer. Activating the inflow of liquid refrigerant and the outflow of refrigerant vapor evaporated in the spiral narrow groove 3,
The heat transfer coefficient in the spiral narrow groove 3 is promoted.

On the other hand, since the cut-out portion 5 of the annular thin-walled member 7 has openings 5a and 5b at both ends in the tube axis direction, the shape resistance is small and the pressure loss hardly increases.

From the above, the heat transfer performance for condensation and boiling can be significantly improved.

In addition, since the inner wall of the outer tube 4 has a narrow spiral groove 3, the annular thin-walled member 7 is in line contact with the top of the narrow spiral groove 3, and can be easily inserted along the spiral by rotating. It is simple and the frictional resistance during insertion is small, so less power is required for insertion.

Effects of the Invention As described above, the present invention provides an annular outer tube having a plurality of spiral grooves on the inner wall, a plurality of cut-out portions having openings at both ends in the tube axis direction, and a plurality of small holes. Since this is a heat transfer tube in which a thin-walled member is inserted and brought into thermal contact with the outer tube, the following effects are achieved.

(1) The cut-and-raised portion functions as a fin with a boundary layer leading edge effect and as a capture plate for unevaporated droplets separated from the tube wall, significantly improving both condensation and boiling transfer performance.

(2) The small holes activate the flow of refrigerant into and out of the spiral grooves, significantly improving both condensation and boiling heat transfer performance.

[Brief explanation of drawings]

Figures 1a and b are a front view and side sectional view of a conventional heat exchanger tube, Figure 2a is a front sectional view of a heat exchanger tube of the present invention, and Figure 2b is a cross section taken along line A-A in Figure 2a. Fig. 3a is a developed view of the annular thin-walled member used in the heat exchanger tube, Fig. 3b is a cross-sectional view taken along line AA in Fig. 3a, and Fig. 4 is a perspective view of the annular thin-walled member. . 3... Spiral narrow groove, 4... Outer tube, 5... Cut-and-raised portion, 5a, 5b... Opening, 6... Small hole, 7...
...Annular thin-walled member, 8...Thin-walled plate.

Claims (1)

[Claims] 1. An annular thin-walled member having a plurality of cut-outs and a plurality of small holes having openings at both ends in the tube axis direction is inserted into an outer tube having a plurality of spiral thin grooves on the inner wall, and the outer tube is A heat exchanger tube in thermal contact with.