JPH03129298A - Condensation heat transfer pipe - Google Patents

Abstract

PURPOSE:To improve the heat transfer efficiency of the inner side of a pipe not only in a refrigerant high dryness area but also in a range of from a low dryness area to a middle dryness area by a method wherein a number of fine protrusions continued in the direction of the axis of the pipe or in a helical direction based on the pipe axis are formed on an inner surface, and the shape thereof is formed approximately in the shape of a circle a part of which makes contact with the inner peripheral surface of the pipe. CONSTITUTION:When protrusions 8 are formed on an inner peripheral surface 6' of a condensation heat transfer pipe 6, condensate is collected in a groove 9 between the adjoining protrusions 8 through the action of a surface tension. Since, even in a region where an amount of a liquid refrigerant in a range of from a low dryness area to a middle dryness area is high, a protrusionsform surface is formed approximately in the shape of a circle, the influence of a surface tension is sharply exercised on the liquid refrigerant, which is difficult to be held on an upper surface 8a of the protrusion, and is easily discharged to a bottom part 8b of the protrusion and the groove 9 between the adjoining protrusions 8. Since the liquid refrigerant flowing in the groove 9 is also held at the bottom part 8b of the protrusion, it is difficult to flow out to the upper surface 8a of the protrusion, and can smoothly flow the groove 9. This constitution enables a fluid state to maintain an annular flow and improves heat transfer efficiency on the inner side of the pipe throughout the whole of a dryness area.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to condensing heat exchanger tubes used in heat exchangers that transfer heat between fluids such as refrigerant and air, such as air conditioners, refrigeration equipment, and automobile equipment. It is something that takes place in between.

2. Description of the Related Art In recent years, heat exchangers have been required to be made more compact in terms of equipment design, and heat exchanger tubes that form the refrigerant side flow path of heat exchangers have also been disclosed in Japanese Utility Model Publication No. 14956/1983 and Utility Model Publication No. 55-1982.
As disclosed in Japanese Patent No. 26706, high efficiency has been achieved by providing a spiral groove on the inner circumferential surface of the pipe.

Hereinafter, the above-mentioned conventional condensing heat exchanger tube will be explained with reference to the drawings.

Figures 3 and 4 show the shapes of conventional condensing heat exchanger tubes, and
The figure shows an example of a heat exchanger using the condensing heat transfer tube. In FIGS. 3 and 4, reference numeral 1 denotes a condensing heat transfer tube having a substantially cylindrical cross section, with a flow path 2 formed inside. Reference numeral 3 denotes a seven-shaped groove provided on the inner circumferential surface 1' of the condensing heat exchanger tube 1, and a large number of grooves are provided continuously in a spiral shape in the axial direction of the condensing heat exchanger tube 1.

The condensing heat exchanger tube 1 configured as described above is generally used as a part of a heat exchanger. In FIG. 5, 4 is an example of a heat exchanger using the condensing heat exchanger tube 1, which is composed of fins 5 arranged in parallel at regular intervals and the condensing heat exchanger tube 1 inserted at right angles to the fins 5. Heat exchange is performed between the airflow flowing between the fins 5 and the refrigerant in the condensing process flowing through the fM path 2 in the condensing heat transfer tube 1. At that time, by providing a 7-shaped groove 3 in a spiral shape on the inner circumferential surface 1' of the condensing heat transfer tube 1, the condensate liquid collects at the lower part of the groove 3 due to surface tension and inhibits heat transfer. The heat transfer coefficient inside the tube was improved due to the thinner average thickness of the membrane.

Problems to be Solved by the Invention However, in the above configuration, a thin condensate film is formed on the entire inner circumferential surface 1' of the condensing heat transfer tube 1, and a remarkable heat transfer promotion effect is obtained only because of the refrigerant. Only in areas of high dryness, i.e. at the beginning of the condensation process. On the other hand, in the latter stage of the condensation process, the dryness of the refrigerant is small and there is a large amount of liquid refrigerant in the pipe, so the liquid refrigerant quickly fills the figure 7-shaped groove 3 and the liquid refrigerant passes across the top of the figure 7 groove 3. I did it,
A significant heat transfer promoting effect due to the above-mentioned condensation mechanism cannot be expected. Therefore, when the refrigerant in the tubes is in a low dryness range, the heat transfer coefficient inside the tubes is low, resulting in a problem that the performance of the heat exchanger 4 using this condensing heat transfer tube 1 is low.

In view of the above problems, the present invention improves the heat transfer coefficient inside the tube not only in the high dryness region of the refrigerant but also in the low to medium dryness region by devising the shape of the inner peripheral surface of the condensing heat transfer tube. The aim is to improve the performance of heat exchangers using condensing heat transfer tubes.

Means for Solving the Problems In order to solve the above problems, the condensing heat exchanger tube of the present invention is provided with a large number of minute protrusions on the inner circumferential surface that are continuous in the tube axis direction or in a spiral direction with respect to the tube axis. The shape is approximately circular with a portion touching the inner circumferential surface of the tube.

Effect The present invention has the above-described configuration, so that even in a low to medium dryness region, that is, a region where there is a large amount of liquid refrigerant, the surface of the protrusion is approximately circular, so that the liquid refrigerant is greatly affected by surface tension. The liquid refrigerant is difficult to be held on the top surface of the protrusion, and is easily removed to the bottom of the protrusion and the groove between the protrusions, and the liquid refrigerant that has flowed into the groove is also held at the bottom of the protrusion, so it is difficult to flow out to the top surface of the protrusion, and the liquid refrigerant is A smooth flow can be obtained along the groove. Therefore, the fluid state can maintain an annular flow not only in the high dryness region but also in the low to medium dryness region, and the average thickness of the condensate film that inhibits heat transfer becomes thinner, so the inside of the tube Heat transfer coefficient can be improved over the entire dryness range.

EXAMPLES Hereinafter, condensing heat exchanger tubes according to examples of the present invention will be described with reference to the drawings.

1 and 2 show the shape of a condensing heat exchanger tube in an embodiment of the present invention. In FIGS. 1 and 2, reference numeral 6 denotes a condensing heat transfer tube having a substantially cylindrical cross section, with a flow path 7 formed inside.

Reference numeral 8 denotes a substantially circular projection provided on the inner circumferential surface 6' of the condensing heat exchanger tube 6, a portion of which is in contact with the inner circumferential surface 6'. There is. In addition, the protrusion 8
A groove 9 is formed between the protrusions 8.

The condensing heat transfer tube 6 configured as described above is used as a part of a heat exchanger as in the conventional example, and is used by flowing the refrigerant in the condensing process into the tube. In this usage condition, by providing the protrusions 8 in a spiral shape on the inner circumferential surface 6' of the condensing heat transfer tube 6, the condensate collects in the grooves 9 between the protrusions 8 due to surface tension, thereby inhibiting heat transfer. The average thickness of the condensed liquid film becomes thinner and the heat transfer coefficient inside the tube is improved, but in the late stage of refrigerant condensation, that is, in the high dryness region, there is little liquid refrigerant, so the fluid state is maintained in an annular flow and the refrigerant liquid is The average thickness of the film can be easily reduced, and even in the early stages of condensation, i.e., in areas where there is a lot of liquid refrigerant in the low to medium dryness range, the protrusion-shaped surfaces are approximately circular, so that the liquid refrigerant can be easily reduced. The refrigerant is difficult to be held on the protrusion top surface 8a due to the influence of surface tension, and is easily removed to the protrusion bottom 8b and the groove 9 between the protrusions 8, and the liquid refrigerant that has flowed into the placement groove 9 is also retained on the protrusion bottom 8b. Therefore, it is difficult for the liquid refrigerant to flow out to the upper surface 8a of the protrusion, and a smooth flow of the liquid refrigerant along the groove 9 can be obtained. Therefore, the fluid state can maintain an annular flow not only in the high dryness region but also in the low to medium dryness region, and the average thickness of the condensate film that inhibits heat transfer becomes thinner, so the inside of the tube The heat transfer coefficient can be improved over the entire dryness range, and the performance of the heat exchanger using this condensing heat exchanger tube 6 can also be improved.

As described above, according to this embodiment, the inner peripheral surface 6' of the condensing heat exchanger tube 6 is provided with a large number of minute projections 8 that continue in a spiral direction with respect to the tube axis, and the shape of the projections 8 is adjusted to the inner peripheral surface of the tube. By forming a substantially circular shape with a part touching the surface, the refrigerant can be maintained in a fluid annular flow not only in the high dryness region but also in the low to medium dryness region. Since the average thickness of the condensate film that inhibits heat becomes thinner, the heat transfer coefficient inside the tube can be improved over the entire dryness range.

Effects of the Invention As described above, the present invention provides a condensing heat exchanger tube with a large number of fine protrusions that continue in the tube axis direction or in a spiral direction with respect to the tube axis, and the shape of the protrusions is adjusted to the inner circumferential surface of the tube. By forming the refrigerant into a substantially circular shape with a part touching, the refrigerant can maintain an annular flow state not only in high dryness areas but also in low to medium dryness areas, inhibiting heat transfer. Since the average thickness of the condensate film becomes thinner, the heat transfer coefficient inside the tube can be improved over the entire dryness range.

[Brief explanation of the drawing]

Fig. 1 is a circumferential cross-sectional view showing the shape of a condensing heat exchanger tube in an embodiment of the present invention, Fig. 2 is an axial cross-sectional view of Fig. 1, and Fig. 3 shows the shape of a conventional condensing heat exchanger tube. FIG. 4 is an axial sectional view of FIG. 3, and FIG. 5 is a perspective view of a heat exchanger using condensing heat transfer tubes. 6... Condensing heat transfer tube, 6'... Inner peripheral surface, 8... Protrusion, 8a... Protrusion top surface, 8b... Protrusion bottom.

Claims (1)

[Claims] It is characterized by having a large number of fine protrusions on the inner circumferential surface that are continuous in the tube axis direction or in a spiral direction with respect to the tube axis, and the shape of the protrusions is approximately circular with a part touching the inner circumferential surface of the tube. condensing heat transfer tube.