JPH09257385A - Heat transfer pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heat transfer rate between a refrigerant and a heat transfer pipe by providing main grooves extending spirally axially of a pipe and a plurality of fine auxiliary grooves coupling the main grooves with each other in an internal surface. SOLUTION: Main grooves 4 are provided spirally and continuously in the direction of a pipe axis in an internal surface of a heat transfer pipe, and are coupled with each other in the direction of the pipe axis with a plurality of fine auxiliary grooves 5. The width of the auxiliary groove 5 is smaller than that of tire main groove 4, while the cross sectional area of a flow passage is smaller than that of the main groove 4. A liquid refrigerant flowing in the heat transfer pipe is held in the main groove 4 and the auxiliary groove 5 with the aid of surface tension whereby there is increased an effectual heat transfer area over which the heat transfer pipe and the liquid refrigerant effective for heat transfer make contact with each other. In a region where the degree of drying of the refrigerant is small and much liquid refrigerant is existent, an excess liquid refrigerant where the refrigerant has a smaller velocity flows through the main groove 4, while in a region where the same degree is large and the liquid refrigerant is little, most of the liquid refrigerant flows through the auxiliary groove 5 while forming a liquid film, and a proper amount of the liquid refrigerant flows through time auxiliary groove 5 at all times. Here, a heat transfer rate between the refrigerant and the heat transfer pipe is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer tube used in a heat exchanger for exchanging heat between a refrigerant such as an air conditioner, a refrigeration equipment, an automobile equipment and a fluid such as air.

[0002]

2. Description of the Related Art In recent years, heat exchangers have been required to be compact from the viewpoint of equipment design, and the heat transfer tubes forming the refrigerant side flow path of the heat exchanger are also provided with a spiral groove on the inner surface. The high efficiency is achieved by.

As a conventional heat transfer tube having a spiral groove on its inner surface, Japanese Utility Model Publication No. 55-14956 and Japanese Utility Model Publication No. 55-
The one disclosed in Japanese Patent No. 26706 is known.

Hereinafter, the conventional heat transfer tube will be described with reference to the drawings. FIG. 10 is a sectional view of the conventional heat transfer tube in a direction perpendicular to the tube axis, and FIG. 11 is a sectional view of the heat transfer tube in the tube axis direction. In FIGS. 10 and 11, reference numeral 1 is a fine trapezoidal groove provided on the inner surface of the heat transfer tube, and a large number of grooves are continuously provided in a spiral shape in the tube axis direction.

Regarding the heat transfer tube constructed as described above,
The operation will be described below by taking the case of use as an evaporator as an example.

FIG. 12 shows an evaporator using a heat transfer tube. In FIG. 12, 2 is a fin arranged in parallel at regular intervals. Reference numeral 3 denotes a conventional heat transfer tube, which is inserted into the fin 2 at a right angle. In this evaporator, heat exchange is performed between the airflow flowing between the fins 2 and the refrigerant flowing horizontally in the heat transfer tubes 3. Then, the airflow is cooled by the heat taken by the refrigerant, and the refrigerant obtains heat from the airflow and evaporates, and the phase changes from liquid to vapor. At this time, the liquid refrigerant flowing inside the horizontal heat transfer tube 3 tries to flow at the bottom of the tube due to the influence of gravity, but since it flows along the spiral groove 1, it must be pulled up to the top of the tube against gravity. Therefore, the effective heat transfer area where the heat transfer tube 3 and the liquid refrigerant effective for heat transfer are in contact with each other is increased, and a thin liquid film is formed in the groove 1.
The heat transfer between the refrigerant and the refrigerant was promoted.

[0007]

In this heat transfer tube, since the groove of the same shape is provided over the entire heat transfer tube, an ideal thin liquid film is formed in the groove in the entire evaporator. The area is small. For example, in the refrigerant inlet side of the evaporator, that is, in the region where the amount of liquid refrigerant is large, the liquid film is thick,
Depending on the conditions, the liquid film is not formed and the groove is buried in the liquid. On the other hand, in the refrigerant outlet side of the evaporator, that is, in the region where the amount of the liquid refrigerant is small, the supply of the liquid refrigerant cannot keep up with the evaporation of the refrigerant in the groove, and the groove tends to dry. Therefore,
There is a drawback in that the heat transfer coefficient between the refrigerant and the heat transfer tube is not sufficiently high in all regions. In addition, since the continuous groove is provided over the entire heat transfer tube, the liquid film formed in the groove has a highly rectified flow, which also contributes to the heat between the refrigerant and the heat transfer tube. There was a drawback that the transmissivity was not high enough in all areas. Furthermore, since the spiral angle of the groove with respect to the tube axis direction is fixed over the entire heat transfer tube, the spiral angle of the groove cannot be increased to suppress pressure loss, and therefore the swirling force of the refrigerant flow cannot be increased. Therefore, the liquid film held in the groove cannot be distributed sufficiently evenly in the circumferential direction of the heat transfer tube, which also ensures that the heat transfer coefficient between the refrigerant and the heat transfer tube is sufficient in all regions. It had the drawback of not being expensive.

The present invention solves the conventional problems, and an object of the present invention is to provide a heat transfer tube having a higher heat transfer coefficient between the refrigerant and the heat transfer tube.

[0009]

In order to solve this problem, a heat transfer tube of the present invention comprises a main groove spirally continuous in the axial direction of the tube, and a plurality of fine auxiliary grooves connecting the main grooves to each other. It is equipped with and inside. According to the present invention, the heat transfer coefficient between the refrigerant and the heat transfer tube can be increased in all regions regardless of the degree of dryness of the refrigerant.

Further, the heat transfer tube of the present invention is provided with a main groove spirally continuous in the tube axial direction and a plurality of fine auxiliary grooves connecting the main grooves to each other on the inner surface, and the auxiliary groove is provided in the tube. The main groove is inclined in the direction opposite to the continuous direction of the main groove. According to the present invention, regardless of the degree of dryness of the refrigerant, the heat transfer coefficient between the refrigerant and the heat transfer tube is increased in the entire region, and the turbulent flow promotes the turbulence of the refrigerant liquid film and the refrigerant and the heat transfer tube. The heat transfer coefficient between the two can be further increased.

Further, the heat transfer tube of the present invention is provided with a main groove spirally continuous in the tube axis direction and a plurality of fine auxiliary grooves connecting the main grooves to each other on the inner surface, and the auxiliary groove is provided in the tube. It is inclined with respect to the axis in the same direction as the continuous direction of the main groove. According to the present invention, regardless of the degree of dryness of the refrigerant, the heat transfer coefficient between the refrigerant and the heat transfer tube is increased in all areas, and the angle of the auxiliary groove is made relatively small to suppress the pressure loss and swirl the refrigerant. By obtaining a strong flow, the thin liquid film formed in the auxiliary groove can be evenly distributed in the circumferential direction, and the heat transfer coefficient between the refrigerant and the heat transfer tube can be further increased.

Further, in the heat transfer tube of the present invention, the flow passage cross-sectional area of the main groove is made larger than that of the auxiliary groove. According to the present invention, the distribution amount of the liquid refrigerant from the main groove to the auxiliary groove can be optimized, and the heat transfer coefficient between the refrigerant and the heat transfer tube can be further increased.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a main groove spirally continuous in the heat transfer tube with respect to the tube axis direction, and a plurality of fine auxiliary members connecting the main grooves to each other. With the groove, in a region where the degree of dryness of the refrigerant is small and the amount of liquid refrigerant is large, since the speed of the refrigerant is low, excess liquid refrigerant that is an obstacle to forming a liquid film in the auxiliary groove flows through the main groove, In a region where the degree of dryness of the refrigerant is high and the amount of the liquid refrigerant is low, the speed of the refrigerant is high, so that most of the liquid refrigerant flows through the auxiliary groove. Therefore, regardless of the degree of dryness of the refrigerant, an appropriate amount of liquid refrigerant always flows in the auxiliary groove in the state of a liquid film,
It has an effect of improving the heat transfer coefficient between the refrigerant and the heat transfer tube.

According to a second aspect of the present invention, the auxiliary groove of the first aspect of the invention is inclined with respect to the tube axis in a direction opposite to the direction in which the main groove is continuous. In addition to the effect of item 1, the liquid refrigerant flowing in the heat transfer tube flows while meandering by repeatedly branching from the main groove to the auxiliary groove and merging from the auxiliary groove to the main groove. Disturbance of the film is promoted, and this also has the effect of improving the heat transfer coefficient between the refrigerant and the heat transfer tube.

According to a third aspect of the present invention, the auxiliary groove of the first aspect is inclined with respect to the pipe axis in the same direction as the main groove continues. In addition to the effect of 1, the main groove and the auxiliary groove are inclined in the same direction with respect to the tube axis, so that the angle of the auxiliary groove is made relatively small to suppress the pressure loss and to obtain a strong swirling flow of the refrigerant. The thin liquid film formed in the auxiliary groove can be evenly distributed in the circumferential direction.
It has an effect of improving the heat transfer coefficient between the refrigerant and the heat transfer tube.

In the invention according to claim 4 of the present invention, the flow passage cross-sectional area of the main groove is made larger than the flow passage cross-sectional area of the auxiliary groove, and since the auxiliary groove is a fine groove, high heat transfer is achieved. Since a thin liquid film that can obtain a high rate can be formed and the main groove is a relatively large groove, excess liquid refrigerant can be drained to a plurality of auxiliary grooves and the liquid refrigerant can be sufficiently mixed, and the refrigerant and heat transfer tube This has the effect of further improving the heat transfer coefficient between them.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a cross-sectional view of a heat transfer tube according to a first embodiment of the present invention in a direction perpendicular to a tube axis, and FIG. 2 is a cross-sectional view of the heat transfer tube according to the same embodiment in a tube axis direction. . 1 and 2, reference numeral 4 denotes a main groove provided on the inner surface of the heat transfer tube, which is continuously provided in a spiral shape in the tube axis direction. A plurality of fine auxiliary grooves 5 connect the main grooves 4 to each other, which are connected in the pipe axial direction. The width of the auxiliary groove 5 is smaller than that of the main groove 4, and the cross-sectional area of the flow path is smaller than that of the main groove 4.

Regarding the heat transfer tube constructed as described above,
The operation will be described below by taking the case of use as an evaporator as an example.

FIG. 3 shows an evaporator using the heat transfer tube of the first embodiment. In FIG. 3, reference numeral 2 denotes fins arranged in parallel at regular intervals, which has the same structure as the conventional structure. 6
Is a heat transfer tube of the present embodiment, which is inserted into the fin 2 at a right angle. In this evaporator, the fin 2 is used as in the conventional configuration.
Heat exchange is performed between the air flow flowing between the heat transfer tubes 6 and the refrigerant flowing horizontally in the heat transfer tubes 6. Then, the airflow is cooled by the heat taken by the refrigerant, and the refrigerant obtains heat from the airflow and evaporates, and the phase changes from liquid to vapor. At this time, the liquid refrigerant flowing in the horizontal heat transfer tube 6 tries to flow at the bottom of the tube due to the influence of gravity, but is held in the main groove 4 and the auxiliary groove 5 by the surface tension, so that the heat transfer tube 6 and the heat transfer tube 6 are transferred. The effective heat transfer area in contact with the heat-effective liquid refrigerant increases. Further, in a region where the degree of dryness of the refrigerant is small and the amount of liquid refrigerant is large, the speed of the refrigerant is low, and therefore excess liquid refrigerant which is an obstacle to forming a liquid film in the auxiliary groove 5 flows through the main groove 4 and the degree of dryness of the refrigerant is high. In the region where the amount of liquid refrigerant is small, the speed of the refrigerant is high, so most of the liquid refrigerant will flow through the auxiliary groove 5 while forming a liquid film. Therefore, an appropriate amount of liquid refrigerant always flows through the auxiliary groove 5 regardless of the degree of dryness of the refrigerant, and the heat transfer coefficient between the refrigerant and the heat transfer tube 6 is improved.

(Second Embodiment) FIG. 4 is a sectional view of a heat transfer tube according to a second embodiment of the present invention in a direction perpendicular to the tube axis, and FIG. 5 is a cross section of the heat transfer tube according to the second embodiment in the tube axis direction. It is a figure. 4 and 5, 7 is a main groove provided on the inner surface of the heat transfer tube,
It is continuously provided in a spiral shape in the tube axis direction. 8
Is a plurality of fine auxiliary grooves that connect the main grooves 7 to each other.
Are connected in a continuous inclination direction and an inclination direction opposite to the pipe axis. The width of the auxiliary groove 8 is smaller than that of the main groove 7, and the cross-sectional area of the flow path is smaller than that of the main groove 7.

Regarding the heat transfer tube constructed as described above,
The operation will be described below by taking the case of use as an evaporator as an example.

FIG. 6 shows an evaporator using the heat transfer tube of the second embodiment. In FIG. 6, reference numeral 2 designates fins arranged in parallel at regular intervals, which is the same as the conventional structure. 9
Is a heat transfer tube of the present embodiment, which is inserted into the fin 2 at a right angle. In this evaporator, the fin 2 is used as in the conventional configuration.
Heat is exchanged between the airflow flowing between the heat transfer tubes 9 and the refrigerant flowing horizontally in the heat transfer tubes 9. Then, the airflow is cooled by the heat taken by the refrigerant, and the refrigerant obtains heat from the airflow and evaporates, and the phase changes from liquid to vapor. At this time, the liquid refrigerant flowing in the horizontal heat transfer tube 9 tries to flow at the bottom of the tube due to the influence of gravity, but is held in the main groove 7 and the auxiliary groove 8 by the surface tension, so that the heat transfer tube 9 and the heat transfer tube 9 are transferred. The effective heat transfer area in contact with the heat-effective liquid refrigerant increases. Further, in a region where the dryness of the refrigerant is low and the liquid refrigerant is high, the speed of the refrigerant is low, so that the excess liquid refrigerant that is an obstacle to forming a liquid film in the auxiliary groove 8 flows through the main groove 7 and the dryness of the refrigerant is high. In the region where the amount of liquid refrigerant is small, the speed of the refrigerant is high, so most of the liquid refrigerant flows through the auxiliary groove 8 while forming a liquid film. Therefore, an appropriate amount of liquid refrigerant always flows through the auxiliary groove 8 regardless of the degree of dryness of the refrigerant, and the heat transfer coefficient between the refrigerant and the heat transfer tube 9 is improved. Further, since the liquid refrigerant flowing in the heat transfer tube 9 flows while meandering by repeatedly branching from the main groove 7 to the auxiliary groove 8 and merging from the auxiliary groove 8 to the main groove 7, the liquid refrigerant formed in the auxiliary groove 8 is formed. Turbulence is promoted in the film, and this also improves the heat transfer coefficient between the refrigerant and the heat transfer tube 9.

(Third Embodiment) FIG. 7 is a sectional view of a heat transfer tube according to a third embodiment of the present invention in a direction perpendicular to the tube axis, and FIG. 8 is a cross section of the heat transfer tube according to the third embodiment in the tube axis direction. It is a figure. In FIGS. 7 and 8, 10 is a main groove provided on the inner surface of the heat transfer tube, which is continuously provided in a spiral shape in the tube axis direction. A plurality of fine auxiliary grooves 11 connect the main grooves 10 to each other, and connect the main grooves 10 in the same inclination direction with respect to the continuous direction of the main grooves 10. The width of the auxiliary groove 11 is smaller than that of the main groove 10, and the cross-sectional area of the flow path is smaller than that of the main groove 10.

Regarding the heat transfer tube constructed as described above,
The operation will be described below by taking the case of use as an evaporator as an example.

FIG. 9 shows an evaporator using the heat transfer tube of the third embodiment. In FIG. 9, reference numeral 2 denotes fins arranged in parallel at regular intervals, which has the same structure as the conventional structure. 1
Reference numeral 2 denotes the heat transfer tube of this embodiment, which is inserted into the fin 2 at a right angle. In this evaporator, heat exchange is performed between the airflow flowing between the fins 2 and the refrigerant flowing horizontally in the heat transfer tube 12 as in the conventional configuration. Then, the airflow is cooled by the heat taken by the refrigerant, and the refrigerant obtains heat from the airflow and evaporates, and the phase changes from liquid to vapor. At this time, the liquid refrigerant flowing inside the horizontal heat transfer tube 12 tries to flow at the bottom of the tube due to the influence of gravity, but since it is held in the main groove 10 and the auxiliary groove 11 by the surface tension, the liquid refrigerant and the heat transfer tube 12 are transferred. The effective heat transfer area in contact with the heat-effective liquid refrigerant increases. Further, in a region where the degree of dryness of the refrigerant is low and the amount of liquid refrigerant is high, the velocity of the refrigerant is low, and therefore excess liquid refrigerant that is an obstacle to forming a liquid film in the auxiliary groove 11 flows through the main groove 10 and the dryness of the refrigerant is high. In the region where the amount of liquid refrigerant is small, the speed of the refrigerant is high, so most of the liquid refrigerant will flow through the auxiliary groove 11 while forming a liquid film. Therefore, an appropriate amount of liquid refrigerant always flows through the auxiliary groove 11 regardless of the degree of dryness of the refrigerant, and the heat transfer coefficient between the refrigerant and the heat transfer tube 12 is improved. Further, the liquid refrigerant flowing in the heat transfer tube 12 repeatedly flows by branching from the main groove 10 to the auxiliary groove 11 and merging from the auxiliary groove 11 to the main groove 10, but the main groove 10 and the auxiliary groove 11 serve as a tube axis. On the other hand, since they are inclined in the same direction, the angle of the auxiliary groove 11 can be made relatively small and the swirling flow of the refrigerant can be strongly obtained while suppressing the pressure loss, and the thin liquid film formed in the auxiliary groove 11 It is evenly distributed in the circumferential direction, and this also improves the heat transfer coefficient between the refrigerant and the heat transfer tube 12.

Furthermore, the cross-sectional area of the main groove 10 is equal to the auxiliary groove 1.
Since it is larger than the flow passage cross-sectional area of 1, the auxiliary groove 11 forms a thin liquid film capable of obtaining a high heat transfer coefficient, while the main groove 10 drains excess liquid refrigerant to the plurality of auxiliary grooves 11. Moreover, the liquid refrigerant can be sufficiently mixed, and the heat transfer coefficient between the refrigerant and the heat transfer tube 12 is further improved.

[0027]

As described above, according to the present invention, in a region where the degree of dryness of the refrigerant is small and the amount of the liquid refrigerant is large, the speed of the refrigerant is small, and thus the excess liquid refrigerant which is an obstacle to forming the liquid film in the auxiliary groove. Flows in the main groove, and in a region where the degree of dryness of the refrigerant is high and the amount of liquid refrigerant is low, the speed of the refrigerant increases, so that most of the liquid refrigerant flows in the auxiliary groove. Therefore, regardless of the degree of dryness of the refrigerant, an appropriate amount of liquid refrigerant will always flow in the auxiliary groove in the state of a liquid film, which has the advantageous effect of improving the heat transfer coefficient between the refrigerant and the heat transfer tube. can get.

Further, since the liquid refrigerant flowing in the heat transfer tube flows while meandering by repeatedly branching from the main groove to the auxiliary groove and merging from the auxiliary groove to the main groove, the liquid film formed in the auxiliary groove is disturbed. Is promoted, which has the advantageous effect of further improving the heat transfer coefficient between the refrigerant and the heat transfer tube.

Further, since the main groove and the auxiliary groove are inclined in the same direction with respect to the pipe axis, it is possible to obtain a strong swirling flow of the refrigerant while suppressing the pressure loss by making the angle of the auxiliary groove relatively small. Therefore, the thin liquid film formed in the auxiliary groove can be uniformly distributed in the circumferential direction, which has an advantageous effect of further improving the heat transfer coefficient between the refrigerant and the heat transfer tube. To be

[Brief description of drawings]

FIG. 1 is a sectional view of a heat transfer tube according to a first embodiment of the present invention in a direction perpendicular to a tube axis.

FIG. 2 is a cross-sectional view of the heat transfer tube in the tube axis direction according to the same embodiment.

FIG. 3 is a perspective view of an evaporator using a heat transfer tube according to the same embodiment.

FIG. 4 is a sectional view of a heat transfer tube according to a second embodiment of the present invention in a direction perpendicular to a tube axis.

FIG. 5 is a sectional view of the heat transfer tube according to the embodiment, taken along the tube axis direction.

FIG. 6 is a perspective view of an evaporator using a heat transfer tube according to the same embodiment.

FIG. 7 is a sectional view of a heat transfer tube according to a third embodiment of the present invention in a direction perpendicular to a tube axis.

FIG. 8 is a cross-sectional view of the heat transfer tube in the tube axis direction according to the same embodiment.

FIG. 9 is a perspective view of an evaporator using a heat transfer tube according to the same embodiment.

FIG. 10 is a sectional view of a conventional heat transfer tube in a direction perpendicular to the tube axis.

FIG. 11 is a sectional view of a conventional heat transfer tube in the tube axis direction.

FIG. 12 is a perspective view of an evaporator using a conventional heat transfer tube.

[Explanation of reference numerals] 4 main groove 5 auxiliary groove 7 main groove 8 auxiliary groove 10 main groove 11 auxiliary groove

Claims (4)

[Claims] 1. A heat transfer tube having, on its inner surface, a main groove spirally continuous in the tube axis direction, and a plurality of fine auxiliary grooves connecting the main grooves to each other. 2. The heat transfer tube according to claim 1, wherein the auxiliary groove is inclined with respect to the tube axis in a direction opposite to the direction in which the main groove is continuous. 3. The heat transfer tube according to claim 1, wherein the auxiliary groove is inclined with respect to the tube axis in the same direction as the main groove continues. 4. The heat transfer tube according to claim 1, wherein the flow passage cross-sectional area of the main groove is larger than the flow passage cross-sectional area of the auxiliary groove.