JPH0510695A - Boiling heat transfer tube - Google Patents

Abstract

PURPOSE:To remarkably improve a heat transfer rate between refrigerant flowing in a passage in a tube and inner periphery in the tube and to improve performance of a heat exchanger by using a boiling heat transfer tube used for the exchanger to deliver heat between the refrigerant and fluid such as the air for an air conditioner, a refrigerator, an automotive device, etc. CONSTITUTION:Parallel grooves 10 continued substantially parallel to an axial direction (n) of a tube, are provided on the top and the bottom of the inner periphery 8a of the tube, and oblique grooves 11a continued obliquely to the axial direction (n) of the tube, are provided on the side of the periphery 8a of the tube. Further, the pitch P of the grooves 10 is formed larger than the pitch P of the grooves 11, the pitch P of the grooves 10 is set to 0.15-0.25mm, and the depth H of the groove is set to 0.15-0.25mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an air conditioner, a refrigerating machine,
The present invention relates to a boiling heat transfer tube used in a heat exchanger that transfers heat between a refrigerant such as an automobile device and a fluid such as air.

[0002]

2. Description of the Related Art In recent years, heat exchangers have been required to be compact in view of equipment design, and heat transfer tubes forming a refrigerant side flow path of the heat exchanger are also disclosed in Japanese Utility Model Publication No. 55-14956 and Japanese Utility Model Publication. As disclosed in Japanese Patent No. 55-26706, high efficiency is achieved by devising such as providing a spiral groove on the inner peripheral surface of the pipe.

A conventional boiling heat transfer tube will be described below. FIG. 4 shows the cross-sectional shape of the boiling heat transfer tube, and FIGS. 5 and 6 show the shape of the heat transfer surface of the conventional boiling heat transfer tube before pipe forming. 4 to 6, reference numeral 1 denotes a boiling heat transfer tube having a substantially cylindrical cross section, and a flow path 2 for the refrigerant is formed inside.
Reference numeral 3 denotes a groove provided on the inner peripheral surface 1a of the boiling heat transfer tube 1, and a large number of grooves are continuously provided in a spiral shape in the tube axis direction m of the boiling heat transfer tube 1. The boiling heat transfer tube 1 is formed through a pipe forming process and a welding process, and has a flat plate-shaped heat transfer surface 4 before the pipe forming process.
After the groove 3 is processed at the stage, the flat plate is formed into a tubular shape, and the end surfaces 5a and 5b at both ends of the heat transfer surface 4 are welded to be formed.

The boiling heat transfer tube 1 constructed as described above is generally used as a part of a heat exchanger. FIG. 8 shows an example of a heat exchanger using the boiling heat transfer tube. Reference numeral 6 denotes a heat exchanger, which is fins 7 arranged in parallel at regular intervals and a boiling heat transfer tube 1 inserted perpendicularly to the fins 7. The heat exchange is performed between the airflow flowing between the fins 7 and the refrigerant flowing horizontally in the flow path 2 in the boiling heat transfer tube 1. At that time, the liquid refrigerant flowing at the bottom of the flow path 2 of the horizontal boiling heat transfer tube 1 is pulled up to the top along the spiral groove 3 against the gravity, and the effective heat transfer at which the tube inner peripheral surface 1a and the liquid refrigerant come into contact with each other. Due to the effect of increasing the area, the apparent heat transfer coefficient between the pipe inner peripheral surface 1a and the refrigerant is improved.

Further, specifically, the shape of the groove 3 of the general boiling heat transfer tube 1 using a freon-based refrigerant has a groove pitch P of 0 with respect to the groove shape dimension defined in FIG. .3 ~
0.4 mm, groove depth H is 0.1 to 0.2 mm, and groove 3
The groove lead angle β, which indicates the difference between the continuous direction and the pipe axis direction m, is 1
It is about 5 to 25 °.

[0006]

However, in the above-mentioned conventional structure, not only the refrigerant flow along the spiral groove 3 but also the refrigerant flow over the groove 3 occurs, and a part of the liquid refrigerant overruns the groove 3. As a result, it is scattered from the inner peripheral surface 1a of the pipe,
The effect of increasing the effective heat transfer area is not sufficiently obtained. In particular, at the top of the flow path 2, a large amount of liquid refrigerant cannot be continuously held in the groove 3 and falls due to the influence of gravity.
Even at the bottom of the pipe, the excess liquid refrigerant except for the amount pulled up to the top will flow over the groove 3 while staying at the bottom under the influence of gravity, and will often be scattered from the pipe inner peripheral surface 1a. Become. As a result, the pipe inner peripheral surface 1a
There was a problem that the improvement of the heat transfer rate between the refrigerant and the refrigerant was small, and sufficient heat transfer performance was not obtained for the expected size reduction of the heat exchanger.

The present invention solves the above-mentioned conventional problems. By devising the shape of the inner peripheral surface of the boiling heat transfer tube, the heat transfer coefficient between the inner peripheral surface of the tube and the refrigerant is significantly improved.
The purpose is to improve the performance of a heat exchanger using a boiling heat transfer tube.

[0008]

In order to achieve this object, the boiling heat transfer tube of the present invention has parallel grooves continuous substantially parallel to the tube axis direction at the top and bottom of the tube inner peripheral surface with respect to the tube axis direction. And a continuous inclined groove is provided on the side of the inner peripheral surface of the pipe. Further, the inner circumferential surface of the pipe is provided with a parallel groove continuous substantially parallel to the pipe axis direction and a continuous inclined groove inclined with respect to the pipe axis direction, and the groove pitch of the inclined groove is made larger than the groove pitch of the parallel groove. Have a configuration. Furthermore, the groove pitch of the parallel grooves is 0.15 to 0.25 mm and the groove depth is 0.15 to
It has a structure limited to 0.25 mm.

[0009]

With this structure, the inclined groove provided on the side of the inner peripheral surface of the pipe maintains the effect of splashing the liquid refrigerant to the top of the flow passage as in the conventional case, while the top of the inner peripheral surface of the pipe is provided at the top of the flow passage. The parallel grooves that are continuous in a direction almost equal to the main flow direction of the refrigerant, reduce the drop of the liquid refrigerant from the parallel grooves, and can obtain a thin refrigerant liquid film flow along the parallel grooves. The parallel grooves provided at the bottom of the surface reduce the scattering of the liquid refrigerant from the parallel grooves and can obtain a thin refrigerant liquid film flow along the parallel grooves, greatly increasing the effective heat transfer area. The apparent heat transfer coefficient can be improved, and the heat transfer coefficient can be substantially improved by reducing the refrigerant liquid film thickness at the top and bottom of the flow path.

Further, since the continuous direction of the parallel groove is substantially the same as the main flow direction of the refrigerant, it is easy for the liquid refrigerant to enter the groove, whereas the inclined groove has a continuous direction deviated from the main flow direction of the refrigerant. Therefore, it is difficult for the liquid refrigerant to enter the groove,
By making the groove pitch of the inclined grooves larger than the groove pitch of the parallel grooves, it is possible to form a thin refrigerant liquid film flow with the fine grooves in the parallel grooves and to suppress the scattering of the liquid refrigerant with the coarse grooves in the inclined grooves. , The parallel groove and the inclined groove can enhance their respective effects.

Further, the groove pitch of the parallel grooves is 0.15 to 0.
By limiting the groove depth to 25 mm and the groove depth to 0.15 to 0.25 mm, the holding force in the groove due to the surface tension of the liquid refrigerant can be significantly increased, and the effect of increasing the effective heat transfer area can be greatly increased compared to the conventional case. In addition to the increase, it is possible to form an extremely thin refrigerant liquid film flow by increasing the surface tension, and it is possible to further improve the substantial heat transfer coefficient.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A boiling heat transfer tube according to an embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 to 3, reference numeral 8 denotes a boiling heat transfer tube having a substantially cylindrical cross section, and a coolant passage 9 is formed inside. Reference numeral 10 is a parallel groove formed on the bottom and the top of the tube inner peripheral surface 8a of the boiling heat transfer tube 8, which are continuously provided in a direction parallel to the tube axis direction n, and the groove pitch P is 0.15 to 0. ．
The groove depth H is 25 mm, and the groove depth H is 0.15 to 0.25 mm. Reference numeral 11 denotes an inclined groove provided on the side of the inner peripheral surface 8a of the boiling heat transfer tube 8, which is continuously provided in a direction having a certain inclination with respect to the tube axis direction n, and the groove pitch P thereof.
Is larger than the groove pitch P of the parallel grooves 10. The boiling heat transfer tube 8 is formed through pipe forming and welding, and the parallel groove 1 is formed at the stage of the flat heat transfer surface 12 before pipe forming.
After the 0 and the inclined groove 11 are formed, the flat plate shape is tubularly formed, and the end surfaces 13a and 13b at both ends of the heat transfer surface 12 are welded.

The operation of the boiling heat transfer tube 8 constructed as above will be described. First, the boiling heat transfer tube 8 is used as a part of a heat exchanger as in the conventional example, and is used by flowing a refrigerant in the tube in a horizontal state. In this usage state, a part of the liquid refrigerant flowing in the flow passage 9 in the pipe easily enters the rough inclined groove 11 having the groove pitch P provided on the side portion of the inner peripheral surface 8a of the pipe, and the flow passage 9 is opposed to gravity. The liquid refrigerant that has been splashed to the top of the flow path 9 and is splashed to the top of the flow path 9 is continuously held in the main flow direction of the refrigerant by the parallel grooves 10 that are continuous in the pipe axis direction n and are dimensioned optimally. At the top of the pipe, the liquid refrigerant is always in contact with the inner peripheral surface 8a of the pipe to form an extremely thin refrigerant liquid film flow.

Further, even at the bottom of the flow path 9, the parallel groove 10 reduces the scattering of the liquid refrigerant from the parallel groove 10 and the parallel groove 1
0, an extremely thin refrigerant liquid film flow can be obtained, and the effect of increasing the effective heat transfer area can be significantly increased compared to the conventional case to improve the apparent heat transfer coefficient, and the refrigerant liquid film at the top and bottom of the flow path 9 can be obtained. By reducing the thickness, it is possible to further improve the actual heat transfer coefficient.

As described above, according to the present embodiment, the parallel grooves 10 which are continuous substantially parallel to the pipe axis direction n are connected to the top and bottom of the pipe inner peripheral surface 8a so as to be inclined with respect to the pipe axis direction n. The inclined groove 11 is provided on the side of the inner peripheral surface 8a of the pipe, and the parallel groove 1
The groove pitch P of the inclined groove 11 is made larger than the groove pitch P of 0, and the groove pitch P of the parallel groove 10 is 0.15 to 0.2.
By setting the groove depth H to 5 mm and the groove depth H to 0.15 to 0.25 mm, the inclined groove 11 provided on the side portion of the pipe inner peripheral surface 8a.
While maintaining the splashing effect of the liquid refrigerant to the top in the same manner as in the conventional case, at the top of the flow path 9, by the parallel groove 10 provided in the top of the pipe inner peripheral surface 8a in a direction substantially equal to the main refrigerant flow direction, A thin refrigerant liquid film flow along the parallel groove 10 can be obtained by reducing the drop of the liquid refrigerant from the parallel groove 10.

Even at the bottom of the flow passage 9, the parallel grooves 10 provided at the bottom of the inner peripheral surface 8 of the pipe and continuous in a direction substantially equal to the main flow direction of the refrigerant reduce the scattering of the liquid refrigerant from the parallel groove 10. A thin refrigerant liquid film flow along the parallel grooves 10 can be obtained, and the effect of increasing the effective heat transfer area can be significantly increased compared to the conventional case to improve the apparent heat transfer coefficient, and the refrigerant liquid at the top and bottom of the flow passage 9 can be obtained. By reducing the film thickness, it is possible to substantially improve the heat transfer coefficient.

Further, by making the groove pitch P of the inclined grooves 11 provided on the side of the pipe inner peripheral surface 8a larger than the groove pitch P of the parallel grooves 10 provided on the top and bottom of the pipe inner peripheral surface 8a, the parallel grooves are formed. In 10, it is possible to form a fine groove suitable for forming a thin refrigerant liquid film flow, and in the inclined groove 11, it is possible to form a rough groove suitable for facilitating the intrusion of the liquid refrigerant into the groove and suppressing the scattering. The effect of can be enhanced. Furthermore,
The groove pitch P of the parallel grooves 10 provided on the top and bottom of the pipe inner peripheral surface 8a is 0.15 to 0.25 mm, and the groove depth H is 0.15.
By limiting to 0.25 mm, the holding force to the groove due to the surface tension of the liquid refrigerant can be greatly increased, the effect of increasing the effective heat transfer area can be significantly increased compared with the conventional one, and the increase of the surface tension can also be achieved. An extremely thin refrigerant liquid film flow can be formed, and the substantial heat transfer coefficient can be further improved, and the performance of the heat exchanger using the boiling heat transfer tube 8 can be improved.

[0019]

As described above, according to the present invention, the parallel grooves continuous substantially parallel to the pipe axis direction are provided on the top and bottom of the inner peripheral surface of the pipe, and the inclined grooves continuously inclined with respect to the pipe axial direction are formed on the inner circumference of the pipe. By providing on the side of the surface, the inclined groove provided on the side of the inner peripheral surface of the pipe maintains the effect of splashing the liquid refrigerant to the top of the flow passage in the same manner as before, while at the top of the flow passage, the top of the inner peripheral surface of the pipe is By the parallel groove continuous in the direction substantially equal to the main flow direction of the refrigerant provided, a thin refrigerant liquid film flow along the parallel groove can be obtained by reducing the drop of the liquid refrigerant from the parallel groove, and also at the bottom of the flow path.
The parallel groove provided on the bottom of the inner peripheral surface of the pipe reduces the scattering of the liquid refrigerant from the parallel groove, and a thin refrigerant liquid film flow along the parallel groove can be obtained, greatly increasing the effective heat transfer area than before. It is possible to improve the apparent heat transfer coefficient by increasing the heat transfer coefficient to a higher level and to improve the actual heat transfer coefficient by reducing the refrigerant liquid film thickness at the top and bottom of the flow path. The performance of the container can be improved.

Further, the inner peripheral surface of the pipe is provided with parallel grooves which are continuous substantially parallel to the tube axis direction and inclined grooves which are inclined and continuous with respect to the tube axis direction, and the groove pitch of the inclined grooves is larger than the groove pitch of the parallel grooves. By increasing the pitch, in the parallel grooves, the fine grooves enhance the holding power of the liquid refrigerant to enable the formation of a thin refrigerant liquid film flow, and in the inclined grooves, the rough grooves allow the liquid refrigerant to pass over the grooves and from the grooves. The scattering can be suppressed, and the heat transfer coefficient improving effect of each of the parallel groove and the inclined groove can be enhanced.

Further, the groove pitch of the parallel grooves is 0.15 to 0.
By limiting the groove depth to 25 mm and the groove depth to 0.15 to 0.25 mm, the holding force in the groove due to the surface tension of the liquid refrigerant can be significantly increased, and the effect of increasing the effective heat transfer area can be greatly increased compared to the conventional case. In addition to the increase, it is possible to form an extremely thin refrigerant liquid film flow by increasing the surface tension, and it is possible to further improve the substantial heat transfer coefficient.

[Brief description of drawings]

FIG. 1 is a circumferential sectional view showing the shape of a boiling heat transfer tube in an embodiment of the present invention.

FIG. 2 is a plan view showing the shape of a heat transfer surface before the pipe making step in the process of manufacturing the boiling heat transfer tube shown in FIG.

3 is a cross-sectional view of the heat transfer surface taken along the line BB of FIG.

FIG. 4 is a circumferential sectional view showing the shape of a conventional boiling heat transfer tube.

5 is a plan view showing a heat transfer surface shape before a pipe making step in a process of manufacturing the boiling heat transfer tube shown in FIG. 4;

6 is a cross-sectional view of the heat transfer surface taken along the line AA in FIG.

FIG. 7 is a partial circumferential sectional view for explaining the groove shape dimension of the conventional boiling heat transfer tube.

FIG. 8 is a perspective view showing a heat exchanger using a conventional boiling heat transfer tube.

[Explanation of symbols]

8 boiling heat transfer tube 8a Inner surface of pipe 10 parallel grooves 11 inclined groove

Claims (3)

[Claims] 1. Boiling provided with parallel grooves continuous substantially parallel to the pipe axis direction at the top and bottom of the pipe inner peripheral surface, and inclined grooves continuous at an inclination with respect to the pipe axial direction at the side parts of the pipe inner peripheral surface. Heat transfer tube. 2. A groove on the inner peripheral surface of the pipe, the parallel groove continuing substantially parallel to the pipe axis direction, and the tilt groove continuing to incline with respect to the pipe axis direction, wherein the groove pitch is larger than the groove pitch of the parallel grooves. Boiling heat transfer tube with a large pitch. 3. The groove pitch of the parallel grooves is 0.15 to 0.25.
mm, and the boiling heat transfer tube according to claim 1 or 2, wherein the groove depth is limited to 0.15 to 0.25 mm.