JPH09126589A - Heat transfer pipe for heat absorber and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure good heat transfer properties and wetting properties of an absorption solution as well as high heat transfer efficiency by forming an acute angle between the side of a corrugated fin and an internal wall surface of a pipe to be processed, and further forming a spiral groove having a wedge shaped cross section. SOLUTION: There are provided a fin 3 which is formed into a spiral shape along an internal wall surface 2 of a pipe 1 to be processed and has a corrugated shape in the spiral direction, and a spiral groove 4 that forms a wedge shaped cross section with the internal wall surface 2 and the side of the fin 3. The fin 3 has a predetermined inclination angle with respect to the internal wall surface 2. An absorption solution is stirred with the corrugated fin 3 upon its flowing along the spiral groove 4, and the stirring action is produced owing to a change in a flow passage cross section in the spiral direction owing to the corrugated shape of the fin 3, and hereby absorption capability of heat is improved. Accordingly, there are ensured excellent heat transfer properties and good wetting properties of the asorption solution together with high heat transfer efficiency.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat transfer tube for a heat absorber, and more particularly to a heat transfer tube used in an absorber of an air-cooled absorption refrigerator.

[0002]

2. Description of the Related Art Generally, an absorber of an absorption refrigerating machine is constructed by arranging a large number of heat transfer tubes horizontally or vertically in a closed container. In such an absorber, for example, an absorption solution of lithium bromide is dropped or sprayed from the upper part of the closed container on the outside of the heat transfer tube to absorb the water vapor generated in the evaporator, and at the same time, to cool water in the heat transfer tube. The water-cooled type, which removes the heat generated during absorption, is the mainstream.

Recently, there is a tendency toward air-cooling of equipment, and the advent of an air-cooling type is also desired in the absorber. In the case of the air-cooled type, the heat transfer tube is used in a vertical type, and the absorption liquid dropped as a falling liquid film on the inner wall of the tube absorbs the heat of the refrigerant vapor introduced into the tube and prevents the temperature rise due to the absorption heat.
The outside of the tube where the fins are attached is forcibly cooled by a fan. Therefore, this type of heat transfer tube is required to improve both heat transfer and mass transfer in which absorbed water (steam) diffuses throughout the absorption liquid.

Conventionally, as the heat transfer tube for the heat absorber, a tube having a grooved inner surface, a flat plate having a heat transfer wall having a special shape processed and welded in a tube, or a smooth tube having a spring inserted therein is used. Has been done.

[0005]

However, according to the conventional heat transfer tube for heat absorber, there is a limit to the processing of the inner wall surface of the pipe to be processed by cutting or the like, or the process of inserting a member for improving the heat transfer property into the pipe to be processed. Therefore, there is a problem that it is particularly difficult to improve the heat transferability of the heat transfer tube and the wettability of the absorbing liquid, which are desired to be compatible when applied to an air-cooled refrigerator.

In a heat transfer tube having a smooth inner wall, the absorbing liquid forms a liquid film on the wall of the heat transferring tube and flows down as a laminar flow, so that heat transfer from the absorbing liquid to the heat transferring tube mainly depends on conduction. In addition, the movement of the water absorbed on the surface of the liquid film largely depends on the diffusion, and the efficiency of the absorbing solution is poor.

On the other hand, the inner grooved pipe is limited in fin height, the number of fins, and the angle formed by the fin and the pipe axis, so that improvement in absorption capacity cannot be expected. Furthermore, welded pipes have problems in pressure resistance of the joint and reliability in long-term use. The spring insertion tube has drawbacks such as increased thermal resistance with the tube wall. Therefore, an object of the present invention is to provide a heat transfer tube for a heat absorber, which has excellent heat transferability, good wettability of an absorbing liquid, and high heat transfer efficiency, and a method for manufacturing the same.

[0008]

The present invention has excellent heat transfer properties, good wettability of absorbing liquid, and high heat transfer efficiency. A corrugated fin provided to be inclined in a predetermined direction,
Provided is a heat transfer tube for a heat absorber having a spiral groove having an acute angle formed by the side surface of the corrugated fin and the inner wall surface and having a wedge-shaped cross section.

The present invention also provides a method for manufacturing the heat transfer tube for a heat absorber, wherein a cutting tool having a sharp cutting blade is inserted inside a pipe to be processed and the cutting blade is rotated to form an inner wall surface of the pipe to be processed. By forming a primary processing tube with spirally continuous fins along the edge, and reducing the outer diameter by subjecting the primary processing tube to contraction processing, the spirally continuous fins along the inner wall surface are deformed into a wavy shape. To form a corrugated fin and incline in a predetermined direction with respect to the inner wall surface, the side surface of the corrugated fin and the inner wall surface form an acute angle, and further, an inner surface groove having a wedge-shaped cross section is formed. A method for manufacturing the same is provided.

According to the present invention, the heat-absorbing area of the fin is increased by forming the continuous fin along the inner wall surface of the pipe to be processed into a corrugated shape. Further, the side surface of the corrugated fin and the inner wall surface of the pipe to be processed form an acute angle, and a spiral groove having a wedge-shaped cross section is formed, so that the absorbing liquid easily infiltrates into the groove portion and the wettability of the inner wall surface is improved. Is improved. The corrugated shape and the spiral groove of the fin are formed by plastic deformation when the primary processing pipe in which the fin is previously formed by cutting inside the pipe to be processed is contracted.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a heat transfer tube for a heat absorber and a method for manufacturing the same according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a heat transfer tube for a heat absorber according to an embodiment of the present invention. As shown in FIG. 1 (a), the heat transfer tube is formed in a spiral shape along an inner wall surface 2 of a pipe 1 to be processed. The fin 3 has a corrugated shape in the spiral direction, and the spiral groove 4 forms a wedge-shaped cross section by the inner wall surface 2 and the side surface of the fin 3. The fins 3 are given a predetermined inclination angle with respect to the inner wall surface 2.

FIG. 1 (b) is a sectional view of the fin 3 taken along the line bb in FIG. 1 (a), where the fin 3 is a crest 3a.
And the valleys 3b are alternately continuous.

The heat transfer tube for the heat absorber having the above structure is
As shown in FIG. 1, the fins 3 are used by vertically arranging them so that the tips of the fins 3 face upward. In this state, the refrigerant vapor is guided into the pipe, and when the absorbing liquid is flown into the pipe from above, the refrigerant is dropped along the inner wall surface 2 and held in the spiral groove 4.

The absorbing liquid is agitated by the corrugated fins 3 as it flows along the spiral groove 4. This stirring action occurs when the flow passage cross section in the spiral direction changes due to the corrugation of the fins 3, and improves the heat absorption capacity.

The method of manufacturing the heat transfer tube for the heat absorber will be described below. First, as shown in FIG. 2, the inner wall surface 2
The mandrel rod 6 having the processing bite 5 at the tip of which causes the spade is inserted into the pipe 1 to be processed, and the mandrel rod 6
By rotating the to-be-processed pipe 1 and moving the pipe 1 to be processed in the direction of A in the figure, a primary pipe having the fins 3 and the spiral groove 4 is formed.

Next, the outer diameter is reduced by pulling out the above-mentioned primary processing pipe with, for example, a die. At this time, the fins formed inside the primary processing pipe are plastically deformed in the spiral direction into a corrugated shape, and the corrugated fins are inclined based on the drawing. The inclination angle of the protrusion is arbitrarily set according to the workability of the fin and the drawing speed. By thus inclining the fin, a wedge-shaped spiral groove having an acute angle is formed between the side surface and the inner wall surface.

As described above, in the heat transfer tube of the present invention, the fins formed in the tube have a heat absorption area enlarged by forming a corrugation in the spiral direction. Further, the fins raised by the processing tool are inclined in a predetermined direction to form a spiral groove having a wedge-shaped cross section with the inner wall surface, which enhances the retention of the absorbing liquid and the corrugated fins. When the absorbing liquid flows down along the stirrer, a stirring action occurs and the absorbing ability of the absorbing liquid can be enhanced.

[0019]

As described above, according to the heat transfer tube for a heat absorber of the present invention, the corrugated fins which are spirally continuous along the inner wall surface of the tube and are inclined in a predetermined direction with respect to the inner wall surface are provided. Since the spiral groove having a wedge-shaped cross section formed by the side surface of the corrugated fin and the inner wall surface has an acute angle, the heat transfer property is excellent and the wettability of the absorbing liquid is good, and high heat transfer efficiency is provided. be able to.

Further, according to the method for manufacturing a heat transfer tube for a heat absorber of the present invention, a cutting tool having a sharp cutting blade is inserted inside the pipe to be processed, and the cutting blade is rotated to move along the inner wall surface of the pipe to be processed. By forming a primary processing pipe having spirally continuous fins and reducing the outer diameter by subjecting the primary processing pipe to a contraction process, the spirally continuous fins along the inner wall surface are deformed into a wavy shape. Since the corrugated fins are formed and inclined in a predetermined direction with respect to the inner wall surface, the side surfaces of the corrugated fin and the inner wall surface form an acute angle, and further the inner surface groove having a wedge-shaped cross section is formed, so that heat transfer is performed. In addition to excellent properties, the wettability of the absorbing liquid is good, and high heat transfer efficiency can be imparted.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a heat transfer tube for a heat absorber of the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of a heat transfer tube for a heat absorber.

[Explanation of symbols]

 1 Pipe to be processed 2 Inner wall surface 3 Fin 3a Mountain 3b Valley 4 Spiral groove 5 Machining tool 6 Mandrel rod

Claims (2)

[Claims] 1. A corrugated fin that is spirally continuous along an inner wall surface of the pipe and is inclined with respect to the inner wall surface in a predetermined direction, a side surface of the corrugated fin, and the inner wall surface. A heat transfer tube for a heat absorber, comprising a spiral groove having an acute angle and a wedge-shaped cross section. 2. A primary tool having a fin which is spirally continuous along the inner wall surface of the pipe to be processed by inserting a cutting tool having a sharp cutting blade into the pipe to be processed and rotating the cutting blade. Forming a working pipe, reducing the outer diameter by subjecting the primary working pipe to a shrinking process, thereby deforming the fin continuously spirally along the inner wall surface into a corrugated fin and forming the corrugated fin. A heat transfer tube for a heat absorber characterized by being inclined in a predetermined direction with respect to an inner wall surface, a side surface of the corrugated fin and the inner wall surface forming an acute angle, and further forming an inner surface groove having a wedge-shaped cross section. Production method.