JPH04313420A - Manufacture of inside surface grooved heat exchanger tube - Google Patents

Abstract

PURPOSE:To form the uniform fin of >=0.3mm height on the surface of a metallic band plate with high operability by grooving, and accordingly, to efficiently manufacture the inside surface grooved heat exchanger tube provided with a heat transfer performance of a higher level than a conventional. technique. CONSTITUTION:In the method for obtaining the inside surface grooved heat exchanger tube by performing grooving to one face through A grooving roll on which an inclined groove is carved and provided, while feeding a metallic band plate, forming it to a tubular body, and thereafter, executing butt welding to both end edges, this method constitutes a characteristic feature of using the grooving roll in which the bottom part of the curved and provided groove has a square cross section, and executing grooving to a fin 10 form in which the tip 13 is a plane and the cross section 14 is roughly trapezoidal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a heat exchanger tube having an inner grooved structure for use in heat transfer devices such as evaporators and condensers.

0002

[Prior Art] Conventionally, in a heat transfer device involving boiling and condensation, a copper material with a spiral groove of fine uneven fins formed on the inner surface has been used as a heat transfer tube with high heat transfer efficiency and low pressure loss. There is. As a means of efficiently manufacturing this type of internally grooved heat exchanger tube, a metal strip plate is formed into a tube shape with the grooved surface facing inside, leaving flat portions at both ends, and then the butt portions The applicant has developed a method for welding the
Publication No. 1).

Furthermore, the present inventors have further improved the above-mentioned manufacturing technique and have proposed a method for manufacturing a heat exchanger tube in which symmetrical inclined grooves are formed on the surface of a metal strip (Japanese Unexamined Patent Publication No. 2-108).
Publication No. 411). In this method, for example, as shown in FIG. 5, grooves are symmetrically carved on one side of a metal strip 1 through two grooving rolls 2 and 3 with different inclination directions. forming inclined grooves 4 with a fin pattern,
Subsequently, the tube is cut by a slitter 5 and bent by a plurality of forming rolls 6, then the butted portions are welded by a welder 7, and finally drawn by a drawing machine 8 to form a heat exchanger tube 9 with internal grooves. It consists of the process of obtaining

Conventionally, the grooves formed in the above-mentioned internally grooved heat exchanger tube have fins 10 in the shape of protrusions with a triangular cross section, as shown in FIG. : 0.3~0.5mm, height H: 0.1~0.
25mm, inclination angle θ: 30~60°, base width W: 0
．． It has dimensions of 1 to 0.3 mm. However, in general, the heat transfer coefficient during heat exchange involving evaporation and condensation tends to increase as the fins become taller until a certain stage.
If the fin height can be formed to be 0.25 mm or more, it is possible to improve heat transfer performance.

[0005]

However, it is extremely difficult to form the triangular shaped fins shown in FIG. 6 and the height of the fins at the stage of manufacturing the grooving roll. That is,
The production of the grooving roll is as shown in FIG.
2. However, since the tip of the grinding wheel wears out relatively easily, when trying to form deep grooves, the width of the root with the tip crushed as shown in Figure 8 is used. It becomes easier to form a wide carved groove of W. This phenomenon can be prevented by frequently replacing the grinding wheel during groove formation, but this will reduce work efficiency and cause significant economic loss. The problem arises that uniform grooves cannot be formed due to variations in depth, width, etc. Therefore, the depth of molding is about 0.25 mm.

The present invention was developed to solve the above problems, and its purpose is to provide a method for manufacturing an internally grooved heat exchanger tube that can smoothly form uniformly shaped fins with a height of 0.3 mm or more. Our goal is to provide the following.

[0007]

[Means for Solving the Problems] A method for manufacturing an internally grooved heat exchanger tube according to the present invention to achieve the above object is to feed a metal strip through a grooving roll in which inclined grooves are carved. In the method of obtaining a heat transfer tube with internal grooves by grooving one side, forming it into a tubular body, and then butt welding both end edges, a grooving roll in which the bottom of the engraved grooves has a square cross section is used. The structural feature is that the tip is flat and grooved in the form of a fin with a substantially trapezoidal cross section.

Copper or aluminum is effectively used as the material for the metal strip from the viewpoint of workability, heat conductivity, etc. Similar to the prior art, grooving is performed by passing a metal strip continuously fed from a raw material coil between a grooving roll with slanted grooves and a lower roll with a smooth surface. .

[0009] In the present invention, it is necessary to use a grooving roll used in the grooving process in which the bottom of the engraved grooves has a rectangular cross section. The grooving roll is shown in FIG.
As shown in the figure, grooves are formed on the roll 11 by grinding with a grinding wheel 12 having a slightly tapered rectangular tip that follows the shape of the fin to be formed. However, since the tip is square, the grindstone is extremely susceptible to wear. Even if the groove is cut small and deep, a groove with a uniform root width W is always formed. Therefore, it is possible to process and form uniform grooves with a square bottom section and a depth of 0.3 mm or more with good workability.

By performing groove processing using the above-mentioned grooved roll, grooves having a fin shape with a flat tip 13 and a substantially trapezoidal cross section 14 are formed on the surface of the metal strip 1, as shown in FIG. engrave. At this time, at the bottom of the groove between each fin, a recess 15 (depth 0.02 to 0.1
If the fins are designed to a specification that forms a fin of approximately 2 mm, the processed material will easily flow into the carved grooves, making it possible to form even taller fins.

[0011] The preferred shape and dimensions of the fin formed in the present invention, which has a flat tip and a substantially trapezoidal cross section, is a height H 0.3.
~ 0.5mm, pitch P 0.3-0.5mm, root width W 0.2-0.3mm, and inclination angle θ of 10° or less to achieve high heat transfer in heat transfer tubes with an inner diameter of 4-12.7mm. Demonstrate performance. In this case, if the height H of the fins is less than 0.3 mm, the heat transfer coefficient will be low, and if it exceeds 0.5 mm, the pressure loss on the refrigerant side will increase, which is disadvantageous in practice. When the pitch P is less than 0.3 mm, the capacity of the refrigerant liquid decreases, and when it exceeds 0.5 mm, the heat transfer area becomes small, and in either case, the performance deteriorates. Also, the root width W is 0
．． If the thickness is less than 2 mm, it will be difficult to make a roll, and if the thickness is less than 0.3
If it exceeds mm 2 , the amount of refrigerant liquid stored will decrease, leading to a decrease in performance. Incidentally, the provision of an inclination angle θ is a necessary design item for processing, but an inclination exceeding 10° is unnecessary.

[0012] The step of forming the tubular body is carried out by bending the grooved metal strip with a plurality of forming rolls with the processed surface facing inside. Then, the abutting portions of both ends are welded using a welding method such as TIG welding, MIG welding, electron beam welding, or high frequency welding. The tubular body after welding is finally subjected to drawing processing to obtain a heat exchanger tube having an inner grooved structure with a constant slope pattern.

[0013]

[Function] The grooving roll used in the present invention has a square cross-section at the bottom of the engraved grooves, and when forming the engraved grooves, instead of using a conventional grinding wheel with a sharp triangular tip, the grooving roll has a square tip with a flat surface. Since this is carried out using a grinding wheel, uniform and deep grooves can be formed without causing wear on the tip of the grinding wheel. Therefore, the workability of producing the grooved roll is significantly improved.

The fins formed using the above-mentioned grooving roll have a flat tip and a substantially trapezoidal cross section, and have a height of 0.3 mm or more, which was considered impossible to form with conventional fin shapes having a triangular cross section. This makes it possible to smoothly process and form fins. Therefore, the heat transfer performance of the resulting heat transfer tube is significantly improved, and the fin tips are not easily crushed when expanding the tube by inserting an inner plug, so there are effects such as no deterioration of heat transfer performance. It will be done.

[0015]

[Example] Example While feeding a metal strip made of phosphorus-deoxidized copper with a width of 31 mm and a thickness of 0.6 mm, a metal strip with a diameter of 100 mm and a width of 40 m is
A grooving roll with a number of 50 grooves, which has an inclination angle of 17° with respect to the running direction of the groove, and has a square cross section at the bottom of the engraved groove (
(5mm on each side is a smooth part) was used to perform groove processing under the condition of a load of 5 tons, and the fin dimensions were pitch P0.4mm,
Fin height with base width W0.3mm and inclination angle θ5°
Slanted grooves varying in width from 0.1 to 0.5 mm were formed. Next, the grooved metal strip was bent through three stages of forming rolls, the butted parts were welded, and finally it was drawn using a drawing machine to form an internally grooved heat exchanger tube with an inner diameter of 9.52 mm. Manufactured.

For each heat exchanger tube manufactured in this way,
The heat transfer coefficient was measured at a mass velocity of 200 kg/m2s. The results are shown in FIG. 4 as a graph of the relationship between fin height and heat transfer coefficient. From the graph in Figure 4, the heat transfer coefficient of each heat transfer tube during evaporation and condensation increases with the height of the fins, and when the fin height is 0.5 mm, it is 6.9 kW/m during evaporation.
2K, and showed a high heat transfer coefficient of 4.5kW/m2K upon condensation.

Comparative Example While feeding the same metal strip as in the example,
mm, width 40 mm, triangular grooves (50 grooves) with a 17° inclination angle to the running direction of the strip using a grooving roll (5 mm smooth sections at both ends) under the condition of a load of 5 tons. The fin dimensions are pitch P0.4mm.
, base width 0.3mm, slope angle 40°, height 0
．． Slanted grooves with triangular cross sections ranging from 1 mm to the forming limit of 0.25 mm were formed. Then, as in the example, bending,
A heat exchanger tube with an inner diameter of 9.52 mm was manufactured by performing welding and drawing processes.

For each heat exchanger tube manufactured in this way,
The heat transfer coefficient was measured at a mass velocity of 200 kg/m2s. The results are also shown in FIG. 4 as a graph of the relationship between fin height and heat transfer coefficient. In this case, when the fin height is 0.25 mm, which is the molding limit, the fin height is 5.5 mm during evaporation.
kW/m2K, and the heat transfer coefficient during condensation was only 3.5 kW/m2K, which was recognized as a lower heat transfer performance than that of the example with a fin height of 0.3 mm.

[0019]

[Effects of the Invention] As described above, according to the present invention, a grooving roll having a rectangular cross-section at the bottom, which facilitates grinding of grooves, is used, and a grooving roll having a height of 0.3 mm or more and having a flat tip and a substantially trapezoidal cross-section is used. It becomes possible to form uniform fins on the metal strip surface by groove processing with good operability. Therefore, it is possible to efficiently manufacture an internally grooved heat exchanger tube having higher heat transfer performance than conventional techniques.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram (partial sectional view) showing a state in which grooves are formed by a grooving roll used in the present invention.

FIG. 2 is a partially enlarged sectional view showing a fin form formed by the present invention.

FIG. 3 is a partially enlarged sectional view showing another fin form formed by the present invention.

FIG. 4 is a graph showing the relationship between fin height and heat transfer coefficient in Examples.

FIG. 5 is a perspective explanatory view showing a heat exchanger tube manufacturing apparatus using a conventional mechanism.

FIG. 6 is a partially enlarged sectional view showing a conventional triangular fin shape.

FIG. 7 is an explanatory diagram (partial sectional view) showing a state in which grooves are formed by a conventional grooving roll.

FIG. 8 is an explanatory diagram (partial cross-sectional view) showing a state in which grooves are formed by a conventional grooving roll.

[Explanation of symbols]

1 Metal strip 2 Grooving roll 3 Grooving roll 4 Slanted groove 5 Slitter 6 Forming roll 7 Welding equipment 8 Drawing machine 9 Heat exchanger tube 10 Fin 11 roll 12 Grinding wheel 13 Tip 14 Approximately trapezoidal cross section 15 Recess P Fin pitch H Fin height W　Fin base width θ　Fin inclination angle

Claims (1)

[Claims] [Claim 1] Grooving is performed on one side of the metal strip using a grooving roll with slanted grooves carved thereon while feeding the plate, and after forming this into a tubular body, both ends are butt welded to form the inner surface. A method for forming a grooved heat exchanger tube, which uses a groove roll having a square cross section at the bottom of the groove, and grooves the heat exchanger tube into a fin shape with a flat tip and a substantially trapezoidal cross section. Production method.