JPH03254359A - Production of heat transfer tube for heat exchanger - Google Patents

Abstract

PURPOSE:To provide the high-performance heat transfer tube for heat exchangers by forming plural groove parts on the surface of a metallic strip blank material, depositing metallic particles and brazing material in the groove parts, heating the blank material to join the metallic particles and the metallic strip blank material to each other, forming the metallic strip blank material to a tubular shape, and butting and welding the ends. CONSTITUTION:The plural hollow groove parts 2a are formed on the surface of the continuously supplied metallic strip blank material 2. The metallic particles 8 and the brazing material 9 are deposited on this metallic strip blank material. The metallic particle and brazing material are heated as well when this metallic strip blank material is heated. After the brazing material melts once, the material solidifies to form secure and porous metallic particle layers on the bottoms of the groove parts. The metallic strip blank material is then formed to the tubular shape by forming rolls, etc., in such a manner that the groove parts are positioned on the inner side and the butt ends are welded to form the tube. The high-performance heat transfer tube for heat exchangers formed with the metallic particle layer on the inside surface of the tube is produced in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing heat exchanger tubes for heat exchangers used in evaporators, etc. of refrigeration and air conditioners.

[Prior Art] Conventionally, in order to improve the heat exchange performance of evaporators, etc. of refrigeration and air conditioners, a large number of heat exchanger tubes for use in the evaporators have been developed and mass-produced. In this heat transfer tube for a heat exchanger, heat exchange is performed by evaporation or boiling of the refrigerant flowing through the tube, so the following improvements are required to improve its heat transfer characteristics.

■ Expand the inner surface area of the tube.

■ Reduce heat transfer resistance by increasing flow turbulence.

■ Activates boiling on the inner surface of the tube.

■ Combine the measures from ■ to ■ as appropriate.

First, for heat transfer tubes that take measures against (■), heat transfer characteristics are improved by molding tall fins inside the heat transfer tube or installing fin material inside the heat transfer tube to expand the inner surface area of the heat transfer tube. There is something that made me However, in this case, the pressure loss of the refrigerant flowing through the tube is about 10 times that of a smooth tube with a smooth inner surface, which poses a problem in use.

A corrugated tube is an example of a heat transfer tube that takes measures for (2). This corrugated pipe causes large turbulence in the refrigerant flow, so
Heat transfer resistance is reduced and heat transfer characteristics are improved. However, even in this case, there is a problem in use because the pressure loss of the refrigerant flowing through the pipe is about five times that of a smooth pipe.

Furthermore, as a heat exchanger tube that takes the measure (2), there is one in which particles are sintered on the inner surface of the tube. This heat exchanger tube is a smooth tube with 5 to 1
Although it has 0 times the heat transfer characteristics, it is difficult to make the diameter smaller and the length longer, and there are problems in that the productivity is low and the manufacturing cost is high.

Therefore, in recent years, heat exchanger tubes having grooves formed on the inner surface have been manufactured in order to increase the inner surface area and increase the turbulence of the refrigerant flow.

In heat exchanger tubes with grooves formed on the inner surface of the tube, the inner surface area of the tube is expanded by approximately 1.5 times that of a smooth tube, but because the grooves are minute, the pressure loss is lower than that of a smooth tube. This is suppressed to about twice that in the case of . In addition, in this heat exchanger tube, the groove is formed to be twisted, for example, about 5 to 30 inches with respect to the tube axis, so the refrigerant flowing inside the tube swirls along this groove. , pressure loss is small, and its heat transfer characteristics are improved two to three times that of smooth tubes.Furthermore, this heat transfer tube can be manufactured continuously by machining, so it is possible to reduce the diameter and length of the tube. It is also possible to scale the heat exchanger tube.For this reason, this heat exchanger tube is used in many evaporators such as room air conditioners or refrigerators.

[Problems to be Solved by the Invention] However, in order to improve the performance of heat pumps such as evaporators, it is necessary to further improve the heat transfer performance of heat exchanger tubes for heat exchangers. In this case, there is a problem that heat transfer tubes with grooves formed on the inner surface of the tube have a limit to the improvement of heat transfer performance, and cannot fully meet the demand for higher performance heat pumps from the field where heat transfer tubes are used. There is a point.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a method for manufacturing a heat exchanger tube for a heat exchanger, which can be made smaller in diameter and longer, can reduce manufacturing costs, and can manufacture a heat exchanger tube with further improved heat transfer performance. purpose.

[Means for Solving the Problems] A method for manufacturing a heat exchanger tube for a heat exchanger according to the present invention includes a step of forming a plurality of grooves on the surface of a continuously supplied metal strip material, and at least one step of forming a plurality of grooves on the surface of a metal strip material that is continuously supplied. a step of depositing metal particles and a brazing material in the groove; and a step of heating the metal strip material to once melt the brazing material and then solidifying it to join the metal particles and the metal strip material to each other. The present invention is characterized by comprising the steps of forming the metal strip material into a tubular shape with the groove portion facing inside, and forming a pipe by welding the abutted ends of the formed body.

[Operations] The inventor of the present application has conducted various experimental studies in order to improve the heat transfer characteristics of the heat transfer tube by forming a structure on the inner surface of the tube in which the refrigerant actively boils. As a result, grooves are formed on the inner surface of the heat exchanger tube,
It has been found that heat transfer characteristics can be further improved by forming a particle layer in this groove, for example, with a thickness approximately half the depth of the groove. In addition, thermal spraying, sintering, and brazing are methods for forming this particle layer, but thermal spraying results in non-uniform particle sizes, and sintering requires a long sintering process and reduces productivity. It has the disadvantage of being bad. However, the inventor of the present application, for example, mixes a brazing material having a particle size smaller than the metal particles with the metal particles, deposits this mixture in the groove,
It has been found that an extremely strong metal particle layer can be quickly formed by once melting the brazing material and then solidifying it to bond the metal particles to the bottom of the groove.

The present invention has been made based on such knowledge, and first, a plurality of concave grooves are formed on the surface of a continuously supplied metal strip material. As this metal band material, a band-shaped plate made of metal with excellent thermal conductivity is used. Next, metal particles and a brazing material are deposited on the metal strip material in which the grooves are formed. For example, when a mixture of metal particles and brazing material is sprinkled onto a metal strip material, the metal particles and brazing material enter the groove due to vibrations while the metal strip material progresses to the next step. Since it is uniformly dispersed, it is not locally unevenly distributed on the metal strip material.

Further, the brazing material is preferably one having approximately the same density as the metal particles, such as a phosphorous brazing material for copper particles, and one having a particle size smaller than that of the metal particles, such as about 171O of the metal particles. is preferred. If such a brazing material is used, the brazing material will be mixed uniformly between the metal particles, and
During heating in the post-process, the brazing material melts in the gaps between the particles and in the gaps between the particles and the band material, and a particle layer is easily formed.

Next, the metal strip material to which the metal particles and brazing material are adhered is heated. In this case, the metal particles and the brazing material deposited in the groove are also heated, and when the brazing material once melts and solidifies, the metal particles and the metal strip material are bonded to each other and firmly attached to the bottom of the groove. A porous metal particle layer is formed.

Next, the metal strip material on which the metal particle layer has been formed is formed into a tube shape using a forming roll or the like so that the groove portion is on the inside, and the butted ends of this formed body are welded to form a tube. As a result, a heat exchanger tube for a heat exchanger in which the metal particle layer is formed on the inner surface of the tube is manufactured.

Therefore, in the heat exchanger tube manufactured by the method of the present invention, the grooves formed on the inner surface of the tube expand the inner surface area and widen the heat transfer surface, and the refrigerant swirls and flows inside the tube. Since the entire inside of the tube is wetted by the refrigerant, the heat transfer surface is effectively utilized. This results in
Improves heat transfer properties. Further, a porous metal particle layer is formed on the bottom surface of the groove, and the refrigerant actively boils in this metal particle layer, so that the heat transfer characteristics are further improved.

Furthermore, in the method of the present invention, heat exchanger tubes for heat exchangers with excellent heat transfer characteristics can be continuously manufactured by subjecting the continuously supplied metal strip material to the above-mentioned series of treatments. , it is possible to make the heat exchanger tube smaller in diameter and longer, and the manufacturing cost thereof can be reduced.

[Embodiments] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a manufacturing line for heat exchanger tubes in an embodiment of the present invention.

In the heat exchanger tube manufacturing line, an unwinding reel 1, a groove processing section 3, a particle hopper 4, a heating furnace 5, a roll forming section 6, and a welding machine 7 are arranged in the feeding direction of the metal strip 2. Then, the metal band 2 wound into a coil is attached to an unwinding reel 1, and the metal band 2 unwound from the reel 1 is supplied to the groove processing section 3 of the heat exchanger tube manufacturing line. .

In the groove processing section 3, a grooved roll 3a and a counter roll 3b are installed above and below the conveyance path of the metal strip 2, respectively, with their axes parallel to each other so as to sandwich the metal strip 2 from the upper and lower surfaces thereof. ing.

A plurality of grooves extending in a direction inclined with respect to the circumferential direction are formed on the circumferential surface of the grooved roll 3a.
No groove is formed on the circumferential surface of b.

Each of the grooved rolls 3a and the opposing rolls 3b is rotated in the direction in which the metal strip 2 is sent out by an appropriate drive device.

The particle hopper 4 is disposed above the metal strip 2 behind the groove processing section 3, and stores a mixture of metal particles 8 and brazing material particles 9. A predetermined amount of this mixture is cut out and applied to the surface of the metal strip 2. Sprinkle on top.

The heating furnace 5 is installed downstream of the particle hopper 4 so as to surround the metal band 2, and heats the metal band 2 passing through the furnace.

In the roll forming section 6, three pairs of forming rolls 8 having calibers are disposed along the conveyance path of the metal strip 2.
a, 6b+6c are arranged, and the metal strip 2 is curved around its longitudinal center line and formed into a tubular shape by passing through these rolls 6a to 6C.

The welding machine 7 is arranged behind the roll forming section 6. The metal strip 2 formed into a tubular shape in the roll-forming section 6 is welded at its butt ends while passing through the welding machine.

Next, a method of manufacturing a heat exchanger tube for a heat exchanger according to this embodiment using the above-mentioned manufacturing line will be described.

First, the tip of the metal band 2 unwound from the reel 1 is caught between the grooved roll 3a and the opposing roll 3b, and the grooved roll 3a and the opposing roll 3b are rotated in the feeding direction of the metal band 2 to form the metal band. 2 continuously. As a result, the groove shape of the circumferential surface of the grooved roll 3a is transferred to the surface of the metal band 2, and a plurality of grooves 2a in a direction inclined with respect to the longitudinal direction of the metal band 2 (FIGS. 2 and 3) are formed. ) is formed.

Next, metal particles 8 and brazing material particles 9 are transferred from the particle hopper 4.
A predetermined amount of the mixture is continuously cut out, and the metal particles 8 and brazing material particles 9 are sprinkled on the surface of the metal strip 2 in which the groove portion 2a is formed. These scattered particles are uniformly dispersed over the entire surface of the metal band 2 due to the vibration, and are deposited in the groove portion 2a. FIG. 2 is a partially enlarged sectional view showing the metal strip 2 with particles scattered thereon. As shown in FIG. 2, for example, if the brazing material particles 9 are of the same density as the metal particles 8 and have a smaller particle size than the metal particles, the gaps between the metal particles 8 and between the metal particles 8 and the surface of the groove 2a can be In between, the brazing material particles 9 are uniformly dispersed and deposited.

Next, the metal strip 2 with the metal particles 8 and the brazing metal particles 9 deposited in the groove 2a passes through a heating furnace 5 and is heated, and the brazing metal particles 9 are once melted. Then, when the metal strip 2 leaves the heating furnace 5, the molten brazing material solidifies, so that the metal particles 8 and the metal strip 2 are joined to each other by the brazing material. As a result, as shown in FIG. 3, a uniform and strong metal particle layer is formed on the metal band 2 with a thickness that is, for example, approximately half the depth of the groove portion 2a.

Next, the metal strip 2 is guided to the roll forming section 6,
The metal strip 2 is curved around its central axis in the longitudinal direction by forming rolls 6a, 6b, and 6c to form it into a tubular shape. After that, the metal strip 2 formed into a tubular shape is welded to a welding machine 7.
The butted ends of the metal strip 2 are welded to form a pipe. Thereby, it is possible to continuously manufacture a heat exchanger tube for a heat exchanger in which a spiral groove and a metal particle layer are formed on the inner surface.

In the heat exchanger tube manufactured by the method of this embodiment, as shown in FIG. 4, during use, the refrigerant 10 flowing through the tube forms vapor bubbles 11 on the surface of the metal particles 8 in the metal particle layer. Therefore, boiling of the refrigerant 10 can be promoted. Furthermore, since the heat transfer tube is manufactured by forming the metal strip 2 into a tubular shape, the groove portion 2a formed diagonally with respect to the feeding direction of the metal strip 2 forms a spiral shape inside the tube, as shown in FIG. None, it is possible to give the refrigerant 10 flowing through the pipe a swirling flow in the direction of the arrow in the figure.

Therefore, according to the method of this embodiment, the heat transfer characteristics of the heat exchanger tube for a heat exchanger can be further improved. In addition, since the formation of the groove portion 2a and the formation of the particle layer are performed on the flat metal strip 2, and the heat exchanger tube is manufactured by forming the tube after forming these, the diameter of the heat exchanger tube can be reduced and the length can be increased. In addition to being easy to manufacture, manufacturing costs can be reduced.

Next, the results of actually manufacturing copper heat exchanger tubes used in room air conditioners and the like using the method of this embodiment described above and evaluating their performance will be described.

First, a groove was formed on a copper plate material having a thickness of 0.5 m + m1 and a width of 30 mm. In this groove processing, the number of grooves is 50,
The depth of the groove was 0.4 vam, and the angle formed by the extending direction of the groove with respect to the feeding direction of the copper plate material, that is, the lead angle was 18°.

Next, copper particles with an average particle size of 50 μm and copper particles with an average particle size of 5 μm
Mixed particles prepared by mixing phosphorous copper wax particles with the number of particles at a mixing ratio of 1:1 were sprinkled on the copper plate material.

Thereafter, this copper plate material is heated, and the phosphor copper wax particles are once melted and then solidified to form a thickness of about 0.15 m+ on the copper plate material.
A positive copper particle layer was formed.

Furthermore, this copper plate material was formed into a tube shape, and the butted ends were welded to obtain a heat exchanger tube for a heat exchanger having an inner diameter of 9.52 m. This heat exchanger tube was designated as Example 1.

Further, a heat exchanger tube made of a copper smooth tube having the same inner diameter as in Example 1 was designated as Conventional Example 1.

The test tube length of the heat transfer tubes according to Example 1 and Conventional Example 1 was set to 5000 mm, and Freon R22 with an evaporation temperature of 7°C was used as the refrigerant flowing inside the tubes, and the film heat transfer performance in the tubes was evaluated. Measured and comparatively evaluated.

The inlet temperature of the refrigerant is 7°C, and the flow rate is 50k.
g/hour.

As a result, in Example 1, the degree of superheat of the refrigerant at the heat transfer outlet was 5 degrees. This shows a heat transfer efficiency approximately seven times higher than that of Conventional Example 1, which was measured in the same manner. In other words, with conventionally used heat transfer tubes in which grooves are formed on the inner surface of the tube, the heat transfer performance can only be improved by about 2 to 3 times compared to smooth tubes, but according to this example, As mentioned above, it is possible to continuously manufacture heat transfer tubes with extremely superior heat transfer performance than conventional grooved tubes.

In addition, when the heat exchanger tube according to this embodiment is used in a small air conditioner such as a room air conditioner, for example, a long heat exchanger tube with an inner diameter of 6.35 to 9.52 m++ and a length of 1000 to 2000 m is used. Manufacturing costs can be reduced by cutting the pieces into pieces of 1 to 2 m each.

[Effects of the Invention] As explained above, according to the present invention, after forming grooves on the surface of a metal strip material and further forming a porous metal particle layer, this metal strip material is processed into a tubular shape. a groove portion capable of imparting turbulence such as a swirling flow to the refrigerant flowing through the pipe;
It is possible to manufacture a high-performance heat exchanger tube that has a synergistic effect with the metal particle layer that can promote boiling of the refrigerant.

Therefore, if this heat exchanger tube is used, the heat exchange performance of a heat pump or the like can be further improved.

Furthermore, in the method of the present invention, it is possible to make the tubes smaller in diameter and longer, and continuous production is possible, so the manufacturing cost of heat exchanger tubes for heat exchangers can be reduced.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a manufacturing line for heat exchanger tubes according to an embodiment of the present invention, Fig. 2 is a partially enlarged cross-sectional view showing a metal strip material with particles dispersed thereon, and Fig. 3 is a perspective view showing a manufacturing line for heat exchanger tubes according to an embodiment of the present invention. Partially enlarged sectional view showing the metal strip material with layers formed, No. 4
The figure is a partially enlarged cross-sectional view showing the boiling of the refrigerant in the metal particle layer, and FIG. 5 is a cross-sectional view showing the usage characteristics of the heat exchanger tube manufactured by the method of this embodiment. 1; unwinding reel, 2: metal band, 2a; groove section, 3; grooved section, 3a; grooved roll, 3b; opposing roll, 4: particle hopper, 5: heating furnace, 6; roll forming section,
6at 6b+ 8c; forming roll, 7;
welding machine, 8; metal particles, 9; brazing metal particles, 10; refrigerant,
11; Steam bubbles Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) A step of forming a plurality of grooves on the surface of a continuously supplied metal strip material, a step of depositing metal particles and a brazing material in at least the grooves of the metal strip material, and a step of depositing metal particles and a brazing material in at least the grooves of the metal strip material. a step of heating to once melt the brazing material and then solidify it to join the metal particles and the metal strip material to each other; a step of forming the metal strip material into a tubular shape with the groove portion inside; 1. A method for manufacturing a heat exchanger tube for a heat exchanger, comprising the step of welding butt ends of molded bodies to form a tube.