JP2004268115A - Method of manufacturing heat transfer coil for heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of heat transfer coils for heat exchangers, which causes no deformation of a heat transfer tube when fitting plate fins, achieves high heat transfer coefficient through high degree of adhesion between the plate fin and the heat transfer tube, and requires low manufacture cost due to few manufacturing steps. <P>SOLUTION: A plurality of metal plate fins 1 are arrayed backward and forward to fit in each engaging hole 3 for inserting a tube 4 to compose a plate fin group 1A, and a stainless steel tube 4, which has a little smaller outer diameter than that of the engaging hole of the plate fin, is inserted into the engaging hole of the plate fin group, and the back edge of the tube is closed with a sealing body 5 and the front edge is attached with a nozzle 7, and a fluid is pressed into the tube from the nozzle to expand a tube diameter and thereby the tube is attached and fitted to the inner surface of the engaging hole of the plate fin. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a heat transfer coil for a heat exchanger such as a cooling or heating coil of an air conditioner, and more particularly to a method of manufacturing a heat transfer coil suitable for cooling or heating a corrosive fluid.
[0002]
[Conventional technology and its problems]
Conventionally, there are cooling / heating coils with stainless steel heat transfer tubes and aluminum or stainless steel heat radiating plate fins attached to them.The fins have fitting holes that are slightly smaller than the outer diameter of the tubes. A coil is manufactured by press-fitting the fitting hole to the outer periphery of the tube and closely contacting the inner periphery of the fitting hole and the outer peripheral surface of the tube. Note that this manufacturing method has conventionally been generally performed, and is not described in a specific technical document.
[0003]
In the above-described conventional manufacturing method, a large number of fins, which may be several thousands of tubes, are arranged in parallel and fitted one by one, so that the work is time-consuming, and the force required to fit the fitting holes of the fins into the tube is increased. Hangs on the tube and deforms the tube, and the deformation of the tube causes uneven contact between the tube and the fins, which may lower the heat transfer coefficient or scratch the surface of the tube and cause corrosion. There is.
[0004]
Further, in order to minimize the deformation of the tube as described above, the wall thickness of the tube must be 1.0 mm or more, which causes a problem that the weight of the entire coil increases and the material cost increases. .
[0005]
Further, in the case of a stainless steel tube conventionally used as a heat transfer tube, for example, a tube made of SUS304, grain boundary corrosion is easily generated due to heating at the time of welding a bend tube and cold working at the time of tube manufacture, There is also a problem that the life of the coil is short.
[0006]
By the way, when a copper tube is used, the fitting hole of the fin is slightly larger than the tube, and the tube is inserted into the fitting hole. There is a fluid expansion method in which the outer circumference of the tube is brought into close contact with the inner circumference of the fin fitting hole and fixed by expanding the tube by pressure. This method requires a small number of steps and has good adhesion between the tube and the fin. Therefore, there is an advantage that the heat transfer coefficient is large (for example, see Patent Document 1).
[0007]
However, copper tubing has a low hardness, so that hydraulic expansion can be easily performed.However, there is a problem that the corrosion resistance is not sufficient and it cannot be used for heat exchange of corrosive fluids. Since the hardness of the tube is large, there is a problem that the hydraulic expansion is difficult.
[0008]
[Patent Document 1]
Japanese Patent No. 2916451 (pages 4 to 5, FIG. 5)
[0009]
【Purpose】
An object of the present invention is to prevent the heat transfer tube from being deformed when the plate fin is attached, to provide a high degree of adhesion between the plate fin and the heat transfer tube, to have a large heat transfer coefficient, and to reduce the number of manufacturing steps. It is an object of the present invention to realize a method of manufacturing a heat transfer coil for a heat exchanger which can be manufactured at low cost.
[0010]
Configuration of the Invention
In order to achieve the above object, the method of the present invention is to arrange and set a large number of metal plate fins in which a large number of fitting holes for tube insertion are regularly formed so that the fitting holes of each metal coincide with each other. The stainless steel tube whose front and rear ends are open and whose outer diameter is slightly smaller than the fitting hole of the plate fin is inserted through the fitting hole of the plate fin group. A nozzle is attached to the front end of the opening while the nozzle is closed, the fluid is pressed into the tube from the nozzle by pressing the nozzle and the seal, and the tube is expanded in diameter. After crimping and fixing to the tube, remove the nozzle and seal from the tube, fix the tube in each fitting hole, and connect the front end and rear end of the tubes to be connected. Some as structure connecting with bent pipe.
[0011]
In addition, the tube fitting hole of the plate fin is formed by the inner surface of a cylindrical body in which the plate fin is extruded to one side, and the plate fin fitting hole cylindrical body is configured to have an enlarged-diameter flange at a tip end.
[0012]
Further, the stainless steel tube has a wall thickness of 0.6 mm or less, a Vickers hardness of 140 HV or more and 155 HV or less by heat treatment at the time of tube production, and a carbon content of 0.01 to 0. 0.03 wt%.
[0013]
【Example】
Hereinafter, embodiments of the method of the present invention will be described in detail based on specific examples shown in the accompanying drawings.
As shown in FIGS. 1 and 2, the plate fin 1 in the method of the present invention has a large number of fitting holes 3, 3 for tube insertion in the plate 2 in a regular manner. Is formed on the inner surface of a cylindrical body 3a extruded on one side, and has a diameter-enlarged flange 3b at the tip of the cylindrical body. The plate fin 1 is made of, for example, aluminum or stainless steel.
[0014]
A large number of the plate fins are arranged and set back and forth so that the fitting holes of each plate coincide with each other, and constitute a plate fin group 1A as shown in FIG. This group of plate fins aligns the fitting holes by arranging a large number of plate fins back and forth and fixing them with a jig, and specifically, fitting holes of two diagonal corners, for example, a right and a top. A plurality of plate fins are arranged and set by inserting a rod for temporary fixing into the fitting hole located at the lower left.
[0015]
At this time, the enlarged diameter flange 3b of the cylindrical body 3a constituting the fitting hole 3 of each plate fin abuts around the fitting hole of the adjacent plate fin, and serves as a spacer for separating the plate fins at a predetermined interval, Therefore, it is not necessary to interpose a spacer between the plate fins.
[0016]
Next, a stainless steel heat transfer tube 4 whose outer diameter is slightly smaller than the inner diameter of the fitting hole 3 of the plate fin is inserted through each fitting hole to penetrate the plate fin group 1A, and is shown in FIG. The rear end of the opening of the tube is closed with a sealing body 5 so that the tube is closed.
[0017]
In addition, the sealing body 5 has an O-ring 6 for sealing around a shaft portion 5a inserted into the tube, and a base portion is formed with a flange portion 5b abutting on the rear end edge of the tube.
[0018]
The tube 4 has a wall thickness of 0.6 mm or less and a carbon content of 0.01 to 0.03 wt%, and has a Vickers hardness of 140 HV or more and 155 HV or less by heat treatment at the time of manufacturing the tube.
[0019]
The reason why the wall thickness is set to 0.6 mm or less is that if the wall thickness is larger than 0.6 mm, it becomes difficult to perform the hydraulic expansion described later, and the lower limit of the wall thickness depends on the purpose of use of the coil and the required strength. It is determined as appropriate.
[0020]
Further, the reason why the carbon content is set to 0.01 to 0.03 wt% is that if the carbon content is less than 0.01 wt%, the production technology becomes sophisticated, the cost becomes large, and the carbon content is larger than 0.03 wt%. This is because the heat of welding at the time of connection of the bend pipe described later causes grain boundary corrosion in the metal structure and shortens the life of the coil.
[0021]
Further, when the Vickers hardness is 140 HV or more and 155 HV or less, if the hardness is less than 140 HV, the strength of the tube is reduced, and depending on the usage environment of the coil, there is a possibility that the internal pressure at the time of using the coil may not be able to be sufficiently endured. If the hardness is greater than 155 HV, it will be difficult to perform the hydraulic expansion described later.
[0022]
The gap α between the outer circumference of the tube 4 and the inner circumference of the fitting hole 3 is appropriately determined depending on the outer diameter and the wall thickness of the tube. For example, when the outer diameter of the tube is 15.2 mm and the wall thickness is 0.4 mm, The gap α is 0.5 mm, and the inner diameter of the fitting hole is 16.2 mm.
[0023]
Next, a nozzle 7 is attached to the opening front end of the tube 4 whose rear end is closed by a sealing body 5, and a fluid is pressed into the tube from the nozzle with the sealing body 5 held down, and the tube is pressed by the pressure of the fluid. The outer diameter of the tube is increased, and the outer peripheral surface of the tube is pressed and fixed to the inner surface of the fitting hole 3 of the plate fin 1.
[0024]
Since the fitting hole 3 of the plate fin 1 is formed by the inner surface of the cylindrical body 3a integral with the plate 2, the contact area with the outer periphery of the tube is large and the heat transfer efficiency between the tube and the plate fin is good. It has become something.
[0025]
The nozzle 7 has an O-ring 8 for sealing around a shaft portion 7a inserted into the tube as in the case of the sealing body 5, and has a base portion formed with a flange portion 7b abutting on the front end edge of the tube. The only difference is that the flow path 9 for the press-fitting fluid is formed in the axial direction.
[0026]
For example, water is used as the fluid to be pressed into the tube, and when a tube having an outer diameter of 15.2 mm and a wall thickness of 0.4 mm is attached to the fitting hole 3 having an inner diameter of 16.2 mm as described above, It is preferable to expand the tube by applying a water pressure of 14 to 30 MPa.
[0027]
After the tube is expanded and fixed in the fitting hole, the sealing body 5 and the nozzle 7 are removed from the tube, and the sealing body 5 and the nozzle 7 are attached to the next tube, and the tube is expanded and fixed in the same manner. .
[0028]
When the tubes have been fixed to all the fitting holes 3, 3, the front plate 10 and the rear plate 11 forming the casing are attached to the front and rear of the plate fin group 1A as shown in FIG. The front end portion and the rear end portion of the tube are respectively enlarged by jigs to form connection enlarged portions 13 and 13 of the U-shaped bend tube 12, and the front end portion and the rear end portion of the tubes to be connected are connected. The channels are connected by the bend pipe 12, and a flow path in which the plurality of tubes and the bend pipe are connected is formed.
[0029]
The bend pipe 12 is fitted into the connection enlarged-diameter portion of the tube and fixed by welding. When TIG welding is used, TIG (Tig) welding is performed to obtain a connection strength enough to withstand the expansion and contraction of the material due to the pressure in the coil and a rapid temperature change. When using a tube with a relatively small wall thickness, for example, 0.5 mm or 0.4 mm, the time required for the connection work is significantly shorter than that of TIG welding. I do.
[0030]
Then, an inlet header 14 and an outlet header 15 are attached to the inlet end and the outlet end of each flow path, respectively, to complete the heat transfer coil as shown in FIGS.
7 and 9, reference numeral 14a denotes a fluid inlet of the inlet header, 14b denotes a mounting flange, 15a denotes a fluid outlet of the outlet header, and 15b denotes a mounting flange.
[0031]
【The invention's effect】
According to the method of the present invention, a number of plate fins are arranged, a tube having a diameter slightly smaller than the inside diameter of the fitting hole is inserted into the fitting hole of the plate fin, and the tube is expanded to connect the tube to the plate fin. Because it is configured to be crimped and fixed to the inner surface of the fitting hole, deformation or damage of the tube as in the case of the conventional method of fitting the fitting hole of the plate fin with the fitting hole with an inner diameter slightly smaller than the outer diameter of the tube to the tube Therefore, the heat transfer efficiency between the tube and the plate fin is good, and the assembling of a large number of plate fins and the tube can be performed accurately in a short time.
[0032]
Further, since the fitting holes of the plate fins are formed on the inner surface of the cylindrical body formed integrally with the plate, the contact area between the plate fins and the tube is large, and the heat transfer efficiency between the plate fins and the tube is increased. Is even better.
[0033]
Furthermore, an enlarged-diameter flange is formed at the end of the cylindrical body constituting the fitting hole of each plate fin, and when the plate fins are arranged and set, the enlarged-diameter flange abuts around the fitting hole of the adjacent plate fin. Therefore, the plate fins are separated at a predetermined interval, so that it is not necessary to separately provide a spacer between the plate fins, so that the number of parts and the number of working steps can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a plate fin used in the method of the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a plate fin used in the method of the present invention.
FIG. 3 is a plan view of a plate fin group.
FIG. 4 is an enlarged cross-sectional view showing a state where a tube is fitted into a fitting hole of a plate fin group and a rear end is closed.
FIG. 5 is an enlarged cross-sectional view showing a state in which a nozzle is attached to a front end portion of the tube and the diameter of the tube is expanded by fluid pressure.
FIG. 6 is an enlarged cross-sectional view showing a state in which a bend tube is attached to a tube.
FIG. 7 is a front view showing a finished product of a heat transfer coil according to the method of the present invention.
FIG. 8 is a rear view showing a completed heat transfer coil according to the method of the present invention.
FIG. 9 is a plan view showing a finished product of a heat transfer coil according to the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plate fin 1A Plate fin group 2 Plate 3 Fitting hole 4 Heat transfer tube 5 Enclosure 6 O ring 7 Nozzle 8 O ring 9 Flow path for press-fitting fluid 10 Front plate 11 Rear plate 12 Bend tube 13 For connection of bend tube Enlarged part 14 Inlet header 15 Outlet header

Claims (6)

(A) A plurality of metal plate fins in which a large number of fitting holes for tube insertion are regularly drilled are arranged and set back and forth so that each of the fitting holes coincides with each other to form a plate fin group,
(B) A stainless steel tube whose front and rear ends are opened and whose outer diameter is slightly smaller than the fitting hole of the plate fin is inserted into the fitting hole of the plate fin group,
(C) The tube is closed by closing the rear end of the tube with a seal and attaching a nozzle to the front end of the tube, pressing the nozzle and the seal, and forcing a fluid into the tube from the nozzle to expand the tube. After crimping and fixing to the inner surface of the fitting hole of the plate fin, remove the nozzle and seal from the tube,
(D) After fixing the tubes in the respective fitting holes in the step (c), the front ends of the tubes to be connected and the rear ends thereof are connected to each other by a bend tube. Manufacturing method of coil. 2. The method for manufacturing a heat transfer coil for a heat exchanger according to claim 1, wherein the tube fitting hole of the plate fin is formed by an inner surface of a cylindrical body in which the plate fin is extruded to one side. The method for manufacturing a heat transfer coil for a heat exchanger according to claim 1, wherein the plate fin fitting hole cylindrical body has an enlarged diameter flange at a tip end. The method for manufacturing a heat transfer coil for a heat exchanger according to claim 1, wherein the stainless steel tube has a Vickers hardness of 140 HV or more and 155 HV or less by heat treatment at the time of manufacturing the tube. The heat transfer coil for a heat exchanger according to claim 1, wherein the stainless steel tube has a wall thickness of 0.6 mm or less, and has a Vickers hardness of 140 HV or more and 155 HV or less by heat treatment during tube production. Production method. The method for manufacturing a heat transfer coil for a heat exchanger according to claim 4 or 5, wherein the stainless steel tube has a carbon content of 0.01 to 0.03 wt%.

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