JPH04220130A - Manufacture of heat exchanger - Google Patents

Abstract

PURPOSE:To eliminate use of lubricating oil, thereby not generating abrasion powder and to dispense with the washing process by inserting the copper tube in the Al-fin, forming the flow passage by joining the copper tubes, pouring the water, heating to the prescribed temperature after sealing the both ends the expanding the copper tube with the vapor pressure of the water. CONSTITUTION:The Al-fin 1 of required sheets on which the hole 3 for inserting the copper tubes are formed preliminarily are laminated by setting the proper gap mutually, and the required pieces of the copper tubes are inserted in this Al fins. The flow passage for heat medium is formed by connecting each copper tube mutually, the water of prescribed value is poured in this flow passage, then both ends of this flow passage are sealed tight. Then the copper tube is expanded by using the vapor pressure and heating the copper tube and the Al fin, overall to the prescribed temperature, and the copper tube is made in adhered closely to the Al fin. Therefore, the washing process after assembling is made needless, because the crushing of the spiral like projection is not generated at all even if a tube with an inner groove is used, so the reduction of the efficiency of the heat conductivity is not generated and the performance of the heat exchanger can be improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a heat exchanger used in an air conditioner or the like, particularly a fin-and-tube heat exchanger combining aluminum fins and copper tubes.

0002

[Prior Art] Generally, in the manufacture of heat exchangers, holes with an inner diameter slightly larger than the outer diameter of the copper tubes are formed in the fins, the copper tubes are inserted into the holes, and then the copper tubes are expanded. A method is adopted in which it is brought into close contact with the fins. As a means of expanding the tube,
There are methods such as pushing a mandrel from one end of the copper tube, closing one end of the channel and injecting high-pressure liquid from the other end, and pushing a copper ball from one end of the copper tube using liquid pressure. In addition, a method has been adopted in which a hole with an inner diameter slightly smaller than the outer diameter of the copper tube is formed in the fin, and the copper tube is forcibly inserted using a press or the like.

[0003] In so-called room air conditioners and package air conditioners, fin-and-tube heat exchangers that combine aluminum fins and copper tubes are often used. This type of heat exchanger is usually manufactured using the mandrel tube expansion method in most cases, but this method has the following drawbacks. ■ It is necessary to use lubricating oil to reduce friction between the mandrel and the inner wall of the copper tube. In addition, some amount of wear powder is unavoidable, and since this wear powder mixes with lubricating oil and adheres to the inner wall surface of the copper pipe, cleaning with an organic solvent is required after the pipe expansion operation is completed. ■ Recently, internally grooved pipes have been widely used, but this type of copper pipe has many spiral protrusions (fins) formed on the inner wall surface.
Abrasion powder is more likely to be generated than in the case of smooth pipes. In addition, the tip of the spiral protrusion is crushed by the mandrel and the depth of the groove is reduced, which tends to reduce the heat transfer efficiency with the refrigerant (fluorocarbon). ■ The shrinkage margin of copper tubes that occurs during tube expansion changes due to subtle variations in tube expansion conditions, so more uniform copper tube characteristics are required, leading to an increase in the manufacturing cost of copper tubes.

0004

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art in manufacturing a heat exchanger for an air conditioner and to provide a more rational manufacturing method. In particular, the main aim of the present invention is to reduce environmental pollution caused by organic solvents, which is currently a major social problem.

[0005]

[Means for Solving the Problems] In order to solve the above problems, in the method for manufacturing a heat exchanger according to the present invention, a required number of aluminum fins in which holes for inserting copper pipes are formed in advance are placed in appropriate positions with respect to each other. After the required number of copper tubes are inserted into the aluminum fins, each copper tube is bonded to each other to form a flow path for the heat medium, and a predetermined amount of water is inserted into the flow path. to seal both ends of the channel. Thereafter, by heating the entire copper tube and aluminum fin to a predetermined temperature, the copper tube is expanded using the vapor pressure of water, and the copper tube is brought into close contact with the aluminum fin.

FIG. 2 shows a typical copper tube (outer diameter: 9.52 mm, wall thickness: 0.5 mm), which is often used as a heat transfer tube for air conditioners.
These are the results of actually measuring the bursting pressure due to internal pressure at high temperatures for 34 mm). As is clear from the figure, 3
The bursting pressure of the copper tube and the saturated vapor pressure of water coincide at around 0.4°C, and the value thereof is approximately 9 MPa.

However, since the rate of change in saturated vapor pressure near 304° C. is as large as about 0.13 MPa/°C, if the amount of water enclosed is too large, it becomes difficult to control the temperature in practical use. Therefore, it is preferable to select the amount of water to be filled so that the saturated water just disappears at a temperature slightly lower than the temperature at which a saturated vapor pressure equal to the bursting pressure occurs. That is, for example, the specific weight of saturated steam at 300°C is about 4
6.2 g/1 tr, so if the amount of sealed water is less than the amount corresponding to this value, the rate of change in saturated vapor pressure due to temperature will be one order of magnitude smaller, 0.016 MPa/℃, making industrial handling easier. become.

[0008] If air is not excluded when water is sealed in a copper tube, the inner surface of the copper tube may be slightly oxidized due to residual oxygen. However, the amount of residual oxygen is at most about 0.6 cc per meter in the case of copper pipes of the above-mentioned general size, and the influence of oxidation can be practically ignored. However, if internal oxidation is extremely objectionable, it is desirable to replace the air remaining in the copper tube with an inert gas or remove it by vacuum suction, and then fill it with water.

After pipe expansion, the copper pipe is cooled to a temperature at which oxidation in the atmosphere is not a practical problem (for example, a temperature slightly over 100°C), and the end portion of the flow path is released to the atmosphere. It blows out by itself due to the air blowing effect caused by internal pressure. Furthermore, by purging with an inert gas, the remaining water dries with the help of residual heat and can be almost completely eliminated.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. This figure shows a partial cross section of a fin-and-tube heat exchanger during heating and tube expansion work. Aluminum fin 1
A hole 3 having an inner diameter slightly larger than the outer diameter of the copper tube 2 is formed in advance by means such as pressing, and the copper tube 2 is inserted into the hole.
is inserted. The ends of the copper tubes 3 are connected by hard brazing a U-bend connecting tube 4 to form one refrigerant flow path 5 as a whole.

Water 6 is injected into the flow path 5, and the terminal portions 7 at both ends of the flow path are tightly sealed using a closing jig, a valve 8, or the like. When such an assembly is loaded into a heating furnace 9 such as a batch furnace or a continuous tunnel furnace and heated to a predetermined temperature in a protective atmosphere, the copper tube 3 expands and plastically deforms due to the vapor pressure of water. , tightly adheres to the inner surface of the hole 3 of the aluminum fin 1. After heating and expanding the tube, the entire assembled product is cooled down and the flow path end section 7 is cooled down with the internal temperature slightly exceeding 100°C.
When the valve 8 is released, the water turns into steam and spurts out on its own. Finally, by supplying an inert gas through the valve 7 to purge the inside of the copper tube, the inner surface of the copper tube is efficiently dried without oxidation with the help of residual heat.

The outer diameter of the copper tube 2 is 9.52 mm, and the wall thickness is 0.
．． 34 mm, and assuming that the total length of the flow path 5 is 20 m,
The internal volume of the flow path 5 is approximately 1.231 tr. If the amount of water required in this case is calculated based on the above-mentioned basis, it will be only about 56 g. The heating temperature for tube expansion is desirably set in the range of 305 to 310°C.

[0013]

[Effects of the Invention] The effects of the present invention are listed below. ■ Unlike mandrel tube expansion, no lubricant is required. Further, since no abrasion powder is generated, there is no need for a cleaning process after assembly (after pipe expansion), which helps prevent pollution and reduces costs. - Even when an internally grooved tube is used, unlike the mandrel tube expansion method, the spiral protrusion does not collapse at all, so there is no decrease in heat transfer efficiency and the performance of the heat exchanger can be improved. ■
This makes it possible to solve the problem of variations in copper pipe shrinkage due to mandrel expansion. ■ By simply adding a heating furnace and auxiliary equipment, it can be applied to a heat exchanger mass production line without major changes to conventional processes.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a heat exchanger showing an embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing the relationship between the bursting pressure of a copper pipe and the saturated vapor pressure of water.

[Explanation of symbols]

1... Aluminum fin 2... Copper tube 3... Hole 4... U-bend connecting pipe 5... Refrigerant flow path 6
...Enclosed water 7...Flow path terminal part 8...
Valve 9...Heating furnace

Claims (4)

[Claims] Claim 1: A required number of aluminum fins with holes for inserting copper pipes formed in advance are stacked with an appropriate gap between each other,
A step of inserting the required number of copper tubes into the aluminum fin,
A process of joining each copper pipe to each other to form a flow path for heat medium, injecting a predetermined amount of water into the flow path, and then sealing both ends of the flow path, and a process of sealing the entire copper tube and aluminum fin. A method for manufacturing a fin-and-tube heat exchanger, comprising the steps of heating the copper tube to a predetermined temperature, expanding the copper tube by the vapor pressure of water, and bringing the copper tube into close contact with aluminum fins. 2. The method of manufacturing a heat exchanger according to claim 1, wherein the air remaining in the flow path is replaced with an inert gas and removed, and then water is sealed. 3. The method of manufacturing a heat exchanger according to claim 1, wherein water is sealed after air remaining in the flow path is removed by vacuum suction. 4. Manufacture of a heat exchanger characterized in that the amount of water sealed is selected so that saturated water disappears at a temperature slightly lower than the temperature at which the vapor pressure of the water is equal to the bursting pressure of the copper tubes. Method.