JP3329222B2 - Heat exchanger manufacturing method - Google Patents

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, and more particularly to a method for manufacturing a heat exchanger having excellent inner surface wettability.

[0002]

2. Description of the Related Art As a method of manufacturing a heat exchanger, for example, a hole is formed in a radiator such as a fin, a heat transfer tube is inserted into the hole, a heat-expandable substance is sealed in the heat transfer tube, and sealed. A method for manufacturing a heat exchanger was proposed in which the heat exchanger was heated by placing it in a furnace, the heat transfer tube was expanded by the expansion pressure of the heat-expandable substance, and the outer surface of the expanded heat transfer tube was brought into close contact with the hole of the radiator.

[0003] This method is simpler than the conventional mechanical expansion method using a mandrel, and is therefore suitable as a method for producing this type of heat exchanger.

[0004]

However, according to the proposed method of manufacturing a heat exchanger, there is no consideration for improving the wettability of the inner surface of the heat transfer tube. There was a problem in the point.

That is, for example, the inner surface of a heat transfer tube in an absorber or an evaporator of a heat exchanger for an air-cooled absorption refrigerator has good wettability with water in order to ensure excellent heat transfer. Is ideal, but for this purpose the following 2
You have to satisfy the point.

(1) No residual oil (in most cases, polybutene oil) is present on the inner surface of the heat transfer tube. (2) The inner surface of the heat transfer tube is covered with an oxide film.

However, in the case of the conventional manufacturing method, it is difficult to realize (1) unless a careful cleaning with an organic solvent is performed. In particular, the inner surface of the heat transfer tube is processed into a complicated uneven shape. When made highly heat conductive, oil removal becomes increasingly difficult.

[0008] As for (2), it is theoretically possible to oxidize only the inner surface of the heat transfer tube, but it is difficult to realize this practically.

Accordingly, an object of the present invention is to provide a method of manufacturing a heat exchanger capable of efficiently removing residual oil on the inner surface of a heat transfer tube and forming an oxide film uniformly on the inner surface of the tube. To provide.

[0010]

According to the present invention, in order to achieve the above object, a heat transfer tube is inserted into a hole of a heat radiator, a heat-expandable substance is sealed inside the heat transfer tube, and the heat transfer tube is sealed. In the method for manufacturing a heat exchanger, the pressure of the heat-expandable substance in the heat transfer tube is increased by heating, and the outer surface of the heat transfer tube expanded thereby is brought into close contact with a hole of the radiator. Inside the heat transfer tube, the residual oil is removed together with the heat-expandable substance, and the inner surface acid of the heat transfer tube is removed.
It is intended to provide a method for manufacturing a heat exchanger, characterized by enclosing an amount of oxygen necessary for gasification.

As a constituent material of the heat transfer tube in the present invention, for example, copper, aluminum, or an alloy thereof is used, and a radiator is also made of such a material.

The heat transfer tube to be expanded according to the present invention may have a smooth inner surface or a shape processed to improve the heat transfer performance such as unevenness. In this case, a particularly remarkable effect is obtained.

As the heat-expandable substance, an inert gas such as nitrogen gas or water is used.

In some cases, the heat exchanger may be constituted by one heat transfer tube. However, in many cases, the heat exchanger usually includes a plurality of heat transfer tubes. Are combined into one interconnected container, in which the heat-expandable material and oxygen are sealed.

As a means for heating the heat transfer tube, heating by a furnace is simple, and in particular, a bright annealing furnace is suitable.

The pressurization of the heat-expandable substance and the oxygen gas in the heat transfer tube due to the heating temperature rise is initially affected to some extent by the consumption of oxygen gas for removing residual oil inside the tube and oxidizing the inner surface of the tube. However, after these reactions are completed, they rise according to Boyle-Charles law.

The amount of the heat-expandable substance and oxygen enclosed is determined according to the material and size of the heat transfer tube, the internal volume of the heat transfer tube, the degree of expansion, and the like, and the heating temperature is also determined in consideration of these conditions. Can be

The heating temperature needs to be determined in consideration of the softening temperature of the heat transfer tube and the radiator, the oxidation start temperature of the remaining oil in oxygen, or the ignition temperature of the oil. 350-400 ° C.

The heat exchanger manufactured according to the present invention is specifically applied to, for example, a heat pipe type heat exchanger using water as a working liquid, particularly an absorber for an air-cooled absorption type refrigerator and an evaporator. Is done.

Next, an embodiment of the present invention will be described.

In FIGS. 1 to 4, 1 is a radiator (fin) arranged at predetermined intervals, 2 is a hole provided at the center of the radiator 1, and 3 is a hole in the hole 2 of each radiator. 2 shows a copper heat transfer tube inserted in FIG.

The heat transfer tube 3 has an outer diameter slightly smaller than the inner diameter of the hole 2 of the radiator 1, and its lower end is joined to the lower collecting tube 4 by hard brazing or the like.

Reference numeral 5 denotes a surplus water discharge port joined at the center of the lower collecting pipe 4, 6 denotes a coolant water supply port attached to an upper end of each heat transfer pipe 3, and 7 denotes an upper collecting pipe joined to this port 6. The heat transfer tubes 3 are communicated with each other via the upper collecting pipe 7, the lower collecting pipe 4, and the coolant water supply port 6.

Reference numeral 8 denotes a steam discharge port attached to the center position of the upper collecting pipe 7, and 9 denotes a refrigerant water supply port 6.
2 shows a water supply pipe connected via a joining pipe 10.

With the above configuration, first, the surplus water discharge port 5 and the steam discharge port 8 are sealed, and then a heat-expandable substance such as nitrogen gas or water and oxygen gas are supplied from the water supply pipe 9. Encapsulate.

Next, the end portion 11 of the water supply pipe 9 is crushed with a pinch roll, and the crushed portion is welded and sealed, and then placed in a bright annealing furnace and heated to increase the pressure of nitrogen gas or steam. The heat transfer tube 3 is expanded.

After the expansion and the close contact of the outer surface of the heat transfer tube 3 with the hole 2 are completed, the entire tube is taken out of the bright annealing furnace, the steam discharge port 8 is opened, and the gas and steam in the heat transfer tube 3 and the accessories are removed. Is discharged.

Next, the coolant water is supplied, the surplus water discharge port 5 is opened, and the coolant water is circulated, whereby the whole is cooled to obtain a finned heat exchanger.

FIG. 5 shows a case where annealed copper material is used as a constituent material of a copper heat transfer tube, nitrogen gas is used as a heat-expandable substance, and the tube has an outer diameter of 15.88 mm and a wall thickness of 0.6 mm. The relationship between the heating temperature, the pressure of the gas sealed in the heat transfer tube, and the increase in the outer diameter of the heat transfer tube is shown. The increase in the outer diameter is indicated by a dashed line curve.

The heat transfer tube is caused by an increase in the pressure of the sealed gas due to the heating and an interaction between the copper heat transfer tube and the high-temperature softening of the copper heat transfer tube.
It is expanded even at relatively low gas pressures such as spots.

Now, as the copper heat transfer tube 3 shown in FIGS.
This heat transfer tube 3 is made of the same material and size as in the above, and further has polybutene oil remaining on the inner surface.
When the length is 1,000 mm, the number of the tubes is 30, the total internal area including the accessories such as the collecting pipes 4 and 7 is 2.4 m ² , and the total internal volume is 8.8 l. A method for determining the amount of oxygen required for removing polybutene oil and oxidizing the inner surface of the tube and the amount of nitrogen gas required for expanding the heat transfer tube 3 will be described.

First, the amount of polybutene oil remaining on the inner surface of the heat transfer tube is empirically about 1 g / m ² ,
The amount of oxygen required for the oxidative removal is 0.107 m
ol / g.

The amount of oxygen consumed for oxidizing copper is 0.04 tS (m) when the thickness of the oxide film is t μm and the oxide area is Sm ² when the oxide film is entirely CuO.
ol).

Accordingly, when the thickness of the oxide film is set to 1 μm, the amount of oxygen required for removing the polybutene oil and forming the oxide film in FIGS.
ol / g) × 2.4 (g) + 0.04 × 2.4 (m ² )
× 1 μm = 0.352 mol, which is converted to a volume of 8.5 l at 20 ° C.

On the other hand, if the heating temperature for expanding the tube is 400 ° C., the gas pressure in FIG. 5 is 78 kgf / cm ^2, which is calculated based on Boyle-Charles' law. It becomes 34 kgf / cm ² .

Since the total internal volume of FIGS. 1 to 4 is 8.81, the volume at the time of enclosing 34 kgf / cm ² (at 1 atm) is 8.81 × 34/1 = 299.54 . Among them, the oxygen amount is 8.51 described above, and the remaining nitrogen gas amount is 291.03 .

As described above, the volume mixing ratio of oxygen gas and nitrogen gas is 34.2 for the former (8.51) and 34.2 for the latter.
(291.03 ) In order to actually apply these relations, first, the air inside the heat transfer tube 3 and the accessory is purged by nitrogen gas charging, and then the nitrogen gas is purged at a pressure of 33.03 kgf /. cm ² (gauge pressure 32.03 kgf
/ Cm ² ), and then the entire pressure is 34.00 kgf / cm ² (gauge pressure 33.00).
kgf / cm ² ).

The above description relates to the case where an oxide film having a thickness of 1 μm is formed. If it is desired to make the film thickness thicker or thinner, the oxygen amount is adjusted according to the degree. It is an advantage of the present invention that the thickness of the oxygen film can be adjusted in this manner.

Next, the case where water is used instead of nitrogen gas will be described. The pressure at point B in FIG. 5, that is, the sum of the steam pressure and the oxygen gas pressure at a heating temperature of 280 ° C. is 64 kgf / cm. Enclose water and oxygen gas in an amount such that the temperature becomes ² and heat and raise the temperature to 20 ° C.
In this case, the same effect as when nitrogen gas of 34 kgf / cm ² is sealed can be obtained.

In this case, the required amount of water is
The internal volume is 8.8 l, the required oxygen amount is 8.5 l,
On the other hand, the specific volume of the saturated steam at 280 ° C. is 0.024
75m ^Two/ Kg, the pressure at 280 ° C
64kgf / cm^TwoThe amount of water to secure
g.

The same size and structure as described above, that is, the thickness of the copper heat transfer tube 3 is 0.6 mm, and the outer diameter is 15.88 m.
m, length 1,000 mm, number of 30 pieces, total internal area including accessory goods 2.4 m ² , total internal volume 8.8 l. Further, the inner diameter of the hole 2 of the radiator 1 is For the embodiment of FIGS. 1 to 4 which are set slightly larger than the outer diameter, nitrogen gas and oxygen gas are actually sealed and sealed so that the pressures obtained above are attained, respectively, and these are filled with a bright annealing furnace. The heat exchanger was manufactured by putting into a container and heating to 400 ° C., and then cooling to room temperature.

In the obtained heat exchanger, it is confirmed that the radiator 1 and the copper heat transfer tube 3 are firmly connected to each other by the expansion action due to the increase in the internal pressure of the heat transfer tube 3. As a result, the formation of a uniform oxide film over the entire inner wall of the heat transfer tube 3 was observed.

Although the example in which water was sealed in place of nitrogen gas was also carried out, as in the case of nitrogen gas sealing, the radiator 1
It was confirmed that the connection between the heat transfer tube 3 and the heat transfer tube 3 and the formation of a uniform oxide film on the entire inner wall of the heat transfer tube 3 were confirmed.

[0043]

As described above, the method for manufacturing a heat exchanger according to the present invention encloses and seals oxygen together with a heat-expandable substance in a heat transfer tube, and expands the heat transfer tube by heating it. Therefore, the enclosed oxygen acts to oxidize (burn) the residual oil,
As a result, oil on the inner surface of the heat transfer tube is efficiently removed.

Since oxygen gas at a high temperature also acts to oxidize the inner surface of the heat transfer tube,
A uniform oxide film is formed on the inner surface of the heat transfer tube.

Even if the inner wall of the pipe is roughened, it is possible to efficiently remove oil and form an oxide film regardless of the degree of complexity.

The present invention has a great effect in providing a heat exchanger having excellent inner surface wettability due to removal of residual oil and formation of an oxide film, thereby ensuring high heat conductivity.

[Brief description of the drawings]

FIG. 1 is an explanatory view of one embodiment of a heat exchanger manufacturing method of the present invention.

FIG. 2 is a side view of FIG. 1;

FIG. 3 is an enlarged view of part (A) of FIG. 2;

FIG. 4 is an enlarged view of a part (b) of FIG. 2;

FIG. 5 is a graph summarizing the interrelationship among the heating temperature, the pressure inside the copper heat transfer tube, and the amount of increase in the outer diameter of the copper heat transfer tube.

[Explanation of symbols]

 1, heat radiator 2, hole 3, copper heat transfer tube 4, lower collecting tube 5, surplus water discharge port 6, refrigerant water supply port 7, upper collecting tube 8, steam discharge port 9, water supply tube 10, joint tube

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F28F 1/32 B21D 53/08 B23K 1/00 330

Claims (6)

(57) [Claims] 1. A heat transfer tube is inserted into a hole of a heat radiator, a heat-expandable substance is sealed and sealed inside the heat transfer tube, and the heat-expandable substance is sealed in the heat transfer tube by heating. In a method for manufacturing a heat exchanger in which the pressure is increased and the outer surface of the heat transfer tube expanded by this is brought into close contact with the hole of the heat radiator, the heat transfer tube has a heat-expandable substance remaining inside the heat transfer tube.
A method for manufacturing a heat exchanger, comprising sealing an amount of oxygen necessary for removing oil and oxidizing the inner surface of the heat transfer tube. 2. The method according to claim 1, wherein the heat-expandable substance is an inert gas. 3. The method according to claim 2, wherein said inert gas is nitrogen gas. 4. The method according to claim 1, wherein the heat-expandable substance is water. 5. The method for manufacturing a heat exchanger according to claim 1, wherein the heat transfer tube has an inner surface subjected to unevenness processing. 6. The method for manufacturing a heat exchanger according to claim 1, wherein the heat transfer tubes are composed of a plurality of heat transfer tubes and communicate with each other.