JPS63216956A - Production of heat-transfer tube of multi-tubular evaporator and finned plate of plate evaporator - Google Patents

Abstract

PURPOSE:To form a coated film having improved adhesion and durability on a heat-transfer tube, by filling the space extending from the finned part of a heat-transfer tube to be thermally sprayed by plasma to a plasma gun with an oxygen-free atmosphere, and reducing and removing the useless matter in the space. CONSTITUTION:The heat-transfer tube 1 (or finned plate) to be thermally sprayed by plasma is sent into a chamber 4 by means of a tube holder 3, and thermally sprayed by the plasma gun 2. At this time, an inert gas is sent into the space extending from the finned part of the tube 1 to the plasma gun 2 to form an oxygen-free atmosphere, the inert gas is mostly sucked by an exhaust fan 6 through a filter 5, and the discharge of the gas into the atmosphere and the circulation to the chamber 4 are controlled by control valves 7. As a result, the infiltration of oxides into a coated film and the oxidation of the coated film can be controlled, and the coated film having high adhesive strength, durability, and excellent heat radiation efficiency is formed on the heat-transfer tube 1.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a heat exchanger tube of a multi-tube evaporator and a plate-type evaporator, each of which has a dramatically increased extra-tube evaporation transfer coefficient or planar evaporation transfer coefficient, respectively. The present invention relates to a method for manufacturing a fin plate.

[Prior Art] Multi-tube evaporators and plate evaporators are widely used in heat exchangers, evaporators, and the like. Incidentally, from the viewpoint of energy saving, new energy development, etc., demands for improved performance of heat transfer tubes of multi-tube evaporators and fin plates of plate evaporators are increasing.

In order to meet this requirement, as shown in FIG. 6, the fins 11 formed on the outer periphery of the tube body are coated with a coating 12 which is thicker on the tip side of the fin and thicker than the base side of the fin. 30 to 6 on the surface of the fins formed on the outer periphery of the heat exchanger tube 1 and the tube body.
A method of manufacturing the heat exchanger tube 1 has been proposed in which metal powder is plasma sprayed in the atmosphere at an inclination angle of 0 degrees to build up the side walls of the tips of the fins.

These are technologies related to applying a predetermined build-up process to so-called loaf-in type heat transfer tubes by plasma spraying, and their purpose is to expand the effective heat transfer area and increase the number of bubbles generated on the outer circumferential surface. be.

Here, the increase in the number of bubbles generated on the outer peripheral surface will be described in detail. Usually, heat is removed by flowing a liquid around the outer periphery of the heat exchanger tube and fin plate, but in this case, the evaporative heat transfer outside the tube is significantly affected by the number of bubbles generated on the outer periphery of the tube. Therefore, in order to improve the performance of a heat transfer tube, it is important to determine how uniformly, in large numbers, and continuously bubbles are generated on the outer surface of the transfer tube.

It is known that in order to achieve this goal, it is necessary to ■ appropriately control the cavity radius of the heat transfer surface to increase the number of bubble nuclei, and ■ make the cavity deep and wide to stabilize the generation of bubbles. There is.

Note that the fin plates of the plate type evaporator are also similar to the heat exchanger tubes described above.

[Problems to be Solved by the Invention] The above-mentioned conventional technology relates to the manufacture of heat transfer tubes by plasma spraying in the atmosphere, and does not take into account oxidation of the coating etc. in the plasma spraying process, and has the following problems. I have a problem.

(1) The adhesion strength of the coating to the base material is reduced, it is easy to peel off, and the durability is poor.

(2) Thermal conductivity deteriorates because oxides are mixed or present in the coating.

(3) When overlaying active metal, the above (1), (
2) Active metals cannot be used as thermal spraying materials because the problem of 2) becomes significant.

[Means for solving the problem] The above problem is solved by keeping the space from the fin part of the heat exchanger tube and fin plate being subjected to plasma spray processing to the plasma gun in a non-oxidizing atmosphere, and from which plasma spraying is carried out. This problem is solved by a method for manufacturing the heat transfer tubes of a multi-tube evaporator and the fin plates of a plate evaporator, which are processed by plasma spraying while constantly suctioning and removing generated waste materials.

Note that there is no problem even if the atmosphere of the heat exchanger tube and the fin plate other than the parts being processed is an oxidizing atmosphere.

[Example] Example 1 will be described with reference to FIG. 1. Plasma spraying is carried out in a chamber with a non-oxidizing atmosphere where the conduction tube is kept under positive pressure.

The conduction tube 1 to be processed is sent to a chamber 4 through a tube holder 3. Inert gas is injected into the chamber 4 by the plasma gun 2 during thermal spraying. In this example, two plasma guns 2 arranged at an angle of 30 to 60 degrees with respect to the normal to the outer surface of the conduction tube are used, and the inert gas flow rate VI and vI2 such as argon gas are both 10 to 150 SL.
I made it M.

Most of this inert gas is passed through the filter 5 by the exhaust fan 6. This quickly removes suspended particles of heat and powder generated during thermal spraying in one direction of the filter.
Since it can be recovered, the vicinity of the thermal spraying point can always be kept clean.

By controlling the control valve 7, the release of the inert gas to the atmosphere, return to the chamber 4, and circulation can be adjusted. In this example, the flow rate VO of the inert gas released to the atmosphere is set to 0~290 SLM, and the flow rate VI3 of the inert gas returned to the chamber and circulated is set to 10~300 SL.
It was set as M.

Therefore, by setting the atmospheric discharge flow rate ■ol to be slightly smaller than the injection amount V■(+VIx) from the plasma gun, the inside of the chamber 4 can be made to have a positive pressure with an inert gas and a non-oxidizing atmosphere can be created.

Furthermore, since the inside of the chamber 4 is under positive pressure, a portion of the inert gas leaks into the atmosphere from the gap between the tube holder 3 and the heat transfer tube 1, thereby preventing the atmosphere from entering the chamber 4. . In this embodiment, the leakage flow rates VO2 and VO5 are set to 1 to 50.
It was named SLM. Since it has an air-tight structure in which the gap between the tube holder 3 and the heat transfer tube 1 is continuously sealed with a curtain of inert gas, it is easy to feed the workpiece 1 into and out of the chamber 4. can.

Embodiment 2 will be explained using Figure 2.First, the inside of the chamber 4 is evacuated by the vacuum pump 8.The conduction pipe 1 to be processed is filled with an inert gas such as argon gas. After passing through the air-tight auxiliary chamber 10, which flows out to the atmosphere,
It is sent into the chamber 4, and similarly sent out of the chamber 4 through the outlet side auxiliary chamber 10.

This is to prevent atmospheric air from entering the chamber 4 which is maintained at negative pressure. Here, sleeves are provided at the atmosphere side and chamber side entrances and exits of the auxiliary chamber 10,
Its inner diameter oI.

0□, 0. ．． 0. By adjusting , the conductance with respect to the flow of argon gas can be adjusted, and the amount of argon gas released into the atmosphere ■0□ and the amount of inflow VII into the chamber 4- can be adjusted.

In chamber 4, there are two
A base plasma gun is installed, and inert gas such as argon gas is injected during thermal spraying. This gas passes through the filter 5 and is purified, and a portion of the gas passes through the control valve C.
v, and is evacuated by the vacuum pump 8, and the remainder is returned to the chamber 4 via the control valve CV2 and the circulation fin 9.

In Examples 1 and 2, in order to perform plasma spraying uniformly, the heat transfer tubes and fin plates are rotated and fed from outside the chamber, but by processing the ends of the tubes and fin plates in advance, each tube and fin plate Connection between plates is possible, allowing continuous supply of workpiece materials and thermal spraying.

The characteristics of the coatings produced in Example 1 and Example 2 will be described below.

The adhesion between the base material and the coating was measured. After bonding the material testing jig to the base material and coating using adhesive,
Adhesion was measured using a material testing machine. FIG. 3 shows the measurement results of the adhesion between the base material and the coating. In this example, the adhesion strength is approximately 70
0 kg/cm2, which is much higher than the value of around 300 kg/cm' in the comparative example.The improvement in strength is only 700 kg/cm', but this is because the adhesive used for measurement was 700 kg. / cI11', so even if it had a strength higher than this, it would break at that point.If a stronger adhesive material were to emerge, it would be confirmed that the adhesive strength would be even higher.

Next, the heat dissipation effect was measured. The results are shown in FIG.

In the figure, ■ is a heat exchanger tube manufactured according to this example (base material is titanium, sprayed material is titanium), ■ is a heat exchanger tube manufactured by normal atmospheric spraying method (base material is titanium, sprayed material is aluminum)
, Moto ■ is a heat exchanger tube with a predetermined depth cavity provided by machining, and Rough ■ is a heat exchanger tube with a smooth surface for comparison.

(2) is uniform due to mechanical processing, but the number of cavities in the back floor is limited and nucleate boiling occurs for that number, so the heat dissipation efficiency is improved compared to (2).

■ In addition to the back floor cavity in ■, a fine cavity is formed inside the back floor gap that forms the cavity and up to the spray head where the mouth of the loaf-in pipe is kept narrow, so the heat dissipation efficiency is much better than in ■. Become.

■ is almost the same principle as ■, but since titanium, which is the same as the base material, is sprayed without oxidation, heat conduction can be greatly improved compared to ■, and the porosity can also be controlled, and a uniform and optimal deep floor space can be created. As shown in FIG. 4, the performance is very good.

The results for the fin plate of the plate type evaporator are almost the same as for the above-mentioned multi-tube type extra-tube evaporation type heat exchanger tube.

A built-up part is formed on the fin tip side to narrow the fin spacing and create an opening interval that facilitates bubble generation, and a deep cavity is provided below it to stabilize bubble generation.

Furthermore, from FIG. 5, it can be seen that the built-up portion is an excellent coating without any unnecessary material being rolled up. Note that the thermal spray material is titanium.

[Effects] Since the space from the fins of the plasma sprayed heat exchanger tube and fin plate to the plasma gun is maintained in an oxidation-free atmosphere, there is almost no entrainment of oxides into the coating or oxidation of the coating. A coating with high adhesion strength, durability, and excellent heat dissipation efficiency can be obtained. Furthermore, active metals such as titanium, aluminum or alloys thereof can be used as spray materials.

In addition, since the unnecessary materials generated during plasma spraying are removed by suction, there is almost no unnecessary material caught in the coating, resulting in a coating with high adhesion strength, durability, and excellent heat dissipation efficiency. is obtained.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are diagrams showing examples of the present invention, and FIG. 3 is a diagram showing the adhesion strength of the coating etc. manufactured by this example.
FIG. 4 is a large-scale photograph according to this embodiment, and FIG. 6 is a diagram showing the plasma spraying method of the fin portion of the heat exchanger tube. 1... Heat exchanger tube (workpiece) 2... Plasma gun 3.
...Pipe holder 4...Chamber 5...Filter 6...Exhaust fan 7...Control valve 8...Vacuum pump 9...Circulation fan 10
...Auxiliary chamber 11...Fin part 12...
・Coating Figure 1 VO+ Figure 2 Figure 3 Film thickness Body surface) Figure 4 Natural 5FL Far (W/A) Figure 5

Claims (1)

[Claims] 1. Maintain an oxygen-free atmosphere in the space between the heat exchanger tube and the fin portion of the fin plate being subjected to plasma spraying and the plasma gun, and remove unnecessary substances generated during plasma spraying from the space by suctioning. A method for manufacturing heat exchanger tubes for multi-tube evaporators and fin plates for plate-type evaporators using plasma spray processing. 2. The heat exchanger tube and plate type evaporator of the multi-tube evaporator according to claim 1, characterized in that titanium, titanium alloy, aluminum, aluminum alloy, or stainless steel is overlaid by plasma spraying. fin plate manufacturing method. 3. Claims 1 or 2, characterized in that the heat exchanger tube or fin plate to be plasma sprayed is plasma sprayed in a container maintained in a non-oxidizing atmosphere.
A method for manufacturing a heat exchanger tube for a multi-tubular evaporator and a fin plate for a plate-type evaporator as described in 2. 4. The multi-tube evaporator according to claim 1, 2 or 3, wherein the suction and removal of unnecessary substances generated in association with plasma spraying is performed using a filter and a fan. Method for manufacturing heat exchanger tubes and fin plates for plate-type evaporators.