JPS60255984A - Manufacture of heat exchanger body - Google Patents

Abstract

PURPOSE:To form a porous layer easily at a heat transfer surface and obtain an exchanger body having a high heat exchanging ratio by covering the heat transfer surface of a heat transfer base body made of magnetic metal such as tube, box, etc. with a metal having lower m.p. than the base body, further sprinkling magnetized powders thereon, and heating said body. CONSTITUTION:Two points of electric contact points are taken at one end of e.g. the magnetic metal tube 1 being heat transfer base body through conducting rolls 2, the heating by conducting electricity is performed, while these points are moved in the direction for the other end of the tube 1. Thereat, the tube 1 is rotated, while it is heated, the magnetic powders 4 are jetted together with gas by a nozzle 3 from one end of the tube 1 to sprinkle them at the heat transfer surface inside the tube 1. The surface of the powder 4 is coated with metal having m.p. lower by >=200 deg.C than that of the tube 1, and magnetized, and said powder is adhered inside the tube 1 due to the magnetic force and the magnetic metal layer is formed. Here, by heating the tube 1 at temp. lower than by >=100 deg.C than its m.p. and higher by >=20 deg.C than m.p. of the covered metal, the covered metal is melted, the powder 4 is adhered inside the tube 1, the porous layer is formed and cooled by cold air from a nozzle 5.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention provides a heat exchanger for a heat exchanger that is inexpensive, has excellent heat exchange efficiency, and is suitable as a base for an evaporation tube or a heat pipe of an air conditioning heat exchanger. The present invention relates to a manufacturing method.

``Prior Art'' Conventionally, in manufacturing heat exchangers for heat exchangers, various methods have been used to increase the surface area, and effects such as capillarity, turbulence, and nucleate boiling have been used to increase the surface area. Attempts have been made to accelerate the effect and improve its heat transfer efficiency, and
It has been put into practical use.

For example, heat exchanger tubes can be formed by rolling, extrusion, drawing, etching, i
! ! In particular, small diameter (mainly 101φ or less) and thin wall (mainly 0.5mmt or less) steel pipes used in refrigeration and air conditioning equipment are manufactured using methods such as electrolytic/electroless plating, cutting, etc. Products with spiral grooves on the inner surface are manufactured by

[Problems/Problems to be Solved by the Invention] By the way, in the above rolling method, (ω) the friction between the rolling tool and the groove formed on the inner surface of the tube is large, and a large pressing force is required +b+ As a result, the rolling tool Short life (C1 slow machining speed +d+) There are drawbacks such as limitations on the number of helical grooves and the helix angle due to the manufacturing of rolling tools or rolling technology.

On the other hand, when looking at the above-mentioned spiral grooved copper tube from the aspect of heat transfer characteristics, although effects due to an increase in surface area and capillarity at the bottom of the spiral grooves are expected, the nucleate boiling phenomenon, which contributes most to the increase in heat transfer coefficient, is It is hardly noticeable, and the turbulence effect during foaming is also small. Therefore, it is possible to induce the nucleate boiling phenomenon by forming a porous layer on the inner surface of the steel pipe. However, in the case of a plate-shaped heat exchanger, a porous layer can be formed on the heat transfer surface by sintering or brazing, but these methods cannot be applied to tubular structures such as the steel pipes mentioned above. It is difficult to do so.

The present invention was made in view of the above circumstances, and it is possible to easily form a porous layer on the heat transfer surface of various heat transfer substrates such as long tubes, plates, and walls. It is an object of the present invention to provide a method for manufacturing a heat exchanger, which can produce a heat exchanger with high strength at low cost.

[Means for Solving the Problems] and "Operation" The present invention provides a heat transfer surface of a metal heat transfer base such as a tube, plate, or wall body with a melting point lower than that of the heat transfer base by 200'C or more. The heat transfer substrate is coated with a metal having a heat transfer surface of 100 degrees Celsius or more below its melting point, and is coated with magnetized magnetic powder, and the magnetic powder is captured on the heat transfer surface by the magnetic force formed by the magnetic powder. The coating metal is heated to a temperature 20°C or more higher than the melting point of the coating metal, and the coating metal on the magnetic powder is melted by heat transfer from the heat transfer base, and the magnetic powder is tightly adhered to the heat transfer surface to transfer heat through the porous layer. It is formed on a substrate.

In this way, in the present invention, the magnetic powder in the form of powder particles is forcibly captured on the heat transfer surface by the magnetic force formed by the magnetized magnetic powder, and in this state, the metal covering the magnetic powder is melted. Since the magnetic powder is welded to the heat transfer surface, it is possible to easily and inexpensively form a porous layer even on the inner surface of a long tube, which was previously considered impossible. can be made strong and homogeneous.

Next, the present invention will be explained in more detail.

In the present invention, when attaching magnetized magnetic powder to the heat transfer surface of the heat transfer base, the magnetic force formed by each Wi magnetic powder is used, so the heat transfer base is made of magnetic metal or A magnetic metal layer must be formed on the surface. In addition, as the magnetic powder, Fe, Ni, C
In addition to magnetic metal powder or magnetic alloy powder such as R, magnetic oxide powder such as magnetite, and composite powder in which a magnetic metal layer is provided on non-magnetic metal powder or alloy powder, ceramic powder, mineral powder, etc. can be used. can.

Further, the heat transfer substrate is preferably heated by high frequency heating, atmospheric heating, or electrical current heating. The heating temperature is set at least 100°C lower than the melting point of the magnetic powder and at least 20°C higher than the melting point of the metal coating on the magnetic powder. This is because it is a safe temperature that does not melt, and is preferably at least 100°C lower than its melting point and 5°C or more lower than the melting point of the coating metal on the magnetic powder.
It is better to raise the temperature by 0 to 100°C.

Furthermore, the metal provided in the outer layer of the magnetic powder is such that the heating temperature of the heat transfer base is 50 to 100 degrees Celsius below the melting point of the metal, as described above.
Since it is preferable that the melting point be higher, in consideration of safety so that the heat transfer substrate does not melt, it is necessary that the melting point is 200° C. or more lower than the melting point of the heat transfer substrate, and the lower the melting point, the easier it is to handle. Metals with relatively low melting points that meet this requirement include 3n, Sn alloys, Zn, Zn alloys, n, and in alloys. It is most convenient because the layer can be easily formed.

On the other hand, as a method for magnetizing the magnetic powder, if the magnetic powder is a metal material, it may be solidified by cold pressing, exposed to a magnetic field of 10 Kgauss or more to be magnetized, and then pulverized. In addition, as a method of magnetizing magnetic powder, regardless of whether it is metal powder or non-metal powder, after filling a body such as plastic with these magnetic powders, the body is
There is a method of exposing each piece of magnetic powder to the above magnetic field and magnetizing it one by one. J3. In order to increase the magnetization strength of magnetic powder, it is possible to expose the magnetic powder to a stronger magnetic field or increase the packing density of the magnetic powder in the body. Further, from the viewpoint of handling, it is most preferable to magnetize the magnetic powder after providing a metal layer and/or a flux layer on its outer surface.

Furthermore, when supplying magnetic powder, if a porous layer is to be formed on one side of a plate-shaped body, it is sufficient to simply scatter the magnetic powder on that surface using gravity, but if a porous layer is to be formed in a long tube, When attempting to form a magnetic powder, it is preferable to transport and supply the magnetic powder using high-pressure gas as a medium. For example, the magnetic powder may be jetted out from a nozzle using high-pressure gas.

In addition, magnetic powder is joined to a heat transfer base made of metal by melting the coating metal on the magnetic powder, but in order to make joining easier, it is recommended to use flux or make the heating part inert or A reducing atmosphere may be used. As for the flux layer, the heat transfer substrate may be subjected to flux treatment in advance, but it is better to form the flux layer on the outermost layer of magnetic powder in advance. This is because, according to the latter, in addition to bonding magnetic powder and a heat transfer base made of gold R, it is also easy to bond magnetic powders together, so it is easy to create a porous structure in which several layers of magnetic powder are bonded. This is because it can be formed into

On the other hand, the purpose of creating an inert or reducing atmosphere in the heating section is to prevent the heat transfer substrate from oxidizing during heating.

Furthermore, when attempting to continuously form a porous layer on the inner surface of a long tube using the method of the present invention, heating is performed locally.
The heating source may be sent sequentially in one direction, or the long tube may be moved continuously in one direction. Further, in order to form a more homogeneous porous layer on the inner surface of the tube, rotational movement may be added to the movement movement in one direction.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

"Example 1" Figure 1 is for explaining the first example of the present invention, and the reference numeral 1 in the figure has an outer diameter of 9.5n+n+φ and a wall thickness of 0°3mm.
, a phosphorus deoxidized steel pipe (heat transfer base) with a length of 5000 mm. Two electrical contacts were made at one end of the copper tube 1 via a conductor roll 2, and while moving these electrical contacts toward the other end of the copper tube 1, electrical heating was performed at 300°C. Further, at this time, the copper tube 1 was rotated at a speed of 5 revolutions per minute. Then, while heating the copper tube with electricity, a jet nozzle 3 sprays magnetic powder 4 and 5 Co gas from one end of the copper tube 1.
% gas was ejected as a medium and sprayed on the inner surface (heat transfer surface) of the copper tube 1. The magnetic powder 4 is obtained by electroplating Sn to a thickness of 15 μm on the surface of Fe powder having an average particle size of 100 μm,
It has an ammonium chloride flux layer formed on the outermost layer, and is magnetized. This Fe powder was magnetized after flux treatment. After filling a plastic bottle with magnetite powder, the plastic bottle was placed between two electromagnets, and the electromagnets were activated to point it in one direction. This was done by exposing it to a K gauss magnetic field for 5 seconds. Note that a cold air blowing nozzle 5 was provided behind the energization heating section, and cold air was continuously blown onto the copper tube 1 from there to cool the copper tube 1.

In this way, a porous layer (approximately 3
A magnetic powder layer) was formed. Then, its heat exchange characteristics were measured under the following conditions using a heat transfer measuring device as shown in FIG. In this heat transfer measuring device, a refrigerant supplied from a heat exchanger 6 flows inside the copper tube 1, and constant temperature water from a constant temperature water tank 7 flows countercurrently to the refrigerant outside the copper tube 1. It flows as it should. The temperature of the constant temperature water was controlled to stabilize the refrigerant system for each refrigerant flow rate (39/hr). In addition, 8a, 8b, 8c in the figure
.

8d shows the temperature sensor, 9a and 9b show the pressure cutter, 10 shows the differential pressure gauge, 11 (Yo shows the pump, 12
a to 12p indicate valves.

Test conditions Refrigerant flow 1 (Kg/hr) 40.60.80 Evaporation temperature
℃) 5 Heating degree (℃) 5±, 5 Condensing temperature ('C) 45 Supercooling degree (''C) 10+0.5 Water amount (J/min) 9.0 Water temperature (''C) 15~25 As above When the evaporative heat transfer characteristics of the copper tube 1 were plotted using a heat transfer measurement device, the results shown by line A in FIG. 3 were obtained. On the other hand, when the characteristic values of a steel pipe without a porous layer formed on its inner surface were similarly plotted as a comparative example, the results were as shown by line B in the figure.

As shown in FIG. 3, the steel pipe manufactured by the method of the present invention exhibited heat exchange characteristics that were about 8 times as excellent as those of the comparative example (smooth steel pipe). This seems to be because nucleate boiling occurs sufficiently in the porous layer formed on the inner surface of the copper tube.

"Example 2" As magnetic powder, magnetite powder with an average particle size of 120 microns was electroplated with 5n-Pb to a thickness of 20 microns on the surface, and a flux layer of ammonium chloride was formed as the outermost layer. The conditions were the same as in Example 1, and a porous layer consisting of approximately four layers of magnetic powder was continuously formed on the inner surface of the steel pipe. The evaporative heat transfer characteristics of this steel pipe were measured under the same conditions as in Example 1, and the experimental results were not shown in the figure.
.

It exhibited approximately 10 times better heat exchange characteristics than smooth steel pipes.

"Effects" As explained above, the method for manufacturing a heat exchanger according to the present invention provides heat transfer surfaces of magnetic metal heat transfer bases such as tubes, plates, and walls that are 200°C lower than the heat transfer base. The heat transfer substrate is coated with a metal that has a melting point and further sprinkled with magnetized magnetic powder, and the magnetic powder is captured on the heat transfer surface by the magnetic force formed by the magnetic powder. The coating is heated to a temperature 20°C or more higher than the melting point of the coating metal above, and the coating metal on the magnetic powder is melted by heat transfer from the heat transfer base, and the magnetic powder is adhered to the heat transfer surface to form a porous layer. Since it is formed on a heat transfer substrate, it is possible to easily and inexpensively form a porous layer on the inner surface of a long tube or housing, which was previously considered impossible. Since it is not affected by the shape of the heat transfer surface or its position relative to gravity, it is possible to form a homogeneous porous layer over the entire heat transfer surface. Therefore, the heat exchanger manufactured by the method of the present invention has extremely good heat exchange characteristics due to capillary phenomenon and nucleate boiling phenomenon, and is suitable for evaporation tubes of air conditioning heat exchangers, heat vibrators, and the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view for explaining one embodiment of the present invention;
Figure 2 is a block diagram of an apparatus suitable for measuring the heat exchange characteristics of a heat exchanger produced by the method of the present invention, and Figure 3 is a diagram showing the evaporation of a heat exchanger obtained by the method of an embodiment of the present invention. It is a graph showing heat transfer characteristics. 1... Steel pipe (heat transfer base), 3... Spray nozzle, 4... Magnetic powder. Applicant Mitsubishi Metals Corporation

Claims (10)

[Claims] (1) The heat transfer surface of a heat transfer base made of magnetic metal, such as a tube, plate, or wall, is coated with a metal that has a melting point 200°C or more lower than that of the heat transfer base, and further magnetized magnetic powder is scattered, With the magnetic powder captured on the heat transfer surface by the magnetic force formed by the magnetic powder, the heat transfer substrate is heated to a temperature that is 100°C or more lower than its melting point and 20°C or more higher than the melting point of the coating metal on the magnetic powder, A method for manufacturing a heat exchanger body, which comprises melting a covering metal on magnetic powder by heat transfer from a heat transfer base, and closely adhering the magnetic powder to a heat transfer surface. (2) The method for manufacturing a heat exchanger according to claim 1, wherein the heat transfer substrate is a magnetic metal or a metal having a magnetic metal layer on the heat transfer surface. (3) The method for manufacturing a heat exchanger according to claim 1, wherein the heat transfer base is a tubular structure, and the tubular structure is rotated. (4) The metal coated on the magnetic powder is 3n, 3n alloy,
2. The method for manufacturing and using a heat exchanger according to claim 1, wherein the metal is a low melting point metal selected from Zn, 7n alloy, In, and In alloy. (5) The method for manufacturing a heat exchanger according to claim 1, wherein magnetization is carried out after providing the la magnetic powder metal layer and/or the flux layer. (6)! 1. The method for producing a heat exchanger according to claim 1, wherein the heat exchanger is made of magnetic powder or has a magnetic layer. (7) The method for manufacturing a heat exchanger according to claim 1, characterized in that the magnetic powder is supplied to the heat transfer surface of the heat transfer base while being dispersed in a gas. (8) The method for producing a heat exchanger according to claim 7, wherein the gas is inert or reducing. (9) A method for manufacturing a heat exchanger according to claim 1, characterized in that a flux layer is provided as the outermost layer of magnetic powder. (10) The method for manufacturing a heat exchanger according to claim 1, characterized in that an inert or reducing atmosphere is formed on the outer surface of the heat transfer substrate being heated.