JPS61228294A - Heating tube and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a porous heating tube having uniformly distributed fine holes whose diameter can be freely set up by using metal particles whose grain size is of free selectivity by bonding plural metal particles layers through a brazing to the surface of a heating tube. CONSTITUTION:The heating surface of a heating tube is formed by providing a porous layer 5 consisting of metal particles 3 of a grain size of 100-300mum, which are bonded and fixed metallurgically through a braze 2 to the inner surface of the tube and manu pores 4. Many pores 4 in the porous layer 5 servo to facilitate occurrence of the ebullition phenomenon of fluid inside the tube and the countless globular metal particles 3 servo to greatly increase the actual heating area. As the metal particles 3, copper particles may be cited, and as an adhesive metarial, styrene-butadiene may preferably be used. Also, as the braze 2, Sn or Sn-Pb alloy may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-performance heat exchanger tube having a porous layer on the inner surface of the tube and a method for manufacturing the same.

(Prior art) As a method for improving the performance of a heat exchanger, irregularities are mechanically provided on the outside or inside of the heat exchanger tubes used in the heat exchanger, as shown in FIGS. 6 and 7. Heat transfer tube with increased actual heat transfer area (the former is called a finned tube, the latter is called a grooved tube)
have been put into practical use, but in both cases, the rate of improvement in heat transfer coefficient is at most 1.5 to 1.5 for pipes without unevenness (called smooth pipes).
It is only 2.5 times.

Therefore, as a method to further improve the heat transfer coefficient, in recent years, a porous layer with many pores made of fine particles has been added to the outside or inside of the tube to increase the heat transfer area and improve nucleate boiling transfer. Porous tubes with improved heat transfer performance have been developed and studied, and it has become clear that they have several times the performance of the finned tubes and grooved tubes.

These porous tube manufacturing methods include: (2) applying a mixture of metal particles and a binder to the inside or outside of the tube and then sintering;
Alternatively, a method has been announced in which metal oxide particles and organic matter are simultaneously electrodeposited and then sintered while the organic matter is heated and evaporated, and a method in which fine metal particles are fixed and deposited inside a tube by zero-ray detonation spraying.

However, the first drawback of the above-mentioned conventional methods is that a porous layer that is homogeneous and highly reproducible cannot be obtained. It is not possible to manufacture heat exchanger tubes with

In other words, in order to obtain stable performance, the metal particles forming the porous layer must not only have a spherical shape and a uniform particle size, but also the arrangement of the particles must be uniform in two or three dimensions. Must be.

For example, if the metal particle size is 10 to 20μ or less, it is sufficient, but if the metal particle size is 30 to 50μ or more, the adhesion force of the binder to the applied layer of the mixture may be lower than that of the metal on a curved surface such as a pipe surface. The particles cannot overcome the gravity exerted on them, move in the direction of gravity, and aggregate, making it impossible to arrange the particles uniformly on the pipe surface. This tendency becomes more pronounced as the pipe diameter becomes smaller.

In method 2, the current density differs between the center and the ends of the tube length, making it impossible to obtain a deposited layer with a uniform thickness, resulting in non-uniform particle arrangement in the three-dimensional (thickness) direction of the porous layer. become. Also, similar to the method, an organic medium (
Since the bonding force of ethylene glycol, isopropyl alcohol, etc. is very weak, the arrangement is easily disrupted by particles falling off or moving by gravity, making it difficult to use a practical method.

In the boiling method, particle shape and particle size are unrestricted;
The arrangement will not be non-uniform, but the pore diameters occupied in the obtained porous layer will be too small, 5 to 10 μm or less.

The second drawback is that both the ni), @, and work methods (1)
It is impossible to freely select the particle size, (21) it is difficult to treat the inner surface of a thin tube with an inner diameter of φ10- or less, and
■, (In O, (3) it is impossible to process a long pipe of 1 m or more directly inside the pipe, and in (C), (4) it is impossible to process it outside the pipe, etc.) Each has poor processing performance.

(Problems to be Solved by the Invention) The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional ones, (to) allow the particle diameter to be freely selected, the pore diameter to be arbitrarily set, and (
2) Pores can be distributed homogeneously; (3)
It is an object of the present invention to provide a porous heat exchanger tube that is easy to manufacture and has few application restrictions, and a method for manufacturing the porous heat exchanger tube.

(Means for Solving the Problems) The present invention relates to a heat exchanger tube in which a plurality of metal particle layers are fixed to the heat transfer surface of the heat exchanger tube via a brazing material.

Furthermore, the present invention is a method for manufacturing a heat exchanger tube including the following steps (f) to (e).

(f); Step of applying a thin layer of adhesive to the heat transfer surface of the heat transfer tube base material or the metal particle layer after the step (described below).

(b); (f) A step of placing metal particles on the adhesive layer after the step and rotating to form a uniform and dense layer of metal particles.

f'): A process of taking out the remaining metal particles after the @ process.

B): After the C9 step, a step of removing the adhesive.

(F): (D) Spraying a brazing material on the metal particle layer after the process,
It relates to the process of heating and brazing.

The technical point when creating a porous layer using fine metal particles is how densely and uniformly the particles, which are the main components, are arranged in two and three dimensions (thickness direction). The present invention solves this problem by using an adhesive as a presetting agent. That is, for example, particles are placed in a heap υ on a part of a flat adhesive-coated surface,
After giving it a slight vibration, when it is turned over, only the particles that were not captured by the adhesive (excess) will fall out, and the particles will be in a state where the particles are densely and uniformly arranged without overlapping each other like a dumpling. This is an application of the fact that it is easily obtained and has sufficient particle adhesion.

Furthermore, according to the present invention, an extremely homogeneous porous membrane can be easily produced in a small diameter tube with an inner diameter of 10 m or less, compared to other methods.

As shown in FIG. 1, the porous tube according to the present invention consists of an ordinary tube 1 with a smooth heat transfer surface and a particle diameter of 100 to 500 metallurgically bonded and fixed to the inner surface of the tube with a brazing filler metal 2. p...
It has a porous layer 5 formed of metal particles 3 and a large number of voids 4.

The large number of voids 4 in the porous layer 5 facilitate the occurrence of nucleate boiling of the fluid within the tube, and at the same time, the countless spherical metal particles 3 increase the actual heat transfer area in a flying manner.

In the present invention, copper particles are preferably used as the metal particles 5. Furthermore, as the adhesive, a styrene-butadiene adhesive is preferably used. Further, as the brazing material 2, tin or a tin-lead alloy can be used.

(Effects of the Invention) The heat transfer efficiency of the heat transfer tube according to the present invention is 5 to 6 times that of a smooth tube and 2 to 3 times that of a grooved tube (inner surface). If used in heat exchangers for industrial use, it will be possible to improve performance or reduce size and weight.

Next, as a raw pipe (smooth pipe), the length is 1000 mm and the outer diameter is 9
．． A specific example of the manufacturing method and performance of a porous pipe using O copper particles with a spherical diameter of 200 pm as the metal particles will be described for a steel pipe with an inner thickness of 5 tea and an inner thickness of 35 m.

(1) After spraying a solution of a styrene-butadiene adhesive dissolved in an organic solvent (triclene) (adhesive content 2 (weight S)) into the tube, air is blown in to volatilize and dry the solvent.

(2) Next, sieved copper particles having a nine-ball diameter of 200 μm are filled from one side of the tube while rotating the tube at an angle of about 20'.

After filling is completed, remove the other stopper and remove the excess copper particles that did not adhere to the tube wall.

(3) Next, spray 1 flux (20% by weight tin chloride solution) into the tube and dry it in a 100°C oven for 10 minutes.

(4) Furthermore, the above (1), +21, r3
) to temporarily fix the second layer of particles.

(5) Next, add tin wax (200 mesh tin powder) to about a,0
After spraying so that it adheres to the equivalent of 1t/i, SSO~
Heat in a 500°C oven for 10 to 20 minutes and braze.

The surface condition of the inner porous tube created by the above method is as follows.
As shown in the photomicrograph (5x magnification), the copper particles are uniformly arranged and in a state of mourning.The photomicrograph (200x magnification) in Fig. 3 shows that not only the copper particles but also the copper particles and the pipe wall are clearly visible. As shown, it is completely soldered with tin wax. In addition, the cross section perpendicular to the tube axis is the same as the one in the micrograph (7x magnification) in Figure 4.
In this case, two layers of copper particles are uniformly distributed along the inner circumference of the pipe.

In Fig. 3, 1' is a steel pipe, 2' is a tin solder, and 3 is a steel pipe.
1 indicates copper particles.

As a result of comparing the heat transfer performance of the porous tube manufactured by the above method with that of a smooth tube and a grooved tube using a fluorocarbon refrigerant (Freon R11), as shown in FIG. , 5 to 6 times that of smooth tubes, and grooved tubes, respectively.
It was 2 to 3 times more.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cross section of a porous tube according to the present invention. Figure 2 is a micrograph (magnification: 5x) showing the surface condition of the porous tube according to the present invention, Figure 3 is a micrograph (magnification: 200x) showing the arrangement of copper particles. The figure is a micrograph (7x magnification) showing a cross section of the same porous tube perpendicular to the tube axis. FIG. 5 is a comparison diagram of heat transfer performance. FIGS. 6 and 7 schematically show heat exchanger tubes used in conventional heat exchangers. Sub-agent 1) Meiji agent Ryo Hagiwara - Figure 5 General 1 Figure 2 Figure 4

Claims (2)

[Claims] (1) A heat exchanger tube in which multiple layers of metal particles are fixed to the heat transfer surface of the tube via a brazing material. (2) A method for manufacturing a heat exchanger tube including the following steps (a) to (e). (A): A step of applying a thin layer of adhesive to the heat transfer surface of the heat transfer tube base material or the metal particle layer after the step (D) below. (B): (B) A step in which metal particles are placed on the adhesive layer after the step and rotated to form a uniform and dense layer of metal particles. (c): After the (b) process, a process of taking out the remaining metal particles. (d): After the step (c), a step of removing the adhesive. (E): (D) Spraying a brazing material on the metal particle layer after the process,
The process of heating and brazing.