JP2002130975A - Method for heat-transfer augmentation by using metal thin-wire porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for heat-transfer augmentation by using a metal thin-wire porous body widely utilized in industrial plants, in which a metal is worked into a thin wire to form a porous body of a high porosity, the porous body is inserted in various ducts, round, rectangular, etc., to augment heat transfer between fluid and the duct wall without working the duct wall, including heat-transfer augmentation for a catalyst tube of steam reforming apparatus by helium-gas heating. SOLUTION: A thin-wire porous body of a high porosity is formed by working a specific metal into a thin wire, and the wire is inserted in a duct to be heated or cooled. A fluid is allowed to flow in the duct to carry out heat-exchange between the fluid and the solid wall of the conduit including the porous body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for promoting heat transfer which is currently used in many industrial plants and the like. In particular, the present invention forms a porous body having a high porosity by thinning a metal, and by inserting this into a flow path, heat exchange between the fluid and the flow path wall without processing the flow path wall surface. It is a way that can be promoted. The present invention is specifically used to promote heat exchange by being inserted into various flow paths such as circular and rectangular tubes, and is also used to promote heat transfer of a steam reformer catalyst tube by helium gas heating. You.

[0002]

2. Description of the Related Art In the prior art, there is a method in which a protrusion such as a fin is attached to an inner wall of a flow path in a direction orthogonal or parallel to a flow to promote heat transfer, or a method in which a twisted tape is inserted to promote heat transfer. .

[0003]

The conventional heat transfer enhancement method has a disadvantage that it is not easy to weld a projection to the inner wall of a circular tube or a rectangular tube or to machine the wall surface. In addition, when welding inspection of the flow path where the projection is welded is required, there is a disadvantage that it is difficult to inspect the welded portion.

[0004]

SUMMARY OF THE INVENTION In order to solve the problems of the prior art and realize a revolutionary heat transfer enhancement technique, the present invention provides a porous body having a high porosity obtained by thinning a metal. A method of promoting heat transfer by utilizing the method has been devised.

That is, in the present invention, instead of a conventional projection such as a fin or a twisted tape provided in a flow path for promoting heat transfer, a thin wire having a high porosity is formed by thinning a specific metal. By forming a porous body, inserting it into the flow path to be heated or cooled, flowing fluid through the flow path, and exchanging heat between the fluid and the solid wall of the flow path including the porous body by a heat transfer promotion method There are copper wires, stainless steel wires and the like as the fine wires, and helium, water vapor and the like as the fluid.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The production of a porous body of a fine metal wire having a high porosity is as follows, taking the case of a circular channel as an example. A cylindrical object that can be inserted into the flow path is manufactured by forming a thin wire having a diameter of about 0.5 mm into a net shape, and a metal thin wire is inserted into the bundle in a spiral or spiral shape. The porosity can be calculated from the volume of the thin wire required for manufacturing the cylindrical object and the diameter and length of the bundled wire inserted into it, so the porosity is set by adjusting the diameter and length of the inserted thin wire I do. By fabricating such a porous body in advance and inserting it into the flow passage as needed, a flow passage having heat transfer and pressure loss suitable for the flow passage can be formed. It is considered that a porosity of 0.9 or more is appropriate from the viewpoint of reducing pressure loss.

In the heat transfer of the horizontal circular flow pipe of the present invention shown in FIG. 1, when a fluid flows into a circular pipe into which a bundle of bundled metal wires is inserted and is heated from around the pipe wall, the flowing fluid is heated. Then, the flow pipe is cooled. In the heat transfer of the vertical single-sided heated square flow channel tube of the present invention in FIG. The incoming fluid is heated and the heated surface is cooled. In the heat transfer of the annular flow path pipe of the present invention in FIG. When a low-temperature fluid flows through the inner pipe, the high-temperature fluid flowing on the outer pipe side of the annular flow path pipe heats the thin metal wire, thereby heating the inner pipe of the annular flow path, and the low-temperature fluid flowing there is heated. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a specific metal (for example, copper or stainless steel) thinned (appropriately 1.0 mm or less) is inserted into a circular pipe flow path as a porous body, and a horizontal circular pipe is surrounded by To remove the heat by flowing the fluid. Alternatively, as shown in FIG. 2, a porous body of a thin metal wire is inserted into a vertical square channel heated from one side, and a fluid is flown to remove heat. FIG. 3 shows a method in which a heated fluid is caused to flow through an annular flow passage to heat the inner wall of the inner tube and heat the fluid flowing therethrough.

The following describes, as an example, a change in the amount of heat removal when a thin metallic copper wire is inserted into a horizontal circular tube heated from the surroundings and cooled by forced convection of air. The porosity was measured in the case of 0.993 or more from the viewpoint of suppressing pressure loss. FIG. 4 shows the effect of increasing the amount of heat removed from a circular tube when this method is used. The horizontal axis is the heating input, and the vertical axis is the value obtained by dividing the amount of heat when a thin metal wire according to the method of the present invention is inserted into a circular tube by the amount of heat removal when nothing is inserted into the flow path.

When the heat input is about 320 W, the maximum temperature of the tube wall rises to about 160 ° C., and the amount of heat removed by the method of the present invention is increased by 20% or more as compared with the case of a circular tube having a smooth surface. Understand. Furthermore, since the effect of increasing the amount of heat removal is increased with respect to the increase in heat input, the higher the heating surface becomes, the more the heat transfer effect by heat radiation increases.
It is expected that the heat removal will also increase.

[0011]

According to the present invention, since the heat transfer surface is not processed, the inspection of the welded portion and the reduction in the structural strength of the heat transfer surface due to the processing are considered in comparison with the conventional method of promoting heat transfer by a projection. No need, it is economically good.

In the heat transfer promoting method using a porous metal thin wire, the heat transfer area to a cylinder having a higher heat transfer coefficient than that of a smooth surface increases, so that the friction loss due to the increase of the surface area increases. However, since the amount of heat transfer from the heating surface and the thin metal wire surface is large, the heat transfer performance is equal to or higher than that of the conventional heat transfer enhancement method. Further, when the fluid is a gas, the heat transfer effect by heat radiation is increased under high temperature conditions, so that the heat transfer performance is further improved. Further, a porous body having a different porosity or a different material is previously manufactured in the flow path. This makes it possible to easily change the heat transfer and the pressure loss of the entire flow channel.

[Brief description of the drawings]

FIG. 1 is a diagram showing the promotion of heat transfer in a conventional horizontal circular channel and a horizontal circular channel in which a porous metal thin body according to the present invention is inserted.

FIG. 2 is a diagram showing the promotion of heat transfer in a vertically heated single-sided square channel in the present invention.

FIG. 3 is a diagram showing heat transfer promotion of an annular flow channel in the present invention.

FIG. 4 is a diagram showing the effect of increasing the amount of heat removal when a porous metal thin wire according to the present invention is inserted into a horizontal circular channel.

Claims (1)

[Claims] A thin metal porous body having a high porosity is formed by thinning a specific metal, inserted into a flow path to be heated or cooled, and a fluid is caused to flow through the flow path to include the porous body. Heat transfer between the solid wall of the flow channel and the fluid.