CN110806135A

CN110806135A - Composite heat conduction pipe containing low-melting-point metal and production method thereof

Info

Publication number: CN110806135A
Application number: CN201911003653.4A
Authority: CN
Inventors: 李为冬
Original assignee: DEQING JINYE ELECTRIC POWER TECHNOLOGY Co Ltd
Current assignee: DEQING JINYE ELECTRIC POWER TECHNOLOGY Co Ltd
Priority date: 2019-10-22
Filing date: 2019-10-22
Publication date: 2020-02-18
Also published as: WO2021077764A1

Abstract

The invention relates to the field of heat exchange equipment manufacturing, in particular to a composite heat conduction pipe containing low-melting-point metal and a production method thereof. The invention is realized by the following technical scheme: the utility model provides a compound heat pipe that contains low melting point metal, contains rigid body inlayer, still contains the rigid body skin and is located the rigid body skin with flexible heat-conducting layer between the rigid body inlayer, flexible heat-conducting layer contains low melting point metal. The invention aims to provide a composite heat conduction pipe containing low-melting-point metal and a production method thereof, wherein the composite heat conduction pipe has good heat conduction performance, can fully and effectively preheat air in the pipe, solves the problem of structural rigidity, is not easy to damage in the links of installation, transportation and end part welding, and keeps the stability of a product.

Description

Composite heat conduction pipe containing low-melting-point metal and production method thereof

Technical Field

The invention relates to the field of heat exchange equipment manufacturing, in particular to a composite heat conduction pipe containing low-melting-point metal and a production method thereof.

Background

Heat exchange boxes and preheating boxes are common industrial components and are widely used in various industrial fields. Taking the power generation industry as an example, a plurality of heat exchange tubes are arranged in a preheating tube box, common air flows in the tubes, and high-temperature gas generated in the previous working procedure, such as flue gas, can flow outside the tubes in the tube box. These high temperature gases conduct heat to the heat exchange tubes and preheat the air in the heat exchange tubes.

In the prior art, a new preheater for a thermal power generation boiler is disclosed in chinese patent publication No. CN2901219Y, which provides a plurality of heat exchange tubes. The structure of the heat exchange tube is a common double-layer structure, the inner ring is a steel tube, and the outer ring is an enamel surface layer.

The enamel surface is arranged outside the steel pipe, because enamel has a certain corrosion isolation effect, the enamel protects the steel of the inner ring, and the heat exchange pipe with the double-layer structure is applied in China for more than 20 years, but the structure has various defects.

Firstly, with the further requirements of environmental protection in China, the flue gas denitration adopts an ammonia process. The sulfur trioxide in the flue gas reacts with ammonia to generate ammonium bisulfate, and the temperature of the substance is reduced to 154 ℃, so that the substance is viscous liquid. The smoke contains a large amount of particles, and the particles and the viscous liquid are polymerized and adhered to the outer surface of the exchange tube, so that the whole air preheater is blocked. In the prior art, the cleaning device can only be used for mechanically cleaning the outer surface of the exchange tube, but due to the brittleness of the enamel layer, the enamel layer of the enamel tube is damaged in the cleaning process, and the corrosion resistance is invalid.

Secondly, the heat conductivity coefficient of the enamel is not high, and the enamel is not ideal in heat conduction efficiency, so that the heat exchange tube has a flat preheating effect on air in the tube.

Thirdly, during installation, the ends of the heat exchange tubes need to be welded to the tube sheet of the tube box. In the process of end welding, the enamel layer cracks due to the difference of the thermal expansion coefficient of the enamel layer and the steel.

Finally, the enamel layer on the outer layer of the heat exchange tube is fragile and has poor impact resistance. This makes the tubes highly susceptible to damage to the enamel layer during shipping and installation.

Disclosure of Invention

The invention aims to provide a composite heat conduction pipe containing low-melting-point metal and a production method thereof, wherein the composite heat conduction pipe has good heat conduction performance, can fully and effectively preheat air in the pipe, solves the problem of structural rigidity, is not easy to damage in the links of installation, transportation and end part welding, and keeps the stability of a product.

The technical purpose of the invention is realized by the following technical scheme: the utility model provides a compound heat pipe that contains low melting point metal, contains rigid body inlayer, still contains the rigid body skin and is located the rigid body skin with flexible heat-conducting layer between the rigid body inlayer, flexible heat-conducting layer contains low melting point metal.

Preferably, the inner rigid body layer is made of carbon steel, and the outer rigid body layer is made of stainless steel.

Preferably, the melting point of the low-melting metal is 50 ℃ to 110 ℃.

Preferably, the low-melting metal is a bismuth alloy.

Preferably, the low-melting-point metal is a gallium alloy.

Preferably, the low-melting metal is metallic sodium.

A method for producing a composite heat conductive pipe containing a low melting point metal, comprising the steps of:

s01, performing inner-layer shot blasting,

performing shot blasting treatment on the inner layer of the rigid body;

s02, a three-layer compounding step,

compounding the rigid body inner layer with the sleeved flexible heat conduction layer, and then sleeving the rigid body outer layer to obtain a composite pipe;

s03, a drawing step,

placing the composite tube into a stainless steel compounding machine for drawing treatment, so that the outer layer of the rigid body is reduced in diameter and is tightly combined with other layers;

s04, a step of cutting,

and cutting to obtain a finished product.

In conclusion, the invention has the following beneficial effects:

1. the stainless steel on the outermost layer has good corrosion resistance, and can be reliably applied to the flue gas corrosion-resistant environment of wet desulphurization.

2. The low-melting-point metal is liquid in a working state, so that the heat conduction effect among layers is greatly enhanced.

3. Outmost and the steel construction design of inlayer for this kind of compound heat conduction stainless steel pipe possesses good structural strength and shock-resistant ability, all links in transportation, installation, clearance, welding can not appear damaged or break.

Detailed Description

The present invention will be described in further detail below.

The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.

Embodiment 1 is a composite heat conductive pipe having a three-layer structure including, from the outside to the inside, a rigid outer layer, a flexible heat conductive layer, and a rigid inner layer. Wherein, the heat conducting pipe flows with ordinary and non-corrosive air, and ordinary carbon steel can be used. And the rigid body outer layer of the outermost layer is made of 316L stainless steel. The stainless steel is not easy to corrode in the working environment contacting with various flue gases, and can be widely applied to flue gas corrosion prevention of wet desulphurization.

The material used for the middle layer, i.e. the flexible heat conducting layer, is a low melting point metal. These low melting point metals are in a solid state in a normal non-operating state, but in an operating state, the temperature of the entire heat transfer pipe is raised, and these low melting point metals are in a liquid state. In the present embodiment, a bismuth alloy is used.

The reason for this is that, in spite of the close fit between the layers of the composite pipe, whether it is enamel or other materials in the prior art, in the microscopic state, the layers are in point contact, i.e., there is a gap. These gaps are filled with air, which greatly reduces the heat transfer effect. In the scheme, the flexible heat conduction layer made of the bismuth alloy material is arranged between the rigid inner layer and the rigid outer layer, the flexible heat conduction layer is changed into a liquid state under the working state, the contact area between the materials is greatly increased, and the flexible heat conduction layer is in surface contact with the rigid inner layer and the rigid outer layer under the microscopic state and has good heat conduction performance. According to the test data, the thermal conductivity coefficient of the traditional technical scheme using enamel is 9 w/(m.k), while the thermal conductivity coefficient of the embodiment reaches 16.2 w/(m.k).

The bismuth alloy is different from other common materials, and does not have chemical reaction on the stainless steel of the outer layer and the stainless steel of the inner layer even at high temperature, so that the workpiece has good stability. And the bismuth alloy is non-flammable and explosive, is also nontoxic and tasteless, and is green and environment-friendly. The working state is liquid, but it is not volatile and oxidized.

Because the stainless steel of the outer layer has stronger structural rigidity, the stainless steel is not easy to break or crack in the transportation and installation processes. In the process of welding and connecting the end part of the composite heat conduction pipe with the pipe box plate, the rigid body inner layer and the rigid body outer layer are both made of rigid materials and can be welded with the pipe box plate, and the rigid body inner layer and the rigid body outer layer are naturally welded into a whole in the welding process, so that the phenomenon that the end part is broken due to different expansion coefficients of the materials is avoided.

The composite heat conducting pipe is produced through the first ball blasting treatment of the inner layer of the rigid body, i.e. the carbon steel layer. Subsequently, a flexible heat conductive layer is sheathed. Then the two layers are sleeved into the rigid outer layer, namely the stainless steel layer. Finally, the composite layer is led into a stainless steel compound machine for drawing treatment, so that the outer layer of the rigid body, namely the stainless steel outer tube, is reduced in diameter and is tightly combined with other layers. Cutting off and sizing to obtain the finished product of the technical scheme.

Example 2, unlike example 1, the material used for the flexible heat conductive layer was a gallium alloy.

Example 3, unlike example 1, the material used for the flexible heat conductive layer was sodium metal, which has a melting point of 97.72 degrees celsius.

In addition, the melting points of the alloys with different formulations and different proportions are different, and in the technical scheme, the alloys are required to be solid in a non-working state, and become liquid at a temperature above the melting point in a working state, and the melting point is preferably 50-110 ℃, such as 70 ℃, 90 ℃, 100 ℃ and the like through tests of the applicant.

Claims

1. A composite heat conducting pipe containing low melting point metal comprises a rigid body inner layer and is characterized in that: still contain rigid body skin with be located the rigid body skin with flexible heat-conducting layer between the rigid body inlayer, flexible heat-conducting layer contains low melting point metal.

2. A composite heat conductive pipe containing low melting point metal according to claim 1, characterized in that: the inner layer of the rigid body is made of carbon steel, and the outer layer of the rigid body is made of stainless steel.

3. A composite heat conductive pipe containing low melting point metal according to claim 1, characterized in that: the melting point of the low-melting-point metal is 50-110 ℃.

4. A composite heat conductive pipe containing low melting point metal according to claim 1, 2 or 3, characterized in that: the low-melting-point metal is bismuth alloy.

5. A composite heat conductive pipe containing low melting point metal according to claim 1, 2 or 3, characterized in that: the low melting point metal is gallium alloy.

6. A composite heat conductive pipe containing low melting point metal according to claim 1, 2 or 3, characterized in that: the low-melting-point metal is metallic sodium.

7. A method for producing a composite heat conductive pipe containing a low melting point metal as claimed in any one of claims 1 to 6, comprising the steps of:

s01, performing inner layer shot blasting, namely performing shot blasting on the inner layer of the rigid body; s02, compounding three layers, namely compounding the rigid body inner layer with the sleeved flexible heat conduction layer, and then sleeving the rigid body outer layer to obtain a composite pipe; s03, a drawing step, namely placing the composite tube into a stainless steel compounding machine for drawing treatment, so that the outer layer of the rigid body is reduced in diameter and is tightly combined with other layers; and S04, cutting to obtain a finished product.