CN113513933B - Heat pipe, heat exchanger and pressure shell integrated structure and processing technology - Google Patents

Abstract

The present invention discloses an integrated structure of a heat pipe, a heat exchanger and a pressure shell, comprising a heat pipe, a heat exchanger and a pressure shell. The heat exchanger is embedded in the inner cavity of the pressure shell, the inner air passage of the heat exchanger is connected to the expansion cavity, and the outer air passage is adjacent to the end face of the regenerator; the heat pipe is inserted between the inner and outer air passages of the heat exchanger from the top of the pressure shell parallel to the axis of the pressure shell; it also comprises an air passage connecting component disposed between the pressure shell and the heat exchanger, which is used to connect the inner and outer air passages of the heat exchanger. The integrated structure realizes the casting of the heat exchanger in the inner cavity of the pressure shell through embedded parts and the processing technology disclosed in this case, and can ensure the airtightness between the heat pipe and the pressure shell and the efficient heat exchange between the heat pipe and the heat exchanger flow passage. This configuration does not require welding, has excellent reliability and long service life; it is used in Stirling engines and is suitable for adapting to non-combustion heat sources; it is used in Stirling refrigerators and is suitable for scenarios where long-distance cold transport is required.

Description

A heat pipe, heat exchanger and pressure shell integrated structure and processing technology

Technical Field

The invention relates to the technical field of Stirling devices, and in particular to an integrated structure of a heat pipe, a heat exchanger and a pressure shell and a processing technology.

Background Art

The Stirling device uses the Stirling cycle as its working principle. It is a closed-cycle machine that works based on the temperature difference of the heat source. The working medium is usually helium, which is environmentally friendly. According to the purpose, it is divided into two categories: the one using the forward Stirling cycle is called a Stirling engine, and the one using the reverse Stirling cycle is called a Stirling refrigerator. The Stirling engine is suitable for use in underwater power, space power, solar dish power generation, cogeneration and other scenarios; refrigerators are used in infrared, superconducting device cooling, biological, pharmaceutical refrigeration and cold chain and other fields.

At least two movers are required inside the Stirling machine to achieve volume changes in the expansion chamber and the compression chamber. The mover whose end is close to the compression chamber is called a power piston or a compression piston, and the mover whose end is close to the expansion chamber is called a displacer or a gas distribution piston; the reciprocating motion of the two movers will drive the working fluid to shuttle back and forth between the expansion chamber and the compression chamber through the adjacent heat exchangers, regenerators, and cooler flow channels. In this process, the pressure of the working fluid will undergo periodic changes that are not synchronized with the displacement of the movers, thereby generating heat-work conversion. The cooler is arranged between the compression chamber and the normal temperature end face of the regenerator. It is usually of the partition fin type or shell and tube type. The compression heat generated by the working fluid during the compression process is carried and released by external airflow or water flow. The heat exchanger is arranged between the expansion chamber and the very low temperature end face of the regenerator. At present, the industry mainly adopts two structural types: tube bundle heat exchanger and fin heat exchanger. The 1KW MCHP model produced by Microgen uses a finned structure; the book "Stirling Engine Technology" published by Harbin Engineering University Press introduces these two structural types and working principles on pages 112 to 125. In a small low-temperature Stirling refrigerator, because the heat exchanger load is small, the fin structure or copper foil is generally folded and brazed to the inner wall of the pressure shell to meet the application requirements. For large machines, especially high-power Stirling engines, the heat exchange load to be borne by the heat exchanger is very large, and the heat exchange capacity can reach tens or even hundreds of kilowatts. Stirling engines driven by direct fuel combustion generally use tube bundle heat exchangers. The advantage of the tube bundle structure is that the internal empty volume is small, but the heat exchange surface area is large, and the working fluid flows in the tube for a long distance, so the heat exchange is sufficient. Its disadvantage is that the two ends of each tube in the tube bundle need to be welded to the corresponding position on the pressure shell, and there are usually dozens to hundreds of welding points, which makes the assembly and welding process complicated; and the welding points are prone to cracking and failure under the dual effects of thermal stress and internal alternating air pressure.

In the actual application of Stirling devices, when it is necessary to transport the cold of the refrigerator over long distances, such as in low-temperature cold storage, or to transmit non-flame combustion heat, such as nuclear reaction heat, it is necessary to set up a secondary circuit for carrying cold or heat between the cold area or the driving heat source and the Stirling device. The secondary circuit can use an adapted fluid or molten salt pump pressure circulation, or a heat pipe can be used as a solution for transporting cold or heat.

The heat pipe is a heat transfer element invented by researchers at the Los Alamos National Laboratory in the United States in the 1960s. Its thermal conductivity exceeds that of any known metal. Heat pipes were previously widely used in aerospace, atomic energy, military and other industries, and are now widely used in electronic heat dissipation. Heat pipes use the phase change process of the medium evaporating at the hot end and condensing at the cold end to quickly conduct heat. Heat pipes are generally composed of a tube shell, a liquid wick and an end cover; the tube shell is made of metal material, and the liquid wick is mostly made of capillary porous materials. After the inside of the heat pipe is evacuated into a vacuum negative pressure state, it is filled with an appropriate amount of working fluid to have the ability to work in the corresponding temperature zone. One end of the heat pipe is the evaporation end, and the other end is the condensation end. When one end of the heat pipe is heated, the liquid in the capillary tube vaporizes rapidly, and the vapor flows to the other end under the power of heat diffusion, and condenses at the cold end to release heat. The liquid then flows back to the evaporation end along the porous material by capillary action, and the cycle continues until the temperatures at both ends of the heat pipe tend to be equal.

Heat pipes can be divided into low-temperature heat pipes, normal-temperature heat pipes and medium- and high-temperature heat pipes according to their temperature. High-temperature heat pipes use liquid metals such as sodium and potassium as working media; low-temperature heat pipes use ammonia, freon, propane, nitrogen, etc. as working media depending on the temperature range of use.

The material selection for the pressure shell on the top of the Stirling device is preferably a material with good thermal strength and strong resistance to cold brittleness, such as a high-temperature alloy. The thermal conductivity of this type of metal is low. If the heat pipe is integrated outside the Stirling pressure shell, the economy of the system will be reduced due to the large heat transfer thermal resistance. If the heat pipe is to be integrated inside the Stirling pressure shell, it is necessary to ensure that the structure of the heat pipe passing through the shell has reliable airtightness. Welding the annular seam of the through hole to plug leaks is a conventional technical solution, but as mentioned earlier, the welding points between the pressure shell and the tube shell will reduce the reliability of the system. If the configuration structure can achieve excellent airtightness under the premise of efficient heat transfer, it will greatly improve the reliability and product strength of the Stirling device.

Summary of the invention

In view of the above technical problems, the present invention proposes an integrated structure of a heat pipe, a heat exchanger and a pressure shell. The integrated structure realizes the casting of the heat exchanger in the inner cavity of the pressure shell through embedded parts and the processing technology disclosed in this case, and can ensure the airtightness between the heat pipe and the pressure shell and the efficient heat exchange between the heat pipe and the heat exchanger flow channel. This configuration does not require welding, has excellent reliability and long service life.

A heat pipe, heat exchanger and pressure shell integrated structure, comprising a heat pipe, a heat exchanger and a pressure shell, wherein the inner air duct of the heat exchanger is connected to an expansion chamber, and the outer air duct is adjacent to the end face of a heat regenerator, and also comprises an air duct connecting portion, wherein the heat exchanger is embedded in the top of the inner cavity of the pressure shell, and the heat pipe is inserted between the inner and outer air ducts of the heat exchanger from the top of the pressure shell parallel to the axis of the pressure shell, and the air duct connecting portion is arranged between the pressure shell and the heat exchanger, and is used to connect the inner air duct and the outer air duct of the heat exchanger.

As a preferred embodiment of the above technical solution, the air duct connecting part is annular, and an annular groove is provided on the side of the air duct connecting part facing away from the heat exchanger. The annular groove is evenly provided with hollow bosses with the same number as the heat pipes along the circumference, and through holes connecting with the inner air duct and the outer air duct of the heat exchanger are evenly provided along the circumference on both sides of the hollow boss in the annular groove, and the heat pipe is inserted into the heat exchanger through the hollow boss.

As a preferred embodiment of the above technical solution, the inner diameter of the hollow boss is larger than the outer diameter of the heat pipe, and the hollow boss is coaxially arranged with the heat pipe.

As a preferred embodiment of the above technical solution, the top of the pressure shell is a hollow structure.

As a preferred embodiment of the above technical solution, the melting point of the material used to make the heat exchanger is lower than the melting point of the material used for the airway connecting part, the melting point of the material used for the pressure shell and the melting point of the material used for the heat pipe.

A processing technology for producing any one of the above-mentioned heat pipes, heat exchangers and pressure shell integrated structures, the specific steps of the processing technology are:

Step 1: prepare the pressure shell, use vacuum casting or drawing die to prepare the pressure shell blank, and machine it to serve as the lower mold for casting the heat exchanger;

Step 2: insert the heat pipes not filled with working medium into the pressure shell along the through holes matched with the number of heat pipes to the designed depth;

Step 3: Assemble the airway connecting part and embed it into the top of the inner cavity of the pressure shell, with the side with the annular groove facing away from the opening direction of the pressure shell, and each hollow boss maintains coaxiality with the heat pipe therein;

Step 4: assemble the upper mold, insert the core column into the through holes at the corresponding positions on the airway connecting part in sequence, insert the upper mold to the designed depth along the direction coaxial with the inner cavity of the pressure shell, and form the contour envelope of the heat exchanger together with the airway connecting part, the core column and the inner cavity of the pressure shell;

Step 5, casting the heat exchanger, casting the heat exchanger into shape in one step;

Step 6, take out the upper mold and the core column;

Step seven, filling the heat pipe with working medium and sealing the heat pipe, thus completing the manufacture of the integrated structure of the heat pipe, heat exchanger and pressure shell.

The beneficial effects of the present invention are:

The creative configuration integrates three components with different functions, namely the heat pipe, the heat exchanger and the pressure shell, during the manufacturing process. Through the embedded parts and the processing technology disclosed in this case, the heat exchanger is cast in the inner cavity of the pressure shell, and the airtightness between the heat pipe and the pressure shell and the efficient heat exchange between the heat pipe and the heat exchanger flow channel can be ensured. This configuration does not require welding, has excellent reliability and long service life. When used in Stirling engines, it is very suitable for nuclear energy heat sources; when used in Stirling refrigerators, it is suitable for scenarios that require long-distance cold transport. It can greatly improve the reliability and product strength of the Stirling device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of the present invention.

FIG. 2 is a longitudinal sectional view of the present invention.

Figure 3 is a schematic diagram of the air channel connecting part and the heat pipe maintaining airtightness

FIG. 4 is a schematic structural diagram of the airway communication portion.

FIG. 5 is a longitudinal cross-sectional view of the heat exchanger during casting.

The figures are marked as follows: 1-heat pipe, 2-heat exchanger, 3-pressure shell, 4-inner air channel, 5-outer air channel, 6-air channel connecting part, 7-annular groove, 8-hollow boss, 9-through hole, 10-upper mold, 11-core column.

DETAILED DESCRIPTION

The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

A heat pipe, heat exchanger and pressure shell integrated structure as shown in Figures 1 to 4 includes a heat pipe 1, a heat exchanger 2, and a pressure shell 3. The inner air duct 4 of the heat exchanger 2 is connected to the expansion chamber, and the outer air duct 5 is adjacent to the end face of the regenerator. It also includes an air duct connecting portion 6. The heat exchanger 2 is embedded in the top of the inner cavity of the pressure shell 3. The heat pipe 1 is inserted between the inner and outer air ducts from the top of the pressure shell 3 parallel to the axis of the pressure shell 3. The air duct connecting portion 6 is arranged between the pressure shell 3 and the heat exchanger 2, and is used to connect the inner air duct 4 of the heat exchanger 2 with the outer air duct 5.

In this embodiment, the air duct connecting portion 6 is annular, and an annular groove 7 is provided on one side of the air duct connecting portion 6. Hollow bosses 8 are evenly provided along the circumference in the annular groove 7. Through holes 9 connecting to the inner air duct 4 and the outer air duct 5 of the heat exchanger 2 are evenly provided along the circumference on both sides of the hollow boss 8 in the annular groove 7. The heat pipe 1 is inserted into the heat exchanger 2 through the hollow boss 8.

In this embodiment, the inner diameter of the hollow boss 8 is larger than the outer diameter of the heat pipe 1 , and the hollow boss 8 is coaxially arranged with the heat pipe 1 .

In this embodiment, the top of the pressure shell 3 is a hollow structure.

In this embodiment, the melting point of the material used to make the heat exchanger 2 is lower than the melting points of the material used for the gas channel communication portion 6 , the pressure shell 3 , and the heat pipe 1 .

A processing technology for producing any one of the above-mentioned heat pipes, heat exchangers and pressure shell integrated structures, as shown in FIG5 , the specific steps of the processing technology are:

Step 1: prepare the pressure shell 3, use vacuum casting or drawing die to prepare the pressure shell 3 blank, and machine it to serve as the lower mold for casting the heat exchanger 2;

Step 2: insert the heat pipe 1 that is not filled with working medium into the pressure shell 3 along the through holes that are matched with the number of heat pipes 1 to the designed depth;

Step 3: Assemble the airway connecting part 6 and embed it into the top of the inner cavity of the pressure shell 3, with the side with the annular groove 7 facing away from the opening direction of the pressure shell 3, and each hollow boss 8 maintains coaxiality with the heat pipe 1 therein;

Step 4: assemble the upper mold 10, insert the core column 11 into the through holes 9 at the corresponding positions on the airway connecting part 6 in sequence, insert the upper mold 10 to the designed depth along the direction coaxial with the inner cavity of the pressure shell 3, and form the outline envelope of the heat exchanger 2 together with the airway connecting part 6, the core column 11, and the inner cavity of the pressure shell 3;

Step 5, casting the heat exchanger 2, and casting the heat exchanger 2 into shape at one time;

Step 6, taking out the upper mold 10 and the core column 11;

Step seven, filling the heat pipe 1 with a working medium and sealing the heat pipe 1, thus completing the manufacture of the integrated structure of the heat pipe, the heat exchanger and the pressure shell.

During the casting process, the heat exchanger liquid will fill the annular columnar space between the outer shell of the heat pipe 1 and the inner hole of the hollow boss 8. After the liquid solidifies, the working fluid in the flow channel of the heat exchanger 2 cannot leak to the environment through the annular gap formed by the heat pipe 1 penetrating the pressure shell 3, thereby ensuring the airtightness of the integrated structure.

The present invention creatively applies the airway connecting part 6 to the processing and manufacturing of the heat exchanger 2. The detailed structure of its configuration enables the heat exchanger 2 to be formed with the heat pipe 1 and the pressure shell 3 using a casting process while ensuring airtightness; the heat pipe 1 is directly embedded in the heat exchanger 2, and efficiently exchanges heat with the working fluid airflow in the flow channel of the heat exchanger 2 in the high thermal conductivity metal, and there is no need to use the welding process of the traditional tube bundle heat exchanger. It has high reliability and long service life, can effectively save production and processing costs, can greatly enhance the product strength of the Stirling device, and has significant engineering value in the hot and cold application scenarios of large and medium-sized Stirling devices.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (5)

1. A heat pipe, heat exchanger and pressure shell integrated structure, comprising a heat pipe, a heat exchanger and a pressure shell, wherein the inner air passage of the heat exchanger is connected with the expansion chamber, and the outer air passage is adjacent to the end surface of the heat regenerator, characterized in that: it also comprises an air passage connecting portion, the heat exchanger is embedded in the top of the inner cavity of the pressure shell, the heat pipe is inserted between the inner and outer air passages of the heat exchanger from the top of the pressure shell parallel to the axis of the pressure shell, and the air passage connecting portion is arranged between the pressure shell and the heat exchanger, and is used to connect the inner air passage and the outer air passage of the heat exchanger; The specific steps of the processing technology of the integrated structure are: Step 1: prepare the pressure shell, use vacuum casting or drawing die to prepare the pressure shell blank, and machine it to serve as the lower mold for casting the heat exchanger; Step 2: insert the heat pipes not filled with working medium into the pressure shell along the through holes matched with the number of heat pipes to the designed depth; Step 3: Assemble the airway connecting part and embed it into the top of the inner cavity of the pressure shell, with the side with the annular groove facing away from the opening direction of the pressure shell, and each hollow boss maintains coaxiality with the heat pipe therein; Step 4: assemble the upper mold, insert the core column into the through holes at the corresponding positions on the airway connecting part in sequence, insert the upper mold to the designed depth along the direction coaxial with the inner cavity of the pressure shell, and form the contour envelope of the heat exchanger together with the airway connecting part, the core column and the inner cavity of the pressure shell; Step 5, casting the heat exchanger, casting the heat exchanger into shape in one step; Step 6, take out the upper mold and the core column; Step seven, filling the heat pipe with working medium and sealing the heat pipe, thus completing the manufacture of the integrated structure of the heat pipe, heat exchanger and pressure shell. 2. The integrated structure of heat pipe, heat exchanger and pressure shell according to claim 1 is characterized in that: the air duct connecting part is annular, and an annular groove is provided on the side of the air duct connecting part facing away from the heat exchanger, and hollow bosses with the same number as the heat pipes are evenly arranged along the circumference in the annular groove, and through holes connected to the inner air duct and the outer air duct of the heat exchanger are evenly arranged along the circumference on both sides of the hollow boss in the annular groove, and the heat pipe passes through the hollow boss and is inserted into the heat exchanger. 3. The integrated structure of heat pipe, heat exchanger and pressure shell according to claim 2 is characterized in that the inner diameter of the hollow boss is larger than the outer diameter of the heat pipe, and the hollow boss is coaxially arranged with the heat pipe. 4. The integrated structure of heat pipe, heat exchanger and pressure shell according to claim 1, characterized in that the top of the pressure shell is a hollow structure. 5. The integrated structure of heat pipe, heat exchanger and pressure shell according to claim 1 is characterized in that the melting point of the material used to make the heat exchanger is lower than the melting point of the material used for the airway connecting part, the melting point of the material used for the pressure shell and the melting point of the material used for the heat pipe.