Additive manufacturing heat exchanger with micro-channel unit cells

Abstract

The invention discloses an additive manufacturing heat exchanger with micro-channel unit cells, and belongs to the technical field of heat exchanger design. The heat exchanger comprises a shell and unit cells, the multiple unit cells are arranged in a layered mode and filled in the shell of the heat exchanger, and the unit cells adjacent to the inner wall of the shell and the wall face form an integrated structure. An inner cavity of the shell is divided into two flowing areas, the interiors of different unit cells are communicated with each other to form a first flowing area, and the outer walls of the unit cells are combined with the wall surfaces to form a second flowing area. The heat exchanger has the characteristics of high heat exchange of a low-temperature medium and low flow resistance of a high-temperature medium path, and is high in heat exchange efficiency and high in design flexibility.

Description

Technical Field

[0001] The invention relates to an additively manufactured heat exchanger with microchannel cells arranged therein, belonging to the technical field of heat exchanger design. Background Art

[0002] The high-pressure regenerative cycle liquid rocket engine needs to significantly shorten the length of the engine gas generator outlet pipeline in consideration of factors such as compact layout and weight reduction, but this leads to problems such as poor uniformity of the turbine inlet gas and high-temperature gas ablation of the turbine. In order to solve this problem, the patent "A high-temperature gas generator and turbine pump integrated rectification and heat exchange device" proposes to integrate the heat exchanger in the gas generator outlet pipe, and realize the high-temperature gas rectification and low-temperature medium heat exchange functions within a short distance through efficient heat exchange between high-temperature gas and low-temperature medium. However, the high-pressure regenerative cycle liquid rocket engine requires a higher heat exchange capacity of the heat exchanger to meet the demand of low-temperature medium for rocket tank pressurization; on the other hand, the high-pressure regenerative cycle liquid rocket engine system requires a reduction in the high-temperature gas line pressure to match the engine system design parameter requirements.

[0003] Traditional heat exchangers mostly adopt tubular and plate structures. Among them, the heat transfer coefficient of tubular heat exchangers is relatively low, and it is difficult to meet the high heat transfer requirements of the heat exchanger after shortening the distance; although the plate structure has a high heat transfer coefficient, the thermal resistance is relatively high, and it is difficult to meet the low pressure drop requirements of the gas path. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and propose an additively manufactured heat exchanger with microchannel cells arranged therein, which has high heat exchange efficiency and high design flexibility through the cell structure and microchannel design.

[0005] The technical solution of the present invention is:

[0006] An additively manufactured heat exchanger with a microchannel unit cell arrangement includes a shell and a unit cell;

[0007] A plurality of unit cells are arranged in layers and filled inside the heat exchanger shell, and the unit cells adjacent to the inner wall of the shell form an integrated structure with the wall surface;

[0008] The inner cavity of the shell is divided into two flow areas. Different unit cells are interconnected to form a first flow area, and the outer wall of the unit cell is combined with the wall surface to form a second flow area.

[0009] Furthermore, the unit cell is a three-periodic minimal surface structure, and a plurality of unit cell structures are periodically arranged in three independent directions.

[0010] Furthermore, a microchannel structure is arranged inside each unit cell, with a microchannel wall thickness of 0.5 to 1 mm and a channel width of 1 to 2 mm, so as to increase the heat exchange area and residence time of the medium flowing through the flow region.

[0011] Furthermore, the microchannel structure in the two interconnected unit cells is arranged in a staggered manner, thereby further increasing the heat exchange area and residence time of the medium.

[0012] Furthermore, the directions of the microchannel structures between two interconnected unit cells are 90 degrees to each other, and the medium flowing out of any unit cell needs to turn 90 degrees after entering the adjacent unit cell to reduce the flow rate.

[0013] Furthermore, the microchannel structure adopts a bionic structure, preferably a spider web microchannel.

[0014] Furthermore, the heat exchanger is manufactured by 3D printing, and the printing material is high-temperature alloy powder.

[0015] Furthermore, the second flow region is a high-temperature medium flow region, and the high-temperature medium flows from top to bottom along the axial direction of the heat exchanger, passing through the orderly arranged multi-layer unit cells.

[0016] Furthermore, the first flow region is a low-temperature medium flow region, and the low-temperature medium enters the unit cell through an inlet channel at the bottom of the shell, flows through each unit cell from bottom to top, and then flows out from an upper outlet.

[0017] The advantages of the present invention compared with the prior art are:

[0018] (1) The present invention uses three-periodic minimal surfaces (TPMS) for digital three-dimensional design of unit cells, which has high design flexibility. TPMS uses implicit functions to accurately express, and the geometric structure is highly controllable; the average curvature is zero everywhere, the surfaces do not intersect each other and are highly smooth; and it has a high surface area to volume ratio. The heat exchanger designed in this way has high heat transfer efficiency and low flow resistance. The implicit structure is highly controllable and adaptable to various design spaces and working environments, meeting the requirements of lightweight and compact design of new heat exchangers.

[0019] (2) The printing material of the heat exchanger of the present invention is high-temperature alloy powder (such as GH4169), which can withstand a pressure of 40 to 50 MPa in oxygen-rich, high-temperature combustion gas and has high structural strength, thus solving the problem of low strength of existing heat exchangers.

[0020] (3) The present invention designs a bionic microchannel structure inside the unit cell and adopts a staggered arrangement to further increase the heat exchange area and residence time of the medium, making the heat exchange more sufficient.

[0021] (4) The present invention combines the characteristics of high heat exchange of low-temperature media and low flow resistance of high-temperature media, and has high heat exchange efficiency and high design flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0023] Figure 1 A schematic diagram of the structure of an additively manufactured heat exchanger in which microchannel cells are arranged according to an embodiment of the present invention;

[0024] Figure 2 This is an example diagram of a unit cell structure according to an embodiment of the present invention;

[0025] Figure 3 The microchannel structure of the embodiment of the present invention is shown in Figure 1, a) is a straight microchannel, b) is a vortex microchannel, and c) is a spider web microchannel;

[0026] Figure 4 The staggered arrangement diagram of microchannels in the embodiments of the present invention, a) is a straight microchannel, b) is a vortex microchannel, c) is a spider web microchannel;

[0027] Figure 5 This is an example of a printed product according to an embodiment of the present invention, a) is a cross section Figure 1 , b) is the cross section Figure 2 , c) is the end view. DETAILED DESCRIPTION

[0028] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0029] The present invention proposes an additively manufactured heat exchanger with a microchannel unit cell arrangement, such as Figure 1 As shown, multiple unit cells are arranged in layers and filled inside the shell of the heat exchanger. The unit cells near the shell form an integrated structure with the wall surface. Different unit cells are interconnected to form a low-temperature medium flow area. The outer wall of the unit cell is combined with the shell wall surface to form a high-temperature medium flow area. Thus, the inner cavity of the heat exchanger is divided into two areas. The high-temperature medium flows from top to bottom along the axis of the heat exchanger, passing through the orderly arranged multi-layer unit cells; the low-temperature medium enters the unit cell through the designed inlet channel, flows through each unit cell from bottom to top, and then flows out from the upper outlet. Among them, the temperature of the low-temperature medium is 100K~300K, and the temperature of the high-temperature medium is 500K~800K.

[0030] The unit cell structure is Figure 2As shown in the figure, the structure is a three-periodic minimal surface (TPMS), and the unit cell structure is periodically arranged in three independent directions. TPMS is a surface defined by a mathematical formula, accurately expressed by implicit functions, and the geometric structure is highly controllable; the average curvature is zero everywhere, the surfaces do not intersect each other and are highly smooth; it has a high surface area to volume ratio. The heat exchanger designed in this way has low flow resistance and high heat transfer efficiency. The implicit structure is highly controllable and adaptable to various design spaces and working environments, and can meet the requirements of lightweight and compact design. TPMS is generally constructed using the level set approximation equation:

[0031]

[0032] Where r is the position vector in Euclidean space; A k represents the amplitude factor; h k represents the kth lattice vector in the reciprocal space; λ k is the period wavelength; p k is the phase offset; C on the right side of the equation is a constant, representing the offset value of the surface.

[0033] A microchannel structure is set inside each unit cell, with a wall thickness of 0.5 to 1 mm and a channel width of 1 to 2 mm. The purpose of setting up the microchannel is to increase the heat exchange area and residence time of the low-temperature medium to make the heat exchange more sufficient. The microchannel adopts a bionic structure, and its design structure is diverse, typically: straight microchannel, vortex microchannel, spider web microchannel, etc. Figure 3 In general, spider web microchannels can improve heat transfer efficiency by about 40%. If the heat transfer demand is high, spider web microchannel structures are preferred. Vortex channels can improve heat transfer efficiency by about 35%, which is the second choice. Straight channels only improve heat transfer efficiency by about 10%, but they are easier to print and can also be considered in design.

[0034] The microchannels are arranged in a staggered manner, which can further increase the heat exchange area and residence time of the medium. Figure 4 As shown in a), b), and c), the directions of the microchannels between the two unit cells are 90° to each other, so that the low-temperature medium flowing out of any unit cell needs to turn 90° after entering the adjacent unit cell, reducing the flow rate and making the heat exchange more complete.

[0035] The heat exchanger is manufactured by 3D printing. The printing material is high-temperature alloy powder (such as GH4169). It can withstand a pressure of 40-50MPa in oxygen-rich high-temperature gas (600-750K). The structural strength is very high. The finished product after printing is as follows Figure 5 As shown in a), b), and c).

[0036] The present invention has a higher strength-to-mass ratio and surface-to-mass ratio by adding a microchannel structure to a macrocell, achieving high heat exchange and low flow resistance design requirements; the structural design is flexible, and the cell size, microchannel structure, and multi-cell arrangement can all be modified in accordance with the design requirements. The present invention is not only applicable to high-pressure regenerative cycle liquid rocket engines, but also to engines with other cycle modes; it can also be applied to aviation, petrochemical, mechanical industry, electric power and other fields to meet the needs of highly integrated and complex systems for new high-performance heat exchangers.

[0037] The above-described embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. An additively manufactured heat exchanger with microchannel cells, characterized in that: Includes shell and unit cell; A plurality of unit cells are arranged in layers and filled inside the heat exchanger shell, and the unit cells adjacent to the inner wall of the shell form an integrated structure with the wall surface; The inner cavity of the shell is divided into two flow areas. Different unit cells are interconnected to form a first flow area, and the outer wall of the unit cell is combined with the wall surface to form a second flow area.

2. The additively manufactured heat exchanger with microchannel unit cells according to claim 1, characterized in that: The unit cell is a three-periodic minimal surface structure, and a plurality of unit cell structures are periodically arranged in three independent directions.

3. The additively manufactured heat exchanger with microchannel cells arranged according to claim 1, characterized in that: A microchannel structure is arranged inside each unit cell, with a wall thickness of 0.5 to 1 mm and a channel width of 1 to 2 mm, so as to increase the heat exchange area and residence time of the medium flowing through the flow area.

4. The additively manufactured heat exchanger with microchannel cells according to claim 3, characterized in that: The microchannel structure in the two interconnected unit cells adopts a staggered arrangement to further increase the heat exchange area and residence time of the medium.

5. The additively manufactured heat exchanger with microchannel cells arranged according to claim 4, characterized in that: The directions of the microchannel structures between two interconnected unit cells are 90 degrees to each other. The medium flowing out of any unit cell needs to turn 90 degrees after entering the adjacent unit cell to reduce the flow rate.

6. The additively manufactured heat exchanger with microchannel cells arranged according to claim 3, characterized in that: The microchannel structure adopts a bionic structure, preferably a spider web microchannel.

7. The additively manufactured heat exchanger with microchannel unit cells according to claim 1, characterized in that: The heat exchanger is manufactured using 3D printing, and the printing material is high-temperature alloy powder.

8. The additively manufactured heat exchanger with microchannel cells arranged according to claim 1, characterized in that: The second flow region is a high-temperature medium flow region, and the high-temperature medium flows from top to bottom along the axial direction of the heat exchanger, passing through the orderly arranged multi-layer unit cells.

9. The additively manufactured heat exchanger with microchannel cells arranged according to claim 1, characterized in that: The first flow region is a low-temperature medium flow region. The low-temperature medium enters the unit cell through the inlet channel at the bottom of the shell, flows through each unit cell from bottom to top, and then flows out from the upper outlet.

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