Tubular heat exchanger based on bionic fish scale microstructure

Abstract

The tubular heat exchanger comprises a plurality of heat exchange tubes, and the multiple bionic fish scale microstructures are distributed on the inner wall face of each heat exchange tube in an arc mode. A bionic concept is combined into the design of an efficient low-resistance heat exchanger, and the tubular heat exchanger of the enhanced heat exchange tube, which has a fish scale-like region characteristic and variable fish scale height, variable fish scale width, variable fish scale inclination and variable fish scale arrangement mode, is designed by utilizing fish scale characteristics on the basis of not changing the size of the heat exchanger; the flow resistance in the heat transfer tube channel of the heat exchanger is slightly increased, meanwhile, the bionic fish scale microstructure characteristic induces generation of secondary flow and vortex, disturbance of fluid in the tube is enhanced, the thickness of a thermal boundary layer of the fluid close to the wall face is reduced, the heat exchange performance is enhanced, and the comprehensive performance of the tubular heat exchanger is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of heat exchangers, and in particular relates to a tubular heat exchanger based on a bionic fish scale microstructure. Background Art

[0002] Heat exchangers are widely used in chemical production, mechanical processing, nuclear power plants, ship power systems and other fields, and are important heat transfer equipment. Most of the heat transfer tubes of tubular heat exchangers use single-phase water as the heat transfer medium, and the convective heat transfer effect is relatively poor, resulting in a large volume of the heat exchanger and high production costs. There is a need to further improve the convective heat transfer coefficient. The use of enhanced heat transfer methods can effectively improve the convective heat transfer coefficient of the fluid in the heat exchange tube. The common practice is to increase the heat transfer area and enhance the fluid disturbance, such as inserting twisted bands in the tube, changing the shape of the heat transfer tube, etc. In addition to round tubes, common ones include corrugated tubes, spiral tubes, spiral twisted band tubes, etc., but while achieving enhanced heat transfer of the fluid in the tube, it also greatly increases the pressure loss in the channel. Combining enhanced heat transfer technology and bionic technology, inspired by the fish scale structure, an enhanced heat exchange tube based on the bionic fish scale microstructure and a tubular heat exchanger composed of the enhanced heat exchange tube in a certain arrangement are proposed. Summary of the invention

[0003] The present invention provides a tubular heat exchanger based on a bionic fish scale microstructure. The bionic fish scale microstructure not only has a good enhanced heat transfer effect, but also can reduce the flow resistance of the flow channel, thereby further improving the comprehensive performance of the heat exchanger.

[0004] To solve the above problems, the technical solution provided by the present invention is as follows:

[0005] An embodiment of the present invention provides a tubular heat exchanger based on a bionic fish scale microstructure, comprising a plurality of heat exchange tubes, wherein the inner wall surface of each heat exchange tube is provided with a plurality of bionic fish scale microstructures distributed in an arc manner, and the plurality of bionic fish scale microstructures are arranged periodically.

[0006] In an optional embodiment of the present invention, the plurality of heat exchange tubes are arranged in a combination of a regular triangle arrangement, a square arrangement and a concentric circle arrangement.

[0007] In an optional embodiment of the present invention, the fluid in the heat exchange tube does not contact the fluid outside the tube, and solid heat transfer is performed only through the tube wall.

[0008] In an optional embodiment of the present invention, the ratio V / D of the height V of the bionic fish scale microstructure to the inner diameter D of the heat exchange tube is in the range of 0 <V / D<0.5。

[0009] In an optional embodiment of the present invention, the ratio W / D of the width W of the bionic fish scale microstructure to the inner diameter D of the heat exchange tube is in the range of 0 <W / D<π。

[0010] In an optional embodiment of the present invention, the ratio H / D of the length H of the bionic fish scale microstructure to the inner diameter D of the heat exchange tube is in the range of 0 <H / D<1。

[0011] In an optional embodiment of the present invention, the ratio L / D of the distance L between adjacent bionic fish scale microstructures in the axial direction of the heat exchange tube and the inner diameter D of the heat exchange tube is in the range of 0 <L / D<10。

[0012] In an optional embodiment of the present invention, the value range of the angle θ between adjacent bionic fish scale microstructures in the circumferential direction of the heat exchange tube is 0<θ<360°.

[0013] Compared with the prior art, the embodiment of the present invention provides a tubular heat exchanger based on a bionic fish scale microstructure, which has but is not limited to the following beneficial effects: (1) The present invention combines the bionic concept with the design principle of a compact heat exchanger to solve the need to increase the convective heat transfer coefficient while minimizing the increase in resistance. The bionic fish scale microstructure is added to the inner wall of the heat exchange tube to strengthen the heat exchange surface and disturb the fluid to form a structural heat exchange unit of a passive residual heat exchanger. The heat exchange performance of the heat exchanger can be significantly enhanced without changing the material or increasing the volume of the heat exchanger. (2) As a symbol of advanced nuclear power plants, passive technology is widely used in various nuclear power plants. Passive safety systems represented by passive residual heat removal systems can improve the safety of reactors under accident conditions. The passive residual heat exchanger is a key energy output device in the passive residual heat removal system, which can transfer the heat of the reactor core to the final heat sink under accident conditions, thereby ensuring the effective cooling and safety of the reactor core. The present invention combines bionic technology with enhanced heat transfer technology. In the design of a passive waste heat exchanger for a nuclear power plant, the convective heat transfer coefficient is increased as much as possible with a small increase in resistance. The bionic fish scale microstructure is used to design a heat exchange tube with fish scale-like regional characteristics and variable height, variable width, variable inclination, and variable arrangement. The flow resistance in the enhanced heat exchange tube channel increases slightly. At the same time, the structural characteristics of the bionic fish scale induce the generation of secondary flow and vortex, enhance the disturbance of the fluid, reduce the thickness of the thermal boundary layer of the fluid near the wall of the heat exchange tube, enhance the heat exchange performance, and further improve the comprehensive performance of the passive waste heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1A schematic diagram of a passive waste heat removal system for a heat exchange tube based on a bionic fish scale microstructure provided in an embodiment of the present application.

[0016] Figure 2 A schematic diagram of the technical concept of a heat transfer tube of a tubular heat exchanger based on a bionic fish scale microstructure provided in an embodiment of the present application.

[0017] Figure 3 Schematic diagram of four arrangements of heat transfer tubes of a tubular heat exchanger based on a bionic fish scale microstructure provided in an embodiment of the present application.

[0018] Figure 4 A structural characteristic diagram of a heat exchange tube with a bionic fish scale microstructure provided in an embodiment of the present application.

[0019] Figure 5 A bionic fish scale microstructure characteristic diagram provided in an embodiment of the present application.

[0020] Figure 6 The velocity streamline cloud diagram distribution of the heat exchange tube cross section with bionic fish scale microstructures of different size characteristics of the present invention.

[0021] Figure 7 The temperature distribution diagram of the cross section of the heat exchange tube with the bionic fish scale microstructure of different size characteristics of the present invention.

[0022] Figure 8 The PEC distribution of the heat exchange tube with bionic fish scale microstructure of different size characteristics of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0024] like Figure 1 As shown, an embodiment of the present invention provides a passive waste heat removal system of a heat exchange tube based on a bionic fish scale microstructure, comprising a pressurizer 1, a power supply 2, a hot pipe 4, a core 5, a cold pipe 6, a tubular heat exchanger 8, a hot water tank 9 and a steam generator 11. The power supply 2 is arranged inside the pressurizer 1, and the core 5 is arranged inside the cold pipe 6. The heat exchanger 8 is arranged inside the hot water tank 9, the pressurizer 1 is connected to the hot pipe 4 through the first pipe 3, the hot pipe 4 is connected to the cold pipe 6, and the cold pipe 6 is connected to the steam generator 11. The hot pipe 4 is connected to the heat exchanger 8 through the second pipe 7, and the heat exchanger 8 is connected to the steam generator 11 through the third pipe 10. Two passages are arranged in parallel on the third pipe 10, and both passages are provided with valves.

[0025] Figure 2 , Figure 3 and Figure 4 Combination Figure 1 , an embodiment of the present invention also provides a tubular heat exchanger 8 based on a bionic fish scale microstructure, including a plurality of heat exchange tubes 8-1, such as a symmetry plane 8-2 in the middle of the heat exchange tube 8-1. A plurality of bionic fish scale microstructures 8-3 are distributed in an arc manner on the inner wall surface of each heat exchange tube 8-1, and the plurality of bionic fish scale microstructures 8-3 are arranged periodically. The bionic fish scale microstructure 8-3 of this embodiment has fish scale-like features, and has structural characteristics of variable height, variable width, variable inclination, and variable arrangement. The bionic fish scale microstructure 8-3 is designed as an arc surface, which is attached to the inner wall surface of the heat exchange tube 8-1 to form a single microstructure fish scale bionic enhanced heat exchange tube unit, and each fish scale bionic enhanced heat exchange tube unit is combined into a non-active residual heat exchanger in a certain arrangement.

[0026] By utilizing the characteristics of fish scales, a bionic fish scale microstructure 8-3 with a fish scale-like shape is designed without changing the size of the heat exchanger 8-1. This enhances the increase in flow resistance in the channel of the heat exchange tube 8-1. At the same time, the structural characteristics of the bionic fish scale induce the generation of secondary flow and vortex, enhance the disturbance of the fluid, reduce the thickness of the thermal boundary layer of the fluid near the wall of the heat exchange tube 8-1, enhance the heat transfer performance, and further improve the comprehensive performance of the passive exhaust heat exchanger.

[0027] like Figure 3 As shown, taking a single heat exchange tube with a bionic fish scale microstructure as an example, a plurality of heat exchange tubes 8 - 1 are arranged in a combination of a regular triangle arrangement, a square arrangement and a concentric circle arrangement.

[0028] Such as 4 and Figure 5 As shown, the length of the heat exchange tube 8-1 is S, and the inner diameter of the heat exchange tube is D. The height of the bionic fish scale microstructure 8-3 is V, the width is W, and the length is H. The upper wall of the bionic fish scale microstructure 8-3 is distributed in an arc, and has good contact with the inner wall of the heat exchange tube 8-1. Along the axial direction of the fluid flow in the heat exchange tube 8-1, the bionic fish scale microstructure 8-3 is periodically arranged, and the distance between adjacent bionic fish scale microstructures 8-3 is L; along the vertical direction of the fluid flow in the heat exchange tube 8-1, that is, in the circumferential direction, the bionic fish scale microstructure 8-3 is periodically arranged, and the angle between adjacent bionic fish scale microstructures 8-3 is θ. The working fluid in the heat exchange tube 8-1 is downstream or countercurrent. The fluid in the heat exchange tube 8-1 does not contact the fluid outside the tube, and solid heat transfer is only carried out through its tube wall.

[0029] The value range of the ratio V / D of the height V of the bionic fish scale micro-structure to the inner diameter D of the heat exchange tube is 0 < V / D < 0.5; the larger the ratio of the height to the inner diameter, the greater the disturbance to the fluid inside the tube, the more conducive to the generation of secondary flow in the fluid, and the better the heat exchange performance. The value range of the ratio W / D of the width W of the bionic fish scale micro-structure to the inner diameter D of the heat exchange tube is 0 < W / D < π; the larger the ratio of the width to the inner diameter, the larger the heat exchange area, and the better the heat exchange performance. The value range of the ratio H / D of the length H of the bionic fish scale micro-structure to the inner diameter D of the heat exchange tube is 0 < H / D < 1; the larger the ratio of the length to the inner diameter, the larger the heat exchange area, and the better the heat exchange performance.

[0030] The value range of the ratio L / D of the axial distance L between adjacent bionic fish scale micro-structures to the inner diameter D of the heat exchange tube is 0 < L / D < 10. The smaller the ratio, the more bionic fish scales there are axially, the better the disturbance, and the better the heat exchange performance. However, its minimum value is affected by the structural strength of the heat exchanger and the operating conditions. At the same time, the resistance also increases more, affecting the comprehensive performance of the passive residual heat removal heat exchanger. The value range of the circumferential angle θ between adjacent bionic fish scale micro-structures is 0 < θ < 360°. The smaller θ is, the more fish scales there are circumferentially, and the better the heat exchange performance. However, its minimum value is affected not only by the structural strength of the heat exchanger and the operating conditions, but also by the width W.

[0031] Preferably, as Figure 4 and Figure 5 shown, the thickness of a single heat exchange tube 8-1 is 1 mm, the inner diameter D is 10 mm, the tube length S is 1000 mm, the axial distance L between adjacent bionic fish scale micro-structures 8-3 is 20 mm, the number of bionic fish scale micro-structures 8-3 circumferentially is 6, the angle θ between adjacent bionic fish scale micro-structures 8-3 is 60°, the height V of the bionic fish scale micro-structure 8-3 is 0.5 mm, the width W is 2 mm, and the length H is 4 mm.

[0032] In the present invention, the heat exchange effect of the micro-structured bionic fish scale enhanced heat exchange tube is significantly improved. Compared with the smooth heat exchange tube, when the inlet Reynolds number is 16840 (corresponding to the inlet average velocity of 1.5 m / s), the convective heat transfer coefficient of the fluid inside the heat exchange tube is increased by 92%. From Figure 6 the cross-sectional velocity streamline cloud maps of the heat exchange tubes with bionic fish scale micro-structures of different size characteristics shown, it can be seen that after the flowing medium inside the tube is disturbed by the bionic fish scales, secondary flow vortices will be formed near the inner wall surface of the tube, increasing the velocity of the flowing medium near the inner wall surface. From Figure 7 the cross-sectional temperature distribution maps of the heat exchange tubes with bionic fish scale micro-structures of different size characteristics shown, it can be seen that due to the increase in the velocity of the fluid near the inner wall surface of the tube, the temperature distribution of the flowing working medium in the cross-section is more uniform, thinning the thickness of the thermal boundary layer, and thus increasing the convective heat transfer coefficient of the flowing working medium inside the tube and enhancing the heat exchange performance. From Figure 8From the PEC distribution of the heat exchange tubes with bionic fish scale microstructures of different size characteristics, it can be seen that the overall enhanced heat transfer effect is very good, and the highest PEC value can reach 1.35.

[0033] In summary, although the present invention has been disclosed as above in terms of preferred embodiments, the above preferred embodiments are not intended to limit the present invention. A person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined in the claims.

Claims

1. A tubular heat exchanger based on a bionic fish scale microstructure, characterized in that: It comprises a plurality of heat exchange tubes, wherein the inner wall surface of each heat exchange tube is provided with a plurality of bionic fish scale microstructures distributed in an arc manner, and the plurality of bionic fish scale microstructures are arranged periodically.

2. The tubular heat exchanger based on bionic fish scale microstructure according to claim 1, characterized in that: The plurality of heat exchange tubes are arranged in one or more combinations of regular triangle arrangement, square arrangement and concentric circle arrangement.

3. The tubular heat exchanger based on bionic fish scale microstructure according to claim 2, characterized in that: The fluid in the heat exchange tube does not contact the fluid outside the tube, and solid heat transfer is performed only through the tube wall.

4. The tubular heat exchanger based on bionic fish scale microstructure according to claim 1, characterized in that: The ratio V / D of the bionic fish scale microstructure height V to the inner diameter D of the heat exchange tube is in the range of 0 <V / D<0.5。 5. The tubular heat exchanger based on bionic fish scale microstructure according to claim 1, characterized in that: The ratio W / D of the width W of the bionic fish scale microstructure to the inner diameter D of the heat exchange tube is in the range of 0 <W / D<π。 6. The tubular heat exchanger based on bionic fish scale microstructure according to claim 1, characterized in that: The ratio H / D of the length H of the bionic fish scale microstructure to the inner diameter D of the heat exchange tube is in the range of 0 <H / D<1。 7. The tubular heat exchanger based on bionic fish scale microstructure according to claim 1, characterized in that: The ratio L / D of the distance L between the adjacent bionic fish scale microstructures along the flow direction of the heat exchange tube and the inner diameter D of the heat exchange tube is in the range of 0 <L / D<10。 8. The tubular heat exchanger based on bionic fish scale microstructure according to claim 1, characterized in that: The value range of the angle θ between adjacent bionic fish scale microstructures in the direction of perpendicular fluid flow of the heat exchange tube is 0<θ<360°.

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