Counter-flow heat exchanger suitable for heat exchange of supercritical fluid and design method of counter-flow heat exchanger

Abstract

The invention discloses a countercurrent heat exchanger suitable for supercritical fluid heat exchange and a design method thereof.The countercurrent heat exchanger comprises a heat exchange component, two cold fluid filler necks and two hot fluid filler necks, the two hot fluid filler necks are located at the two ends of the heat exchange component respectively, and the two cold fluid filler necks are perpendicular to the direction of the hot fluid filler necks; the inlets are formed in the side walls of the two ends of the heat exchange component in opposite directions; the heat exchange component is integrally formed and is of a honeycomb structure formed by arranging a plurality of capillary finned tubes in parallel, and a cylindrical shell is arranged outside the honeycomb structure. Each capillary finned tube is composed of six fins and a capillary tube, the fins are evenly distributed around the capillary tube in the radial direction, and the fins are connected to form a triangular tube. The heat exchange efficiency is further improved, the product structure composition is simple, the core heat exchange component adopts the 3D printing technology, and the manufacturability is high.

Description

Technical Field

[0001] The present invention relates to a countercurrent heat exchanger suitable for supercritical fluid heat exchange and a design method thereof, and in particular to a capillary fin-tube heat exchanger structure with high heat exchange efficiency and high structural efficiency suitable for supercritical fluid and a design method thereof, belonging to the technical field of capillary tube heat exchangers. Background Art

[0002] Using a cold fluid medium at room temperature, low pressure, and a small flow rate to cool and exchange heat with a supercritical fluid at high temperature (723K), high pressure (15MPa), and large flow rate requires a compact and lightweight heat exchanger. The physical properties of supercritical fluids change dramatically, and their flow characteristics and heat transfer laws in the tubes are different from those of conventional fluids. In addition, due to the high pressure of supercritical fluids, conventional heat exchangers need to consider the pressure bearing problem, and the structural weight and volume are difficult to meet the system requirements. In addition, the conventional heat exchanger has a large heat exchange tube diameter, resulting in low heat exchange efficiency. The printed circuit board heat exchanger has a compact structure and good heat exchange performance, but the processing technology of this type of heat exchanger is complex, the manufacturing cost is high, and the cold and hot side plates are similar, which is more suitable for situations with similar cold and hot fluid densities, volume flow rates, etc. In summary, it is necessary to develop a new type of high-pressure compact heat exchanger. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and provide a countercurrent heat exchanger suitable for supercritical fluid heat exchange, which can be suitable for supercritical fluid and the situation where the fluid pressures on both sides are unequal, and has low manufacturing cost and is easy to process.

[0004] The technical solution of the present invention is: in the first aspect, a countercurrent heat exchanger suitable for supercritical fluid heat exchange is provided, comprising: a heat exchange component, two cold fluid take-over nozzles, and two hot fluid take-over nozzles, wherein:

[0005] Two hot fluid nozzles are located at two ends of the heat exchange component, and two cold fluid nozzles are perpendicular to the hot fluid nozzles and are located on the side walls at two ends of the heat exchange component, respectively, with inlet directions opposite to each other.

[0006] The heat exchange component is integrally formed and is a honeycomb structure composed of a plurality of capillary fin tubes arranged in parallel, and the outside of the honeycomb structure is a cylindrical shell;

[0007] Each capillary fin tube is composed of six fins and a capillary tube. The fins are evenly distributed around the capillary tube in the radial direction. Each fin on each capillary fin tube is adjacent to a fin on another capillary fin tube. The fins are connected to form a triangular channel. The six capillary fin tubes adjacent to each capillary fin tube are arranged in a regular hexagon.

[0008] Arc-shaped end plates perpendicular to the capillary finned tubes are respectively arranged at both ends of the heat exchange component, forming a hot fluid collecting chamber with the shell and the hot fluid receiving nozzle; the capillary finned tube is not provided with fins at a distance close to the arc-shaped end plates, and only the capillary tube is retained, and the space outside this capillary tube constitutes a cold fluid collecting chamber.

[0009] Preferably, the structure of the hot fluid collecting chamber is specifically as follows:

[0010] The arc-shaped end plate is connected to the shell, and the top of the arc faces the center direction of the heat exchange component; both ends of the capillary extend to the arc-shaped end plate, and the capillary holes corresponding to the capillary are processed on the arc-shaped end plate; two hot fluid pipe nozzles and the shell at both ends of the heat exchange component are formed into one body by welding, and the hot fluid pipe nozzle, the arc-shaped end plate and the shell together form a hot fluid collecting chamber, and the hot fluid flowing into the collecting chamber from the hot fluid pipe nozzle passes through the diversion effect of the capillary holes on the arc-shaped end plate and flows into the capillary of the heat exchange component for heat exchange.

[0011] Preferably, the structure of the cold fluid collecting chamber is as follows:

[0012] The cut-off ends at both ends of each fin are at a certain distance from the arc-shaped end plate, that is, the triangular channel formed by the connection between the fins is cut off before the arc-shaped end plate, and the end face of the triangular channel and the arc-shaped end plate form a cavity through which only the capillary tube passes; the two cold fluid connecting nozzles are respectively distributed on the side walls of the cut-off part of the fin of the heat exchange component, and are welded to the side walls of the heat exchange component to form a whole; the space between the cut-off end of the fin and the arc-shaped end plate is the cold side fluid collecting chamber, and the cold fluid flowing into the collecting chamber through the cold fluid connecting nozzle is diverted through the triangular channel formed by the fins and flows into the heat exchange channel for heat exchange.

[0013] Preferably, the distance between the cut-off ends at both ends of the fin and the arc-shaped end plate is ≥5.4 mm.

[0014] Preferably, the center distance between adjacent capillaries is 4.9 mm±0.1.

[0015] Preferably, the cold fluid take-over nozzle at the cold fluid inlet faces downward, and the cold fluid take-over nozzle at the cold fluid outlet faces upward.

[0016] In a second aspect, a design method for a countercurrent heat exchanger suitable for supercritical fluid heat exchange is provided, comprising:

[0017] Determine the heat exchange channel length of the heat exchanger according to the installation space;

[0018] The number of heat exchange tubes, the outlet temperature of the hot fluid, and the flow resistance of the hot fluid process are simulated and analyzed to obtain the corresponding relationship between the three. The number of heat exchange tubes is selected based on the flow resistance requirements under subsequent flow conditions.

[0019] When the number of heat exchange tubes is determined, the corresponding relationship between the hot fluid outlet temperature, the cold fluid outlet temperature, and the hot fluid flow resistance under different cold fluid flow conditions is simulated and analyzed, and the cold fluid flow corresponding to the critical point temperature when the hot fluid outlet temperature will not drop further when the phase change latent heat is fully utilized and the cold fluid flow is continuously increased is selected;

[0020] According to the number of heat exchange tubes and the flow rate of cold fluid, the flow velocity of the medium in the tube, the pressure of the hot fluid in the heat exchange tube and the pressure of the cold fluid in the channel formed by the fins on the outside of the heat exchange tube are considered, and the minimum values ​​of the heat exchange tube diameter, wall thickness, fin thickness, and outer wall thickness of the heat exchanger are selected under the conditions of heat exchange effect, strength requirements and 3D printing process capabilities;

[0021] The cold side fluid is designed to be "bottom-in and top-out", that is, the cold fluid nozzle at the cold fluid inlet is placed downward, and the cold fluid nozzle at the outlet is placed upward.

[0022] Preferably, the corresponding relationship among the number of heat exchange tubes, the outlet temperature of the hot fluid and the flow resistance of the hot fluid process is: the number of heat exchange tubes does not affect the outlet temperature of the hot fluid, but when the number of heat exchange tubes decreases, the flow resistance of the hot fluid process increases.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The heat exchange core component of the present invention is designed as a series of capillary tubes with fins, wherein the capillary tubes have a small inner diameter, high pressure bearing capacity, good heat exchange performance and compact structure; the fins are extended on the outer side of the capillary tubes, which effectively increases the heat transfer area on the cold fluid side, and the overall heat exchange efficiency of the heat exchanger is further enhanced;

[0025] (2) The product structure of the present invention is simple, and its core heat exchange component adopts 3D printing technology, which has simple process, low cost and high manufacturability;

[0026] (3) The present invention rationally designs the characteristic dimensions of the tube side and the shell side according to the working conditions of the cold and hot fluids, and further reduces the volume and weight of the heat exchanger while meeting the pressure-bearing strength, making the heat exchanger structure more compact. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a one-dimensional calculation model of a countercurrent heat exchanger of the present invention;

[0028] Figure 2 It is a three-dimensional schematic diagram of the capillary fin-tube heat exchanger of the present invention;

[0029] Figure 3 It is a two-dimensional schematic diagram of the capillary fin tube heat exchanger of the present invention; the symbols in the figure are: 1-heat exchange component, 2-DN4 pipe nozzle, 3-DN18 pipe nozzle;

[0030] Figure 4 It is a schematic diagram of a single fin tube of the present invention;

[0031] Figure 5 Schematic diagram of the cross section of the capillary fin tube heat exchanger of the present invention, wherein (a) is a schematic diagram of the overall cross section, and (b) is a schematic diagram of a partial enlargement of the cross section;

[0032] Figure 6 It is a partial cross-sectional view of the heat exchanger of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be described below in conjunction with the accompanying drawings.

[0034] The present invention designs a countercurrent heat exchanger suitable for supercritical fluid heat exchange, which adopts a capillary fin tube heat exchanger structure with a simple form and greatly improved manufacturability by combining 3D printing technology. The heat exchange effect and flow resistance characteristics of the product are verified by experiments to meet the system design requirements.

[0035] The capillary fin-tube heat exchanger has the characteristics of small heat exchange channel size, high pressure bearing capacity, excellent heat exchange characteristics, and simple manufacturing process. Through the reasonable design of the characteristic dimensions of the tube side and the shell side, the capillary fin-tube heat exchanger can withstand higher pressure on the tube side and lower pressure on the shell side, which is just suitable for the situation where the pressure of the heat exchange fluid on both sides is unequal. In addition, the extended fins effectively increase the heat transfer area on the cold fluid side, and the overall heat exchange capacity of the heat exchanger is further improved.

[0036] 1. Countercurrent heat exchanger suitable for supercritical fluid heat exchange

[0037] The counter-flow heat exchanger designed in the present invention is a capillary fin-tube heat exchanger, comprising: a heat exchange component, two cold fluid take-over nozzles, and two hot fluid take-over nozzles, wherein the two hot fluid take-over nozzles are respectively located at both ends of the heat exchange component, and the two cold fluid take-over nozzles are perpendicular to the direction of the hot fluid take-over nozzles, and are respectively located on the side walls at both ends of the heat exchange component and have opposite inlet directions; wherein the heat exchange component is integrally formed, and is a honeycomb structure composed of a plurality of capillary fin tubes arranged in parallel, and the outer portion of the honeycomb structure is a cylindrical shell, and each capillary fin tube is composed of six fins and a capillary tube, such as Figure 4As shown in the figure, the fins are uniformly distributed around the capillary tubes in the radial direction, each fin on each capillary fin tube is adjacent to a fin on a capillary fin tube, the fins are connected to form a triangular channel, and the six capillary fin tubes adjacent to each capillary fin tube are arranged in a regular hexagon (the center spacing of the capillary tubes is 4.9mm±0.1); arc-shaped end plates perpendicular to the capillary fin tubes are respectively arranged at both ends of the heat exchange component, the arc-shaped end plates are connected to the shell, and the arc tops face the center direction of the heat exchange component; the capillary fin tube is not provided with fins (the fins are cut off) at a distance close to the arc-shaped end plate, and only the capillary tube is retained; the two ends of the capillary tube extend to the arc-shaped end plate and form capillary holes corresponding to the capillary tube on the arc-shaped end plate; the two ends of the fin are at a certain distance from the arc-shaped end plate (the shortest distance is about 5.4mm), that is, the triangular channel formed by the connection of the fins is cut off. Before the arc-shaped end plate, the end face of the triangular channel and the arc-shaped end plate form a cavity through which only the capillary tube passes; the two hot fluid connecting nozzles are respectively distributed at both ends of the heat exchange component, and are formed into one body with the outer shells at both ends of the heat exchange component by welding; the area between the hot fluid connecting nozzle and the arc-shaped end plate is a hot side fluid collecting chamber, and the hot fluid flowing into the collecting chamber passes through the diversion effect of the capillary holes on the arc-shaped end plate and flows into the capillaries of the heat exchange component for heat exchange; the two cold fluid connecting nozzles are respectively distributed on the side walls of the fin cut-off part of the heat exchange component, and are formed into one body with the side walls at both ends of the heat exchange component by welding; the space between the fin cut-off end and the arc-shaped end plate is the cold side fluid collecting chamber, and the cold fluid connecting nozzle is arranged on the outer shell of this space, and the cold fluid flowing into the collecting chamber through the cold fluid connecting nozzle passes through the diversion of the triangular channel formed by the fins and flows into the heat exchange channel for heat exchange.

[0038] 2. Parameter modeling and calculation principle of countercurrent heat exchanger;

[0039] The heat exchange tube contains supercritical fluid, and its physical properties change dramatically. Therefore, the one-dimensional discrete method is used in the design process to cut the heat exchanger into several modules as calculation nodes. Each calculation node has constant physical properties. The AMESim one-dimensional calculation model is as follows: Figure 1 As shown, the relationship between the given flow rate, temperature, and outlet pressure of the low-pressure cold fluid channel inlet and the given flow rate, temperature, and outlet pressure of the high-pressure hot fluid channel is analyzed. The specific method is:

[0040] The influence of the number of nodes on the heat transfer calculation results is verified, and combined with the consumption of computing resources, the countercurrent heat exchanger is divided into ten computing nodes, and the pipeline heat exchange module in the model considers phase change. The parameters and variables in the model are defined in Table 1.

[0041] Table 1 Parameter and variable definitions

[0042]

[0043]

[0044] For the forced convection heat transfer coefficient in a pipe, the most common relationship is:

[0045]

[0046] Where: Nu f Re represents the Nusselt number or heat transfer factor of the fluid, Re f represents the fluid Reynolds number, Pr f It represents the Prandtl number of the fluid. When the fluid is heated, n=0.4, and when the fluid is cooled, n=0.3.

[0047] The heat transfer coefficient of the medium in the tube is positively correlated with Re. The flow velocity of the medium in the tube should be increased as much as possible. Combined with the 3D printing process and precision, the inner diameter of the heat exchange tube is set to 1mm±0.1mm and the outer diameter is set to 2mm±0.1mm.

[0048] 3. Parameter design of countercurrent heat exchanger

[0049] After the heat exchanger heat exchange channel length is determined according to the installation space, the number of heat exchange tubes, the outlet temperature of the hot fluid, and the flow resistance of the hot fluid process are simulated and analyzed first to obtain the corresponding relationship between the three. The number of heat exchange tubes does not affect the outlet temperature of the hot fluid, but when the number of heat exchange tubes is small, the flow resistance of the hot fluid process is large. The number of heat exchange tubes is selected in combination with the flow resistance requirements under subsequent flow conditions;

[0050] When the number of heat exchange tubes is determined, the corresponding relationship between the hot fluid outlet temperature, the cold fluid outlet temperature, and the hot fluid flow resistance under different cold fluid flow conditions is simulated and analyzed, and the cold fluid flow corresponding to the critical point temperature when the hot fluid outlet temperature will not drop further when the phase change latent heat is fully utilized and the cold fluid flow is continuously increased is selected;

[0051] According to the number of heat exchange tubes and the flow rate of cold fluid, the flow velocity of the medium in the tube, the pressure of the hot fluid in the heat exchange tube and the pressure of the cold fluid in the channel formed by the fins on the outside of the heat exchange tube are considered, and the minimum values ​​of the heat exchange tube diameter, wall thickness, fin thickness, and outer wall thickness of the heat exchanger are selected under the conditions of heat exchange effect, strength requirements and 3D printing process capabilities;

[0052] The cold side fluid is designed to be "in from the bottom and out from the top" to adapt to the fact that the density of the cold fluid is reduced after being heated, reducing resistance and mixed flow problems. Therefore, the cold fluid nozzle at the cold fluid inlet is placed downward, and the cold fluid nozzle at the outlet is placed upward; the cold and hot fluid collecting chambers are mainly designed based on the compactness of the product and the simplicity of processing and molding;

[0053] Example

[0054] According to the known hot fluid flow conditions and the hot fluid target outlet temperature, adjust the number of heat exchange tubes and the cold fluid flow, respectively obtain the influence of the number of heat exchange tubes and the cold fluid flow on heat transfer and flow resistance, and determine the appropriate number of heat exchange tubes and cold fluid flow. The details are as follows:

[0055] If the cold fluid flow rate is 0.05 kg / s, the outlet temperature and flow resistance of the hot fluid process under different numbers of heat exchange tubes are shown in the following table. It is found that the number of tube passes does not affect the outlet temperature of the hot fluid, but when the number of tube passes is small, the flow resistance of the hot fluid process is large, as shown in Table 2. Combined with the flow resistance requirements under subsequent large flow conditions, the number of heat exchange tubes is selected as 469.

[0056] Table 2 Correspondence between hot fluid outlet parameters and the number of heat exchange tubes

[0057] Number of heat exchange tubes Hot fluid outlet temperature Thermal fluid flow resistance (pressure drop) 91 311K 40.2bar 169 312K 14.8bar 331 312K 4.3bar 469 312K 2.2bar

[0058] Under the above number of tube passes (469), the flow rate of the cold fluid was investigated. The outlet temperature and process flow resistance of the hot fluid flow and the outlet temperature of the cold fluid under different cold fluid flow conditions are shown in Table 3. It was found that when the cold fluid flow rate was small, the outlet temperature of the cold fluid was higher than the boiling temperature, indicating that its phase change latent heat had been fully utilized and the outlet had been completely vaporized, but at this time the outlet temperature of the hot fluid was still higher than the design target of 310K±5K. When the cold fluid flow rate increased to 0.05kg / s, the outlet temperature of the hot fluid met the design requirements, and when the cold fluid flow rate was further increased, the utilization rate of the latent heat of vaporization of the cold fluid decreased, and the heat transfer performance of the countercurrent heat exchanger would not be further increased. Therefore, the optimal cold fluid flow rate was 0.05kg / s.

[0059] Table 3 Correspondence between cold and hot fluid outlet parameters and cold fluid flow rate

[0060]

[0061]

[0062] Based on multiple rounds of parameter design and combined with the 3D printing process, the specific geometric parameters of the heat exchanger are shown in Table 4. The heat exchange tube with a diameter of 1 mm can withstand a high pressure of 15 MPa. The outside of the heat exchange tube is a low-pressure cold fluid. Therefore, the outer wall thickness of the heat exchanger is designed to be 0.5 mm ± 0.05 mm, which meets the strength requirements while further reducing the volume and weight of the heat exchanger.

[0063] Table 4 Heat exchanger geometric parameter model

[0064] parameter Structural solution Heat exchanger diameter D(mm) 125 Fin tube number N 451 Fin tube diameter mm 1 Fin tube wall thickness mm 0.5 Fin thickness mm 0.4 Heat exchanger outer wall thickness (mm) 0.5 Heat exchanger length mm 700

[0065] As shown in the attached figure Figure 2 , Figure 3As shown in the figure, the capillary fin tube heat exchanger is mainly composed of heat exchange components and pipe nozzles, and the cross section of the heat exchange component is as follows: Figure 5 , which contains 451 φ1mm capillary fin tubes (such as Figure 4 ).

[0066] Capillary fin tubes can be divided into capillary tubes and uniform fins; the capillary tube diameter is designed to be 1mm mainly to take into account two aspects. One is to increase the flow velocity of the medium in the tube as much as possible and enhance heat exchange, so the smaller the heat exchange tube diameter, the better; on the other hand, affected by the 3D printing process and precision, the heat exchange tube diameter and wall thickness cannot be too small. In summary, the capillary tube diameter is designed to be 1mm±0.5mm. Based on experience and combined with the 3D printing process, the fin thickness and height are taken as 0.4mm and 1.73mm respectively. In order to evenly arrange 451 capillary fin tubes in a regular hexagon, the tube spacing is determined to be 4.9mm and the shell diameter of the heat exchange component is 125mm.

[0067] Partial cross-sectional view of the heat exchanger Figure 6 The fluid collecting chamber is divided into a high-temperature and high-pressure supercritical fluid collecting chamber and a cold fluid collecting chamber. The cold and hot fluid collecting chambers are designed mainly based on the compactness of the product and the simplicity of processing and molding. Among them:

[0068] The high-temperature and high-pressure supercritical fluid collecting chamber is composed of an arc-shaped end plate and an outer shell. Combined with 3D printing technology, the end plate is designed as an arc surface structure. All heat exchange tubes penetrate the arc-shaped end plate. Capillary holes are set on the end plate. The hot fluid enters the heat exchange channel of the heat exchange tube through the capillary holes on the arc-shaped end plate.

[0069] The cold fluid collecting chamber is composed of an arc-shaped end plate (shared with the hot fluid collecting chamber), an outer shell and a capillary fin end face, which contains all the finless heat exchange tubes. After the cold fluid flows in, it will flush the heat exchange tubes horizontally and then enter Figure 5 In the triangular heat exchange channel composed of fins shown.

[0070] like Figure 6 As shown, the high-pressure hot fluid flows into the liquid collecting cavity through the axial nozzle and is dispersed into the interior of each fin tube, and the low-pressure cold fluid flows into the liquid collecting cavity through the side nozzle and is dispersed into the triangular channel formed by each fin. The flow direction of the hot and cold fluids is countercurrent (such as Figure 3 ), the heat exchange effect is good. In addition, the cold side fluid is designed to be "in from the bottom and out from the top" to adapt to the cold fluid being heated, the density is reduced, and the resistance and mixed flow problems are reduced.

[0071] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in this field.

Claims

1. A countercurrent heat exchanger suitable for supercritical fluid heat exchange, characterized in that include: Heat exchange components, two cold fluid take-over nozzles, two hot fluid take-over nozzles, wherein: Two hot fluid nozzles are located at two ends of the heat exchange component, and two cold fluid nozzles are perpendicular to the hot fluid nozzles and are located on the side walls at two ends of the heat exchange component, respectively, with inlet directions opposite to each other. The heat exchange component is integrally formed and is a honeycomb structure composed of a plurality of capillary fin tubes arranged in parallel, and the outside of the honeycomb structure is a cylindrical shell; Each capillary fin tube is composed of six fins and a capillary tube. The fins are evenly distributed around the capillary tube in the radial direction. Each fin on each capillary fin tube is adjacent to a fin on another capillary fin tube. The fins are connected to form a triangular channel. The six capillary fin tubes adjacent to each capillary fin tube are arranged in a regular hexagon. Arc-shaped end plates perpendicular to the capillary finned tubes are respectively arranged at both ends of the heat exchange component, forming a hot fluid collecting chamber with the shell and the hot fluid receiving nozzle; the capillary finned tube is not provided with fins at a distance close to the arc-shaped end plates, and only the capillary tube is retained, and the space outside this capillary tube constitutes a cold fluid collecting chamber.

2. A countercurrent heat exchanger suitable for supercritical fluid heat exchange according to claim 1, characterized in that: The structure of the hot fluid collecting chamber is as follows: The arc-shaped end plate is connected to the shell, and the top of the arc faces the center direction of the heat exchange component; both ends of the capillary extend to the arc-shaped end plate, and the capillary holes corresponding to the capillary are processed on the arc-shaped end plate; two hot fluid pipe nozzles and the shell at both ends of the heat exchange component are formed into one body by welding, and the hot fluid pipe nozzle, the arc-shaped end plate and the shell together form a hot fluid collecting chamber, and the hot fluid flowing into the collecting chamber from the hot fluid pipe nozzle passes through the diversion effect of the capillary holes on the arc-shaped end plate and flows into the capillary of the heat exchange component for heat exchange.

3. A countercurrent heat exchanger suitable for supercritical fluid heat exchange according to claim 1, characterized in that: The structure of the cold fluid collecting chamber is as follows: The cut-off ends at both ends of each fin are at a certain distance from the arc-shaped end plate, that is, the triangular channel formed by the connection between the fins is cut off before the arc-shaped end plate, and the end face of the triangular channel and the arc-shaped end plate form a cavity through which only the capillary tube passes; the two cold fluid connecting nozzles are respectively distributed on the side walls of the cut-off part of the fin of the heat exchange component, and are welded to the side walls of the heat exchange component to form a whole; the space between the cut-off end of the fin and the arc-shaped end plate is the cold side fluid collecting chamber, and the cold fluid flowing into the collecting chamber through the cold fluid connecting nozzle is diverted through the triangular channel formed by the fins and flows into the heat exchange channel for heat exchange.

4. A countercurrent heat exchanger suitable for supercritical fluid heat exchange according to claim 1, characterized in that: The distance between the cut-off ends at both ends of the fin and the arc-shaped end plate is ≥5.4mm.

5. A countercurrent heat exchanger suitable for supercritical fluid heat exchange according to claim 1, characterized in that: The center distance between adjacent capillaries is 4.9 mm ± 0.

1.

6. A countercurrent heat exchanger suitable for supercritical fluid heat exchange according to claim 1, characterized in that: The cold fluid take-over nozzle at the cold fluid inlet faces downward, and the cold fluid take-over nozzle at the outlet faces upward.

7. A design method for a countercurrent heat exchanger suitable for supercritical fluid heat exchange, characterized in that include: Determine the heat exchange channel length of the heat exchanger according to the installation space; The number of heat exchange tubes, the outlet temperature of the hot fluid, and the flow resistance of the hot fluid process are simulated and analyzed to obtain the corresponding relationship between the three. The number of heat exchange tubes is selected based on the flow resistance requirements under subsequent flow conditions. When the number of heat exchange tubes is determined, the corresponding relationship between the hot fluid outlet temperature, the cold fluid outlet temperature, and the hot fluid flow resistance under different cold fluid flow conditions is simulated and analyzed, and the cold fluid flow corresponding to the critical point temperature when the hot fluid outlet temperature will not drop further when the phase change latent heat is fully utilized and the cold fluid flow is continuously increased is selected; According to the number of heat exchange tubes and the flow rate of cold fluid, the flow velocity of the medium in the tube, the pressure of the hot fluid in the heat exchange tube and the pressure of the cold fluid in the channel formed by the fins on the outside of the heat exchange tube are considered, and the minimum values ​​of the heat exchange tube diameter, wall thickness, fin thickness, and outer wall thickness of the heat exchanger are selected under the conditions of heat exchange effect, strength requirements and 3D printing process capabilities; The cold side fluid is designed to be "bottom-in and top-out", that is, the cold fluid nozzle at the cold fluid inlet is placed downward, and the cold fluid nozzle at the outlet is placed upward.

8. The design method of a countercurrent heat exchanger suitable for supercritical fluid heat exchange according to claim 7, characterized in that: The number of heat exchange tubes, the outlet temperature of the hot fluid and the flow resistance of the hot fluid process The corresponding relationship between them is: the number of heat exchange tubes does not affect the outlet temperature of the hot fluid, but when the number of heat exchange tubes decreases, The flow resistance of the hot fluid process increases.

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