Supercritical fluid variable slot width PCHE core and manufacturing method thereof

Abstract

The application discloses a supercritical fluid variable-slot-width PCHE core and a manufacturing method thereof, and the core comprises a hot-side heat exchange plate, a cold-side heat exchange plate and a top plate; a plurality of the hot-side heat exchange plates and the cold-side heat exchange plates are stacked together in an interlaced manner from bottom to top, and the top plate is arranged on the top of the uppermost hot-side heat exchange plate or cold-side heat exchange plate; a plurality of slotted fins are arranged on the hot-side heat exchange plate and the cold-side heat exchange plate, the slot width of the slotted fin gradually changes along the flow direction, the fin gap of the cold-side heat exchange plate forms a cold flow channel, and the fin gap of the hot-side heat exchange plate forms a hot flow channel. The application adopts photochemical etching technology to etch unslotted fins on the metal plate, then opens slots on the fins through high-precision cutting technology, and finally combines the heat exchange plates into a whole through vacuum diffusion welding technology. The application can adapt to the property change of the supercritical fluid in the heat exchange process, improve the comprehensive performance of the PCHE, simplify the heat exchange plate processing and assembly process, and improve the slotting process reliability of the fins.

Description

Technical Field

[0001] This invention belongs to the field of heat exchange technology, specifically relating to a supercritical fluid variable-width PCHE core and its manufacturing method. Background Technology

[0002] When the temperature and pressure of a fluid exceed its critical temperature and critical pressure, the fluid is called a supercritical fluid. The properties of supercritical fluids change drastically with temperature. Below the quasi-critical temperature, supercritical fluids exhibit "liquid-like" characteristics such as high density and high thermal conductivity; above the quasi-critical temperature, they exhibit "gas-like" characteristics such as low viscosity and high diffusivity. The excellent flow and heat transfer properties of supercritical fluids have led to their widespread application in advanced Brayton cycle power generation systems, transcritical refrigeration heat pump systems, and regenerative cooling of aero-engines.

[0003] Printed circuit heat exchangers (PCHEs) are microchannel plate heat exchangers with advantages such as high temperature and pressure resistance, compact structure, and good heat exchange performance. PCHEs are suitable as heat exchange devices in extreme conditions or space-constrained applications and have great application potential in many supercritical fluid heat exchange fields, such as regenerators in supercritical carbon dioxide Brayton cycles, intercoolers in ultra-high temperature reactors, and heat exchangers in floating natural gas liquefaction platforms.

[0004] PCHE channels can be divided into two categories: continuous finned and discontinuous finned. Continuous finned channels include straight channels, zigzag channels, and wavy channels, while discontinuous finned channels include S-shaped finned channels, airfoil finned channels, and slotted airfoil finned channels. Among these, the slotted airfoil finned channel (patent number: CN201910186489.9) has the best overall performance. Existing PCHE channels use a single fin structure and uniform arrangement, with the channel unit repeating periodically along the flow direction. However, the properties of the supercritical fluid change continuously during heat exchange, and the mismatch between the channel geometry and the supercritical fluid properties can lead to a decrease in PCHE flow or heat transfer performance. Furthermore, PCHE heat exchange channels are processed using photochemical etching technology, which involves lateral erosion and etching arcs, making it difficult to guarantee the processing accuracy of the fin slots. Therefore, further optimization of the PCHE channel structure and manufacturing process is needed. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a supercritical fluid variable-slot width PCHE core and its manufacturing method. By varying the slot width to match the changes in the physical properties of the supercritical fluid, the overall performance of the PCHE is improved. At the same time, the improved manufacturing method enhances the reliability of the slotted PCHE fins.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A supercritical fluid variable-width PCHE core, the core comprising a hot-side heat exchange plate, a cold-side heat exchange plate, and a top plate;

[0008] Several hot-side heat exchange plates and cold-side heat exchange plates are stacked alternately from bottom to top, with a top plate set on top of the uppermost hot-side heat exchange plate or cold-side heat exchange plate; several slotted fins are provided on both the hot-side and cold-side heat exchange plates, and the slot width of the slotted fins gradually changes along the flow direction. The fin gaps of the cold-side heat exchange plate form cold flow channels, and the fin gaps of the hot-side heat exchange plate form hot flow channels.

[0009] A further improvement of the present invention is that the slot width of the slotted fins of the cold-side heat exchange plate gradually increases along the flow direction.

[0010] A further improvement of the present invention is that the slot width of the slotted fins of the hot-side heat exchange plate gradually decreases along the flow direction.

[0011] A further improvement of the present invention is that the slotted fins on the hot-side heat exchange plate and the cold-side heat exchange plate are longitudinally symmetrical slotted fins, and the fins have a symmetrical structure along the flow direction.

[0012] A further improvement of the present invention is that the longitudinally symmetrical slotted fins include slotted spindle-shaped fins, slotted rhomboid fins, and slotted elliptical fins.

[0013] A further improvement of the present invention is that the slotted fin structure on the hot-side heat exchange plate and the cold-side heat exchange plate is the same. By changing the arrangement direction of the heat exchange plate or the direction of fluid flow, the change in slot width can be matched with the change in the physical properties of the supercritical fluid on the hot and cold sides.

[0014] A further improvement of the present invention is that the slotted fins on the hot-side heat exchange plate and the cold-side heat exchange plate are arranged in a staggered or sequential manner.

[0015] A further improvement of the present invention is that the slotting method of the slotted fins on the hot-side heat exchange plate and the cold-side heat exchange plate is to form a slotted flow channel by longitudinally penetrating the fins from the centerline of the windward side.

[0016] A further improvement of the present invention is that the ratio of the slot width to the fin width of the slotted fins on the hot-side heat exchange plate and the cold-side heat exchange plate is between 0.2 and 0.8.

[0017] A method for manufacturing a supercritical fluid variable-groove-width PCHE core includes:

[0018] Ungrooved fins are etched onto a metal plate to be processed using photochemical etching technology to create an ungrooved mother plate.

[0019] By cutting grooves on the fins, the fin groove width varies along the longitudinal direction according to a set ratio to obtain a variable groove width heat exchange plate.

[0020] Depending on the heat exchanger type, the variable-width heat exchange plates are stacked. For co-current PCHE, the hot and cold fluids flow in the same direction, and the hot and cold side heat exchange plates are stacked alternately in opposite directions. For counter-current PCHE, the hot and cold fluids flow in opposite directions, and the hot and cold side heat exchange plates are stacked in the same direction.

[0021] The heat exchange plates are combined into a whole by vacuum diffusion welding technology to form a supercritical fluid variable-groove PCHE core.

[0022] Compared with existing PCHE core structures and manufacturing methods, the present invention has at least the following beneficial technical effects:

[0023] (1) High-efficiency, low-resistance fin shape. Longitudinal symmetrical slotted fins can effectively reduce flow resistance and enhance heat transfer. On the one hand, the pointed tip of the longitudinal symmetrical slotted fin and the small angle between the tangent of the fin's leading edge and the flow direction can avoid the normal impact of the working fluid on the fin, and the curvature change at the leading edge of the fin is small, which can reduce the velocity gradient around the fin. On the other hand, the longitudinal symmetrical slotted fin is a discontinuous fin, which can suppress the development of the thermal boundary layer and improve the convective heat transfer coefficient. At the same time, the slotting of the fin can increase the heat transfer area and improve the overall heat transfer performance of PCHE.

[0024] (2) Matching the slot width variation with the changes in supercritical fluid properties enhances the overall performance of the PCHE. Gradually varying the fin slot width along the flow direction adapts to the changes in the properties of the supercritical fluid during heat transfer, thus improving the overall flow and heat transfer performance of the PCHE. For cold channels, the density of the supercritical fluid decreases and its velocity increases during heating; gradually increasing the slot width along the flow direction reduces the increase in resistance caused by the increased velocity. For hot channels, the density of the supercritical fluid increases and its velocity decreases during cooling; gradually decreasing the slot width along the flow direction reduces the decrease in heat transfer performance caused by the reduced velocity.

[0025] (3) Simplify the heat exchanger plate processing and assembly process. For common longitudinally asymmetrical fins such as airfoil fins, the geometric structures of the heat exchanger plates on the hot and cold sides are different, requiring separate design and processing. The fins used in this invention are longitudinally symmetrical slotted fins. Changes in the flow direction do not affect their flow heat transfer characteristics, and heat exchanger plates with the same structure and variable slot width can be used on the hot and cold sides. By changing the arrangement direction of the heat exchanger plates or the fluid flow direction, the channel structure can be matched with the changes in the physical properties of the supercritical fluid on the cold and hot sides. By adjusting the stacking direction of the heat exchanger plates, the processing of co-current and counter-current PCHE cores can be achieved, thereby simplifying the PCHE heat exchanger plate processing and assembly process.

[0026] (4) Improve the reliability of PCHE fin grooving process. Using photochemical etching technology to create an ungrooved master plate ensures the smooth formation of complex fin structures. Employing high-precision cutting technologies such as laser cutting, wire cutting, and precision machining to groove the fins overcomes problems such as lateral erosion and etching arcs present in photochemical etching, improving the processing accuracy of micro-grooving of the fins and ensuring the precise realization of the groove width variation pattern. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a supercritical fluid variable-width PCHE core.

[0028] Figure 2 The variation of supercritical carbon dioxide density with temperature at 30 MPa and 7.8 MPa is shown.

[0029] Figure 3 This is a schematic diagram showing the fin arrangement of the cold-side heat exchange plate along the flow direction.

[0030] Figure 4 This is a schematic diagram showing the fin arrangement of the heat exchange plate on the hot side along the flow direction.

[0031] Figure 5 This is a schematic diagram of a longitudinally symmetrical slotted fin structure, in which... Figure 5 (a) is a slotted spindle-shaped fin. Figure 5 (b) is a slotted diamond-shaped fin. Figure 5 (c) is a slotted elliptical fin.

[0032] Figure 6 This is a manufacturing process diagram for a supercritical fluid variable-groove PCHE core.

[0033] Explanation of reference numerals in the attached figures:

[0034] W f - Fin width; W s - Slot width;

[0035] 1-Top plate; 2-Hot side heat exchange plate; 3-Cold side heat exchange plate. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings.

[0037] Figure 1The diagram shows a supercritical fluid variable-width PCHE core, which includes a hot-side heat exchange plate 2, a cold-side heat exchange plate 3, and a top plate 1. Several hot-side heat exchange plates 2 and cold-side heat exchange plates 3 are stacked alternately from bottom to top, and the top plate 1 is located on top of the uppermost hot-side heat exchange plate 2 or cold-side heat exchange plate 3. Several slotted fins are formed on both the hot-side heat exchange plate 2 and the cold-side heat exchange plate 3, and the slot width of the slotted fins gradually changes along the flow direction. The fin gaps of the cold-side heat exchange plate 3 form cold flow channels, and the fin gaps of the hot-side heat exchange plate 2 form hot flow channels.

[0038] Figure 2 The figure shows the change in supercritical carbon dioxide density with temperature under typical operating conditions of a supercritical carbon dioxide Brayton cycle regenerator. The pressure on the high-pressure side (cold side) is 30 MPa, and the pressure on the low-pressure side (hot side) is 7.8 MPa. The vertical axis of the figure is a logarithmic scale to visually display the changes in density by multiples. During the heat exchange process of supercritical carbon dioxide on the cold and hot sides, the supercritical carbon dioxide on the cold side absorbs heat, its temperature increases, its density decreases, and its rate of change increases. Conversely, the supercritical carbon dioxide on the hot side releases heat, its temperature decreases, its density increases, and its rate of change decreases.

[0039] Figure 3 and Figure 4 The diagram shows the slotted fin arrangement along the flow direction on the cold-side and hot-side heat exchange plates. The heat exchange plates are machined with slotted fins, the slot width of which gradually changes along the flow direction to match the changes in the properties and velocity of the supercritical fluid during heat exchange. For the cold-side heat exchange plate, the supercritical fluid is heated, its density decreases, and its velocity increases, so the slot width gradually increases along the flow direction. For the hot-side heat exchange plate, the supercritical fluid is cooled, its density increases, and its velocity decreases, so the slot width gradually decreases along the flow direction. The slotted fins are longitudinally symmetrical. The cold-side and hot-side heat exchange plates have the same structure. The change in slot width to match the changes in the properties of the supercritical fluid on the cold and hot sides is achieved by changing the arrangement direction of the heat exchange plates or the fluid flow direction. The slotted fins on the heat exchange plates can be arranged in a staggered or parallel configuration.

[0040] Figure 5 The diagram shows a longitudinally symmetrical slotted fin structure. Longitudinally symmetrical slotted fins have a symmetrical structure along the flow direction, including slotted spindle-shaped fins, slotted rhomboid fins, and slotted elliptical fins. The slotting type of the slotted fins is a longitudinal straight slot, formed by a longitudinal channel penetrating the fin along the centerline of the windward side. To avoid impurities clogging the channel while ensuring the pressure resistance of the PCHE core, the slot width should not be too small or too large. The slot width W... s With fin width W f The ratio is between 0.2 and 0.8. Figure 5 This illustrates the case where the slot width is 30% of the fin width.

[0041] Figure 6 The diagram illustrates the manufacturing process of a supercritical fluid variable-slot-width PCHE core. First, ungrooved fins are etched onto a metal plate using photochemical etching technology to create an ungrooved master plate. Next, grooves are created on the fins using high-precision cutting techniques such as laser cutting, wire cutting, and precision machining. The groove width varies longitudinally according to a set ratio, resulting in variable-slot-width heat exchange plates. Then, these plates are stacked according to the heat exchanger configuration. For co-current PCHEs, the hot and cold fluids flow in the same direction, and the hot and cold side heat exchange plates are stacked alternately in opposite directions. For counter-current PCHEs, the hot and cold fluids flow in opposite directions, and the hot and cold side heat exchange plates are stacked in the same direction. Finally, the heat exchange plates are bonded together as a single unit using vacuum diffusion welding technology to form the supercritical fluid variable-slot-width PCHE core.

[0042] The working principle of this invention is as follows:

[0043] (1) Longitudinal symmetrical slotted fins have high efficiency and low resistance characteristics, which can effectively reduce flow resistance and enhance heat transfer. On the one hand, the longitudinal symmetrical slotted fins have sharp tips and a small angle between the tangent of the fin leading edge and the flow direction, which can avoid the normal impact of the working fluid on the fins. In addition, the curvature change of the fin leading edge is small, which can reduce the velocity gradient around the fins. On the other hand, the longitudinal symmetrical slotted fins are discontinuous fins, which can suppress the development of the thermal boundary layer and improve the convective heat transfer coefficient. At the same time, the slotting of the fins can increase the heat transfer area and improve the overall heat transfer performance of PCHE.

[0044] (2) The gradual change in fin slot width along the flow direction matches the changes in the physical properties of the supercritical fluid during heat transfer, which can improve the overall flow and heat transfer performance of PCHE. For cold channels, the density of the supercritical fluid decreases and its velocity increases during heating; gradually increasing the slot width along the flow direction can reduce the increase in resistance caused by the increase in flow velocity. For hot channels, the density of the supercritical fluid increases and its velocity decreases during cooling; gradually decreasing the slot width along the flow direction can reduce the decrease in heat transfer performance caused by the decrease in flow velocity.

[0045] (3) The fins used in this invention are longitudinally symmetrical slotted fins. The fins have a symmetrical structure along the flow direction, and changing the flow direction does not affect their flow heat transfer characteristics. The hot and cold sides can use heat exchange plates with the same structure and variable slot width, without the need for separate design and processing. By changing the arrangement direction of the heat exchange plates or the fluid flow direction, the channel structure can be matched with the changes in the physical properties of the supercritical fluid on the hot and cold sides. By adjusting the stacking direction of the heat exchange plates, the processing of the PCHE core in both co-current and counter-current flow can be achieved, which simplifies the processing and assembly process of the PCHE heat exchange plates.

[0046] (4) Etching ungrooved fins and fabricating ungrooved master plates using photochemical etching technology can ensure the smooth formation of complex fin structures. Using high-precision cutting technologies such as laser cutting, wire cutting, and precision machining to groove the fins can overcome problems such as lateral erosion and etching arcs in photochemical etching technology, ensuring the processing accuracy of microgrooving of fins and the precise realization of groove width variation rules, thereby improving the reliability of PCHE fin grooving process.

[0047] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for manufacturing a supercritical fluid variable-groove PCHE core, characterized in that, The core includes a hot-side heat exchange plate, a cold-side heat exchange plate, and a top plate; Several hot-side heat exchange plates and cold-side heat exchange plates are stacked alternately from bottom to top, with a top plate set on top of the uppermost hot-side heat exchange plate or cold-side heat exchange plate; several slotted fins are provided on both the hot-side and cold-side heat exchange plates, and the slot width of the slotted fins gradually changes along the flow direction. The fin gaps of the cold-side heat exchange plate form a cold flow channel, and the fin gaps of the hot-side heat exchange plate form a hot flow channel. The slotted fins on the hot-side heat exchange plate and the cold-side heat exchange plate are longitudinally symmetrical slotted fins, and the fins have a symmetrical structure along the flow direction. The slotted fins of the cold-side heat exchange plate have a slot width that gradually increases along the flow direction, while the slotted fins of the hot-side heat exchange plate have a slot width that gradually decreases along the flow direction. The manufacturing method includes: Ungrooved fins are etched onto a metal plate to be processed using photochemical etching technology to create an ungrooved mother plate. By cutting grooves on the fins, the fin groove width varies along the longitudinal direction according to a set ratio to obtain a variable groove width heat exchange plate. Depending on the heat exchanger type, the variable-width heat exchange plates are stacked. For co-current PCHE, the hot and cold fluids flow in the same direction, and the hot and cold side heat exchange plates are stacked alternately in opposite directions. For counter-current PCHE, the hot and cold fluids flow in opposite directions, and the hot and cold side heat exchange plates are stacked in the same direction. The heat exchange plates are combined into a whole by vacuum diffusion welding technology to form a supercritical fluid variable-groove PCHE core.

2. The method for manufacturing a supercritical fluid variable-width PCHE core according to claim 1, characterized in that, Longitudinal symmetrical slotted fins include slotted spindle-shaped fins, slotted rhomboid fins, and slotted elliptical fins.

3. The method for manufacturing a supercritical fluid variable-groove PCHE core according to claim 1, characterized in that, The slotted fin structure on the hot-side heat exchange plate and the cold-side heat exchange plate is the same. By changing the arrangement direction of the heat exchange plate or the direction of fluid flow, the change in slot width can be matched with the change in the physical properties of the supercritical fluid on the hot and cold sides.

4. The method for manufacturing a supercritical fluid variable-width PCHE core according to claim 1, characterized in that, The slotted fins on the hot-side heat exchange plate and the cold-side heat exchange plate are arranged in a staggered or sequential manner.

5. The method for manufacturing a supercritical fluid variable-width PCHE core according to claim 1, characterized in that, The slotted fins on the hot-side and cold-side heat exchange plates are slotted by longitudinally penetrating the fins along the centerline of the windward side to form a slotted flow channel.

6. The method for manufacturing a supercritical fluid variable-groove PCHE core according to claim 1, characterized in that, The ratio of the slot width to the fin width of the slotted fins on the hot-side heat exchange plate and the cold-side heat exchange plate is between 0.2 and 0.8.

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