A semi-cone type micro-channel printed circuit board heat exchanger structure and a design method thereof

Abstract

The application discloses a semi-cone type micro-channel printed circuit board type heat exchanger structure and a design method thereof. The heat exchanger is formed by etching semi-cone type micro-channels on heat exchange sheets, which significantly increases the welding area of the sheets, and improves the structural strength and pressure bearing capacity. Meanwhile, the semi-cone type channels are formed by periodically and rapidly shrinking or expanding the fins, the throats are connected with each other, and the tails are connected with each other. The heat transfer is strengthened by the jet effect at the inlet of the expansion section and the throttling effect at the outlet of the channel, the mixing effect of the fluid in the expansion section is enhanced, the boundary layer is destroyed by the throttling effect, and the turbulent heat transfer is strengthened. The flow of the fluid in the channel is streamline as a whole, and the pressure drop can be effectively controlled. In addition, the design of the tail of the channel helps to prevent impurities from being blocked. Compared with the traditional straight channel and zigzag channel, the semi-cone type micro-channel has excellent heat transfer enhancement effect, the pressure drop is significantly reduced, and the overall quality and volume of the heat exchanger are reduced.

Description

Technical Field

[0001] This invention belongs to the field of heat exchanger design and manufacturing technology, and relates to the structural optimization and application of high-efficiency microchannel heat exchangers. Specifically, it relates to a semi-conical microchannel printed circuit board heat exchanger structure and its design method, which aims to improve the thermal-hydraulic performance and structural strength of the heat exchanger, and enhance its pressure resistance. Background Technology

[0002] Printed Circuit Heat Exchangers (PCHEs), as a new type of high-efficiency, compact microchannel heat exchanger, employ diffusion bonding technology in their fabrication and are currently the only heat exchangers whose mechanical properties closely resemble those of the base material. Due to their compact structure, high heat transfer efficiency, and resistance to high temperatures and pressures, this technology shows promising development prospects in applications with high requirements for heat exchanger size, weight, and reliability, including next-generation nuclear technology, aerospace, and underwater vehicles, and is expected to occupy an important position in a wider range of industrial applications in the future.

[0003] The microchannel structure determines the overall performance and application scenarios of PCHE heat exchangers. The structural design of microchannels not only affects the heat transfer efficiency of the heat exchanger but also determines its pressure resistance, fluid resistance, and applicability in specific application scenarios. In existing technologies, heat exchanger channel designs are mainly divided into two categories: continuous finned channels and discontinuous finned channels. Continuous channels maintain channel integrity during heat exchange, while discontinuous channels enhance fluid turbulence and mixing effects by introducing interruptions in the fin structure, thereby improving heat transfer efficiency. To improve the thermo-hydraulic performance of printed circuit board heat exchangers, the fin form of microchannels has evolved from continuous to discontinuous, achieving excellent enhanced heat transfer effects. However, the welding area between the plates in discontinuous fins is relatively small, requiring high welding standards, which leads to a decrease in the overall structural strength of the heat exchanger, reduced pressure resistance, and decreased reliability in practical applications. This limits the application range of discontinuous finned printed circuit board heat exchangers.

[0004] Under high temperature and pressure conditions, heat exchangers not only need to possess efficient heat transfer capabilities but also sufficient pressure resistance to cope with harsh working environments. Therefore, printed circuit board heat exchangers with continuous finned channels are still widely used, primarily including straight-channel and zigzag-channel types. Because straight channels have low resistance and low heat transfer intensity, they perform poorly in applications requiring high-efficiency heat exchange. In contrast, while zigzag channels offer high heat transfer intensity, their greater flow resistance leads to increased system pressure drop. Therefore, although zigzag channels are superior to straight channels in heat transfer efficiency, their high resistance characteristics limit their widespread use in certain applications.

[0005] In summary, while traditional printed circuit board (PCB) heat exchangers can meet the requirements for efficient heat transfer to a certain extent, there is still significant room for improvement in handling high-temperature and high-pressure conditions and reducing system pressure drop. Especially under high-temperature and high-pressure conditions, ensuring the safe operation of the heat exchanger is the primary goal. Improving the thermo-hydraulic performance of the heat exchanger can not only reduce the weight of the heat exchange equipment but also reduce system energy loss. Therefore, designing a heat exchanger structure that combines high heat transfer efficiency, low resistance, strong pressure resistance, and lightweight characteristics has become an urgent technical problem to be solved. Summary of the Invention

[0006] (I) Purpose of the Invention

[0007] To address the shortcomings of existing printed circuit board (PCB) heat exchangers, such as insufficient thermal-hydraulic performance, limited pressure resistance, and the need for further improvement in overall performance under high temperature and high pressure conditions, this invention aims to provide a semi-conical microchannel PCB heat exchanger structure and its design method. By introducing a semi-conical microchannel design into the heat exchanger, the channel geometry is optimized to enhance fluid mixing, reduce channel resistance, and improve heat transfer efficiency. Simultaneously, the welding area between channel plates is increased, thereby improving the thermal-hydraulic performance of traditional continuous finned PCB heat exchangers and further enhancing their pressure resistance. This meets the high requirements for overall performance in certain applications, including efficiency, pressure drop, volume, weight, and reliability.

[0008] (II) Technical Solution

[0009] To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution:

[0010] The first objective of this invention is to provide a semi-conical microchannel printed circuit board heat exchanger structure for efficient heat exchange under high temperature and high pressure conditions. It is suitable for applications with high requirements for heat transfer efficiency, fluid pressure drop, equipment size, and pressure resistance. The structure includes a heat exchanger core, wherein:

[0011] The heat exchanger core comprises at least multiple layers of stacked heat exchange plates. Each heat exchange plate has microchannels etched on it. The heat exchange plates are connected by diffusion welding to form a multi-layer heat exchange structure with fluid channels. Specifically, the heat exchange plates through which hot fluid flows are formed as hot-side heat exchange plates, and their microchannels form hot-side fluid channels. The heat exchange plates through which cold fluid flows are formed as cold-side heat exchange plates, and their microchannels form cold-side fluid channels. The hot-side and cold-side heat exchange plates are arranged in an alternating stacked manner.

[0012] And among them,

[0013] At least one of the hot-side fluid channel and the cold-side fluid channel adopts a semi-conical microchannel structure. The semi-conical microchannel structure is composed of periodically arranged rapidly contracting sections and rapidly expanding sections along the fluid flow direction and forms a continuous channel as a whole. The semi-conical microchannel structure is formed by the periodic rapid contraction and rapid expansion of the semi-conical fins between adjacent microchannels.

[0014] The fin throat of the semi-conical microchannel in one cycle is connected to the fin throat of the adjacent cycle, and the fin tail in one cycle is connected to the fin tail of the adjacent cycle, thereby forming a continuous microchannel structure with periodic changes in the direction of fluid flow.

[0015] The relative lengths of the rapid expansion and rapid contraction sections within one cycle of the semi-conical microchannel are designed as follows: when the fluid Reynolds number is less than or equal to 15000, the length of the rapid expansion section is greater than or equal to the length of the rapid contraction section; when the fluid Reynolds number is greater than 15000, the length of the rapid expansion section is greater than, equal to, or less than the length of the rapid contraction section, thereby adapting to different fluid flow conditions.

[0016] The semi-conical microchannel induces Dean vortices through rapid expansion and contraction sections, causing the vortex structure to continuously evolve and be disturbed. This enhances the mixing between hot and cold fluids, disrupts the boundary layer, and promotes turbulence, thereby improving heat transfer efficiency. The fluid flow is streamlined overall, reducing fluid pressure drop and improving the overall performance of the heat exchanger.

[0017] The second objective of this invention is to provide a design method for the above-mentioned semi-conical microchannel printed circuit board heat exchanger structure, wherein the method, when implemented, includes at least the following steps:

[0018] SS1. Determine the basic parameters and operating conditions of the heat exchanger.

[0019] Based on the application scenario and actual operating conditions, determine the basic parameters of the heat exchanger, including at least the heat load, operating temperature range, pressure range, allowable pressure drop, and physical properties of the hot and cold fluids at the operating temperature and pressure (such as density, viscosity, thermal conductivity, specific heat capacity, etc.).

[0020] SS2. Multi-layer structure design of heat exchanger and setting of microchannel geometric parameters

[0021] Based on the basic parameters and operating conditions of the heat exchanger, the multi-layer structure of the hot and cold side heat exchange plates is designed, and the structural type of the fluid channels on both sides is determined. It is selected that all fluid channels on both sides adopt semi-conical microchannels, or that the hot side fluid channel is designed as a semi-conical microchannel while the cold side fluid channel is designed as a straight channel. By alternately stacking the hot and cold side heat exchange plates, alternating hot and cold side fluid channels are formed. At the same time, the geometric parameters of the semi-conical microchannel are set, including at least the throat diameter, tail diameter, channel spacing, channel fin height ratio, and the length ratio of the rapid contraction section to the rapid expansion section. Through CFD numerical simulation, the influence of different combinations of microchannel geometric parameters on heat transfer performance and fluid resistance is evaluated, and the optimal parameter combination under different operating conditions is preliminarily determined.

[0022] SS3. Heat Exchanger Performance Evaluation and Design Parameter Optimization

[0023] After completing the preliminary structural design, the heat exchanger performance was evaluated. By analyzing the heat transfer coefficient, pressure drop, fluid flow characteristics, and operating temperature range, the Nusselt number (Nu), friction factor (f), and the heat exchange enhancement index (PEC) for the same power consumption were used as performance evaluation indicators to assess the heat transfer effect, pressure drop characteristics, and energy efficiency of the heat exchanger design. Based on the evaluation results, the microchannel geometry parameters and multi-layer structure layout were optimized to achieve the best balance between efficiency, pressure drop, volume, weight, and reliability. The mathematical expression for the heat exchanger enhancement index (PEC) for the same power consumption is:

[0024]

[0025] In the formula, j and f are the heat factor and friction factor of the heat exchanger, respectively. s f s The heat transfer factor and friction factor of the reference heat exchanger are given, and among them, Nu is the Nusselt number, and Pr is the Prandtl number;

[0026] SS4. Complete the fabrication of microchannels and plate welding.

[0027] Microchannels are fabricated on heat exchange plates using electrochemical etching, heat exchange plates are manufactured using selective laser melting (SLM) or electron beam melting (EBM) 3D printing technology, or heat exchange plates are manufactured by machining. After processing, diffusion welding is used to weld the heat exchange plates of each layer, ensuring that the joints between the layers have the same structural strength as the base material. Diffusion welding improves the structural strength and pressure resistance of the heat exchanger under high temperature and high pressure conditions by controlling temperature, time and pressure parameters.

[0028] SS5. Quality Control and Performance Verification

[0029] After welding is completed, the heat exchanger is subjected to sealing and pressure tests to ensure no leakage. Heat exchange performance is tested under actual or simulated operating conditions to verify whether key parameters such as heat exchange efficiency and pressure drop meet the design requirements. Based on the test results, the design parameters are finally adjusted and optimized.

[0030] (III) Technical Effects

[0031] Compared with the prior art, the semi-conical microchannel printed circuit board heat exchanger structure and its design method of the present invention have the following beneficial and significant technical effects:

[0032] (1) This invention, by adopting a semi-conical channel design, increases the welding area between the plates, resulting in structural strength superior to discontinuous finned channels and commonly used straight and zigzag continuous channels. Furthermore, the channel strength design method is simple. While achieving enhanced heat transfer, it also possesses higher pressure resistance, improving the reliability of printed circuit board heat exchangers, making it particularly suitable for use under high temperature and high pressure conditions.

[0033] (2) By optimizing the geometric design of the microchannel, the present invention utilizes the jetting effect generated by the fluid at the inlet of the expansion section of the semi-conical channel, which generates a large velocity gradient on the cross section, enhancing the mixing of cold and hot fluids. At the outlet of the expansion section, a throttling effect is generated, and the fluid velocity along the flow direction gradually increases, the boundary layer is continuously destroyed, and the fluid turbulence is enhanced, thereby achieving enhanced heat transfer.

[0034] (3) The present invention utilizes a semi-conical channel tail design, where the velocity is at its minimum. Impurities entering the channel are most likely to deposit at this point, which also has the largest diameter within the entire channel, thus preventing blockage to some extent. This design is particularly suitable for situations where impurities are unavoidable in the fluid, improving the operational stability and reliability of the heat exchanger, effectively reducing the risk of maintenance and downtime due to channel blockage, reducing maintenance costs, and improving the overall reliability of the system.

[0035] (4) Under the same design conditions, the heat transfer coefficients on both the cold and hot sides of the semi-conical channel printed circuit board heat exchanger of the present invention are about three times that of the traditional straight channel, while the pressure drop is significantly lower than that of the zigzag channel. This indicates that the semi-conical channel of the present invention has a relatively good enhanced heat transfer effect, especially in the laminar flow region and the transition region, where the comprehensive enhanced heat transfer performance is excellent.

[0036] (5) The mass and volume of the semi-conical channel printed circuit board heat exchanger of the present invention are significantly reduced compared with the mass and volume of the traditional straight channel printed circuit board heat exchanger, and the pressure drop is much lower than that of the traditional zigzag channel printed circuit board heat exchanger. It is particularly suitable for heat exchangers with high requirements for comprehensive performance such as efficiency, pressure drop, volume, weight and reliability. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 The diagrams show typical traditional continuous and discontinuous channels, where (A) is a straight channel, (B) is a zigzag channel, (C) is an S-shaped channel, and (D) is an airfoil channel.

[0039] Figure 2 This is a schematic diagram of the semi-conical channel structure in the printed circuit board heat exchanger of the present invention;

[0040] Figure 3 This is a schematic diagram of the main parameters of the semi-conical channel in this invention;

[0041] Figure 4 The diagram shows the distribution of the fluid velocity field (A) and temperature field (B) in a single-cycle semi-conical channel.

[0042] Figure 5 This is a schematic diagram comparing the enhanced heat transfer effect of a semi-conical channel and a traditional zigzag channel. In this diagram, (A) shows the variation of Nusselt number Nu with Reynolds number Re, (B) shows the variation of friction factor f with Reynolds number Re, and (C) shows the variation of heat exchanger performance enhancement coefficient PEC with Reynolds number Re.

[0043] Figure 6 This is a schematic diagram comparing the performance of printed circuit board heat exchangers with semi-conical channels and traditional straight channels and zigzag channels. In the diagram, (A) is a pressure drop comparison diagram and (B) is a mass comparison diagram.

[0044] Figure 7 This is a flowchart illustrating the structural design method of the semi-conical microchannel printed circuit board heat exchanger of the present invention.

[0045] Explanation of reference numerals in the attached figures:

[0046] Straight channel 1, zigzag channel 2, S-shaped channel 3, airfoil channel 4, fin 5, semi-conical channel 6, throat 7, tail 8. Detailed Implementation

[0047] To clearly illustrate the technical features of this invention, a heat exchanger design for a specific application scenario is described below in conjunction with the accompanying drawings, and the invention is explained in detail. In the following description, many specific details are set forth to provide a thorough understanding of the invention. However, the invention can also be implemented in other ways different from those described herein; therefore, the scope of protection of this invention is not limited to the specific embodiments disclosed below.

[0048] This invention aims to provide a semi-conical microchannel printed circuit board heat exchanger structure and its design method. By introducing a semi-conical microchannel design into the heat exchanger, the channel geometry is optimized to enhance fluid mixing, reduce channel resistance, and improve heat transfer efficiency. Simultaneously, the welding area between channel plates is increased, thereby improving the thermal-hydraulic performance of traditional continuous finned printed circuit board heat exchangers and further enhancing their pressure resistance. This meets the high requirements for comprehensive performance in certain applications, including efficiency, pressure drop, volume, weight, and reliability. In practical applications, the geometric design of the semi-conical microchannel in this invention generates jetting and throttling effects during fluid flow through the periodic changes of rapidly contracting and rapidly expanding sections. This design effectively enhances the mixing of cold and hot fluids while continuously disrupting the fluid boundary layer, enhancing turbulence and significantly improving heat transfer efficiency. Furthermore, the design at the channel tail minimizes fluid velocity, effectively reducing the risk of impurity deposition and preventing channel blockage. These characteristics make this invention particularly suitable for heat exchange scenarios under high temperature and high pressure conditions, especially in applications requiring high pressure resistance, heat transfer efficiency, and reliability.

[0049] Example 1

[0050] As a concrete example, supercritical carbon dioxide (S-CO2) Brayton cycle power generation technology, with its outstanding advantages such as high efficiency, compactness, and stealth, not only meets the development needs of next-generation advanced energy conversion technologies but also aligns with the future development trend of nuclear power plants, and is expected to replace steam power cycles as the optimal solution for next-generation marine vehicle power equipment. Due to the high temperature and pressure parameters of the S-CO2 cycle regenerator and the large amount of heat involved in the regeneration process, the regenerator's volume and weight account for a significant proportion of the overall system. Furthermore, since the efficiency of the S-CO2 cycle system is highly sensitive to pressure drop, reasonable control of the regenerator's pressure drop is crucial for S-CO2 cycle technology. Therefore, improving the compactness, efficiency, and reliability of the S-CO2 regenerator within a limited space is a key focus of space-efficient optimization for marine vehicle power systems.

[0051] like Figure 1As shown, S-CO2 regenerators generally use printed circuit board heat exchangers. In practical applications, continuous channels are the main type, including straight channels 1 and zigzag channels 2. Other optional solutions include discontinuous channels, commonly S-shaped channels 3 and airfoil channels 4. A discontinuous channel can be seen as breaking down the fins 5 of a continuous channel, treating the head and tail of the fins 5, and rearranging the fins 5. Although the discontinuous channel fins 5 have excellent thermo-hydraulic performance, from... Figure 1 It can be seen that the welding area of ​​the discontinuous channel fin is small, which results in its poor compressive strength.

[0052] like Figure 2 , 3 As shown, for S-CO2 regenerators, this invention proposes a semi-conical microchannel printed circuit board heat exchanger structure. The heat exchanger core includes at least multiple layers of stacked heat exchange plates. Each heat exchange plate is etched with microchannels. The heat exchange plates are connected by diffusion bonding to form a multi-layer heat exchange structure with fluid channels. Specifically: heat exchange plates through which hot fluid flows are formed as hot-side heat exchange plates, and their microchannels form hot-side fluid channels; heat exchange plates through which cold fluid flows are formed as cold-side heat exchange plates, and their microchannels form cold-side fluid channels; the hot-side and cold-side heat exchange plates are arranged in an alternating stacked manner. Furthermore, at least one of the hot-side and cold-side fluid channels adopts a semi-conical microchannel structure. The semi-conical channel 6 is formed by the periodic rapid contraction or expansion of channel fins 5 between adjacent microchannels along the flow direction. The channel consists of periodically arranged rapidly contracting and rapidly expanding sections, forming a continuous channel.

[0053] like Figure 2 , 3 As shown, the semi-conical channel 6 is an inwardly contracted channel δ based on the traditional semi-circular straight channel 1, which increases the welding area between the fins and the plate. Within one cycle of the semi-conical channel 6, the fin throat 7 connects to the throat 7 of the fin in the adjacent cycle, and the fin tail 8 within one cycle connects to the tail 8 of the fin in the adjacent cycle. The thickness e at the connection point between the tail 8 and the tail 8 of the fin in the adjacent cycle is the minimum thickness of the channel. The pitch of the semi-conical channel is l, and the length of the rapid expansion section and the contraction length are l... div and l con , l div and l con The ratio of expansion to contraction is called the expansion-contraction ratio.

[0054] The design conditions are as follows: the design pressure of the cold fluid is 10 MPa, and the design temperature is 200℃; the design pressure of the hot fluid is 20 MPa, and the design temperature is 400℃; the design flow rates of both the cold and hot fluids are 52.5 kg / s. In this embodiment, the printed circuit board heat exchanger adopts a design scheme combining a semi-conical channel and a straight channel. The hot-side fluid channel uses a semi-conical channel 6, while the cold-side fluid uses a conventional straight channel 1 with a semi-circular cross-sectional shape. The hydraulic diameter of the semi-conical channel 6 used for the hot-side fluid is 0.76 mm, the thickness e = 0.8 mm, and the expansion / contraction ratio is 1. The hydraulic diameter of the straight channel 1 used for the cold-side fluid is 0.79 mm, and the thickness e = 1 mm.

[0055] This invention induces Dean vortices through a semi-conical channel structure, and allows the vortex structure to continuously evolve and agitate within the periodic semi-conical channel, thereby enhancing thermofluid mixing and scouring the boundary layer, thus achieving enhanced heat transfer. Figure 4 As shown, velocity and temperature distribution contour maps are presented for the cold and hot sides of the channel over one cycle. Along the flow direction, the fluid on both sides first flows through a rapidly expanding section, where the velocity decreases, reaching a minimum at the tail of the semi-conical channel, and then enters a rapidly contracting section where the velocity increases again, resulting in continuous velocity variation. A large velocity and temperature gradient is generated across the entire cross-section of the expanding section, and two vortices appear at the maximum cross-section, causing a strong flow perpendicular to the mainstream direction and enhancing the mixing of the cold and hot fluids. As the fluid enters the contracting section, the velocity gradually increases, and the flow gradually evolves from two vortices to one vortex. The fluid exhibits a large temperature gradient near the wall, and the continuous increase in velocity thins the boundary layer.

[0056] Figure 5 The variations of Nusselt number (Nu), friction factor (f), and heat transfer enhancement index (PEC) with Reynolds number (Re) for semi-conical and zigzag channels compared to straight channels at the same power consumption are presented. PEC represents the heat exchanger enhancement index under the same pump power consumption. In the formula, the subscript 's' represents the standard structure. 'j' is the Colburn factor and... In the formula, Pr is the Prandtl number.

[0057] For thermal design within a straight-through PCHE, Gnielinski correlation was used for calculation:

[0058]

[0059] f = (1.82lgRe - 1.64) -2

[0060]

[0061] The experimental verification range is Re = 2300 to 10. 6 Pr = 0.6–10 5 T b / T w =0.5~1.5. For Nu and f of zigzag channels, the following correlation formula is used for calculation:

[0062] Nu = 0.0176Re 0.809 Pr 1 / 3 f = 0.3905Re -0.0355

[0063] The application range of this correlation is Re = 3000 to 2.06 × 10⁻⁶. 6 .

[0064] from Figure 5 It can be seen that when Re is low, the heat transfer enhancement of the semi-conical channel is better than that of the zigzag channel and the straight channel, but the resistance increase of the zigzag channel is higher than that of the semi-conical channel. When Re is higher than 15000, the heat transfer enhancement of the semi-conical channel is comparable to that of the zigzag channel, but the resistance increase of the zigzag channel is higher than that of the semi-conical channel. Comparing the heat transfer enhancement index under the same power consumption, the heat transfer enhancement effect is significant when Re is lower than 15000. Throughout the entire Re range, it is higher than that of the zigzag channel. Therefore, the semi-conical channel is a very good heat transfer enhancement element, especially with better overall heat transfer enhancement performance in the laminar and transition regions.

[0065] like Figure 6 As shown, the design results of printed circuit board (PCB) heat exchangers using semi-conical, traditional straight-channel, and zigzag-channel designs are presented. Under the same heat transfer conditions, compared to the straight-channel PCB heat exchanger, the semi-conical channel PCB heat exchanger reduces the cold-side pressure drop by 0.2 times and increases the hot-side pressure drop by only 1.1 times, while the zigzag channel PCB heat exchanger increases the pressure drops on the cold and hot sides by 7 and 9.5 times, respectively. The mass of the semi-conical and zigzag channel PCB heat exchangers is reduced by 23% and 28%, respectively, and the mass of the PCB heat exchanger is also reduced accordingly. Overall, the semi-conical channel PCB heat exchanger achieves a significant weight reduction while maintaining ultra-low pressure drop, and its overall performance is superior.

[0066] Preferably, the microchannels on both the hot-side and cold-side heat exchange plates in this invention can be designed as semi-conical microchannels. Alternatively, a free combination of semi-conical and straight channels can be used according to actual operating conditions. The semi-conical channels are used to enhance heat transfer and generate turbulence, while the straight channels are used to reduce pressure drop and balance flow distribution. Alternatively, depending on specific application requirements, a regional layout can be designed on the same heat exchange plate, with some areas using semi-conical channels to enhance heat transfer and some areas using straight channels to reduce pressure drop.

[0067] Preferably, the semi-conical microchannel in this invention is formed by a semi-conical fin through periodic rapid contraction or rapid expansion, and the geometric dimensions of the semi-conical fin can be processed by an electrochemical etching process. After etching, the minimum diameter of the throat of the semi-conical microchannel is not less than 1 mm, the ratio of the rib height to the diameter of the channel is less than 0.35, the expansion-contraction ratio of the channel, i.e., the ratio of the length of the rapidly expanding section to the length of the rapidly contracting section, is controlled between 0.25 and 4, and the spacing between adjacent channels is controlled between 6 and 24 mm.

[0068] Preferably, the thickness of the fins at the tail and tail connection of the semi-conical microchannel in this invention can be determined by the temperature and pressure parameters of the fluid and the etching depth of the channel, so as to ensure that the heat exchanger meets the minimum thickness required for structural strength under high temperature and high pressure conditions, and ensures that it maintains stable performance in long-term operation, reducing equipment failures caused by fin deformation or damage.

[0069] Preferably, the cross-section of the semi-conical microchannel in this invention can be semi-circular, trapezoidal, or rectangular. The specific cross-sectional shape can be optimized and selected according to the fluid conditions and heat exchange requirements to achieve optimized regulation of fluid flow under different conditions and achieve the best thermal-hydraulic performance.

[0070] Preferably, the rapid contraction and rapid expansion sections of the semi-conical microchannel in this invention can adopt linear or nonlinear profile designs. The specific profile is selected according to the fluid dynamics characteristics and heat transfer requirements. The linear profile design is used to ensure the stability of fluid flow and the pressure drop does not increase significantly. The nonlinear profile design includes profiles defined using parabolic, exponential, or sine functions to enhance fluid disturbance.

[0071] Preferably, the periodic arrangement of the semi-conical microchannels in this invention can be non-uniformly designed. By gradually changing the expansion-contraction ratio, pitch, or throat diameter of the channels in the flow direction, the fluid properties can be gradually changed to adapt to the characteristics of fluid properties changing with temperature.

[0072] Preferably, the design of the semi-conical microchannel in this invention can introduce a bifurcation or merging structure, dividing a channel into two or more sub-channels at a preset position, or merging multiple channels into one, to form a complex three-dimensional flow path, thereby increasing the degree of fluid mixing, improving heat transfer efficiency, and optimizing local heat transfer performance by adjusting fluid distribution.

[0073] Preferably, the semi-conical microchannel in this invention can be manufactured using 3D printing technology, selective laser melting, or electron beam melting. By flexibly adjusting the geometric parameters of the microchannel during the manufacturing process, the surface quality of the channel can be optimized and the structural strength improved, ensuring that the heat exchanger has excellent performance and durability under complex operating conditions. Alternatively, the semi-conical microchannel in this invention can also be manufactured using machining methods. While ensuring the geometric accuracy of the microchannel, the surface of the channel can be optimized through polishing or sandblasting post-processing to reduce fluid friction and improve heat transfer performance.

[0074] Example 2

[0075] Based on Embodiment 1 above, Embodiment 2 provides a design method for the above-mentioned semi-conical microchannel printed circuit board heat exchanger structure. This method, when implemented, includes at least the following steps:

[0076] SS1. Determine the basic parameters and operating conditions of the heat exchanger.

[0077] Based on the application scenario and actual operating conditions, determine the basic parameters of the heat exchanger, including at least the heat load, operating temperature range, pressure range, allowable pressure drop, and physical properties of the hot and cold fluids at the operating temperature and pressure (such as density, viscosity, thermal conductivity, specific heat capacity, etc.).

[0078] SS2. Multi-layer structure design of heat exchanger and setting of microchannel geometric parameters

[0079] Based on the basic parameters and operating conditions of the heat exchanger, the multi-layer structure of the hot and cold side heat exchange plates is designed, and the structural type of the fluid channels on both sides is determined. It is selected that all fluid channels on both sides adopt semi-conical microchannels, or that the hot side fluid channel is designed as a semi-conical microchannel while the cold side fluid channel is designed as a straight channel. By alternately stacking the hot and cold side heat exchange plates, alternating hot and cold side fluid channels are formed. At the same time, the geometric parameters of the semi-conical microchannel are set, including at least the throat diameter, tail diameter, channel spacing, channel fin height ratio, and the length ratio of the rapid contraction section to the rapid expansion section. Through CFD numerical simulation, the influence of different combinations of microchannel geometric parameters on heat transfer performance and fluid resistance is evaluated, and the optimal parameter combination under different operating conditions is preliminarily determined.

[0080] SS3. Heat Exchanger Performance Evaluation and Design Parameter Optimization

[0081] After completing the preliminary structural design, the heat exchanger performance was evaluated. By analyzing the heat transfer coefficient, pressure drop, fluid flow characteristics, and operating temperature range, the Nusselt number (Nu), friction factor (f), and the heat exchange enhancement index (PEC) for the same power consumption were used as performance evaluation indicators to assess the heat transfer effect, pressure drop characteristics, and energy efficiency of the heat exchanger design. Based on the evaluation results, the microchannel geometry parameters and multi-layer structure layout were optimized to achieve the best balance between efficiency, pressure drop, volume, weight, and reliability. The mathematical expression for the heat exchanger enhancement index (PEC) for the same power consumption is:

[0082]

[0083] In the formula, j and f are the heat factor and friction factor of the heat exchanger, respectively. s f s The heat transfer factor and friction factor of the reference heat exchanger are given, and among them, Nu is the Nusselt number, and Pr is the Prandtl number;

[0084] SS4. Complete the fabrication of microchannels and plate welding.

[0085] Microchannels are fabricated on heat exchange plates using electrochemical etching, heat exchange plates are manufactured using selective laser melting (SLM) or electron beam melting (EBM) 3D printing technology, or heat exchange plates are manufactured by machining. After processing, diffusion welding is used to weld the heat exchange plates of each layer, ensuring that the joints between the layers have the same structural strength as the base material. Diffusion welding improves the structural strength and pressure resistance of the heat exchanger under high temperature and high pressure conditions by controlling temperature, time and pressure parameters.

[0086] SS5. Quality Control and Performance Verification

[0087] After welding is completed, the heat exchanger is subjected to sealing and pressure tests to ensure no leakage. Heat exchange performance is tested under actual or simulated operating conditions to verify whether key parameters such as heat exchange efficiency and pressure drop meet the design requirements. Based on the test results, the design parameters are finally adjusted and optimized.

[0088] In summary, this embodiment 2 provides a design method for a semi-conical microchannel printed circuit board heat exchanger. Through reasonable geometric parameter setting and multi-layer structure design, the heat transfer performance and pressure resistance of the heat exchanger are significantly improved. This method not only optimizes the heat transfer efficiency and fluid resistance of the microchannel through CFD simulation, but also employs advanced processing technology and welding techniques to ensure the structural strength and long-term stability of the heat exchanger. Finally, through rigorous quality control and performance testing, the heat exchanger is ensured to have excellent comprehensive performance under high temperature and high pressure conditions.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A design method of a semi-cone type micro-channel printed circuit board heat exchanger structure, the semi-cone type micro-channel printed circuit board heat exchanger structure being used for high-efficiency heat exchange under high-temperature and high-pressure conditions, comprising a heat exchanger core, the heat exchanger core comprising at least a plurality of layers of heat exchange plates stacked on each other, each layer of heat exchange plates being etched with micro-channels, and the layers of heat exchange plates being connected by diffusion welding to form a multi-layer heat exchange structure with fluid channels, wherein: The heat exchange plate through which the hot fluid flows in the microchannel is formed as a hot side heat exchange plate, and the microchannel thereof is formed as a hot side fluid channel; the heat exchange plate through which the cold fluid flows in the microchannel is formed as a cold side heat exchange plate, and the microchannel thereof is formed as a cold side fluid channel; the hot side heat exchange plate and the cold side heat exchange plate are arranged in a layer-by-layer alternating superposition manner; and at least one of the hot side fluid channel and the cold side fluid channel adopts a semi-cone type microchannel, the semi-cone type microchannel is composed of periodically arranged rapid contraction sections and rapid expansion sections along the fluid flow direction and forms a continuous channel as a whole, and the semi-cone type microchannel is formed through the periodic rapid contraction and rapid expansion of the semi-cone type fins between adjacent microchannels; the fin throat of one period of the semi-cone type microchannel is connected with the fin throat of the adjacent period, and the fin tail of one period is connected with the fin tail of the adjacent period, so as to form a periodically changing continuous microchannel structure in the fluid flow direction; the relative lengths of the rapid expansion section and the rapid contraction section in one period of the semi-cone type microchannel are designed as follows: when the fluid Reynolds number is less than or equal to 15000, the length of the rapid expansion section is greater than or equal to the length of the rapid contraction section; when the fluid Reynolds number is greater than 15000, the length of the rapid expansion section is greater than, equal to or less than the length of the rapid contraction section, so as to adapt to different fluid flow working conditions; the semi-cone type microchannel induces Dean vortex through the rapid expansion section and the rapid contraction section and makes the structure of the vortex continuously evolve and disturb, so as to enhance the mixing between the hot fluid and the cold fluid, destroy the boundary layer and promote the turbulent flow, thereby improving the heat transfer efficiency, the fluid flow is overall streamlined, the fluid pressure drop is reduced, and the overall performance of the heat exchanger is improved; ​ The design method comprises the following steps: SS1. Determine the basic parameters and working conditions of the heat exchanger According to the application scene and the actual working condition performance requirement, the basic parameters of the heat exchanger are determined, at least including the heat load, the working temperature range, the pressure range, the allowable pressure drop and the physical property parameters of the cold and hot fluids at the working temperature and pressure; SS2. Design of multi-layer structure of heat exchanger and setting of microchannel geometric parameters According to the basic parameters and working conditions of the heat exchanger, the multi-layer structure of the hot side and cold side heat exchange plates of the heat exchanger is designed, and the structure types of the fluid channels on the two sides are determined. The fluid channels on the two sides are all selected to adopt semi-cone type microchannels, or the fluid channels on the hot side are designed to adopt semi-cone type microchannels while the fluid channels on the cold side are designed to adopt straight channels. By alternately stacking the hot side heat exchange plates and the cold side heat exchange plates, the alternating hot side fluid channels and cold side fluid channels are formed. At the same time, the geometric parameters of the semi-cone type microchannels are set, at least including the throat diameter, the tail diameter, the channel spacing, the channel rib height ratio, the length ratio of the rapid contraction section to the rapid expansion section, and the influence of different microchannel geometric parameter combinations on the heat transfer performance and fluid resistance is evaluated through CFD numerical simulation, so as to preliminarily determine the optimal parameter combination under different working conditions; SS3. Performance evaluation and design parameter optimization of heat exchanger After the preliminary structure design is completed, the heat exchanger performance is evaluated, through the analysis of heat transfer coefficient, pressure drop, fluid flow characteristics and working temperature range, using Nusselt number Nu , friction factor f and heat transfer enhancement index under the same power consumption PEC as performance evaluation indexes, the heat transfer effect, pressure drop characteristics and energy efficiency performance of the heat exchanger design are evaluated, and according to the evaluation results, the micro-channel geometric parameters and multi-layer structure layout are optimized, so as to realize the best balance of the heat exchanger in efficiency, pressure drop, volume, weight and reliability, and the mathematical expression of heat transfer enhancement index under the same power consumption PEC is PEC ( j / j s ) / ( f / f s ) 1 / 3 , wherein j , f are heat factor and friction factor of the heat exchanger respectively, j s , f s are heat transfer factor and friction factor of the reference heat exchanger respectively, and j = Nu / ( Re · Pr 1 / 3 ), Nu is Nusselt number, Re is Reynolds number, Pr is Prandtl number; SS4. Complete the processing of the microchannel and the welding of the plate The micro-channels on the heat exchange plates are processed by electrochemical etching process, the heat exchange plates are manufactured by using selective laser melting or electron beam melting 3D printing technology, or by mechanical processing, after processing, the layers of heat exchange plates are welded by diffusion welding process, and the joint between the layers of plates has the same structural strength as the base material, the diffusion welding improves the structural strength and pressure resistance of the heat exchanger under high temperature and high pressure conditions by controlling the temperature, time and pressure parameters; SS5. Quality control and performance verification After welding, the sealing test and pressure test of the heat exchanger are carried out to ensure no leakage; the heat exchange performance test is carried out under actual working condition or simulated working condition to verify whether the heat exchange efficiency and pressure drop parameters meet the design requirements; according to the test results, the design parameters are finally adjusted and optimized.

2. The method of designing a semi-conical microchannel printed circuit board heat exchanger structure as claimed in claim 1, wherein, The micro-channels on the hot side heat exchange plates and the cold side heat exchange plates are designed as semi-cone type micro-channels, or according to the actual working condition requirements, the semi-cone type channels and straight channels are designed in free combination, wherein the semi-cone type channels are used for heat exchange enhancement and turbulence generation, and the straight channels are used for reducing pressure drop and balancing flow distribution, or according to specific application requirements, regional layout is designed on the same heat exchange plate, part of the region uses semi-cone type channel to enhance heat exchange, and part of the region uses straight channel to reduce pressure drop.

3. The method of designing a semi-conical microchannel printed circuit board heat exchanger structure as claimed in claim 1, wherein, The semi-cone type micro-channels are formed by periodic rapid contraction or rapid expansion of semi-cone type fins, and the geometric size of the semi-cone type fins is processed by electrochemical etching process, after etching, the minimum diameter of the throat of the semi-cone type micro-channels is not less than 1 mm, the ratio of the rib height of the channel to the diameter of the channel is less than 0.35, the expansion ratio of the channel, i.e. the ratio of the length of the rapid expansion section to the length of the rapid contraction section, is controlled between 0.25 and 4, and the distance between adjacent channels is controlled between 6 and 24 mm.

4. The method of designing a semi-conical microchannel printed circuit board heat exchanger structure according to claim 3, wherein The thickness of the fin at the tail and tail connection of the semi-cone type micro-channel is determined by the temperature, pressure parameters of the fluid and the etching depth of the channel, to ensure that the heat exchanger meets the minimum thickness required by the structural strength under high temperature and high pressure conditions, and to ensure that it maintains stable performance in long-term operation, reduces equipment failure caused by fin deformation or damage.

5. The method of designing a semi-conical microchannel printed circuit board heat exchanger structure as claimed in claim 1, wherein, The cross section of the semi-cone type micro-channel is semi-circular, trapezoidal or rectangular, the specific cross section shape is selected according to the fluid working condition and heat exchange requirement, to realize the optimization adjustment of fluid flow under different working conditions, and to realize the best thermal hydraulic performance.

6. The method of designing a semi-conical microchannel printed circuit board heat exchanger structure as claimed in claim 1, wherein, The rapid contraction section and rapid expansion section of the semi-cone type micro-channel adopt linear or nonlinear profile design, the specific profile design is selected according to the fluid dynamics characteristics and heat transfer requirement, wherein the linear profile design is used to ensure the stability of fluid flow, and the pressure drop increases little, the nonlinear profile design includes the profile defined by parabola, exponential function or sine function, which is used to enhance the disturbance of fluid.

7. The method of designing a semi-conical microchannel printed circuit board heat exchanger structure as claimed in claim 1, wherein, The periodic arrangement of the semi-cone type micro-channel adopts non-uniform design, by gradually changing the expansion ratio, pitch or throat diameter of the channel in the flow direction, the gradual change of fluid characteristics is realized, to adapt to the characteristics of fluid physical properties changing with temperature.

8. The method of designing a semi-conical microchannel printed circuit board heat exchanger structure as claimed in claim 1, wherein, The design of the semi-cone micro-channel introduces a bifurcation or merging structure, which divides one channel into multiple sub-channels or combines multiple channels into one at a predetermined position, forming a complex three-dimensional flow path, thereby increasing the mixing degree of the fluid and improving the heat transfer efficiency, while optimizing the local heat transfer performance by adjusting the fluid distribution.

9. The method of designing a semi-conical microchannel printed circuit board heat exchanger structure as claimed in claim 1, wherein, The manufacturing of the semi-cone micro-channel adopts the selective laser melting or electron beam melting method in 3D printing technology for processing, and by flexibly adjusting the geometric parameters of the micro-channel during the manufacturing process, the surface quality of the channel is optimized and the structural strength is improved, ensuring that the heat exchanger has excellent performance and durability under complex working conditions; or, the semi-cone micro-channel is manufactured by mechanical machining, which ensures the geometric precision of the micro-channel, and through polishing or sandblasting post-processing process, the channel surface is optimized to reduce fluid friction and improve heat transfer performance.

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