Heat exchanger

Abstract

The application belongs to the technical field of heat exchanger heat transfer enhancement, and provides a heat exchanger, which comprises a flat tube and a fin, the flat tube has an outer surface for heat exchange with air; the fin is arranged on the outer surface of the flat tube, the fin comprises a root heat exchange section and an overhanging heat exchange section connected in sequence along the air flow direction, the root heat exchange section is connected with the outer surface of the flat tube, the overhanging heat exchange section extends outward from the root heat exchange section and is arranged in suspension, wherein the height of the root heat exchange section and the height of the overhanging heat exchange section are arranged in non-equal height along the air flow direction in sequence. The application solves the problems that the existing flat tube shovel cutting type equal height overhanging fin is difficult to adapt to the development rule of the air flow boundary layer along the flow direction, the available heat exchange area is insufficient, and the fin heat exchange efficiency is uneven.

Description

Technical Field

[0001] This application belongs to the field of heat exchanger enhanced heat transfer technology, and particularly relates to a heat exchanger. Background Technology

[0002] Heat exchangers are key components in refrigeration equipment, air conditioning equipment, heat pump systems, and electronic cooling systems. Their performance directly affects the overall energy efficiency, operational stability, and structural compactness of the system. In common air-cooled heat exchangers, refrigerant or other heat exchange media flow within pipes, flat tubes, or microchannels, while air flows externally over the outer surfaces of fins and channels. Heat exchange occurs between the two through the tube walls and fins. Since the air-side heat transfer coefficient is typically much lower than the refrigerant-side heat transfer coefficient, air-side thermal resistance is often a significant factor limiting the overall performance improvement of the heat exchanger. To reduce air-side thermal resistance, fins are often incorporated to increase the heat exchange area, enhance airflow turbulence, and disrupt the thermal boundary layer.

[0003] However, most existing flat tubes use a constant-height fin structure, meaning the fin height remains essentially constant along the airflow direction. This implies that in existing flat tubes with constant-height fins, the inlet and downstream sections have the same height. The airflow boundary layer in the inlet section is thinner, and excessively tall fins may cause unnecessary pressure loss; conversely, the boundary layer in the downstream section is thicker, and the same height may not be sufficient to disrupt it. Furthermore, most existing designs arrange the fins on the surface of the flat tube, resulting in insufficient usable heat exchange area.

[0004] Therefore, the existing equal-height fin structure still suffers from limitations in usable heat exchange area, excessive inlet disturbance and insufficient downstream disturbance, making it difficult to adapt to problems such as the development of the airflow boundary layer along the flow direction, downstream heat exchange attenuation, and excessive inlet resistance. Summary of the Invention

[0005] The purpose of this application is to provide a heat exchanger that solves the technical problems of insufficient usable heat exchange area and uneven heat exchange efficiency of existing flat tubes, which are difficult for the fins on the flat tubes to adapt to the development of the airflow boundary layer along the flow direction.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: This application provides a heat exchanger, comprising: Flat tube, with an outer surface for heat exchange with air; Fins are disposed on the outer surface of the flat tube. The fins include a root heat exchange section and a cantilever heat exchange section connected sequentially along the airflow direction. The root heat exchange section is connected to the outer surface of the flat tube, and the cantilever heat exchange section extends from the root heat exchange section outward from the flat tube and is suspended. The heights of the root heat exchange section and the cantilever heat exchange section are set at non-equal heights along the airflow direction.

[0007] The beneficial effects of the heat exchanger provided in this application are as follows: Compared with the prior art, the heat exchanger of this application includes a flat tube and multiple rows of fins arranged on the flat tube. Each fin includes a root heat exchange section and a cantilevered heat exchange section connected sequentially along the airflow direction. The root heat exchange section is connected to the outer surface of the flat tube, and the cantilevered heat exchange section extends from the root heat exchange section beyond the flat tube and is suspended, thereby locally forming a cantilevered structure on the fin that is suspended outside the flat tube. This cantilevered heat exchange section can be far away from the direct support surface of the flat tube, which is beneficial to increasing the contact area with air and forming a more sufficient turbulence area in the airflow path, effectively increasing the heat exchange area on the fin for contact with air, thereby improving the heat exchange efficiency of the fin.

[0008] Specifically, the fin height is set as a function of the airflow direction, making it no longer a constant but a non-uniform height structure that can gradually change according to heat transfer and drag control requirements. This non-uniform fin height setting creates different disturbance intensities at different flow directions, establishing a matching relationship between the local fin height, the length of the cantilevered heat transfer section, and the fin's heat transfer efficiency, thereby improving overall heat transfer performance and engineering applicability.

[0009] The first improvement to the fin height setting is that the non-equal height is set such that the height of the root heat exchange section and the height of the cantilever heat exchange section gradually increase along the airflow direction.

[0010] The above technical solution has the following advantages or beneficial effects: By gradually increasing the height of the fins, the lower height of the air inlet section can reduce initial resistance, while the higher height of the downstream section can enhance the ability to disrupt the thickened boundary layer. This helps to improve the problem of downstream heat transfer attenuation in traditional equal-height fins, thereby improving the heat transfer efficiency of the fins.

[0011] A second improvement is made to the fin height setting, wherein the non-equal height is set such that the height of the root heat exchange section and the height of the cantilever heat exchange section gradually decrease along the airflow direction.

[0012] The above technical solution has the following advantages or beneficial effects: The fins have a gradually decreasing height, making them suitable for scenarios where rapid turbulence needs to be established at the inlet while reducing flow obstruction downstream. By gradually lowering the fin height downstream, the airflow channel becomes more relaxed, which helps reduce downstream pressure loss, weakens vortex buildup in the outlet area, and effectively improves the stability of exhaust air.

[0013] A third improvement is made to the fin height setting, wherein the non-uniform height is set such that the height of the root heat exchange section and the height of the cantilever heat exchange section are linearly and gradually changed.

[0014] The above technical solution has the following advantages or beneficial effects: The top edge of the fins is made to have a linear gradient structure. The linear gradient structure has the advantages of simple geometry, clear processing path and easy modeling. It can be obtained by drawing a slanted straight line top edge and then stretching or thin-wall stretching. It is suitable for heat exchanger products with high requirements for processing cost and dimensional consistency.

[0015] A fourth improvement is made to the fin height setting, wherein the non-uniform height is set such that the height of the root heat exchange section and the height of the cantilever heat exchange section are gradually changed in segments.

[0016] The above technical solution has the following advantages or beneficial effects: By designing the top edge of the fins with a segmented, gradually changing structure, multiple height control points can be used to create a polygonal top edge. This not only satisfies the design requirements for varying local heights but also reduces the difficulty of machining complex curves. Compared to completely freeform surfaces, segmented, gradually changing structures are more suitable for batch processing and dimensional inspection.

[0017] A fifth improvement is made to the fin height setting, wherein the non-uniform height is set such that the height of the root heat exchange section and the height of the cantilever heat exchange section gradually change as a power function.

[0018] The above technical solution has the following advantages or beneficial effects: The top edge of the fins is made to have a power function gradient structure. The advantage of the power function gradient structure is that the concentrated area of ​​height change can be controlled by a single parameter, which makes it convenient to switch between different application scenarios.

[0019] A sixth improvement is made to the fin height setting, wherein the non-uniform height is set such that the height of the root heat exchange section and the height of the cantilever heat exchange section are smoothly and gradually changed.

[0020] The above technical solution has the following advantages or beneficial effects: Setting the fin height using a smooth, gradual function allows for a low-slope transition between the air inlet and outlet, preventing abrupt changes at the fin's top edge at the inlet or outlet, thereby reducing the risk of localized stress concentration and airflow separation.

[0021] The length of the cantilevered heat exchange section is improved, and the length ratio χ of the cantilevered heat exchange section satisfies: 0.20≤χ≤0.75.

[0022] The above technical solution has the following advantages or beneficial effects: By limiting the proportion of the cantilevered heat exchange section in the entire fin by the length ratio χ, the cantilevered heat exchange section can form sufficient disturbance and heat exchange area, without causing a decrease in fin efficiency or insufficient structural rigidity due to excessive cantilever, thus effectively improving the overall heat exchange efficiency of the fin.

[0023] The fin efficiency of the cantilevered heat exchange section is improved, wherein the fin efficiency ηc of the cantilevered heat exchange section is ≥0.5.

[0024] The above technical solution has the following advantages or beneficial effects: By limiting the length ratio χ of the cantilevered heat exchange section together with the fin efficiency ηc, the problem of inefficient heat exchange caused by simply pursuing a longer cantilevered heat exchange section can be avoided.

[0025] The structure of the fins on the flat tube is improved, wherein the fins are shaped by cutting on the outer surface of the flat tube, and the root heat exchange section is integrally connected to the outer surface of the flat tube.

[0026] The above technical solution has the following advantages or beneficial effects: The fins are integrally formed on the flat tube by cutting, which reduces the contact thermal resistance in traditional assembled structures and ensures continuous heat transfer between the fins and the flat tube. In addition, the manufacturing method of forming the fins on the flat tube by cutting allows for the processing of non-uniform height cantilever structures, which is beneficial for the design of fins with varying heights along the airflow direction. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A three-dimensional structural diagram of the heat exchanger provided in the embodiments of this application. Figure 1 ; Figure 2 A three-dimensional structural diagram of the heat exchanger provided in the embodiments of this application. Figure 2 ; Figure 3 A side view of the heat exchanger provided in the embodiments of this application. Figure 1 ; Figure 4 A side view of the heat exchanger provided in the embodiments of this application. Figure 2 ; Figure 5 A three-dimensional structural schematic diagram of the first layout of the fins on the flat tube provided in the embodiments of this application; Figure 6 A schematic diagram showing the functional variations of the first and third layouts of the fins on the flat tube provided in the embodiments of this application; Figure 7A three-dimensional structural schematic diagram of a second layout of the fins on the flat tube provided in an embodiment of this application; Figure 8 A schematic diagram showing the functional variations of the second and third layouts of the fins on the flat tube provided in the embodiments of this application; Figure 9 A three-dimensional structural schematic diagram of the fourth layout of the flat tube upper fins provided in the embodiments of this application; Figure 10 A schematic diagram illustrating the functional variation of the fourth layout of the fins on the flat tube provided in the embodiments of this application; Figure 11 A three-dimensional structural schematic diagram of the fifth layout of the fins on the flat tube provided in the embodiments of this application; Figure 12 A schematic diagram illustrating the functional variation of the fifth layout of the fins on the flat tube provided in the embodiments of this application; Figure 13 A three-dimensional structural schematic diagram of the sixth layout of the fins on the flat tube provided in the embodiments of this application; Figure 14 This is a schematic diagram illustrating the functional variation of the sixth layout of the fins on the flat tube provided in the embodiments of this application.

[0029] The following are the labeling elements in the figure: 1-flat tube; 2-Fin; 21-Root heat exchange section; 22-Cantilever heat exchange section. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0031] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0032] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0034] In related technologies, fins on common flat tubes are a structure used to enhance air-side heat transfer. By utilizing the fins on flat tubes, the local airflow path can be changed through the protruding fin-shaped structure, causing the airflow to accelerate, deflect, separate, or reattach near the fins, thereby enhancing fluid disturbance near the wall, reducing the thickness of the thermal boundary layer, and increasing the intensity of convective heat transfer between the fin surface and the air.

[0035] However, most fins on flat tubes currently employ a constant-height structure, meaning the fin height remains essentially constant along the airflow direction. While this constant-height structure facilitates fabrication and modeling, it suffers from the following drawbacks: First, the disturbance intensity of fins with uniform height remains relatively constant along the flow direction, making it difficult to adapt to the gradual development of the thermal boundary layer along the flow direction. When airflow enters the finned region, the thermal boundary layer near the inlet is relatively thin, and the temperature difference between the airflow and the fin surface is large. At this point, a good heat transfer effect can be achieved without excessive geometric disturbance. If the fin height in the inlet region is too large, it may cause a sharp deflection of the local airflow, forming additional flow resistance, causing some airflow energy to be consumed in ineffective disturbance and increased pressure drop. As the airflow continues to flow downstream, the thermal boundary layer gradually thickens, the near-wall temperature gradient decreases, and the heat transfer intensity easily decays. At this point, stronger disturbance is needed to disrupt the already thickened thermal boundary layer, but the downstream disturbance capability of fins with uniform height does not increase with the thickness of the boundary layer, thus easily leading to insufficient downstream heat transfer.

[0036] Second, the uniform height structure cannot control flow resistance according to the heat exchange requirements of different regions. For air-cooled heat exchangers, improving heat exchange performance often comes with an increase in air-side pressure drop. If the inlet, transition, and downstream sections of the fins have the same height, it is impossible to achieve a precise match between local flow resistance and local heat transfer enhancement. For example, the inlet section can use a lower height to reduce wind resistance, while the downstream section can use a higher height to enhance boundary layer disruption; or, the inlet section can use a higher height to create strong disturbance, while the downstream section can use a lower height to reduce flow blockage. However, traditional uniform height fin structures cannot achieve such differentiated designs.

[0037] Third, while some existing complex fin structures can enhance heat transfer, they often suffer from difficulties in 3D modeling, complex manufacturing processes, or difficulty in controlling structural parameters. For example, some fins enhance heat transfer through complex curved surfaces, torsional surfaces, serrations, perforations, or multi-scale turbulence structures. However, these structures require extensive complex surface manipulation in commonly used modeling tools, and face challenges such as high manufacturing difficulty, poor dimensional consistency, and high costs in actual stamping, bending, or extrusion molding.

[0038] Therefore, this application provides a novel heat exchanger that improves the fin structure on the flat tube, enabling the fins to achieve both enhanced heat transfer and simple geometric parameters, convenient modeling, and fabrication feasibility. The fins allow for different local disturbance capabilities and local heat transfer areas at different flow directions, and can be gradually varied according to heat transfer and resistance control requirements. This allows the fin structure to match the development law of the air-side boundary layer, effectively solving the problems of insufficient usable heat transfer area, excessive inlet disturbance and insufficient downstream disturbance, high resistance, heat transfer attenuation, and uneven fin efficiency that traditional flat tube fins struggle to adapt to the development law of the airflow boundary layer along the flow direction. A detailed description follows.

[0039] The heat exchanger provided in this application embodiment can be applied to refrigeration equipment such as refrigerator condensers, air conditioner heat exchangers, heat pump heat exchangers, microchannel heat exchangers and other compact air-cooled heat exchangers. It is beneficial to increase the heat exchange per unit volume in a limited space, thereby reducing the thermal resistance on the air side and improving the overall energy efficiency.

[0040] Please refer to the following: Figure 1 and Figure 2 The heat exchanger includes at least a flat tube 1 and fins 2 disposed on the flat tube 1. The flat tube 1 has an outer surface for heat exchange with air, and the fins 2 are integrally connected to the outer surface of the flat tube 1. In this embodiment, one or more refrigerant flow channels can be provided inside the flat tube 1, allowing the refrigerant to flow in a predetermined direction. Multiple rows of fins 2 are arranged at intervals on the outer surface of the flat tube 1, and air flow channels are formed between adjacent fins 2, which helps to increase the heat exchange area on the air side and enhance the turbulence on the air side.

[0041] Please refer to the following: Figure 1 , Figure 2 and Figure 3 Each fin 2 includes a root heat exchange section 21 and a cantilever heat exchange section 22 connected sequentially along the airflow direction. The root heat exchange section 21 is integrally connected to the outer surface of the flat tube 1. The root heat exchange section 21 is used to conduct heat from the flat tube 1 to the fin 2 and form a stable structural support.

[0042] The cantilevered heat exchange section 22 extends beyond the root heat exchange section 21 into the flat tube 1 and is suspended in mid-air. This can be understood as, for example... Figure 1 and Figure 3 As shown, the cantilevered heat exchange section 22 is integrally formed with the root heat exchange section 21, and the cantilevered heat exchange section 22 is the fin portion of the flat tube 1 that is suspended. Because the cantilevered heat exchange section 22 is not completely attached to the outer surface of the flat tube 1, air can flow through the outer surface, sides, and extended ends of the cantilevered heat exchange section 22, thereby creating more sufficient fluid turbulence and heat exchange contact. This means that the flowing air will first pass through the root heat exchange section 21 of the fin 2, and then reach the cantilevered heat exchange section 22 located outside the flat tube 1. This allows the airflow to flow through the upper and lower surfaces, side surfaces, or end regions of the cantilevered heat exchange section 22, thereby increasing airflow turbulence and effective heat exchange area.

[0043] Based on the above, the structure of fin 2 is further specifically designed, such as... Figure 1 , Figure 2 and Figure 3 As shown, the heights of the root heat exchange section 21 and the cantilever heat exchange section 22 of the fin 2 are set at non-equal heights along the airflow direction. This means that the overall height of the fin 2 will vary non-equally along the airflow direction.

[0044] Compared with the prior art, the heat exchanger provided in this application includes a flat tube 1 and multiple rows of fins 2 arranged on the flat tube 1. Each fin 2 includes a root heat exchange section 21 and a cantilevered heat exchange section 22 connected sequentially along the airflow direction. The root heat exchange section 21 is connected to the outer surface of the flat tube 1, and the cantilevered heat exchange section 22 extends from the root heat exchange section 21 beyond the flat tube 1 and is suspended, thereby locally forming a cantilevered structure on the fin 2 that is suspended outside the flat tube 1. The cantilevered heat exchange section 22 can be far away from the direct support surface of the flat tube 1, which helps to increase the contact area with air and form a more sufficient disturbance area in the airflow path, effectively increasing the heat exchange area on the fin 2 for contact with air, thereby improving the heat exchange efficiency of the fin 2.

[0045] While the cantilevered heat exchange section 22 increases the air contact area, it is located far from the connection area with the flat tube 1. Heat must be conducted along the root heat exchange section 21 to reach the cantilevered heat exchange section 22. When the length of the cantilevered heat exchange section 22 is long or the overall height of the fins 2 is large, the temperature of the cantilevered heat exchange section 22 may gradually approach the air temperature, resulting in some areas of the cantilevered heat exchange section 22 not being fully involved in effective heat exchange. In other words, simply increasing the cantilevered heat exchange section 22 does not necessarily increase the heat exchange capacity proportionally; instead, it may reduce overall performance due to the increased material thermal conduction path, decreased fin efficiency, and increased air-side resistance.

[0046] Therefore, while retaining the root heat exchange section 21 and the cantilevered heat exchange section 22 in fin 2, the height H(x) of fin 2 is set as a function that varies along the airflow direction. This makes the height of fin 2 no longer constant, but a non-uniform height structure that can gradually change according to heat exchange and resistance control requirements. By using a non-uniform height setting for fin 2, different disturbance intensities can be generated at different flow directions, creating a matching relationship between the local height of fin 2, the length of the cantilevered heat exchange section 22, and the heat exchange efficiency of fin 2, thereby improving overall heat exchange performance and engineering applicability.

[0047] As can be seen, the heat exchanger provided in this application embodiment allows the local height of the fins 2 to change along the airflow direction by setting them at different heights. This makes the local disturbance intensity match the development of the airflow boundary layer, which is beneficial to improving the downstream heat exchange attenuation problem of traditional equal-height fins 2, thereby improving the overall heat exchange efficiency.

[0048] Regarding the length setting of the cantilevered heat exchange section 22, please refer to one embodiment of this application. Figure 4 The length ratio χ of the cantilevered heat exchange section 22 satisfies: 0.20≤χ≤0.75.

[0049] Specifically, it is preferable to set the effective flow length of fin 2 as Lf and the flow length of cantilever heat exchange section 22 as Lc. Then, the length ratio χ of cantilever heat exchange section 22 is defined as follows:

[0050] Where Lf represents the effective length from the airflow inlet end to the airflow outlet end of fin 2, and Lc represents the length of the cantilevered heat exchange section 22 along the airflow direction. A larger χ indicates a higher proportion of the cantilevered heat exchange section 22 within the entire fin 2. If χ is too small, the disturbance effect and expansion of the heat exchange area of ​​the cantilevered heat exchange section 22 are limited; if χ is too large, the heat conduction path of the cantilevered heat exchange section 22 is too long, which may lead to insufficient utilization of the cantilevered end temperature, reduced fin 2 efficiency, and increased risk of structural deformation. Therefore, in this embodiment, χ preferably satisfies 0.20≤χ≤0.75, and more preferably 0.35≤χ≤0.65.

[0051] By limiting the length ratio χ of the cantilevered heat exchange section 22, it is possible to avoid the cantilevered heat exchange section 22 being too short, resulting in disturbance and insufficient heat exchange area, and it is also possible to avoid the cantilevered heat exchange section 22 being too long, resulting in low efficiency of fin 2, insufficient structural rigidity, or excessive flow resistance.

[0052] Therefore, in the heat exchanger of the present application embodiment, the fin 2, by limiting the length ratio of the cantilevered heat exchange section 22 to χ in the entire fin 2, can form sufficient disturbance and heat exchange area, and will not cause the efficiency of the fin 2 to decrease or the structural rigidity to be insufficient due to excessive cantilever, thus effectively improving the overall heat exchange efficiency of the fin 2.

[0053] In practical applications, let the height of fin 2 at any flow direction position x be H(x), where 0≤x≤Lf. Unlike traditional fins with uniform height 2, H(x) in this application is not a constant, causing fin 2 to form a non-uniform height structure along the airflow direction. This height H(x) can be understood as the height of fin 2 in the direction perpendicular to the outer surface of the flat tube 1, or as the distance between the top edge of fin 2 and the root reference plane connected to the outer surface of the flat tube 1.

[0054] In the embodiments of this application, the core function of the non-uniform height structure is not simply to increase or decrease the area of ​​fin 2, but to regulate the local geometry of fin 2 according to the airflow conditions along the path. When the airflow first enters the fin 2 region, the thermal boundary layer is relatively thin. If the height of fin 2 is too large, it will cause excessive wind resistance and local pressure drop. As the airflow flows to the downstream region, the thermal boundary layer gradually thickens. If the height of fin 2 is insufficient, it cannot effectively disturb the near-wall fluid. Therefore, by changing H(x), the disturbance capability of different positions of fin 2 can be matched with the development law of the airflow boundary layer.

[0055] As shown in the table below, simulations of conventional fin 2 and cantilever fin 2 were performed. The calculations show that adding the cantilever heat exchange section 22 can improve the overall heat transfer performance JF factor by 19%.

[0056]

[0057] In the table above, Re represents the Reynolds number. Re is used to characterize the airflow state and is a dimensionless parameter for evaluating the airflow characteristics of a heat exchanger. It is defined as follows:

[0058] Where: ρ is the air density, kg / m³; u is the average air velocity, m / s; Dh is the hydraulic diameter of the flow channel, m; μ is the aerodynamic viscosity, Pa•s.

[0059] The Reynolds number reflects the ratio of inertial force to viscous force during airflow. The larger the Re number, the stronger the inertial effect and the stronger the fluid disturbance capability, which usually corresponds to a stronger convective heat transfer capability.

[0060] j represents the Colburn factor (Colburn j-factor, heat transfer factor), which is an important dimensionless parameter for evaluating the air-side heat transfer enhancement capability of finned heat exchangers. Its definition is:

[0061] Where: Nu is the Nusselt number; Re is the Reynolds number; Pr is the air Prandtl number.

[0062] The Nusselt number is defined as: Where: h is the air-side convective heat transfer coefficient, W / (m²•K); λ is the air thermal conductivity, W / (m•K).

[0063] The j-factor comprehensively reflects the ability of the fin structure to resist fluid disturbance and heat transfer boundary layer disruption. The larger the j-value, the more obvious the heat transfer enhancement effect under unit flow intensity.

[0064] JF represents the comprehensive performance evaluation factor (comprehensive heat transfer performance factor). JF is used to comprehensively evaluate the balance between heat transfer enhancement effect and flow resistance, and it is defined as follows:

[0065] Where: j is the Colburn heat transfer factor of the improved structure; j0 is the Colburn heat transfer factor of the reference structure; f is the friction factor of the improved structure; and f0 is the friction factor of the reference structure.

[0066] In the embodiments of this application, the Re-j-JF relationship of conventional constant-height fins and cantilever fin structures is compared to evaluate the improvement effect of cantilever structures on air-side heat transfer performance. The table data above shows that, under the same Re conditions, cantilever fins have higher j-factors and JF values. This indicates that cantilever structures can increase air turbulence, expand the effective heat transfer area, and achieve better heat transfer performance after comprehensively considering flow resistance.

[0067] As can be seen, since H(x) varies with x, the top edge of fin 2 can form the following structures: straight hypotenuse, broken line edge, spline curve edge, power function curve edge, or smooth transition curve edge. These will be explained in detail below.

[0068] Example 1 For the height setting of fin 2, please refer to the first embodiment of this application. Figure 5 and Figure 6 The non-uniform height setting of the fins 2 can preferably be such that the height of the root heat exchange section 21 and the height of the cantilever heat exchange section 22 gradually increase along the airflow direction.

[0069] This structure is suitable for applications where the boundary layer at the inlet is thin and gradually thickens downstream. A lower inlet height reduces inlet impulsiveness and initial drag, while a higher downstream height enhances disturbance and disruption of the thick boundary layer, thereby increasing downstream heat transfer intensity. Its height function can be expressed as:

[0070] Wherein, Hin is the inlet height of fin 2, Hout is the outlet height of fin 2, and Hout > Hin; m is the height growth control factor, 0.5 ≤ m ≤ 3. When m = 1, it degenerates into a linear gradient. Thus, by adjusting m, it is possible to adapt to different airflow boundary layer development intensities and different air-side flow velocity conditions in the heat exchanger.

[0071] Furthermore, within the range 0 ≤ x ≤ Lf, H(x) satisfies:

[0072] Wherein, Hin is the height of the inlet end, Hout is the height of the outlet end, and Hout > Hin.

[0073] It is evident that the gradually increasing non-uniform height structure is particularly suitable for heat exchangers with a significantly thickened downstream thermal boundary layer. When air enters the heat exchanger, the boundary layer in the inlet region is thin, and the heat exchange temperature difference is large. A relatively low fin height 2 is sufficient to ensure basic heat exchange while reducing inlet wind resistance. As the air flows downstream, the boundary layer thickness increases, and the local thermal resistance increases. At this point, the gradually increasing fin height 2 can enhance airflow deflection and local disturbance in the downstream region, allowing for more thorough mixing of the low-velocity fluid near the wall with the mainstream air, thereby improving downstream heat exchange attenuation.

[0074] Compared to the uniform-height fins 2, the gradually increasing structure does not apply the same disturbance across the entire flow direction, but instead concentrates the stronger disturbance at the downstream location where enhanced heat transfer is more needed. This avoids increasing ineffective resistance at the inlet section while improving the downstream boundary layer disruption capability, achieving a balance between heat transfer performance and flow resistance.

[0075] In this way, the height of fin 2 is gradually increased, so that the lower height of the air inlet section can reduce the initial resistance, and the higher height of the downstream section can enhance the ability to damage the thickened boundary layer. This is beneficial to improving the problem of downstream heat transfer attenuation of traditional equal-height fin 2, thereby improving the heat transfer efficiency of fin 2.

[0076] Example 2 Regarding the height setting of fin 2, please refer to the second embodiment of this application. Figure 7 and Figure 8 The non-uniform height setting of the fins 2 can preferably be such that the height of the root heat exchange section 21 and the height of the cantilever heat exchange section 22 gradually decrease along the airflow direction.

[0077] This structure is suitable for applications requiring strong inrush at the inlet and reduced drag or smoother airflow at the downstream. A higher inlet height rapidly disrupts the initial boundary layer and enhances mixing; a lower downstream height reduces flow channel blockage, lowers outlet drag, and improves airflow stability. Its height function can be expressed as:

[0078] Wherein, Hin is the inlet height of fin 2, Hout is the outlet height of fin 2, and Hin > Hout; m is the height attenuation control factor, 0.5 ≤ m ≤ 3. When m = 1, it degenerates into a linear gradient. Thus, by adjusting m, it is possible to adapt to different airflow boundary layer development intensities and different air-side flow velocity conditions in the heat exchanger.

[0079] Furthermore, within the range 0 ≤ x ≤ Lf, H(x) satisfies:

[0080] Wherein, Hin is the height of the inlet end, Hout is the height of the outlet end, and Hin > Hout.

[0081] It is evident that the tapered structure is suitable for scenarios requiring rapid establishment of disturbances at the inlet section and reduction of flow obstruction downstream. For example, when the air inlet velocity is low or the heat exchange demand in the inlet region is high, a higher inlet fin height 2 can cause the airflow to deflect and mix immediately upon entering the heat exchange region, thereby increasing the heat exchange intensity at the inlet section. Subsequently, the height of fin 2 gradually decreases downstream, allowing the airflow channel to gradually relax, which helps reduce downstream pressure loss, weakens vortex buildup in the outlet region, and effectively improves the stability of air exhaust.

[0082] The tapered structure can also be used in heat exchangers that require defrosting, drainage, or dust prevention. In some air-cooled heat exchangers, the inlet area often bears a large heat transfer load, while the downstream area needs to maintain smooth airflow. In this case, the tapered non-uniform height cantilever fins 2 can form an enhanced heat transfer zone at the inlet and a low-resistance flow guiding zone downstream, making the heat transfer and flow organization more rational.

[0083] Example 3 Regarding the height setting of fin 2, please refer to the third embodiment of this application. Figure 6 and Figure 8 The non-uniform height setting of the fins 2 can preferably be: the height of the root heat exchange section 21 and the height of the cantilever heat exchange section 22 are linearly and gradually changed.

[0084] Specifically, the height of fin 2 satisfies a linear gradient relationship:

[0085] The top edge of fin 2 is made to have a linear gradient structure. The linear gradient structure has the advantages of simple geometry, clear processing path and easy modeling. It can be obtained by drawing a slanted straight top edge and then stretching or thin-wall stretching. It is suitable for heat exchanger products with high requirements for processing cost and dimensional consistency.

[0086] Example 4 For the height setting of fin 2, please refer to the fourth embodiment of this application. Figure 9 and Figure 10 The non-uniform height setting of the fins 2 can preferably be: the height of the root heat exchange section 21 and the height of the cantilever heat exchange section 22 are gradually changed in segments.

[0087] Specifically, the height of fin 2 satisfies a segmented gradual change relationship:

[0088] Where i = 0, 1, 2, ..., N-1, N is the number of height segments divided along the flow direction, 3 ≤ N ≤ 6, and Hi is the height of fin 2 corresponding to the i-th height control point.

[0089] The top edge of the segmented gradient structure is composed of multiple straight line segments connected together. Compared with linear gradients, segmented gradients allow for more flexible local control. For example, the inlet section can be set to have a lower height, the middle section to increase rapidly, and the outlet section to maintain a stable height; alternatively, the inlet section can be set to have a higher height, the middle section to decrease slowly, and the outlet section to form a low-resistance guide section. By changing the values ​​of each control point Hi, different height distributions can be obtained.

[0090] The segmented gradient structure combines parametric design capabilities with ease of manufacturing. Because its top edge consists of a finite number of straight line segments, complex surface machining and high-order curve fitting are unnecessary. In graphics tools, it can be formed by drawing a polyline sketch and extruding it; in mold manufacturing, it can also be achieved through polyline cutting edges or segment height control.

[0091] As an example, in one specific embodiment, N=4, and fin 2 is divided into four height segments along the flow direction. If a gradually increasing design is adopted, it can be set as follows: H0=1.4Hbase, H1=1.3Hbase, H2=1.1Hbase, H3=1.0Hbase.

[0092] Hbase represents the height of fin 2 at the baseline. This structure results in stronger disturbances at the inlet section, with the disturbances gradually decreasing in the middle and rear sections.

[0093] In another specific embodiment, N=4. If a decreasing design is adopted, we can set: H0=0.9Hbase, H1=1.1Hbase, H2=1.3Hbase, H3=1.4Hbase.

[0094] This structure creates a weak disturbance at the inlet section, which gradually intensifies downstream, making it suitable for heat exchangers that enhance disturbance heat transfer.

[0095] This allows the top edge of fin 2 to have a segmented, gradually changing structure. This segmented, gradually changing structure can form a polygonal top edge through multiple height control points, which can both satisfy the design of local height differences and reduce the difficulty of machining complex curves. Compared with completely freeform surfaces, the segmented, gradually changing structure is more suitable for batch processing and dimensional inspection.

[0096] Example 5 For the height setting of fin 2, please refer to the fifth embodiment of this application. Figure 11 and Figure 12 The non-uniform height setting of fin 2 can preferably be: the height of the root heat exchange section 21 and the height of the cantilever heat exchange section 22 gradually change as a power function.

[0097] Specifically, the height of fin 2 satisfies a power function gradient relationship:

[0098] Where m is the height change control factor, 0.5≤m≤3.

[0099] The top edge of fin 2 is designed with a power function gradient structure. The advantage of this structure is that the concentrated area of ​​height variation can be controlled by a single parameter m, allowing for flexible switching between different application scenarios. When m=1, it is a linear gradient; when m<1, the curve rises or falls rapidly in the inlet section and then flattens out; when m>1, the curve changes slowly in the inlet section and changes rapidly near the outlet.

[0100] For the gradually increasing fin type 2, if m>1, the inlet region maintains a low height, which can minimize inlet resistance. However, after the downstream boundary layer thickens significantly, the height increases rapidly, forming a strong disturbance heat transfer zone. If m<1, the height after the inlet increases rapidly, which can establish disturbance within a short distance. This is suitable for scenarios where the heat exchanger flow length is short or where rapid heat transfer enhancement is required.

[0101] For the gradually decreasing fin type 2, if m>1, the inlet region maintains a relatively high height, forming a continuous strong disturbance, and the height decreases rapidly near the outlet, forming a low-resistance exhaust section at the outlet. If m<1, the height decreases rapidly after the inlet, which can quickly reduce the pressure drop after a short-range strong disturbance is formed at the inlet, making it suitable for low-volume systems that are sensitive to resistance.

[0102] Example 6 For the height setting of fin 2, please refer to the sixth embodiment of this application. Figure 13 and Figure 14 The non-uniform height setting of the fins 2 can preferably be such that the height of the root heat exchange section 21 and the height of the cantilever heat exchange section 22 are smoothly and gradually changed.

[0103] Specifically, the height of fin 2 satisfies a smooth gradient relationship:

[0104] Where a and b are control coefficient factors, and m and n are control power factors, a>0, b>0, m≥1, n≥1.

[0105] This function features a smooth transition. By setting a, b, m, and n, the midpoint position of the height change curve, the rate of change of the preceding and following segments, and the inlet and outlet slopes can be adjusted. Compared to a simple linear function, the smooth transition function reduces geometrical abrupt changes at the inlet and outlet, resulting in a smoother transition of airflow as it enters and exits the fin region 2.

[0106] The smooth, gradual change in fin height is particularly suitable for heat exchangers sensitive to noise, pressure drop, and localized separation. Because the fin height changes gently at the inlet and outlet, the likelihood of sudden airflow impacts or detachment from the fin surface is reduced, thus mitigating localized eddies and pressure fluctuations. Furthermore, the smooth fin edge also helps reduce processing stress concentration and improves the structural stability of the fin.

[0107] As an example, in a specific embodiment, if a=0.5, b=0.6, m=2, n=3, then the height function is:

[0108] The function changes relatively smoothly near the outlet and more significantly in the inlet region, making it suitable as one of the preferred curves for non-uniform height cantilever fins 2. This structure can form a low-height guiding section in the airflow inlet region to enhance heat transfer, while the slope rises rapidly to form a strong inlet-facing heat transfer section; and a higher-height enhanced heat transfer section is formed in the downstream region of the airflow to enhance the disturbance and disruption of the thickened thermal boundary layer, thereby improving the overall heat transfer performance of the cantilever fins 2, while the slope change amplitude is slowed down to avoid a significant increase in drag.

[0109] By using a smooth, gradual change function to set the fin height, a low-slope transition can be achieved between the air inlet and outlet, preventing abrupt changes in the top edge of fin 2 at the inlet or outlet, thereby reducing the risk of localized stress concentration and airflow separation. This structure is suitable for heat exchangers that require high flow stability, consistent appearance, or smooth processing transitions.

[0110] Example 7 In practical applications, the heat transfer effect of the cantilevered heat exchange section 22 is not only related to the air-side disturbance, but also to the thermal conductivity of the fin material, the thickness of the fin, and the cantilever length. If the length of the cantilevered heat exchange section 22 is too long or the thermal conductivity of the material is insufficient, the temperature of the cantilevered heat exchange section 22 may be close to the air temperature, so that although the area is increased, the actual heat transfer contribution is limited.

[0111] Therefore, regarding the efficiency limitation of the fins 2 of the cantilever heat exchange section 22, in one embodiment of this application, the efficiency ηc of the fins 2 of the cantilever heat exchange section 22 is ≥0.5.

[0112] Specifically, the efficiency ηc of the fins 2 of the cantilevered heat exchange section 22 satisfies:

[0113]

[0114] Where h is the air-side convective heat transfer coefficient, λs is the thermal conductivity of fin 2 material, tf is the thickness of fin 2, and Lc is the flow length of the cantilevered heat exchange section 22.

[0115] The above relationship can be used to evaluate the thermal conductivity effectiveness of the cantilevered heat exchange section 22 along its length. When mLc is small, ηc is close to 1, indicating that the temperature distribution of the cantilevered section is relatively uniform and the heat exchange area utilization rate is high; when mLc is large, ηc decreases, indicating that the temperature at the cantilever end decays significantly and the heat exchange efficiency of some areas is insufficient. Therefore, in this embodiment, ηc is preferably ≥ 0.5 to ensure that the cantilevered heat exchange section 22 has sufficient effective heat exchange contribution.

[0116] Therefore, by limiting the length ratio χ of the cantilevered heat exchange section 22 together with the efficiency ηc of the fin 2, the problem of inefficient heat transfer caused by simply pursuing a longer cantilevered heat exchange section 22 can be avoided. In other words, this application does not simply increase the area of ​​the fin 2, but establishes a constraint relationship between the cantilever length, local height and thermal conductivity of the fin 2, so that the cantilevered heat exchange section 22 can both disturb the air and effectively transfer heat.

[0117] In addition, regarding the overall height setting of fin 2, in the embodiments of this application, the height of fin 2 satisfies: 0.5 H0≤H(x)≤1.8 H0 Wherein, H0 is the reference height of the traditional equal-height fins. By adjusting the range based on the aforementioned reference height using the above formula, it is possible to avoid insufficient heat exchange area and insufficient disturbance capacity due to fin height being too low, and also to avoid airflow blockage, increased noise, excessive pressure drop, or reduced thermal conductivity at the cantilever end due to fin height being too high.

[0118] Regarding the structure of the fins 2 on the flat tube 1, please refer to one embodiment of this application. Figure 1 and Figure 2 The fins 2 are shaped by cutting on the outer surface of the flat tube 1, and the root heat exchange section 21 is integrally connected to the outer surface of the flat tube 1.

[0119] Therefore, since fins 2 and flat tubes 1 are made from the same material and processed continuously, the height variation of fins 2 along the flow direction can be controlled by changing the cutting trajectory. Compared with traditional plug-in, welded, or plate-type fins 2, since fins 2 and the substrate are manufactured separately, it is difficult to achieve a continuously varying height function along the flow direction, and it is even more impossible to naturally form a non-uniform height cantilever structure. The heat exchanger provided in this application embodiment achieves non-uniform height cantilever control of fins 2 through a cutting manufacturing method, thereby obtaining a new air-side flow enhancement mechanism.

[0120] The heat exchanger provided in this application embodiment has a fin structure 2 formed by shoveling on the flat tube 1. The area of ​​the cantilevered heat exchange section 22 is not formed by adding extra length to the fin 2, but by adopting a completely different manufacturing process: First, a continuous fin structure 2 is formed on the flat tube 1 substrate of the whole length by shoveling; then, by removing part of the substrate material of the flat tube 1, the fin 2 that was originally integrally formed with the flat tube 1 loses its support in a local area, thereby naturally forming the area of ​​the cantilevered heat exchange section 22.

[0121] As can be seen, the fin 2 is integrally formed on the flat tube 1 by cutting, which can reduce the contact thermal resistance in the traditional assembled structure and ensure continuous heat transfer between the fin 2 and the flat tube 1. In addition, the manufacturing method of forming the fin 2 on the flat tube 1 by cutting can be further realized to process non-uniform height cantilever structures, which is beneficial for the design of the fin 2 to vary in height along the air flow direction.

[0122] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A heat exchanger, characterized in that, include: Flat tube, with an outer surface for heat exchange with air; Fins are disposed on the outer surface of the flat tube. The fins include a root heat exchange section and a cantilever heat exchange section connected sequentially along the airflow direction. The root heat exchange section is connected to the outer surface of the flat tube, and the cantilever heat exchange section extends from the root heat exchange section outward from the flat tube and is suspended. The heights of the root heat exchange section and the cantilever heat exchange section are set at non-equal heights along the airflow direction.

2. The heat exchanger according to claim 1, characterized in that, The non-equal height setting is: the height of the root heat exchange section and the height of the cantilever heat exchange section gradually increase along the airflow direction.

3. The heat exchanger according to claim 1, characterized in that, The non-equal height setting is: the height of the root heat exchange section and the height of the cantilever heat exchange section gradually decrease along the airflow direction.

4. The heat exchanger according to claim 1, characterized in that, The non-uniform height setting is: the height of the root heat exchange section and the height of the cantilever heat exchange section are linearly and gradually changed.

5. The heat exchanger according to claim 1, characterized in that, The non-uniform height setting is: the height of the root heat exchange section and the height of the cantilever heat exchange section are gradually changed in segments.

6. The heat exchanger according to claim 1, characterized in that, The non-uniform height setting is: the height of the root heat exchange section and the height of the cantilever heat exchange section gradually change as a power function.

7. The heat exchanger according to claim 1, characterized in that, The non-uniform height setting is: the height of the root heat exchange section and the height of the cantilever heat exchange section are smoothly and gradually changed.

8. The heat exchanger according to claim 1, characterized in that, The length ratio χ of the cantilevered heat exchange section satisfies: 0.20≤χ≤0.

75.

9. The heat exchanger according to claim 8, characterized in that, The fin efficiency ηc of the cantilevered heat exchange section is ≥0.

5.

10. The heat exchanger according to any one of claims 1 to 9, characterized in that, The fins are shaped by cutting on the outer surface of the flat tube, and the root heat exchange section is integrally connected to the outer surface of the flat tube.

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