A dual density microchannel evaporator and its separate heat pipe system

Abstract

The application provides a double-density micro-channel evaporator and a split heat pipe system thereof, wherein a heat exchange micro-channel layer comprises high-density micro-channels and low-density micro-channels on an upper surface, the low-density micro-channels are located on both sides of the high-density micro-channels, the shell is divided into two parts, namely a middle shell and two side shells, the middle shell covers the upper part of the high-density micro-channel layer, the middle shell wraps the high-density micro-channel layer, the two side shells cover the upper part of the low-density micro-channels, and the two side shells wrap the low-density micro-channel layer; the fluid inlet is arranged at the middle position of the middle shell, the fluid outlet is arranged at the middle position of the two side shells, and the fluid outlet is connected with the low-density micro-channels. The evaporator can solve the problems of local hot spots and easy overheating of heating components which cannot be solved by immersion cooling, and can also solve the problems of complex structure and large floor area of the immersion structure.

Description

Technical Field

[0001] This invention relates to the field of heat exchange, and particularly to a split heat pipe system using a dual-density microchannel evaporator. Background Technology

[0002] A heat exchanger is a device that exchanges heat between hot and cold fluids. Heat exchangers are widely used in many fields. In industries such as electronics, petrochemicals, communications, and aerospace, the unique operating environments impose special requirements on the size and weight of heat exchangers, demanding higher heat exchange capacity. In 1981, scholars proposed using microchannels for heat dissipation, which could reduce the size of the heat exchanger and significantly improve its heat exchange capacity by utilizing the high specific surface area of ​​the microchannels. However, although it has a strong heat exchange capacity, the overall pressure loss is also relatively high due to the small hydraulic diameter of the microchannels.

[0003] Numerous studies have found that microchannel heat exchangers still suffer from uneven temperature distribution. In 1991, researchers proposed a manifold microchannel heat exchanger based on existing microchannel heat exchangers, significantly reducing its overall pressure loss. However, extensive research indicates that the fluid distribution within the manifold microchannels is not uniform, leading to uneven temperature distribution.

[0004] With the continuous development and widespread adoption of heat dissipation equipment, its power density is constantly increasing, leading to a gradual increase in the heat generated inside the equipment. Effective heat dissipation has become one of the key factors in ensuring the long-term stable operation of heat dissipation equipment. However, traditional heat dissipation technologies face challenges in meeting the demands for efficient heat dissipation and miniaturized equipment.

[0005] Currently, high-power heat dissipation equipment widely employs two heat dissipation methods. The first is forced air cooling, which relies on fans to push air. This method is simple in design and easy to maintain, such as discrete heat pipes, but suffers from high power consumption, high noise, and the need for large-area heat sinks that are difficult to modify flexibly. The second method utilizes pump-driven microchannel liquid cooling radiators. These radiators increase the contact area between heat and fluid through tiny channel structures, achieving efficient heat dissipation within a smaller space and improving cooling efficiency. However, traditional microchannel cooling technology has two main problems: firstly, the inlet and outlet pressure drop is too large due to the small hydraulic diameter; and secondly, the temperature distribution inside the microchannel is uneven.

[0006] Patent CN117419589A discloses a multi-stage separated gravity heat pipe microchannel heat exchanger, relating to the field of heat pipe heat exchanger technology. It includes a fixed shell with a connecting plate inside, which divides the internal space of the fixed shell into an evaporation zone connected to the outside and a sealed condensation zone, thus isolating heat exchange between the two zones. The evaporation zone contains multi-stage evaporation devices, and the condensation zone contains multi-stage condensation devices. A working fluid connects the multi-stage evaporation and condensation devices. An evaporation medium flows through the evaporation zone, vaporizing the liquid working fluid within the multi-stage evaporation devices. A cooling medium flows through the condensation zone, liquefying the gaseous working fluid within the multi-stage condensation devices, forming a cycle of the working fluid between liquid and gaseous states. This multi-stage heat exchanger features a multi-stage evaporation-condensation working fluid cycle, with the evaporation and condensation temperatures and pressures of the working fluid within the plates decreasing progressively, resulting in excellent cooling performance.

[0007] Patent CN117824179A discloses a multi-stage split microchannel gravity heat pipe final-stage coupled refrigeration system, including a heat exchange device. The heat exchange device includes an evaporator section, with a hot-end fan on one side of the evaporator section to blow high-temperature air towards the evaporator section and vaporize the liquid working fluid inside the evaporator section. The heat exchange device also includes a condenser section, with a cold-end fan on the side of the condenser section away from the hot-end fan to blow cooling air towards the condenser section and liquefy the gaseous working fluid inside the condenser section. An ascending section and a descending section are connected between the evaporator section and the condenser section. An ascending enhancement section is connected in parallel to the ascending section, and a descending enhancement section is connected in parallel to the descending section. Switching devices are provided between the ascending section and the ascending enhancement section, and between the descending section and the descending enhancement section. By setting up a multi-stage evaporator-condenser cycle in the existing split gravity heat pipe heat exchanger and adding an additional refrigeration system at the final stage of the system, the entire device can achieve a stronger cooling capacity to cope with the sudden increase in cooling capacity required by data centers.

[0008] However, the aforementioned patents focus on improving the performance of microchannel heat sinks without considering the uneven power distribution inherent in the heat sink itself. Typically, the heat generated inside the device is more concentrated than in other areas. Insufficient heat dissipation in the central area may lead to overheating or even damage to the device, while excessive heat dissipation around the perimeter may result in energy waste. Therefore, effective heat dissipation measures are needed to balance this uneven power distribution. Summary of the Invention

[0009] The purpose of this invention is to provide a split heat pipe system using a dual-density microchannel manifold evaporator to achieve heat distribution to different areas. The dual-density microchannel manifold evaporator effectively reduces the temperature difference on the walls of the microchannel heat sink, addressing the uneven heat dissipation requirements of the heat dissipation equipment and improving the internal temperature distribution. Simultaneously, this radiator also combines the advantages of a manifold structure, enhancing convection disturbance, optimizing the fluid flow path, and reducing the pressure drop at the inlet and outlet.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows:

[0011] A dual-density microchannel evaporator includes an upper outer shell and a lower heat exchange microchannel layer. The outer shell includes a fluid inlet on its upper surface and a fluid inlet manifold on its lower surface, the fluid inlet manifold being connected to the fluid inlet. The heat exchange microchannel layer includes high-density microchannels and low-density microchannels on its upper surface, the low-density microchannels being located on both sides of the high-density microchannels. The outer shell is divided into two parts: a middle outer shell and two side outer shells. The middle outer shell covers and encloses the high-density microchannel layer, while the side outer shells cover and enclose the low-density microchannel layer. The fluid inlet is located in the middle of the middle outer shell, and the fluid outlet is located in the middle of the side outer shells. The fluid outlet is connected to the low-density microchannels.

[0012] As an improvement, the middle outer shell and the two side outer shells are manufactured separately; each of the two side outer shells is provided with a fluid outlet.

[0013] As an improvement, the average height of the fins in the low-density microchannel heat dissipation zone is higher than that of the fins in the high-density microchannel heat dissipation zone.

[0014] As an improvement, the fins of the high-density microchannel heat dissipation area are inclined towards the low-density microchannel heat dissipation area. From the center of the heat dissipation area towards the fins of the low-density microchannel heat dissipation area, the height of the fins of the high-density microchannel heat dissipation area gradually increases. In the area connected with the low-density microchannel heat dissipation area, the height of the fins of the high-density microchannel heat dissipation area is the same as that of the low-density microchannel heat dissipation area.

[0015] As an improvement, the housing includes closed walls located at opposite ends, with a fluid outlet formed between the two opposite closed walls.

[0016] As an improvement, the heat exchange microchannel layer adopts a segmented microchannel design. Both the high-density microchannel and the low-density microchannels on both sides adopt straight rectangular fin channels, and the structures of the low-density microchannels on both sides are completely equal.

[0017] As an improvement, the increase in fin height in the high-density microchannel heat dissipation area gradually decreases from the center of the heat dissipation area toward the fins of the low-density microchannel heat dissipation area.

[0018] As an improvement, considering the heat transfer efficiency of the fins inside the radiator, the convective heat transfer area of ​​the actual fluid flowing through the microchannels of the radiator after correction is calculated, and the fitting formula is as follows:

[0019] (1.1)

[0020] (1.2)

[0021] in, This represents the actual contact area between the fluid and the wall of the radiator's microchannels, including the bottom area of ​​the microchannels and the side areas of the fins. ; Fin efficiency is the ratio of actual heat transfer to ideal heat transfer in a fin. For channel length, ; For channel width, ; For the channel height, ; The width of the fin. ; The number of fins; The convective heat transfer coefficient between the fluid and the radiator surface. ; The thermal conductivity of the fins is... .

[0022] A gravity-driven, split-type heat pipe system includes a finned radiator, a dual-density microchannel manifold evaporator, a vapor riser, and a condensate downcomer. The system is filled with a certain volume of refrigerant. The finned radiator cools the gaseous refrigerant entering it, while the dual-density microchannel manifold evaporator absorbs the heat generated by the cooling target using the liquid refrigerant. The vapor riser and condensate downcomer connect the finned radiator and the dual-density microchannel manifold evaporator to form a circulation loop. The lower part of the microchannel layer is thermally connected to the main heating element.

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

[0024] (1) The evaporator of the present invention can improve the problem that immersion cooling cannot solve the problem of local hot spots and easily cause the heating components to overheat by setting the shell and channels of different densities. At the same time, it can also solve the problem of complex immersion structure and large footprint.

[0025] (2) This invention fully considers the special heat dissipation requirements of heat dissipation equipment and adopts a dual-density microchannel design. Increasing the heat exchange surface area in the high-density microchannel region enhances heat exchange with the fluid and improves heat transfer efficiency. However, too many high-density microchannels lead to high fluid flow resistance in the radiator. By setting low-density fins, not only can high heat dissipation performance be maintained, but the flow resistance of the fluid in the microchannel region can also be reduced. This design optimizes the heat dissipation effect and improves the stability and reliability of the system.

[0026] (3) Because the high-density area undergoes forced convection and has a large heat exchange, by setting the fins to be tilted towards the low-density area, the fluid in the fins of the low-density area can flow out quickly while simultaneously scouring the upper part of the fins in the low-density area. This enhances heat transfer in the upper part of the fins in the low-density area, improving the heat exchange effect. Through the above settings, the number of fins can be reduced, saving costs, while also improving the heat exchange effect.

[0027] (4) This invention uses a split heat pipe to construct a heat dissipation system that is in direct contact with the heat dissipation component. It achieves indirect liquid cooling phase change heat dissipation for the heat dissipation component with the highest power consumption and the most critical impact on performance in the server, effectively controlling the temperature of the heat dissipation component. At the same time, it has the advantages of split heat pipes, which are flexible and convenient, can be arranged over long distances, are easy to modify, have a compact structure, and can be used in hard or soft connection forms according to the specific needs of the server, making it highly adaptable. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the dual-density microchannel manifold evaporator of the present invention.

[0029] Figure 2 This is a schematic diagram of the split structure of the dual-density microchannel manifold evaporator of the present invention.

[0030] Figure 3 This is a schematic diagram showing the dimensions of the dual-density microchannel manifold evaporator of the present invention.

[0031] Figure 4 This is a schematic diagram of the heat exchange microchannel layer structure of the present invention.

[0032] Figure 5 This is a schematic diagram of the flow inside the manifold evaporator of the present invention.

[0033] Figure 6 This is a schematic diagram of the split heat pipe system of the present invention. Detailed Implementation

[0034] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0035] Unless otherwise specified, in this article, " / " represents division, and "×" and "*" represent multiplication when formulas are involved.

[0036] A dual-density microchannel evaporator, such as Figure 1As shown, the evaporator includes an upper outer shell 1 and 3 and a lower heat exchange microchannel layer 2. The outer shell 1 includes an inlet 11 on the upper surface and a fluid inlet manifold 12 on the lower surface, with the fluid inlet manifold 12 connected to the fluid inlet 11. The heat exchange microchannel layer 2 includes a high-density microchannel 21 and a low-density microchannel 22 on the upper surface, with the low-density microchannel 22 located on both sides of the high-density microchannel 21. The outer shell 1 is divided into two parts: a middle outer shell 1 and two side outer shells 3. The middle outer shell covers the high-density microchannel layer 21 and encloses it, which helps optimize the flow path. The two side outer shells 3 cover the low-density microchannel 22 and enclose it. The fluid inlet 11 is located in the middle of the middle outer shell 1, and the fluid outlet 31 is located in the middle of the two side outer shells 3. The fluid outlet 31 is connected to the low-density microchannel 22. The evaporator is connected to the split heat pipe during use and serves as the evaporation end of the split heat pipe. It utilizes the working fluid filled inside the heat pipe for phase change heat dissipation. The lower surface of the heat exchange microchannel layer 2 is thermally connected to the heat source.

[0037] This invention fully considers the special heat dissipation requirements of heat dissipation equipment and adopts a dual-density microchannel design. Increasing the heat exchange surface area in the high-density microchannel region enhances heat exchange with the fluid and improves heat transfer efficiency. However, too many high-density microchannels lead to high fluid flow resistance in the radiator. By setting low-density fins, not only can high heat dissipation performance be maintained, but the flow resistance of the fluid in the microchannel region can also be reduced. This design optimizes the heat dissipation effect and improves the stability and reliability of the system.

[0038] The evaporator of this invention, by setting up an outer shell and channels of different densities, can also improve the problem that immersion cooling cannot solve the problem of local hot spots and easily leads to overheating of heating components. At the same time, it can also solve the problem of complex immersion structure and large footprint.

[0039] As an improvement, the middle outer shell 1 and the two side outer shells 3 are manufactured separately. Each of the two side outer shells 3 is provided with a fluid outlet 31.

[0040] In this application, the outer casing is divided into high-density and low-density microchannels. This is because the high-density microchannel layer 21 experiences more intensive heat exchange, requiring a more efficient heat dissipation method. Therefore, by dividing the outer casing to cover microchannels of different densities, the high-density microchannel area can be more fully contacted with the lower-temperature coolant, thereby maximizing heat transfer efficiency and effectively reducing the temperature difference on the microchannel heat sink wall. Meanwhile, the low-density microchannel layer 22 does not require such intensive heat exchange; therefore, it can be directly cooled using the coolant flowing from the high-density microchannel layer 21, reducing flow resistance inside the radiator and improving economy and sustainability.

[0041] As a preferred option, such as Figure 2 , 5 As shown, the inlet of the inlet manifold 12 is located in the middle of the intermediate housing 1, and it is a double-conical structure extending from the middle to both ends. The conical manifold design not only reduces the velocity difference of the fluid flow and reduces the turbulence loss of the fluid, but also enables smooth regulation of the fluid flow before the fluid enters the high-density microchannel 21 region, avoiding the problems of local overheating or uneven cooling.

[0042] As a preferred option, such as Figure 2 As shown, the intermediate outer shell 1 includes closed walls located at opposite ends, with a fluid outlet formed between the two opposite closed walls, allowing fluid to flow into the low-density microchannels. The closed walls at both ends effectively seal off the high-density microchannels, allowing fluid to flow out of the high-density microchannels through the fluid outlet after heat exchange.

[0043] Preferably, the inlet manifold extends from the inlet to the closed walls at both ends. This arrangement allows the fluid to flow from the center to both ends, and because the conical ends of the conical structure are located at the closed walls, the fluid flow can be smoothly regulated, avoiding problems such as local overheating or uneven cooling.

[0044] Preferably, the upper surface of the intermediate outer shell 1 includes a first plane and a rectangular boss protruding upward from the first plane. The boss extends along both ends of the enclosed wall, and a fluid inlet manifold 11 is disposed in the middle of the boss. The inlet 12 extends along the boss. After the fluid enters the evaporator from the inlet manifold 11, it extends to both sides along the boss, allowing the fluid to enter the evaporator more smoothly and flow steadily through the microchannel layer. This design can reduce the turbulence and eddies generated by the fluid, maintain the stable flow state of the fluid, and further improve the heat exchange efficiency.

[0045] As a preferred option, the heat exchange microchannel layer 2 adopts a segmented microchannel design. The high-density microchannel 21 and the two low-density microchannels 22 on both sides adopt traditional straight rectangular flow channels, and the structures of the two low-density microchannels 22 on both sides are completely equal.

[0046] As a preferred option, such as Figure 3 As shown, the high-density microchannel heat dissipation area is long. ,Width fin width Channel width Channel height The number of channels is 130-180; the low-density microchannel heat dissipation area on the left. , ,in , , The number of channels is 25-35. The low-density microchannels on the right are exactly the same as those on the left, therefore... , .

[0047] The microchannel layer employs a segmented microchannel design with carefully selected parameters, such as the fin-to-channel width ratio and the aspect ratio of channel height and width, based on the heat dissipation requirements of each component. Through the density and size design of the two microchannels, uniform heat distribution can be achieved, reducing system pressure drop. The microchannels use water as the heat exchange fluid and employ a traditional straight rectangular fin flow channel design to increase flow stability, improve radiator temperature uniformity, and thus enhance equipment operational reliability.

[0048] When the fin height and spacing are not exactly the same, the above parameters are taken as average data.

[0049] As a preferred option, considering the heat transfer efficiency of the fins inside the radiator, the convective heat transfer area of ​​the actual fluid flowing through the microchannels of the radiator after correction is calculated, and the fitting formula is as follows:

[0050] (1.1)

[0051] (1.2)

[0052] in, This represents the actual contact area between the fluid and the wall of the radiator's microchannels, including the bottom area of ​​the microchannels and the side areas of the fins. ; Fin efficiency is the ratio of actual heat transfer to ideal heat transfer in a fin. For channel length, ; For channel width, ; For the channel height, ; The width of the fin. ; The number of fins; The convective heat transfer coefficient between the fluid and the radiator surface. ; The thermal conductivity of the fins is... .

[0053] The above optimization formula is the method for calculating the optimal contact area. Through this optimization, heat distribution can be further made more uniform, reducing system pressure drop and improving the heat sink's temperature uniformity, thereby enhancing equipment operational reliability.

[0054] As a further preferred option, the high-density microchannel heat dissipation area is long. ,Width fin width Channel width Channel height The number of channels is 150; the low-density microchannel heat dissipation area on the left. , ,in , , The number of channels is 29. The low-density microchannels on the right are exactly the same as those on the left, therefore... , .

[0055] The optimal parameters calculated by the formula are a convective heat transfer area of ​​0.0266 m² for the high-density microchannels. 2 The convective heat transfer area of ​​the low-density microchannel is 0.0065 m². 2 The convective heat transfer area of ​​high-density microchannels is four times that of low-density microchannels. Through these optimizations, more uniform heat distribution can be achieved, reducing system pressure drop and improving radiator temperature uniformity, thereby enhancing equipment operational reliability.

[0056] Preferably, the evaporator is used as the evaporation end of a split heat pipe system, and the system is filled with a certain volume of heat exchange fluid.

[0057] Preferably, the evaporator uses coolant as the heat exchange fluid. After entering from the manifold inlet, the fluid flows evenly into the high-density microchannel region for initial heat exchange. The heated coolant enters the low-density microchannel region through the fluid outlets on both sides for secondary heat exchange. Finally, it merges into a stream at the outlet layer and flows out from the outlet manifold, thereby achieving the target cooling.

[0058] As an improvement, the average height of the fins in the low-density microchannel heat dissipation zone is higher than that of the fins in the high-density microchannel heat dissipation zone.

[0059] As an improvement, the fins of the high-density microchannel heat dissipation area are inclined towards the low-density microchannel heat dissipation area. From the center of the heat dissipation area towards the fins of the low-density microchannel heat dissipation area, the height of the fins of the high-density microchannel heat dissipation area gradually increases. In the area connected with the low-density microchannel heat dissipation area, the height of the fins of the high-density microchannel heat dissipation area is the same as that of the low-density microchannel heat dissipation area.

[0060] Because the high-density area undergoes forced convection and has a large heat exchange, by tilting the fins towards the low-density area, the fluid in the low-density area can flow out quickly while simultaneously scouring the upper part of the low-density fins. This enhances heat transfer in the upper part of the low-density fins, improving their heat exchange efficiency. This design reduces the number of fins, saving costs, while simultaneously improving heat exchange performance.

[0061] As an improvement, the increase in fin height in the high-density microchannel heat dissipation zone gradually decreases from the center of the heat dissipation zone towards the fins of the low-density microchannel heat dissipation zone. This design allows the fluid to tend towards a uniform fin height near the low-density region, ensuring that the fluid flows horizontally over the upper part of the fins rather than upwards, thus further enhancing heat transfer and improving the heat exchange efficiency.

[0062] The specific workflow is as follows: Fluid enters the evaporator through inlet 11 and then flows into the double-cone manifold channel 12. After being buffered at the manifold, the fluid impacts downwards into the high-density microchannel region 21 and flows to both sides along the microchannel direction. In the high-density microchannel region 21, due to the dense layout of the microchannels and the forced convection cooling method, the contact area between the fluid and the microchannel wall increases, achieving efficient heat transfer. After enhanced heat exchange in the intermediate region, the fluid continues to flow along the flow direction of the fluid microchannels through the low-density microchannel region 22. When the fluid flows from the high-density microchannel 21 into the low-density microchannel 22, because the low-density fins are tall, have a large space, and a low fin distribution density, the high-speed fluid is dispersed, reducing the strong impact of the fluid at the outlet. Subsequently, the fluid exchanges heat along the low-density microchannel region 22, further cooling the evaporator outlet. After the coolant fully absorbs heat in the microchannel layer, it evaporates into a gaseous state. Finally, the gaseous fluid converges through the outlets 31 on both sides and flows out of the evaporator. The outflowing coolant flows along the steam riser pipe to the guide vane radiator, where it releases heat and condenses into a liquid state. It then flows back to the evaporator along the condensate return pipe, completing the entire heat exchange process.

[0063] Figure 6 Demonstrates the use of Figure 1-5 The gravity-type split heat pipe system of the microchannel evaporator includes an evaporator as the evaporation end, a finned radiator as the condensation end, a vapor riser pipe and a condensate return pipe connecting the evaporation and condensation ends, and a working fluid charged within the gravity-type split heat pipe system. Liquid refrigerant enters the manifold microchannel evaporator from the refrigerant inlet manifold, evaporates in the evaporator, and flows out from the refrigerant outlet manifold, carrying away the heat absorbed by the evaporator. Gaseous refrigerant enters the evaporation end, cools into a liquid state, and then flows back into the evaporator, completing the refrigerant cycle and heat transfer. The lower part of the third layer 3 is thermally connected to the main heating component to cool it down. The finned radiator is connected to heat dissipation components such as a fan to dissipate heat.

[0064] While the present invention has been disclosed above with reference to preferred embodiments, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A dual-density microchannel evaporator, the evaporator comprising an upper outer shell and a lower heat exchange microchannel layer, the outer shell comprising a fluid inlet on the upper surface and a fluid inlet manifold on the lower surface, the fluid inlet manifold being connected to the fluid inlet; the heat exchange microchannel layer comprising high-density microchannels and low-density microchannels on the upper surface, the low-density microchannels being located on both sides of the high-density microchannels; the outer shell being divided into two parts, namely a middle outer shell and two side outer shells, the middle outer shell covering the upper part of the high-density microchannel layer and enclosing the high-density microchannel layer, the side outer shells covering the upper part of the low-density microchannel layer and enclosing the low-density microchannel layer; the fluid inlet being located in the middle of the middle outer shell, the middle outer shell and the side outer shells being manufactured separately; each of the side outer shells being provided with a fluid outlet, the fluid outlet being located in the middle of the side outer shells; the fluid outlet being connected to the low-density microchannels; the average height of the fins in the heat dissipation area of ​​the low-density microchannels being higher than the average height of the fins in the heat dissipation area of ​​the high-density microchannels; The fins of the high-density microchannel heat dissipation area are inclined towards the low-density microchannel heat dissipation area. From the center of the heat dissipation area towards the fins of the low-density microchannel heat dissipation area, the height of the fins of the high-density microchannel heat dissipation area gradually increases. In the area where it connects with the low-density microchannel heat dissipation area, the height of the fins of the high-density microchannel heat dissipation area is the same as that of the low-density microchannel heat dissipation area.

2. The evaporator as described in claim 1, characterized in that, The housing includes closed walls located at opposite ends, with a fluid outlet formed between the two opposite closed walls.

3. The evaporator as described in claim 1, characterized in that, The heat exchange microchannel layer adopts a segmented microchannel design. Both the high-density microchannel and the low-density microchannels on both sides adopt straight rectangular fin flow channels, and the structures of the low-density microchannels on both sides are completely equal.

4. A gravity-type split heat pipe system, comprising a finned radiator, a dual-density microchannel evaporator, a vapor riser, and a condensate downcomer, wherein a certain volume of refrigerant is charged in the system; the finned radiator is responsible for cooling the gaseous working fluid entering it, the dual-density microchannel manifold evaporator uses the liquid working fluid to absorb the heat generated by the cooling target, and the vapor riser and condensate return pipe connect the finned radiator and the dual-density microchannel manifold evaporator to form a circulation loop; the dual-density microchannel evaporator is the evaporator as described in any one of claims 1-3; the lower part of the heat exchange microchannel layer is thermally connected to the main heating component.

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