A multi-channel series-parallel mixed micro-channel pulsating heat pipe radiator

Abstract

The application discloses a multi-flow-channel series-parallel mixed connection micro-channel pulsating heat pipe radiator, which comprises a micro-channel flat tube, a sealing structure, a filling pipe and fins. The micro-channel flat tube is internally provided with a plurality of parallel flow channels. Part of the adjacent parallel flow channels are connected in series and communicated at the heads to form a series connection communication zone, and part of the adjacent parallel flow channels are connected in parallel and communicated to form a parallel connection communication zone. The series connection communication zone and the parallel connection communication zone are also connected with each other at the end of the micro-channel flat tube to form an overall flow circulation loop. The multi-flow-channel series-parallel mixed connection micro-channel pulsating heat pipe radiator has the reflux advantage of the parallel connection structure and the strong anti-gravity characteristic of the series connection structure.

Description

Technical Field

[0001] This invention relates to the field of heat exchange technology, specifically to a microchannel pulsating heat pipe radiator with multiple flow channels connected in series and parallel. Background Technology

[0002] Microchannel flat tubes have the characteristics of narrow pipes, flat shape, easy bending, horizontal heat exchange between channels, and excellent heat transfer performance. When used to make heat pipes, they can meet the capillary diameter requirements of pulsating heat pipes and achieve large-area contact with planar heat sources.

[0003] Current research on microchannel flat tube heat pipe structural design mainly focuses on pure parallel or pure series configurations. Parallel heat pipes have interconnected flow channels, resulting in a smaller pressure difference between the two evaporation and condensation sections, stronger recirculation of the working fluid from the condensation section, and the ability to adaptively form rising and falling tubes based on the heat dissipation scenario, leading to superior heat transfer limits. However, at low tilt angles, they are severely constrained by gravity, resulting in poor heat transfer performance. Series heat pipes exhibit better heat transfer performance at low tilt angles and stronger resistance to gravity. However, at large tilt angles, their recirculation of the working fluid is not as strong as that of parallel heat pipes, resulting in a smaller heat transfer limit. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a microchannel pulsating heat pipe radiator with multi-channel series-parallel hybrid interconnection, which simultaneously possesses the recirculation advantages of a parallel structure and the strong anti-gravity characteristics of a series structure.

[0005] This invention provides a microchannel pulsating heat pipe radiator with multiple flow channels connected in series and parallel, including a microchannel flat tube. The microchannel flat tube has multiple partition plates inside, which divide the internal cavity of the microchannel flat tube into several parallel flow channels along the length direction. Some adjacent parallel flow channels are connected end to end in a serpentine manner to form a series interconnection area, and some adjacent parallel flow channels are connected in parallel to form a parallel interconnection area. The series interconnection area and the parallel interconnection area are also interconnected at the ends of the microchannel flat tube, forming an overall flow loop.

[0006] Furthermore, when the heating power varies at different points in the heat source, the parallel interconnection zone should preferably be designed to be located at a position with higher heating power. The parallel interconnection zone is located in the middle of the microchannel flat tube, with series interconnection zones on both sides of the parallel interconnection zone; or, the series interconnection zone is located in the middle of the microchannel flat tube, with parallel interconnection zones on both sides of the series interconnection zone; or, the series interconnection zone and the parallel interconnection zone are alternately arranged.

[0007] Furthermore, in the series interconnection zone, interconnection channels are alternately arranged at both ends of the parallel channels, with each interconnection channel simultaneously connecting only two adjacent parallel channels, thus creating a serpentine, series-connected flow. In the parallel interconnection zone, the interconnection channels at both ends simultaneously connect to all parallel channels, enabling parallel interconnection of all parallel channels. Furthermore, the two ends of the microchannel flat tube are sealed by a sealing structure; the sealing structure includes a sealing end cap, on which a filling tube is connected; the sealing end cap has a deep groove for inserting the microchannel flat tube, and the deep groove has a bottom; after the microchannel flat tube is inserted to the bottom of the groove, it is sealed by welding or adhesive; or, the ends of the microchannel flat tube are clamped and welded to form a sealing structure after the interconnected flow channels are processed.

[0008] Furthermore, the interconnecting flow channel is formed by partially cutting off the end of the partition plate; or, by simultaneously cutting off part of the outer wall of the flat tube and the partition plate to construct the interconnecting flow channel, the cross-section of the interconnecting flow channel can be triangular or rectangular; or, when the sealing structure is a sealing end cap, the interconnecting flow channel can also be formed by machining a stepped connecting hole at the bottom of the deep groove of the sealing end cap.

[0009] Furthermore, the microchannel flat tube, after multiple bends, forms a serpentine structure with multiple parallel straight tube segments. Two parallel straight tube segments at each end of the flat tube are tightly fitted together to form an evaporation section, while the remaining parallel straight tube segments are condensation sections. The connecting section between the evaporation and condensation sections is an adiabatic section. The outer straight tube segment of the evaporation section directly contacts the heat source, absorbs heat, and then dissipates it. The inner straight tube segment of the evaporation section crosses the outer straight tube segment, absorbs heat, and then dissipates it. This non-uniform heat flux density enhances the internal imbalance of the heat pipe, thereby improving its performance.

[0010] Furthermore, the number of flow channels in the parallel interconnected area n 1% of the total number of flow channels in the flat tube n The ratio of 0 x It conforms to formula (1).

[0011] In the formula n 1. n 0 represents an integer. a 1 represents the area of ​​the heat source where the power value is greater than 0.5 after normalization, in square meters (m²). 2 ; a all This represents the total area of ​​the heated region, in m². 2 ; θ This represents the acute angle between the straight line connecting the centroids of the condenser section and the evaporator section of the heat pipe and the horizontal plane when the condenser section is on top and the evaporator section is on the bottom, expressed in degrees. x When = 1, the heat pipe is a purely parallel interconnected heat pipe. x When the value is 0, the heat pipe is a purely series-connected heat pipe.

[0012] Furthermore, the equivalent hydraulic diameter of the interconnecting channels between the series interconnection zone and the parallel interconnection zone... d 串 , d 并 They respectively satisfy formula (2):

[0013] In the formula: k As a parallel factor, it should be greater than 1, and it is especially important when the working fluid viscosity is high and the saturation temperature-pressure ratio d is high. P sat / d T sat When smaller, k The larger value should be taken, parallel factor. k The selectable values ​​are 1.1 to 1.5; T min 、T max These are the lowest and highest temperatures in the heat pipe operating scenario, respectively, in K. d 串 , d 并 These are the equivalent hydraulic diameters of the interconnecting channels in the series and parallel interconnecting zones of the heat pipes, respectively, in meters. σ The surface tension of the working fluid is expressed in N·m. -1 ; ρ l , ρ v These are the densities of the working fluid in the liquid and gas phases, respectively, in kg·m³. -3 g is the acceleration due to gravity, taken as 9.8 m / s². -2 .

[0014] Furthermore, fins are inserted into the condensation section for heat dissipation.

[0015] Advantages of this invention: Compared with the prior art, the present invention has the following significant advantages: 1. The heat pipe radiator proposed in this invention combines the advantages of pure parallel interconnected heat pipes and pure series interconnected heat pipes: the liquid return capacity of the parallel interconnected zone is stronger and the heat transfer limit is higher; the performance of the series interconnected zone at a low tilt angle is better.

[0016] 2. The heat pipe radiator proposed in this invention has a compact heat exchange system design and small size. The heat pipes are connected to each other with sealed end caps, resulting in a smaller and more concentrated overall size. At the same time, the heat pipe evaporation section adopts a design of being closely attached to each other and having a heat source attached to one side, which cleverly realizes non-uniform heat flux density heating in the evaporation section area. Non-uniform heat flux density heating can improve the imbalance inside the heat pipe, thereby improving the performance of the heat pipe. 3. The microchannel flat tube pulsating heat pipe proposed in this invention has excellent heat exchange performance and high applicability. The internal structure of the heat pipe is simple, without a liquid wick, and can run horizontally driven by pressure difference. The gas and liquid move in the same direction, thus resulting in excellent heat transfer performance. The outer surface of the heat pipe is flat, which makes it easy to attach to the chip heat source without the need for a substrate. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the microchannel pulsating heat pipe radiator with multi-channel series-parallel hybrid interconnection proposed in this invention. Figure 2 This is a schematic diagram of the flow path of a microchannel pulsating heat pipe; Figure 3 This is a schematic diagram of the direct weld sealing flow channel; Figure 4 This is a schematic diagram of a flow channel designed to achieve connectivity by cutting away the outer wall and partition wall of a flat tube. Figure 5 This is a schematic diagram of a flow channel designed to achieve connectivity by cutting away the outer wall and partition wall of a flat tube. Figure 6 This is a schematic diagram of a flow channel scheme that achieves connectivity by machining stepped holes at the bottom of a closed end cap groove.

[0018] In the figure: microchannel flat tube 1, sealing end cap 2, fin 3, filling tube 4, evaporation section 101, condensation section 102, insulation section 103, flat tube outer wall 1011, partition plate 1012, series interconnection area 1013, parallel interconnection area 1014, stepped connecting hole 1015, tank bottom 2011. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0020] Example 1 like Figure 1As shown, this embodiment provides a multi-channel series-parallel hybrid interconnected microchannel pulsating heat pipe radiator, including a microchannel flat tube 1. The microchannel flat tube 1 is formed into a serpentine structure by multiple 180° bends, with a bending diameter of 7~13 mm. It has multiple parallel straight tube sections, of which two parallel straight tube sections at both ends of the flat tube are closely attached to form an evaporation section 101, and the remaining parallel straight tube sections are condensation sections 102. The connecting section between the evaporation section 101 and the condensation section 102 is an insulation section 103. Fins 3 are inserted on the condensation section 102 for heat dissipation. The two ends of the microchannel flat tube 1 are sealed by a sealing structure. The outer plane of the evaporation section 101 is directly attached to the heat source for heat dissipation, and the heat is transferred to the condensation section 102 and then dissipated by the fins 3.

[0021] See Figure 1 In practical applications, the straight pipe section on the lower side of the evaporation section 101 is directly attached to the heat source to absorb heat and then transmit it out, while the straight pipe section on the upper side crosses the straight pipe section on the lower side to absorb heat and then transmit it out. The non-uniform heat flux density can enhance the internal imbalance of the heat pipe, thereby improving the performance of the heat pipe.

[0022] Specifically, see Figure 2 The microchannel flat tube 1 includes an outer wall 1011, within which a cavity is formed. Multiple partition plates 1012 are provided inside the cavity. The outer wall 1011 and partition plates 1012 divide the internal cavity of the microchannel flat tube 1 into several parallel flow channels along its length. Some adjacent parallel flow channels are connected end-to-end in a serpentine pattern to form a series interconnected region 1013, while some adjacent parallel flow channels are connected in parallel to form a parallel interconnected region 1014. The series interconnected region 1013 and the parallel interconnected region 1014 are also interconnected at the ends of the microchannel flat tube 1, forming a unified flow loop. Within the series interconnected region 1013, the flow channels are interconnected in a serpentine pattern, with rising and falling pipes for the working fluid arranged alternately. Within the parallel interconnected region 1014, the flow channels are interconnected in parallel, and during operation, the rising and falling pipes for the working fluid are adaptively formed according to the heat dissipation scenario.

[0023] As a preferred embodiment of the present invention, see [link to previous document]. Figure 1 and Figure 2 The sealing structure includes a sealing end cap 2, to which a filling pipe 4 is connected. The inner diameter of the filling pipe 4 is 0.8 to 1.2 times the equivalent hydraulic diameter of the microchannel flat tube flow channel. The heat pipe working fluid is filled through the filling pipe 4, with a filling rate of 50% to 70%.

[0024] As a preferred embodiment of the present invention, see [link to previous document]. Figure 2 The sealing cap 2 has a deep groove with the same outline as the outer wall 1011 of the flat tube end. After the end of the microchannel flat tube 1 is inserted into the bottom of the deep groove, it is sealed by welding or adhesive. The insertion length of the flat tube is 2 to 5 times the thickness of the flat tube.

[0025] As a preferred embodiment of the present invention, see [link to previous document]. Figure 3 To simplify the dimensions of the heat pipe, the cap 2 at the end with the filling tube can be retained while the cap 2 at the other end without the filling tube can be discarded. After the interconnected flow channels are processed at the end of the microchannel flat tube 1, the end on this side can be directly clamped and welded to form a sealing structure, which can achieve the same sealing effect and simplify the dimensions.

[0026] As a preferred embodiment of the present invention, see [link to previous document]. Figures 2-6 When the heating power is different at different parts of the heat source, the parallel interconnection zone should be designed to be located at the position with higher heating power. In this embodiment, it is assumed that the heating power at the center of the heat source is higher and the power at the two wings is lower. Therefore, the parallel interconnection zone 1014 is set in the middle of the microchannel flat tube 1, and the two sides of the parallel interconnection zone 1014 are the series interconnection zones 1013.

[0027] Of course, if the heating power of the two wings of the heat source is high and the power of the center is low, the series interconnection zone 1013 can also be located in the middle of the microchannel flat tube 1, and the two sides of the series interconnection zone 1013 are parallel interconnection zones 1014; or, the series interconnection zone 1013 and the parallel interconnection zone 1014 can be alternately arranged.

[0028] Specifically, the series interconnection zone 1013 has interconnection channels alternately arranged at both ends of the parallel flow channels, and each interconnection channel connects only two adjacent parallel flow channels at the same time, so that the serpentine head and tail are connected in series. The interconnection channels at both ends of the parallel interconnection zone 1014 connect all parallel flow channels at the same time, realizing parallel interconnection of each parallel flow channel.

[0029] Interconnected flow channels can be achieved in the following ways: (1) See Figure 2 Without touching the outer wall 1011 of the flat tube, the partition plates 1012 at both ends of the parallel flow channels in the series interconnection zone 1013 are alternately cut out to form interconnection channels. The parallel flow channels and interconnection channels are combined to form a large serpentine series interconnection channel. The working fluid in the parallel flow channel can only enter the adjacent parallel flow channel after flowing through the interconnection channel at one end. The partition plates 1012 at both ends of the parallel interconnection zone 1014 are cut out to form interconnection channels. The parallel flow channels are connected in parallel with the interconnection channels. The working fluid in the parallel flow channel can directly enter any other parallel flow channel after flowing through the interconnection channel at one end.

[0030] (2) See Figure 4 and Figure 5 Similar to the method in (1), except that while cutting off the partition plate 1012, the outer wall 1011 of the flat tube is cut off to construct the interconnected flow channel. The cross-section of the interconnected flow channel can be triangular or rectangular, and the processing is simpler.

[0031] (3) See Figure 6Without removing the partition plate 1012, the deep groove on the sealing end cap 2 has a groove bottom 2011. Stepped connecting holes 1015 are machined in the groove bottom 2011 to form an interconnected flow channel, and the working fluid connection effect remains unchanged.

[0032] The parallel interconnection zone 1014 has stronger liquid return capacity and a higher heat transfer limit; while the series interconnection zone 1013 performs better at low tilt angles. Specifically, the number of flow channels in the parallel interconnection zone 1014... n 1% of the total number of flow channels in the flat tube n The ratio of 0 x It conforms to formula (1).

[0033] In the formula n 1. n 0 represents an integer. a 1 represents the area of ​​the heat source where the power value is greater than 0.5 after normalization, in square meters (m²). 2 ; a all This represents the total area of ​​the heated region, in m². 2 ; θ This represents the acute angle between the straight line connecting the centroids of the condenser section and the evaporator section of the heat pipe and the horizontal plane when the condenser section is on top and the evaporator section is on the bottom. The unit is °. x When = 1, the heat pipe is a purely parallel interconnected heat pipe. x When the value is 0, the heat pipe is a purely series-connected heat pipe.

[0034] The equivalent hydraulic diameter of the interconnecting channels of the series interconnection zone 1013 and the parallel interconnection zone 1014 d 串 , d 并 They respectively satisfy formula (2):

[0035] In the formula: k As a parallel factor, it should be greater than 1, and it is especially important when the working fluid viscosity is high and the saturation temperature-pressure ratio d is high. P sat / d T sat When smaller, k The larger value should be taken, parallel factor. k The selectable values ​​are 1.1 to 1.5; T min 、T max These are the lowest and highest temperatures in the heat pipe operating scenario, respectively, in K. d 串 , d 并These are the equivalent hydraulic diameters of the interconnecting channels in the series and parallel interconnecting zones of the heat pipes, respectively, in meters. σ The surface tension of the working fluid is expressed in N·m. -1 ; ρ l , ρ v These are the densities of the working fluid in the liquid and gas phases, respectively, in kg·m³. -3 g is the acceleration due to gravity, taken as 9.8 m / s². -2 .

[0036] In a preferred embodiment of the present invention, the two closely fitting parallel straight pipe sections of the evaporation section 101 are connected by a thermally conductive contact material, such as thermally conductive silicone grease, high thermal conductivity ceramics, or carbon fiber thermal pads. During installation, the sections should fit tightly and be clean to ensure no gaps or impurities between the parallel straight pipe sections and the thermally conductive contact material. The condensation section 102 is fixed to the fins 3 by welding, and the surface of the fins 3 is further enhanced with corrugations, louvers, or other heat exchange structures.

[0037] In summary, this invention proposes a microchannel pulsating heat pipe radiator with multi-channel series-parallel hybrid interconnection, which simultaneously possesses the reflux advantages of parallel structures and the strong anti-gravity characteristics of series structures: the parallel interconnection zone has stronger liquid return capacity and higher heat transfer limit; the series interconnection zone has better performance at low tilt angles.

[0038] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the scope of protection of the present invention.

Claims

1. A microchannel pulsating heat pipe radiator with multiple flow channels connected in series and parallel, characterized in that: The microchannel flat tube (1) is provided with multiple partition plates (1012) inside. The partition plates (1012) divide the internal cavity of the microchannel flat tube (1) into several parallel flow channels along the length direction. Among them, some adjacent parallel flow channels are connected end to end in a serpentine manner to form a series interconnection area (1013), and some adjacent parallel flow channels are connected in parallel to form a parallel interconnection area (1014). The series interconnection area (1013) and the parallel interconnection area (1014) are also connected to each other at the end of the microchannel flat tube (1) to form an overall flow loop. The microchannel flat tube (1) is bent multiple times to form a serpentine structure with multiple parallel straight tube segments. The two parallel straight tube segments at both ends of the flat tube are closely attached to each other to form an evaporation section (101), and the remaining parallel straight tube segments are condensation sections (102). The connecting section between the evaporation section (101) and the condensation section (102) is an adiabatic section (103). The outer straight tube segment of the evaporation section (101) directly attaches to the heat source to absorb heat and then transmits it out. The inner straight tube segment crosses the outer straight tube segment to absorb heat and then transmits it out. The non-uniform heat flux density can enhance the internal imbalance of the heat pipe, thereby improving the performance of the heat pipe. The number of channels in the parallel interconnection zone (1014) n 1% of the total number of flow channels in the flat tube n The ratio of 0 x It conforms to formula (1). In the formula n 1. n 0 represents an integer. a 1 represents the area of ​​the heat source whose power value is greater than 0.5 after normalization. a all Indicates the total area of ​​the heated region; θ This represents the acute angle between the line connecting the centroids of the condenser section and the evaporator section of the heat pipe and the horizontal plane when the condenser section is on top and the evaporator section is on the bottom. x When = 1, the heat pipe is a purely parallel interconnected heat pipe. x When the value is 0, the heat pipe is a purely series-connected heat pipe.

2. The microchannel pulsating heat pipe radiator with multi-channel series-parallel hybrid interconnection according to claim 1, characterized in that: The parallel interconnection zone (1014) is located in the middle of the microchannel flat tube (1), and the two sides of the parallel interconnection zone (1014) are the series interconnection zones (1013). Alternatively, the series interconnection area (1013) is located in the middle of the microchannel flat tube (1), and the two sides of the series interconnection area (1013) are parallel interconnection areas (1014). Alternatively, the series interconnection zone (1013) and the parallel interconnection zone (1014) can be set alternately.

3. The multi-channel series-parallel hybrid interconnected microchannel pulsating heat pipe radiator according to claim 2, characterized in that: The series interconnection zone (1013) has interconnection channels alternately set at both ends of the parallel channels. Each interconnection channel connects only two adjacent parallel channels at the same time, so that the serpentine head and tail are connected in series. The interconnection channels at both ends of the parallel interconnection zone (1014) connect all parallel channels at the same time, so that each parallel channel is connected in parallel.

4. The multi-channel series-parallel hybrid interconnected microchannel pulsating heat pipe radiator according to claim 3, characterized in that: The two ends of the microchannel flat tube (1) are sealed by a sealing structure; The sealing structure includes a sealing end cap (2), on which a filling tube (4) is connected. The sealing end cap (2) has a deep groove for inserting a microchannel flat tube (1). The deep groove has a bottom (2011). After the microchannel flat tube (1) is inserted to the bottom (2011), it is sealed by welding or adhesive. Alternatively, the ends of the microchannel flat tube (1) are welded together after the interconnected flow channels are processed to form a sealed structure.

5. The microchannel pulsating heat pipe radiator with multi-channel series-parallel hybrid interconnection according to claim 3, characterized in that: The interconnecting flow channel is formed by partially cutting off the end of the partition plate (1012); Alternatively, an interconnected flow channel can be constructed by simultaneously cutting off part of the outer wall (1011) of the flat tube and the partition plate (1012). The cross-section of the interconnected flow channel can be triangular or rectangular.

6. The microchannel pulsating heat pipe radiator with multi-channel series-parallel hybrid interconnection according to claim 4, characterized in that: When the sealing structure is a sealing end cap (2), an interconnected flow channel can also be formed by machining a stepped connecting hole (1015) at the bottom (2011) of the deep groove of the sealing end cap.

7. The multi-channel series-parallel hybrid interconnected microchannel pulsating heat pipe radiator according to any one of claims 3-6, characterized in that: The equivalent hydraulic diameter of the interconnecting channels between the series interconnecting zone (1013) and the parallel interconnecting zone (1014) d 串 , d 并 They respectively satisfy formula (2): Parallel factor k It should be greater than 1, and when the working fluid viscosity is high and the saturation temperature-pressure ratio d is high. P sat / d T sat When smaller, k The larger value should be taken, parallel factor. k The selectable values ​​are 1.1 to 1.5; T min 、T max These represent the minimum and maximum temperatures during the heat pipe's operation, respectively.

8. The microchannel pulsating heat pipe radiator with multi-channel series-parallel hybrid interconnection according to claim 1, characterized in that: The condensation section (102) is fitted with fins (3) for heat dissipation.

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