An evaporative cooling structure

Abstract

An evaporative cooling structure belongs to the field of evaporative cooling thermal protection technology. A cross-scale porous media unit includes a skeleton, a plurality of mutually interpenetrating macropores are provided in the skeleton, and a plurality of directionally distributed mesopores and small pores are arranged on the skeleton; the evaporative cooling structure includes a rectifier plate, on which a water absorption layer and a cross-scale porous media unit are sequentially laid, a fixed bracket bottom plate is provided therebetween, a plurality of first and second channels are respectively provided on the rectifier plate and the fixed bracket bottom plate, a water storage tank is provided under the rectifier plate, and an inlet is provided at the bottom of the rectifier plate; the coolant flows into the water storage tank from the inlet, enters the water absorption layer through the rectifier plate, and the coolant is sucked out, and the cross-scale porous media unit sucks water in the water absorption layer to its surface, and a heat load is applied to the outer surface of the cross-scale porous media unit. The coolant in the pores absorbs heat, undergoes a gas-liquid phase change, and becomes steam that is carried away by outflow, thereby playing a cooling role; the present invention has the advantages of controllable cross-scale pore structure characteristics and high cooling efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of evaporative cooling thermal protection, and in particular relates to an evaporative cooling structure. Background Art

[0002] With the advancement of aerospace technology, the temperatures and heat flux densities of critical hot components in aerospace turbine engines, liquid rocket engines, and hypersonic vehicles are increasing. The rapid development of high-temperature resistant materials has outstripped these demands, necessitating the use of efficient active cooling methods for thermal protection of these high-temperature components. Evaporative cooling technology based on porous media plays a key role in addressing these challenges. The cooling fluid first flows through the porous medium, removing heat through intense convection. Subsequently, a dense air film forms on the wall surface, minimizing heat transfer from the hot mainstream to the wall. This cooling method is known as evaporative cooling. Compared to other thermal protection technologies such as regenerative cooling and film cooling, evaporative cooling offers higher cooling efficiency and holds great potential for thermal protection of walls with extremely high heat flux densities. Evaporative cooling was first proposed in the 1940s, primarily for thermal protection of rocket combustion chambers. Evaporative cooling primarily involves two heat transfer principles. First, convective heat transfer of the cooling fluid within the porous wall. The tortuous microchannels within the porous medium, combined with its large surface area, enhance the heat transfer capacity between the cooling fluid and the solid framework of the porous medium, efficiently removing heat. After the cooling fluid seeps through the porous wall, it forms a protective air film covering the surface. This film thickens the temperature boundary layer, effectively reducing heat transfer from the hot mainstream to the wall. Compared with film cooling, evaporative cooling provides a more adherent air film. As the inlet temperature of aircraft turbine engines continues to rise, evaporative cooling is considered an important thermal protection method for high-temperature blades. Evaporative cooling is also widely used for rocket engine throat cooling and hypersonic vehicle wall cooling.

[0003] Defects and shortcomings of existing technology:

[0004] 1. The local heat load borne by the evaporative carrier in the leading edge structure of aerospace power equipment is unevenly distributed. The coolant demand in high-heat-load areas is higher than that in low-heat-load areas. Evaporative cooling structures with uniform pore size distribution, in order to meet the cooling needs of high-temperature areas, will result in excess coolant supply and overflow in low-temperature areas, failing to match the heat load with the coolant, resulting in coolant waste and even adverse effects such as freezing. Conversely, this will cause a serious mismatch between the heat load and cooling capacity in high-temperature areas, leading to localized ablation. This is one of the main obstacles to improving the efficiency of phase-change evaporative cooling and the ultimate heat flux density.

[0005] 2. While phase-change evaporative cooling brings high cooling capacity, the unstable phase change process inside the porous medium can lead to severe steam blockage and large temperature oscillations. As the core component of the evaporative cooling system, the pore topology of the porous medium directly determines the heat transfer efficiency and cooling performance of the system. However, the preparation process has limitations in porosity regulation and pore connectivity optimization, resulting in significant randomness in the pore distribution within the structure. This disordered structural feature restricts the effectiveness of the cooler.

[0006] 3. Existing porous materials mostly adopt fixed structure design, while the special-shaped curved surface structure in high-temperature components is complex, the preparation and installation of the cooling structure is difficult, and the porous medium preparation process is complicated. For large-area, special-shaped high-temperature components, it is difficult to achieve large-scale integrated preparation and spatial structure conformity requirements.

[0007] 4. Pumping coolant to the porous medium takes up a significant amount of space, but the design space for evaporative cooling systems is limited. Furthermore, to meet the precise cooling requirements under dynamic heat load conditions, a dynamic matching mechanism between the pump supply unit and the porous medium must be established, increasing system complexity and control difficulty.

[0008] The patent application document with publication number CN 119262344 A discloses a phase-change transpiring cooling porous structure and its application in an aircraft reentry capsule. A porous unit comprising a small-porosity porous portion and a large-porosity porous portion is designed, and the liquid separation cavity is divided into multiple liquid separation cavities according to the heat flow distribution on the reentry capsule surface to achieve flow control in different heat flow areas. The porous unit structure with small porosity and large porosity effectively achieves the rapid separation of coolant gas and liquid in the porous layer, improving the efficiency and reliability of phase-change transpiring cooling. However, the pore diameters of the above-mentioned structure are basically the same, which cannot achieve cross-scale pore design, and the coolant flow is controlled by a regulating valve, which increases the complexity of the system. In addition, the structural shape is a regular rectangle, which is difficult to achieve conformal design, thus limiting its effect and application scope. Summary of the Invention

[0009] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an evaporative cooling structure, design a cross-scale porous media unit with a regular hexagonal structure, and achieve adaptation to large-size and irregular curved surface structures through module assembly and cross-scale pore design. At the same time, it can accurately control the internal pore structure parameters of each module according to the actual heat load distribution, thereby achieving directional control of the coolant under non-uniform heat load, and can minimize the consumption of primary energy while maximizing the working range. It does not require additional pumps to achieve fluid flow control, and has the advantages of conformal design, adjustable pore structure characteristics, fast liquid supply rate and high cooling efficiency.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] An evaporative cooling structure includes a rectifier plate, on top of which a water absorption layer and a plurality of connectable modular cross-scale porous media units are sequentially laid, a fixed bracket bottom plate is provided between each cross-scale porous media unit and the water absorption layer, a plurality of first channels are arranged on the rectifier plate, a plurality of second channels are arranged on the fixed bracket bottom plate, a water storage bin is provided below the rectifier plate, and an inlet is provided at the bottom of the water storage bin.

[0012] The cross-scale porous media unit is a regular hexagonal structure. Multiple cross-scale porous media units can be assembled modularly. The pore size, porosity, channel size, etc. of each modular unit can be independently designed, thereby realizing local flow allocation of the evaporative cooling structure under non-uniform heat load.

[0013] The cross-scale porous media unit includes a skeleton, in which a plurality of mutually interpenetrating macropores are arranged randomly, and cross-scale pores are arranged on the skeleton, which are a plurality of mesopores and a plurality of small pores, and the plurality of mesopores are distributed in a direction.

[0014] The directionally distributed mesopores are distributed from the bottom plate of the fixed support to the outer surface of the cross-scale porous medium unit.

[0015] The mesopore diameter is between the diameters of the macropores and the micropores.

[0016] The cross-scale porous medium unit is fixedly connected to the bottom plate of the fixed support via the fixed support.

[0017] The water-absorbing layer is filled with hydrophilic packed fiber material.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. In response to the problems of complex structures of large-scale, special-shaped curved high-temperature components and difficulty in large-scale integrated preparation, the present invention proposes a cross-scale porous media unit with a regular hexagonal structure, which has flexible and diverse assembly shapes. By splicing a modular unit composed of multiple cross-scale porous media units, an infinite assembly space is achieved, as well as rapid manufacturing and assembly of large-scale, special-shaped curved thermal protection structures. This meets the shape-matching requirements of complex high-temperature structures, has excellent maintainability and scalability, and is suitable for a variety of extreme environments.

[0020] 2. In order to solve the problems of uneven local heat load distribution and local ablation caused by mismatch between heat load and coolant, the present invention proposes a combination of modular assembly and gradient pore structure design. The pore size, porosity, channel size, etc. of the cross-scale porous media unit of each module can be independently designed and controlled, so that cross-scale porous media unit modules with larger porosity and smaller pore size are arranged in local high-temperature areas, and cross-scale porous media unit modules with smaller porosity and larger pore size are arranged in low-temperature areas, so that more coolant is transported to locations with higher heat flux density, thereby realizing local flow allocation, adapting to uneven heat load distribution, and greatly improving cooling efficiency and maximum heat flux density.

[0021] 3. To address the problems of steam blockage and large temperature oscillation caused by random distribution of porous structures and difficulty in controlling porous structures, the cross-scale porous medium unit provided by the present invention contains three types of pore structures: large pores, mesopores, and small pores. The shape structure and pore structure characteristics (pore size, porosity, and pore density) of the large pores can be precisely controlled to provide channels for the escape of steam. The directionally distributed mesopores are designed to enhance the system's liquid supply rate. The strong capillary force of the mesopores and small pores provides driving force for the supply of coolant without any additional power input, reducing the system's mass increment and simplifying the complexity and difficulty of operation.

[0022] 4. To address the problem that the evaporative cooling system relies on pumping coolant, resulting in a large system space occupation and complex design, the present invention uses capillary action to draw the coolant from the water storage tank to the water absorption layer, without the need for an additional pump to accurately control and distribute the flow, thereby achieving fluid flow regulation, greatly reducing the system load and improving energy utilization efficiency.

[0023] In summary, the cross-scale porous media unit with a regular hexagonal structure proposed in the present invention can slow down steam blockage and enhance the system's liquid supply rate, without the need for an additional pump to regulate the fluid flow rate. Moreover, through module assembly and cross-scale pore regulation, it can adapt to large-size and irregular curved surface structures. At the same time, according to the actual heat load distribution, the pore structure parameters of the cross-scale porous media unit inside each module are precisely regulated to achieve directional regulation of the coolant under non-uniform heat load, thereby achieving more efficient and reliable evaporative cooling performance. It is particularly suitable for scenarios with strict requirements on extreme heat flux density and structural complexity, such as aerospace, energy equipment, and electronic cooling. It has the advantages of conformal design, cross-scale pores, adjustable pore structure characteristics, fast liquid supply rate, and high cooling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 3D schematic diagram of the cross-scale porous media unit of the present invention.

[0025] Figure 2 It is a top view of the cross-scale porous media unit of the present invention.

[0026] Figure 3Schematic diagram of the assembly of multiple cross-scale porous media units of the present invention.

[0027] Figure 4 Schematic diagram of the internal pore structure of the cross-scale porous media unit of the present invention.

[0028] Figure 5 Schematic diagram of the internal pore structure of the cross-scale porous media unit cross-section of the present invention.

[0029] Figure 6 This is a schematic diagram of the modular evaporative cooling structure of the present invention.

[0030] Figure 7 Schematic diagram of the structure of a typical area of ​​a high-temperature wall surface of a spacecraft according to an embodiment of the present invention.

[0031] Figure 8 This is a schematic diagram of the evaporative cooling structure surface in a typical area of ​​a high-temperature wall of a spacecraft according to an embodiment of the present invention.

[0032] Figure 9 This is a top view of the evaporative cooling structure in a typical area of ​​a high-temperature wall of a spacecraft according to an embodiment of the present invention.

[0033] Among them, 1. inlet; 2. water storage tank; 3. rectifier plate; 4. water absorption layer; 5. fixed bracket bottom plate; 6. cross-scale porous medium unit; 61. skeleton; 62. macropore; 63. mesopore; 64. small pore; 7. fixed bracket; 8. first channel; 9. second channel. DETAILED DESCRIPTION

[0034] The technical solution adopted by the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0035] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0036] like Figures 1 to 3 As shown, the present invention first provides a cross-scale porous media unit 6, which has a regular hexagonal structure. The design of the regular hexagonal structure can freely and flexibly meet the layout requirements of any infinitely large complex structure, efficiently fill the space, and through modular assembly, the cross-scale porous media unit 6 can be assembled infinitely in space, and an evaporative cooling structure suitable for complex structures and large-area high-temperature components can be designed.

[0037] like Figure 4As shown, the cross-scale porous media unit 6 contains three types of pore structures: macropores 62, mesopores 63, and micropores 64. The macropores 62 in the cross-scale porous media unit 6 are randomly arranged. By manipulating their shape and pore structure characteristics (pore size, porosity, and pore density), the porous structure of the evaporative cooling system can be flexibly designed. Furthermore, cross-scale variations in pore size and porosity along any direction can be easily achieved for the evaporative cooling of complex high-temperature components.

[0038] In addition, if Figure 5 As shown, the pores 63 in the cross-scale porous media unit 6 are directionally distributed, which greatly simplifies the coolant flow path and enhances the liquid supply rate of the cooling system.

[0039] like Figure 6 As shown, a typical structure of high-efficiency evaporative cooling is designed using the cross-scale porous medium unit 6 provided by the present invention as an evaporative cooling carrier.

[0040] An evaporative cooling structure includes a rectifier plate 3, on top of which a water absorption layer 4 and a plurality of connectable modular cross-scale porous media units 6 are sequentially laid, a fixed bracket base plate 5 is provided between each cross-scale porous media unit 6 and the water absorption layer 4, a plurality of first channels 8 are arranged on the rectifier plate 3, a plurality of second channels 9 are arranged on the fixed bracket base plate 5, a water storage tank 2 is provided below the rectifier plate 3, and an inlet 1 is provided at the bottom of the water storage tank 2.

[0041] The cross-scale porous media unit 6 is a regular hexagonal structure. Multiple cross-scale porous media units 6 can be assembled modularly. The pore size, porosity, channel size, etc. of each modular unit can be independently designed, thereby realizing local flow adjustment of the evaporative cooling structure under non-uniform heat load.

[0042] Multiple modular cross-scale porous media units 6 with regular hexagonal structures can be freely and flexibly spliced ​​into various shapes to meet the layout requirements of any infinitely large and complex structure and improve space filling efficiency.

[0043] The cross-scale porous media unit 6 includes a skeleton 61, in which a number of mutually interpenetrating large pores 62 are arranged. The large pores 62 are randomly arranged to ensure unobstructed steam discharge. The skeleton 61 is provided with cross-scale pores, which are respectively mesopores 63 designed to enhance the system liquid supply rate and distributed from the fixed bracket bottom plate 5 to the outer surface of the cross-scale porous media unit 6, and small pores 64 that provide capillary force.

[0044] The diameter of the mesopore 63 is between the diameters of the macropore 62 and the small pore 64 .

[0045] The skeleton 61 of the cross-scale porous media unit 6 takes a G-type TPMS structure as an example, and the skeleton 61 can be designed as other TPMS types and other arbitrary geometric shapes.

[0046] The capillary force of the small pores 64 in the cross-scale porous media unit 6 can draw the coolant from the water absorption layer 4 to the surface of the cross-scale porous media unit 6 without requiring additional power.

[0047] The cross-scale porous medium unit 6 is vertically fixedly connected to the fixed support base plate 5 via a fixed support 7 .

[0048] The water-absorbing layer 4 is filled with hydrophilic stacked fiber material.

[0049] Example

[0050] This embodiment takes the thermal protection of the high-temperature wall of a manned spacecraft as an example, and selects a typical area of ​​the side wall as the implementation object. The schematic diagram of the typical area structure is as follows: Figure 7 As shown. Using the cross-scale porous medium unit 6 provided by the present invention as the evaporative cooling carrier, a typical structure of efficient evaporative cooling is designed, such as Figure 8 As shown. The coolant flows from the inlet 1 into the water storage tank 2, and then enters the water absorption layer 4 through several first channels 8 on the rectifier plate 3. The water absorption layer 4 is filled with hydrophilic stacked fiber materials and has extremely strong capillary force. It can continuously draw the coolant in the water storage tank 2 to the water absorption layer 4 without any additional power; a number of second channels 9 are arranged on the bottom plate 5 of the fixed bracket, and a plurality of cross-scale porous media units 6 use capillary force to draw water in the water absorption layer 4 to the surface of the cross-scale porous media unit 6. The plurality of cross-scale porous media units 6 are assembled and fixed in modules through a plurality of fixed brackets 7. A heat load is applied to the outer surface of the cross-scale porous media unit 6, and the coolant in the pores absorbs heat and undergoes a gas-liquid phase change to become steam and is carried away by the outflow, thereby playing a cooling role. When a gradient heat load is applied to the outer surface of the cross-scale porous media unit 6, the pore size of the module composed of the plurality of cross-scale porous media units 6 changes gradiently along the x-axis direction, and the assembly effect is as shown in FIG. Figure 9 As shown, the coolant supply uniformity is improved under non-uniform heat load conditions.

[0051] The cross-scale porous media unit 6 and modular design concept provided by the present invention can easily realize the customization of pore structure characteristics and the preparation and installation of complex structures and large-scale evaporative cooling structures, while maximizing the working range and minimizing the consumption of primary energy, which is conducive to the integration of space and system. The cross-scale porous structure evaporative cooling technology breaks through the cooling limit of traditional evaporative cooling technology. At the same time, no additional pump is required for precise flow control and distribution, realizing fluid flow regulation, greatly reducing the system load and improving energy utilization efficiency.

[0052] The working principle of the present invention is:

[0053] The coolant flows into the water storage tank 2 from the inlet 1, and then enters the water absorption layer 4 through several first channels 8 on the rectifier plate 3. The water absorption layer 4 is filled with hydrophilic stacked fiber materials and has extremely strong capillary force, which can continuously draw the coolant in the water storage tank 2 to the water absorption layer 4 without any additional power; several second channels 9 are arranged on the bottom plate 5 of the fixed bracket, and the cross-scale porous medium unit 6 uses capillary force to draw water in the water absorption layer 4 through several second channels 9 arranged on the bottom plate 5 of the fixed bracket to the surface of the cross-scale porous medium unit 6, and the cross-scale porous medium unit 6 is fixed by the fixed bracket 7; a heat load is applied to the outer surface of the cross-scale porous medium unit 6, and the coolant in the pores absorbs heat, undergoes a gas-liquid phase change, and turns into steam and is carried away by the outflow, thereby playing a cooling role.

Claims

1. An evaporative cooling structure, characterized in that: The invention comprises a rectifier plate (3), wherein a water absorption layer (4) and a plurality of modular cross-scale porous media units (6) that can be spliced ​​are sequentially laid on the rectifier plate (3), a fixed bracket bottom plate (5) is provided between each cross-scale porous media unit (6) and the water absorption layer (4), a plurality of first channels (8) are arranged on the rectifier plate (3), a plurality of second channels (9) are arranged on the fixed bracket bottom plate (5), a water storage tank (2) is provided below the rectifier plate (3), and an inlet (1) is provided at the bottom of the water storage tank (2).

2. The evaporative cooling structure according to claim 1, characterized in that: The cross-scale porous media unit (6) is a regular hexagonal structure, and a plurality of cross-scale porous media units (6) can be assembled in a modular manner. The pore size, porosity, and channel size of each modular unit can be independently designed, thereby realizing local flow adjustment of the evaporative cooling structure under non-uniform heat load.

3. An evaporative cooling structure according to claim 1 or 2, characterized in that: The cross-scale porous medium unit (6) includes a skeleton (61), a plurality of mutually interpenetrating macropores (62) are arranged in the skeleton (61), and the macropores (62) are randomly arranged. The skeleton (61) is provided with cross-scale pores, which are a plurality of mesopores (63) and a plurality of small pores (64), and the plurality of mesopores (63) are distributed in a direction.

4. The evaporative cooling structure according to claim 3, characterized in that: The plurality of directionally distributed mesopores (63) are distributed from the fixed support bottom plate (5) to the outer surface of the cross-scale porous medium unit (6).

5. The evaporative cooling structure according to claim 3, characterized in that: The diameter of the mesopore (63) is between the diameters of the macropore (62) and the micropore (64).

6. The evaporative cooling structure according to claim 1, characterized in that: The cross-scale porous medium unit (6) is fixedly connected to the fixed bracket bottom plate (5) via a fixed bracket (7).

7. The evaporative cooling structure according to claim 1, characterized in that: The water-absorbing layer (4) is filled with hydrophilic stacked fiber material.

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