A liquid storage filter for a heat pump system suitable for microgravity conditions

Abstract

The invention discloses a liquid storage filter for a heat pump system suitable for microgravity conditions, which is composed of a body, a plugging cover, a wire mesh sintered filter element and a "petal" shaped wire mesh, wherein the wire mesh sintered filter element adopts a "sandwich" shaped sandwich structure, the innermost side is a skeleton structure, which ensures that the filter element has a certain strength and rigidity; the outermost side is a filter layer, which has the functions of gas blocking liquid passing, capillary adsorption, etc.; between the skeleton structure and the filter layer is a transition layer, which connects the inner and outer structures to ensure the continuity of capillary suction; its "petal" shaped wire mesh is also composed of a skeleton layer and a filter layer, the skeleton layer ensures that the wire mesh has a certain rigidity, and the filter layer has the functions of gas blocking liquid passing, capillary adsorption, etc. The present invention can realize liquid passing gas blocking and impurity filtering under microgravity conditions.

Description

Technical Field

[0001] The present invention relates to the field of spacecraft thermal control technology, and in particular to a liquid storage filtration technology for a heat pump system under microgravity conditions. Background Art

[0002] As the heat consumption of spacecraft continues to increase, the demand for heat dissipation capacity of thermal control systems is getting higher and higher. Existing thermal control methods (typical heat pipes, pump-driven fluid loops, etc.) can no longer meet the demand for dissipating large heat consumption. If heat pump technology is introduced to increase the temperature of the radiator, the required area of ​​the radiator can be greatly reduced.

[0003] A heat pump is a device that transfers heat from a heat source to a heat sink (radiator). It is currently very mature in the ground refrigeration industry. However, using it in a space microgravity environment will bring a series of problems. The most core problem is the management of oil, gas, and liquid in the heat pump system under a microgravity environment. The reservoir of the heat pump system is the most affected. In a ground gravity environment, the mixture of oil and liquid working fluid in the reservoir is always located at the bottom of the reservoir, while the gaseous working fluid is always located at the top of the reservoir. Under the action of gravity, the liquid working fluid and the gaseous working fluid can be easily separated, thereby ensuring that the working fluid entering the expansion valve downstream of the reservoir does not contain gas. However, in a microgravity environment, the gaseous working fluid will be concentrated in the middle part of the reservoir, and the liquid working fluid will gather on the wall of the reservoir. The reservoir will lose the gas-liquid separation function, which will cause the gaseous working fluid to enter the expansion valve, causing a serious decrease in the system's cooling capacity. Therefore, it is necessary to develop a reservoir suitable for a microgravity environment.

[0004] At present, there are some patents and solutions related to liquid reservoirs for space two-phase fluid circuits, such as 200810076728.7 "Liquid collection and gas-liquid isolation device under microgravity conditions", 200810076772.8 "Gas and liquid collection device under microgravity conditions", 201910605763.1 "A visual microgravity gas capture test device", 200910123860.3 "A compensator for space fluid circuits", etc. These patents and solutions are all proposed for space two-phase fluid systems. Their structural form is a single-port form (equivalent to being connected in parallel to the fluid circuit). Their main function is to discharge the liquid working medium in the liquid reservoir through the capillary force principle when the fluid circuit is short of liquid. This is significantly different from the liquid reservoir used in the heat pump system. First, the liquid reservoir used in the heat pump system is a dual-port type, connected in series to the system, with its inlet connected to the outlet of the condenser and its outlet connected to the inlet of the electronic expansion valve; second, during the operation of the heat pump system, the inside of the liquid reservoir is not static, but high-speed fluid is constantly entering and flowing out, and its internal gas-liquid interface is very complex; finally, in addition to the liquid storage function, the liquid reservoir used in the heat pump system must also have the function of gas-liquid separation, and must be able to prevent gas from entering the downstream expansion valve. In summary, there are significant differences between the liquid reservoir used in the heat pump system and the liquid reservoir used in the two-phase fluid circuit, especially in the microgravity environment of space.

[0005] At present, there are no application examples of heat pump systems in space environments at home and abroad, and research on space heat pump systems is also relatively rare. Most of the literature was proposed during the manned moon landing in the United States in the 1960s. As for liquid storage filters for heat pumps suitable for microgravity environments, no relevant literature has been found. Summary of the invention

[0006] In view of this, the present invention provides a design scheme for a liquid storage filter for a heat pump system, which can achieve liquid-to-gas blocking and impurity filtering under microgravity conditions, and match the application of the heat pump system in a space environment.

[0007] The present disclosure provides a liquid storage filter for a heat pump system suitable for microgravity conditions, comprising: a body, a plugging cover, a wire mesh sintered filter element and a "petal" shaped wire mesh; wherein:

[0008] The plugging cover is located at the bottom end of the body and is connected to the body to form a closed space for liquid storage and filtration, while providing an outlet for the liquid storage filter;

[0009] The wire mesh sintered filter element is a multi-layer stainless steel wire mesh sintered together and rolled into a cylindrical shape. One end is sealed and connected to the plugging cover. It is used for passing liquid and blocking gas. At the same time, it has a certain strength and rigidity to provide support for the "petal" shaped wire mesh.

[0010] The "petal"-shaped wire mesh is a stainless steel wire mesh that surrounds the periphery of the filter element in a petal-like form, with the outer surface in contact with the inner wall of the body, and is used to capture the wall liquid and transport it to the wire mesh sintered filter element.

[0011] Furthermore, the body is integrated with an inlet, a pressure sensor interface, a pressure relief valve interface, and an observation window, wherein: the inlet is in the form of a plunger joint commonly used in the aerospace field, and the pressure sensor interface and the pressure relief valve interface are interchangeable universal interfaces.

[0012] Furthermore, the main part of the wire mesh sintered filter element adopts a "sandwich" structure, the innermost side of which is a skeleton structure to ensure that the filter element has a certain strength and rigidity; the outermost side is a filter layer, which has the functions of blocking gas and liquid, capillary adsorption, etc.; there is a transition layer between the skeleton structure and the filter layer, connecting the inner and outer layers to ensure the continuity of capillary suction.

[0013] Furthermore, the skeleton structure is sintered by several layers of stainless steel wire mesh below 100 mesh; the filter layer is sintered by several layers of stainless steel wire mesh above 500 mesh; the transition layer is a mixed weave of multiple layers of stainless steel wire mesh of 100-300 mesh.

[0014] Furthermore, the wire mesh sintered filter element adopts a segmented structure, including a top cone, a sintered wire mesh body and a joint which are connected in sequence; wherein the sintered wire mesh body is the main part of the filter element, and the joint and the top cone are used to fix the filter element in the liquid storage filter body.

[0015] Furthermore, the "petal" shaped wire mesh consists of two parts: a skeleton layer and a filter layer, wherein the skeleton layer adopts a single 100-mesh wire mesh to ensure that the "petal" shaped wire mesh has a certain rigidity; the filter layer adopts a wire mesh of the same specification as the filter layer in the wire mesh sintered filter element, and the size is slightly larger than the skeleton layer wire mesh size.

[0016] Furthermore, the plugging cover and the body, as well as the three parts of the wire mesh sintered filter element, are connected by vacuum electron beam welding.

[0017] The present disclosure also provides a method for manufacturing a main body of a wire mesh sintered filter element applied to the above-mentioned liquid storage filter, comprising the following steps:

[0018] Several layers of stainless steel wire mesh with mesh size below 100 are sintered to form the innermost skeleton structure;

[0019] Several layers of stainless steel wire mesh with mesh size of 500 or above are sintered to form the outermost filter layer;

[0020] A transition layer between the skeleton structure and the filter layer is formed by mixing multiple layers of stainless steel wire mesh with mesh sizes of 100 to 300;

[0021] Finally, the multiple layers of stainless steel mesh are sintered together and then rolled and welded. After welding, the size is ensured by wire cutting.

[0022] The specific number of layers and mesh size of the filter layer are calculated based on the physical properties of the working fluid stored in the liquid storage filter and the working parameters, with the flow resistance formed by the working fluid flowing through the capillary structure being no greater than the bubbling pressure as the basic criterion.

[0023] The present disclosure also provides a method for manufacturing a "petal"-shaped wire mesh applied to the above-mentioned liquid storage filter, comprising the following steps:

[0024] Place the skeleton layer screen in the middle, and use the filter layer screen to wrap around the skeleton layer screen. Wrap 3 layers on one side and fold them. Perform dense spot welding to fix the folding points.

[0025] At the same time, the left and right sides of the filter screen are folded 20mm each for hemming to prevent burrs on the edge of the screen, and then intensive spot welding is performed to fix it;

[0026] Spot weld at larger intervals at other locations where spot welding is not dense, so that the 7 layers of wire mesh form a whole;

[0027] The wire mesh plate is folded into a "petal" shape, and the root of each "petal" is spot welded to the wire mesh sintered filter element, and it is necessary to ensure that each "petal" is in close contact with the inner wall of the liquid storage filter to ensure smooth liquid passage.

[0028] Furthermore, the distance between the welding points of the dense spot welding is 10 mm;

[0029] At the locations where spot welding is not done densely, the distance between welding spots is 50 mm.

[0030] Compared with the existing ground heat pump system liquid storage device, the beneficial effects of the present disclosure are:

[0031] (1) When the heat pump system is shut down, the liquid working medium inside the liquid storage filter tends to be distributed on the solid wall under microgravity. Under the capillary force of the "petal"-shaped wire mesh and the wire mesh sintered filter element, the liquid working medium on the wall can be sucked into the wire mesh sintered filter element. At the moment the heat pump system is turned on, the electronic expansion valve is slightly opened, and a low-pressure area is formed at the outlet of the liquid storage filter under the suction effect of the compressor. The liquid working medium gathered inside the filter element can flow smoothly into the compressor under the action of the pressure difference, ensuring stable liquid supply at the moment of startup.

[0032] (2) During the continuous operation of the heat pump system, a continuous gas-liquid mixture enters the liquid storage filter. The gas-liquid interface at rest is difficult to maintain. The entire liquid storage filter is in a gas-liquid mixed state, and a large number of small bubbles appear. When the gas-liquid mixture hits the "petal"-shaped wire mesh and the wire mesh sintered filter element, the wire mesh will capture the liquid medium. Under the action of capillary force, the liquid medium gradually moves toward the inside of the filter element. At the same time, a meniscus is formed at the wire mesh interface to prevent the entry of the gaseous medium and achieve the separation of the gas-liquid medium.

[0033] (3) The internal filter element of the liquid storage filter is made of sintered wire mesh. Multiple layers of wire mesh are sintered together and rolled into a cylindrical shape, which not only enables it to have the function of wire mesh passing liquid and blocking gas, but also has a certain strength and rigidity to provide support for the "petal" shaped wire mesh;

[0034] (4) Low cost, stable processing technology and good versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The figure is a schematic structural diagram of an exemplary embodiment of a liquid storage filter of a heat pump system suitable for microgravity.

[0036] Figure 2 It is a schematic diagram of the cross-sectional structure of the liquid storage filter.

[0037] Figure 3 This is a schematic diagram of the structure of a wire mesh sintered filter element.

[0038] Figure 4 Schematic diagram of the spot welding position of the "petal" shaped wire mesh.

[0039] Figure 5 It is a schematic diagram of the cross-sectional structure of a "petal" shaped wire mesh. DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0041] Figure 1 This is a schematic structural diagram of an exemplary embodiment of a liquid storage filter for a heat pump system suitable for microgravity according to the present disclosure. Figure 2 is a cross-sectional view of the liquid storage filter, the liquid storage filter comprises:

[0042] Main body 1, plug cover 2, wire mesh sintered filter element 3 and "petal" shaped wire mesh 4. Among them:

[0043] The body 1 is the main pressure-bearing part of the liquid storage filter, and the wall thickness is calculated according to the maximum working pressure of the heat pump system. The body 1 integrates the inlet, pressure sensor interface, pressure relief valve interface and observation window. The inlet is a plunger joint commonly used in the aerospace field, and the pressure sensor and pressure relief valve interface are interchangeable and universal. The pressure sensor is installed to monitor the pressure level inside the liquid storage filter, and it also serves as the maximum pressure point of the entire heat pump system (the pressure value here is approximately equal to the compressor exhaust pressure value); the pressure relief valve is installed to ensure the safety of the liquid storage filter. When the internal pressure of the liquid storage filter exceeds 2 times the maximum working pressure, the pressure relief valve is opened to quickly unload the internal pressure of the liquid storage filter. A sapphire observation window is designed on the side of the body 1 close to the plug cover 2. It has two functions. One is to observe the stock of the working fluid inside the liquid storage filter, and the other is to observe the distribution and operation of the gas and liquid inside the liquid storage filter during the operation of the heat pump system (it can be photographed with a high-speed camera).

[0044] The plugging cover 2 is mainly connected to the main body 1 by vacuum electron beam welding to form a closed space, and provides an outlet for the liquid storage filter to be connected to the downstream electronic expansion valve.

[0045] The wire mesh sintered filter element 3 is the core component of the liquid storage filter, which is the key to realize the liquid supply when the heat pump system is started and the gas-liquid separation when it is running, and is sealed with the plug cover 2. Figure 3 As shown, a segmented structure is adopted, including three parts: a top cone, a sintered wire mesh body and a joint, and the three parts are connected by vacuum electron beam welding.

[0046] Among them, the sintered wire mesh adopts a "sandwich" sandwich structure:

[0047] The innermost layer is a skeleton structure, preferably sintered with several layers of stainless steel wire mesh below 100 mesh, to ensure that the filter element has a certain strength and rigidity after molding;

[0048] The outermost layer is a filter layer, which is preferably made of several layers of 500 mesh or more stainless steel wire mesh sintered together. As the core working layer of the filter element, it has the functions of gas-liquid blocking and capillary adsorption. The specific number of layers and meshes needs to be calculated based on the physical properties (surface tension, viscosity, etc.) of the working fluid stored in the liquid storage filter and the working parameters (temperature, flow rate, etc.). The basic judgment criterion is that the flow resistance formed by the working fluid flowing through the capillary structure is not greater than the bubbling pressure.

[0049] Between the skeleton structure and the filter layer is a transition layer made of 100-300 mesh multi-layer stainless steel wire mesh, which connects the inner and outer layers to ensure the continuity of capillary suction.

[0050] Finally, the multiple layers of stainless steel mesh are sintered together and then rolled into a circle for welding. After welding, wire cutting is used to ensure the size.

[0051] The "petal" shaped wire mesh 4 is also a core component of the liquid storage filter, and its main function is to capture the wall liquid and transport it to the wire mesh sintered filter element 3. Figure 5 As shown, it is also composed of two parts: a skeleton layer and a filter layer. The skeleton layer adopts a single 100-mesh wire mesh to ensure that the "petal"-shaped wire mesh 4 has a certain rigidity; the filter layer adopts a wire mesh of the same specification as the filter layer in the wire mesh sintered filter element 4, and the size is slightly larger than the skeleton layer wire mesh size.

[0052] When making the screen, first place the skeleton screen in the middle, use the filter screen to wrap around the skeleton screen, wrap 3 layers on one side and fold, then follow the steps Figure 4 The middle spot welding position is spot welded intensively (the distance between the welding points is about 10mm); at the same time, the left and right sides of the filter screen are folded 20mm for hemming to prevent burrs on the edge of the screen, and then spot welded intensively (the distance between the welding points is about 10mm); other positions that are not spot welded intensively are spot welded with larger intervals (the distance between the welding points is about 50mm) to form the 7 layers of screen into a whole. Finally, the spot welded screen plate is placed according to Figure 5 The style is folded into a "petal" shape, and the root of each "petal" is fixed to the wire mesh sintered filter element by 3 spot welding, and it is necessary to ensure that each "petal" is in close contact with the inner wall of the liquid storage filter to ensure smooth liquid passage.

[0053] In order to further understand the present invention, the microgravity adaptability of the liquid storage filter is explained. In a microgravity environment, the gas-liquid two-phase distribution is that the liquid phase tends to gather at the solid wall surface, and the gas phase tends to gather at the center position. Conventional liquid storage filters cannot supply liquid or contain a large number of bubbles in the liquid supply under a microgravity environment due to the obstruction of bubbles. Since the liquid storage filter in the present invention is provided with a wire mesh sintered filter element 3 and a "petal"-shaped wire mesh 4, the liquid phase gathered on the wall surface will be captured by the "petal"-shaped wire mesh 4 under the action of capillary force, and the liquid phase will be transported to the outer filter layer of the wire mesh sintered filter element 3 through the connected wire mesh. When the heat pump system is turned on, a low-pressure area will be formed downstream of the liquid storage filter, and the liquid phase captured in the wire mesh will enter the downstream of the liquid storage filter under the action of the pressure difference to form a liquid supply. Through the reasonable design of the number of wire mesh layers and mesh counts, it is ensured that the capillary force in the wire mesh is greater than the flow resistance, so that the liquid storage filter can form a continuous liquid supply.

[0054] In order to further understand the present invention, the preferred design scheme of the wire mesh sintered filter element 3 and the "petal" shaped wire mesh 4 of the liquid storage filter is described. For a heat pump system with a cooling capacity of 2.5kW, an evaporation temperature of 5°C, and a condensation temperature of 70°C, the stainless steel wire mesh specifications of the wire mesh sintered filter element 3 and the "petal" shaped wire mesh 4 of the liquid storage filter are shown in Tables 1 and 2.

[0055] Table 1 Wire mesh sintered filter element 3 wire mesh specifications (from inside to outside)

[0056]

[0057] Table 2 "petal" shaped screen 4 screen specifications

[0058]

[0059]

[0060] The resistance through the wire mesh is calculated by the following formula

[0061]

[0062] Among them: μ is the dynamic viscosity of the working fluid, ΔL is the flow length, m is the mass flow rate, K is the wire mesh permeability, A is the cross-sectional area of ​​the working fluid flowing through the wire mesh, and ρ is the working fluid density.

[0063] The formula for calculating screen permeability is:

[0064]

[0065] Among them, d is the wire diameter of the wire mesh; t is the grid spacing (the sum of the wire diameter and the aperture).

[0066] The capillary driving force of the screen is calculated as follows:

[0067]

[0068] Among them, σ is the surface tension, θ is the contact angle, and r is the radius of the mesh.

[0069] In the above preferred design scheme, the calculated total resistance of the wire mesh is 421.30Pa, and the calculated capillary driving force of the wire mesh sintered filter element 3 is 454.29Pa, which is greater than the total resistance of the wire mesh. Therefore, the preferred design scheme can achieve gas-liquid separation and continuous liquid supply under microgravity conditions.

[0070] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A liquid storage filter for a heat pump system suitable for microgravity conditions, characterized in that: include: Body, plugging cover, wire mesh sintered filter element and "petal" shaped wire mesh, of which: The plugging cover is located at the bottom end of the body and is connected to the body to form a closed space for liquid storage and filtration, while providing an outlet for the liquid storage filter; The wire mesh sintered filter element is a multi-layer stainless steel wire mesh sintered together and rolled into a cylindrical shape. One end is sealed and connected to the plug cover. It is used for passing liquid and blocking gas. At the same time, it has a certain strength and rigidity to provide support for the "petal" shaped wire mesh. The "petal"-shaped wire mesh is a stainless steel wire mesh that surrounds the periphery of the filter element in a petal-like form, and the outer surface contacts the inner wall of the body, and is used to capture the wall liquid and transport it to the wire mesh sintered filter element; The main part of the wire mesh sintered filter element adopts a "sandwich" sandwich structure, the innermost side of which is a skeleton structure to ensure that the filter element has a certain strength and rigidity; the outermost side is a filter layer, which has the functions of gas barrier and liquid permeability and capillary adsorption; between the skeleton structure and the filter layer is a transition layer, which connects the inner and outer layers to ensure the continuity of capillary suction; The "petal" shaped wire mesh consists of two parts: a skeleton layer and a filter layer. The skeleton layer adopts a single 100-mesh wire mesh to ensure that the "petal" shaped wire mesh has a certain rigidity. The filter layer adopts a wire mesh of the same specification as the filter layer in the wire mesh sintered filter element, and its size is slightly larger than that of the skeleton layer wire mesh.

2. The liquid storage filter according to claim 1, characterized in that: The body is integrated with an inlet, a pressure sensor interface, a pressure relief valve interface, and an observation window, wherein the inlet is in the form of a plunger joint in the aerospace field, and the pressure sensor interface and the pressure relief valve interface are interchangeable universal interfaces.

3. The liquid storage filter according to claim 1, characterized in that: The skeleton structure is sintered by several layers of stainless steel wire mesh below 100 mesh; the filter layer is sintered by several layers of stainless steel wire mesh above 500 mesh; the transition layer is mixed and woven by multiple layers of stainless steel wire mesh of 100-300 mesh.

4. The liquid storage filter according to claim 1 or 3, characterized in that: The wire mesh sintered filter element adopts a segmented structure, including a top cone, a sintered wire mesh body and a joint which are connected in sequence; wherein the sintered wire mesh body is the main part of the filter element, and the joint and the top cone are used to fix the filter element in the liquid storage filter body.

5. The liquid storage filter according to claim 1, characterized in that: The plugging cover and the body, as well as the three parts of the wire mesh sintered filter element, are all connected by vacuum electron beam welding.

6. A method for manufacturing a main body of a wire mesh sintered filter element used in a liquid storage filter according to any one of claims 1 to 5, comprising the following steps: Several layers of stainless steel wire mesh with mesh size below 100 are sintered to form the innermost skeleton structure; Several layers of stainless steel wire mesh with mesh size of 500 or above are sintered to form the outermost filter layer; A transition layer between the skeleton structure and the filter layer is formed by mixing multiple layers of stainless steel wire mesh with mesh sizes of 100 to 300; Finally, the multiple layers of stainless steel mesh are sintered together and then rolled and welded. After welding, the size is ensured by wire cutting. The specific number of layers and mesh size of the filter layer are calculated based on the physical properties of the working fluid stored in the liquid storage filter and the working parameters, with the flow resistance formed by the working fluid flowing through the capillary structure being no greater than the bubbling pressure as the basic criterion.

7. A method for making a "petal" shaped wire mesh used in the liquid storage filter according to any one of claims 1 to 5, comprising the following steps: Place the skeleton layer screen in the middle, and use the filter layer screen to wrap around the skeleton layer screen. Wrap 3 layers on one side and fold them. Perform dense spot welding to fix the folding points. At the same time, the left and right sides of the filter screen are folded 20mm each for edge wrapping to prevent burrs on the edge of the screen, and then dense spot welding is performed to fix it; Spot welding is performed at other locations where spot welding is not densely performed, so that the 7 layers of wire mesh are formed into a whole; Fold the wire mesh plate into a "petal" shape, and fix the root of each "petal" to the wire mesh sintered filter element by spot welding. Make sure that each "petal" is in close contact with the inner wall of the liquid storage filter to ensure smooth liquid passage.

8. The method according to claim 7, characterized in that The distance between the welding points of the dense spot welding is 10 mm; the distance between the welding points at the position without dense spot welding is 50 mm.

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