A method for manufacturing a large heat exchange capacity low flow resistance low temperature helium cabin

Abstract

The application discloses a method for manufacturing a large-heat-exchange-capacity low-flow-resistance low-temperature helium cabin, which comprises radiation red copper plates, red copper cooling coil pipes and a helium cabin support, the interior of the radiation red copper plate of the helium cabin is sprayed with special low-temperature black paint to make the internal emissivity greater than 0.92, and the radiation efficiency is greatly improved, the red copper cooling coil pipe adopts three-branch flow parallel cooling of the radiation red copper plate of the helium cabin, the temperature rise of the cooling helium flow is reduced, and the temperature difference of the whole helium cabin is very small, the low-temperature freezing red copper pipe bending process of the special equipment is adopted to ensure that the cooling coil pipe is not concave and wrinkled, the cooling helium flow resistance meets the requirements, the optimized low-temperature tin soldering welding process and the use of red copper pressing sheets and special aluminum foils greatly improve the heat transfer area and ensure the heat transfer efficiency.

Description

Technical Field

[0001] This invention relates to the fields of cryogenic vacuum and aerospace technology, and mainly to a method for manufacturing a cryogenic helium chamber with high heat exchange and low flow resistance. Background Technology

[0002] In scientific research and aerospace fields, instruments and equipment need to operate in extremely low-temperature vacuum environments. Therefore, a 20K cryogenic helium-helium chamber needs to be designed. The helium chamber cools the instruments and equipment to 100K through radiative heat transfer, while the enormous heat generated by the equipment must be absorbed and carried away by the helium chamber through radiative heat transfer. The helium chamber consists of five radiative cooling screens, each constructed by cryogenic soldering of a copper plate and cooling coils. The cooling screens are suspended from a support frame by bolts. The overall structure is shown in [reference needed]. Figure 1 The instruments and equipment are placed inside the helium chamber, which is then contained within a vacuum container. The coil contains a cryogenic helium flow, supplied by a cryogenic helium refrigerator through cryogenic cooling pipes. The temperature of the cryogenic helium chamber is controlled by the cryogenic helium flow; the principle of the entire system is explained in [link to system description]. Figure 2 .

[0003] The temperature of the instruments is 100K, which is 20K higher than the temperature of the helium chamber's cold shield. In a vacuum environment, the heat generated by the instruments is absorbed by the copper plate of the helium chamber through radiative heat transfer. The copper plate then transfers the heat to the cooling coils, where it is carried away by the cryogenic helium flow. The entire helium chamber is suspended on a helium chamber support frame. To reduce heat conduction, insulating gaskets are designed between the helium chamber and the support frame, and between the support frame and the base.

[0004] Meanwhile, the instrumentation requires uniform temperature and small temperature difference throughout the helium chamber. Therefore, the cooling coil uses multiple parallel streams to cool the helium chamber. This way, after the low-temperature helium stream is heated, the temperature difference between the inlet and outlet is very small. The optimal cooling process and cooling flow rate need to be calculated through flow rate calculation.

[0005] In addition, the allowable flow resistance of the cooling helium flow provided by the helium refrigerator is <0.1 bar, which places high demands on the manufacturing of the cooling coil. Each cooling path uses a single tube to reduce the resistance generated by the joints. The bends must be smooth and free of wrinkles and dents, which places high demands on the copper tube bending process and is very difficult.

[0006] Due to the enormous heat generated by the equipment (maximum 500W), ensuring that heat is transferred to the copper plate of the helium chamber via radiation requires significantly improving the radiation heat transfer efficiency. Ensuring that the heat absorbed by the copper plate is transferred to the copper tube and further to the cooling helium flow requires optimizing the welding process to increase the soldering area, while simultaneously employing multiple methods to maximize the heat transfer area between the copper tube and the copper plate. Summary of the Invention

[0007] This invention provides a method for manufacturing a cryogenic helium chamber with high heat exchange and low flow resistance. It details the manufacturing process of each stage of production and manufactures a cryogenic helium chamber that meets the special application requirements of aerospace and cryogenic vacuum fields.

[0008] This invention is achieved through the following technical solution:

[0009] A method for manufacturing a cryogenic helium chamber with high heat exchange and low flow resistance includes the following steps:

[0010] (1) Calculate the pipe resistance based on the heat load and the required cooling flow rate, and determine the number of parallel cooling pipes;

[0011] (2) Based on the cooling pipe and integral plate welding pipe section diagram, establish a heat transfer model to check whether the inlet and outlet temperature difference meets the design requirements;

[0012] (3) Determine the pipe length and cooling pipe flow according to the design, cut the copper plates according to the size requirements, braze and splice them, and level them.

[0013] (4) Clean and degrease the copper tubes and copper plates, clamp them with a clamp, and use a copper pressure plate to intermittently rivet the cooling copper tubes and copper plates together. Then, use the method of sectional vertical welding to perform low-temperature soldering.

[0014] (5) The helium chamber support is assembled on the fitter's platform according to the dimensions, and then the helium chamber cold shield is installed on the helium chamber support;

[0015] (6) Apply a special low-temperature black paint coating to the inside of the helium chamber to increase the emissivity of the copper plate.

[0016] Furthermore, in step (1), in order to ensure that the flow resistance of the cooling helium flow from the refrigerator is <0.1 bar, the resistance of multiple flow streams is calculated.

[0017] Furthermore, in step (3), it is determined that a three-stream cooling helium chamber is used, a jointless copper tube is used as a cooling plate, and a low-temperature freezing method is used to bend the cooling plate.

[0018] Furthermore, in step (4), the copper tube is straightened and cut, and then bent according to the size requirements using a special low-temperature freezing platform.

[0019] Furthermore, in step (5), the entire helium chamber cold screen consists of 5 pieces, and the copper pipes between them are welded together using stainless steel flexible tubing; then, vacuum helium mass spectrometry leak detection is performed to ensure that there is no leakage at the weld.

[0020] Furthermore, in step (5), an insulating pad is installed between the helium chamber cold shield and the support.

[0021] Furthermore, in step (6), aluminum foil is affixed to the outside of the helium chamber.

[0022] To ensure a large heat exchange rate, the following measures are taken:

[0023] 1. Apply low-temperature F952 black paint to the inside of the helium chamber's cold shield. The process is as follows:

[0024] a. Protect the pre-sprayed objects as required.

[0025] b. After cleaning the pre-sprayed helium chamber with acetone or aviation gasoline, allow its surface to air dry.

[0026] c. Shake the F952 heat-sinking black paint for 30 minutes to ensure it is well mixed. After the surface has dried or been oven-dried, spray the paint, ensuring each coat does not produce runs. After each coat, allow the surface to dry (approximately 10-20 minutes) before applying the next coat, repeating this process 8-10 times. The black coating thickness should be controlled at 40-80 micrometers. Spraying is now complete.

[0027] d. Use a hot air blower to blow the surface for more than 3 hours.

[0028] The F952 low-temperature black paint applied to the helium chamber is not easy to peel off in a low-temperature environment of 20K. The helium chamber cold screen coated with low-temperature black paint becomes a high-emissivity plate. After professional testing, the reflectivity is >0.92. This greatly improves the radiation heat transfer efficiency and ensures that the heat of the instrument equipment, up to 500W, can be absorbed by the copper plate of the helium chamber cold screen through radiation heat transfer.

[0029] 2. To ensure heat conduction between the copper plate and the copper tube, copper clamping sheets are first used to rivet the copper tube and copper plate together, ensuring a tight fit. Secondly, the low-temperature soldering process for the copper tube and copper plate is optimized to prevent cold solder joints. A sectional vertical soldering method is adopted (see...). Figure 3 Using a clamp to hold the copper plate upright, after welding one side of the copper tube, we flip it over and weld the other side, trying to fill the gap between the copper tube and the copper plate with solder. Finally, after welding, we apply a layer of special aluminum foil to the entire cold shield (see...). Figure 4 This further greatly increases the heat transfer area between the copper tube and the copper plate.

[0030] 3. To ensure the cooling helium flow resistance from the refrigeration unit is <0.1 bar and the temperature difference is small, we first calculated the resistance of multiple flow streams, then performed model analysis to confirm that the temperature difference met the requirements. Finally, we determined to use a three-stream cooling helium chamber, employing DN25X1.5mm seamless copper tubing as the cooling coil. The cooling coil was bent using a tube bending machine with a cryogenic freezing method (see...). Figure 5 This avoids dents and wrinkles in the coil, thus preventing increased resistance.

[0031] 4. The helium chamber support is made of aluminum alloy profile, which is convenient for disassembly, assembly and transportation. G10 gaskets with extremely low thermal conductivity are designed between the support and the helium chamber, as well as between the support and the base, to reduce heat leakage.

[0032] 5. Due to the large size of the helium chamber, in order to ensure dimensional accuracy, the installation of the helium chamber support frame and the overall assembly of the helium chamber must be completed on a fitter's platform.

[0033] The advantages of this invention are:

[0034] 1. The interior of the helium chamber's cold shield is coated with a special low-temperature black paint using a special process, which improves the emissivity of the copper plate and makes large heat exchange possible.

[0035] 2. The soldering process was optimized by using copper plates and special aluminum foil to greatly increase the conduction area between the copper plate and the copper tube, thereby improving the heat transfer efficiency.

[0036] 3. The helium chamber is cooled by a multi-stream cooling system, and the cooling coils are bent using a cryogenic freezing method with specialized equipment. This achieves the performance requirements of the helium chamber with small temperature difference and low flow resistance. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the helium chamber structure of the present invention;

[0038] Figure 2 This is a schematic diagram of the helium chamber cooling system of the present invention;

[0039] Figure 3 This is a diagram illustrating the helium chamber cold screen soldering process of the present invention.

[0040] Figure 4 This is a diagram of the aluminum foil application for the helium chamber cooling screen of the present invention;

[0041] Figure 5 This is a diagram of the low-temperature freezing bending cooling coil of the present invention;

[0042] Figure 6 This is an overall assembly view of the helium chamber of the present invention.

[0043] In the diagram, 1-bracket, 2-cooling coil, 3-copper plate, 4-copper pressure plate. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0045] like Figure 1As shown, the entire helium chamber mainly includes a support frame 1, cooling coils 2, copper plates 3, and copper pressure plates 4. First, the cooling coils 2 are riveted to the copper plates 3 using the copper pressure plates 4. Then, the cooling coils 2 and copper plates 3 are soldered together (e.g., ...). Figure 3 This creates a helium chamber cold shield, which consists of five cold shields: front, rear, left, right, and top. Support 1 is assembled from 100x100 standard aluminum alloy profiles using detachable fasteners, and the cold shields are mounted on support 1 using detachable bolts.

[0046] Figure 2 This is a schematic diagram of the helium chamber cooling system of the present invention. Figure 2 As shown, the instruments and equipment are placed inside the helium chamber, which is itself housed in a vacuum container. The coil contains a cryogenic helium flow, supplied by a cryogenic helium refrigerator through cryogenic cooling pipes. The temperature of the cryogenic helium chamber is controlled by the cryogenic helium flow.

[0047] like Figures 3-6 As shown, the manufacturing process of a cryogenic helium chamber with high heat exchange and low flow resistance is as follows:

[0048] 1. Calculate the pipe resistance based on the heat load and required cooling flow rate to determine the number of parallel cooling pipes. Preferably, to ensure that the cooling helium flow resistance from the refrigerator is <0.1 bar, multi-stream flow resistance calculations are performed.

[0049] 2. Based on the sectional drawings of the cooling pipes and the welded pipes of the integral plate, establish a heat transfer model to verify whether the inlet and outlet temperature difference meets the design requirements.

[0050] 3. Determine the pipe length and cooling pipe flow according to the design. Cut copper plates to size requirements, braze and splice them, and level them. Straighten and cut the copper pipes, and use a special low-temperature freezing platform to bend them according to size requirements (e.g., ...). Figure 5 Preferably, a three-stream cooling helium chamber is used, with seamless copper tubing as the cooling plate, and the cooling plate is bent using a cryogenic freezing method.

[0051] 4. Clean and degrease the copper pipes and plates 3, clamp them with fixtures, and intermittently rivet the cooling copper pipes and plates together using copper pressure plates 4. Then, perform low-temperature soldering using a sectional vertical welding method. After welding, clean the helium chamber cold screen and dry it with hot nitrogen gas (e.g., Figure 3 ).

[0052] 5. The helium chamber support frame 1 is assembled on the fitter's platform according to the dimensions. Then, the helium chamber cold shield is bolted onto the helium chamber support frame 1. An insulating gasket made of G10 material is installed between the helium chamber cold shield and the support frame 1. The entire helium chamber cold shield consists of 5 pieces, and the copper pipes between them are welded using stainless steel flexible tubing. Then, a vacuum helium mass spectrometry leak test is performed to ensure that there are no leaks in the welds.

[0053] 6. A special low-temperature F952 black paint coating is applied to the interior of the helium chamber using a specialized process to increase the emissivity of the copper plates. On the exterior of the helium chamber, special aluminum foil is applied to further increase the heat transfer between the copper tubes and copper plates, thereby improving the heat transfer efficiency.

[0054] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. A method for manufacturing a cryogenic helium chamber with high heat exchange and low flow resistance, characterized in that, It consists of the following steps: (1) Calculate the pipe resistance based on the heat load and required cooling flow rate, and determine the number of parallel cooling pipes; in order to ensure that the cooling helium flow resistance from the refrigerator is <0.1 bar, calculate the resistance of multiple flow streams; (2) Based on the cooling pipe and integral plate welding pipe section diagram, establish a heat transfer model to check whether the inlet and outlet temperature difference meets the design requirements; (3) Determine the pipe length and cooling pipe flow according to the design, cut the copper plates according to the size requirements, braze and splice them, and level them. (4) Clean and degrease the copper tube and copper plate (3); straighten and cut the copper tube, and bend it according to the size requirements using a special low-temperature freezing platform; determine to use a three-flow cooling helium chamber, use a jointless copper tube as the cooling plate, and use a tube bending machine to bend the cooling coil (2) using a low-temperature freezing method to avoid the dents and wrinkles of the coil, so as not to increase resistance; use a clamp to clamp it, and use a copper pressure plate (4) to rivet the cooling coil (2) onto the copper plate (3), and the cooling coil (2) and the copper plate (3) are connected. The copper plates (3) are intermittently riveted together, and then low-temperature soldering is performed using a sectional vertical welding method. The copper plates are erected using a clamp. After welding one side of the copper tube, the other side of the copper tube is welded in reverse. The solder is used to fill the gap between the copper tube and the copper plate as much as possible. The cooling coil (2) and the copper plate (3) are welded together. This forms a helium chamber cold screen. The helium chamber has five cold screens: front, back, left, right and top. The copper tubes between the five cold screens are welded using stainless steel flexible tubes. After welding, the helium chamber cold screens are cleaned and dried with hot nitrogen. (5) The helium chamber support (1) is assembled on the fitter's platform according to the dimensions, and then the helium chamber cold screen is installed on the helium chamber support (1); a heat insulation gasket made of G10 material is installed between the helium chamber cold screen and the helium chamber support (1); then a vacuum helium mass spectrometry leak test is performed to ensure that there is no leakage in the weld. (6) Apply low-temperature F952 black paint to the inside of the helium chamber cold screen to increase the emissivity of the copper plate, and attach aluminum foil to the outside of the helium chamber. The process for spraying low-temperature F952 black paint inside the helium chamber's cold shield is as follows: a) Protect the pre-sprayed objects as required; b) Clean the pre-sprayed helium chamber with acetone or aviation gasoline and allow its surface to dry; c) Shake the F952 heat-sinking black paint for 30 minutes to mix it thoroughly, and after the surface has dried or been oven-dried, spray the paint. Each spray should be applied in a way that prevents sagging. After each coat, allow the surface to dry before applying the next coat, repeating this process 8-10 times. The thickness of the black coating should be controlled at 40-80 micrometers. d) Blow the surface with a hot air blower for at least 3 hours. The cooling system of the helium chamber works by placing the instruments and equipment inside the helium chamber, which is then placed in a vacuum container. The coil contains a low-temperature helium flow, supplied by a low-temperature helium refrigerator through a low-temperature cooling pipe. The temperature of the low-temperature helium chamber is controlled by the low-temperature helium flow.

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