Structure for improving temperature uniformity of low-temperature test box

Abstract

The utility model discloses a structure of improving low temperature calibration box temperature uniformity, including shell and inner bag, and the shell and inner bag are the heat preservation area between, be provided with combination heat preservation structure in heat preservation area, and the inner bag space adopts modularization area and divides, and the inner bag is divided into circulating stirring area, air duct mixing area and work test area through back baffle, upper baffle and lower baffle, and circulating stirring area is located one side of work test area, and is communicated with work test area, and circulating stirring area lower end is communicated with air duct mixing area, and air duct mixing area is located the lower part of work test area and circulating stirring area both sides. Its adopt multiple air duct design and deflector, and the fan fin of fan matching well, ensure that airflow evenly covers entire box, and the inner airflow distribution is even. Adopt combination heat preservation structure, and the adaptability is stronger, and the heat insulation performance is excellent, adopts the sealing treatment, avoids the heat loss or the external heat infiltration. Modularization design box body structure, scientific partition, optimize the box body internal structure, reduce airflow resistance.

Description

Technical Field

[0001] This utility model relates to the field of temperature and humidity measurement technology, and in particular to a structure for improving the temperature uniformity of a low-temperature calibration chamber. Background Technology

[0002] Cryogenic chambers are devices used to simulate low-temperature environments and are widely used in scientific research, industry, medical fields, and metrology verification. Their technological background involves multiple aspects, including refrigeration technology, temperature control, structural design, materials science, and intelligent technology. With technological advancements, cryogenic chambers have continuously improved in terms of temperature uniformity, control accuracy, energy efficiency, environmental friendliness, and intelligence, meeting the stringent requirements of scientific research, industry, medical fields, and metrology verification for low-temperature environments. In the future, cryogenic chambers will continue to develop towards higher efficiency, intelligence, and environmental friendliness.

[0003] The current structure of low-temperature testing chambers and similar products can be categorized as follows: The system employs active forced convection via a fan to ensure uniform temperature within the chamber. The air circulation system mainly uses vertical or horizontal circulation to ensure uniform temperature within the chamber.

[0004] Vertical circulation involves air entering from the top and returning from the bottom, making it suitable for tall enclosures. Horizontal circulation, on the other hand, involves air entering from one side and returning from the other, making it suitable for wide enclosures.

[0005] In fan systems, centrifugal or axial fans are commonly used to ensure uniform airflow. The fans are typically located at the rear or top of the enclosure, working in conjunction with the ductwork to create a circulation system, depending on the circulation method.

[0006] However, existing technologies have the following drawbacks: 1. Uneven airflow distribution inside the chamber: The air duct design of traditional low-temperature test chambers may lead to uneven airflow distribution, resulting in large temperature differences inside the chamber.

[0007] 2. Insufficient fan performance: Insufficient fan volume or air pressure results in the airflow not being able to effectively cover the entire enclosure.

[0008] 3. Insufficient thermal insulation performance: Poor thermal insulation performance of the enclosure leads to heat loss or external heat infiltration, affecting temperature uniformity.

[0009] 4. Uneven cooling system: An unreasonable design of the cooling system leads to uneven cooling effect inside the cabinet.

[0010] 5. An unreasonable design of the enclosure structure may lead to airflow turbulence or heat loss.

[0011] Chinese patent application CN 110285845 A discloses a temperature and humidity calibration chamber and a method for improving its temperature uniformity and fluctuation. Inside the chamber, a fan, a refrigeration evaporator, and a heating coil are sequentially arranged along the air inlet direction of the rear air duct. A finned heat exchanger is horizontally positioned at the air duct outlet inside the chamber, with an impeller mounted on its outer side. The chamber also has a bottom surface, forming a buffer zone between the bottom surface and the bottom plate of the chamber. This patent application employs a conventional circulation structure, focusing on the addition of a finned heat exchanger and a matching fan impeller within the circulation duct. The design and verification of the added finned heat exchanger are then specifically explained, and the final design of the bottom opening is briefly described. While the design of the finned heat exchanger is supported by theoretical calculations, its actual performance, as well as the impeller and bottom opening, were determined through verification experiments, indicating significant uncertainties related to different operating conditions and equipment. Because it did not optimize or analyze other aspects of the air duct, it only optimized and adjusted the final temperature field index by adding finned heat exchangers and matching fan impellers. Without excluding other influencing factors, there are many influencing variables between different devices, which will lead to the final improvement effect on the temperature field index of different devices not being completely consistent.

[0012] Chinese Patent 208653524 U discloses a novel temperature and humidity testing chamber, comprising a chamber body divided into a constant temperature chamber and a testing chamber by a first temperature-conducting plate. The constant temperature chamber is further divided into an upper constant temperature chamber and a lower constant temperature chamber by a partition. The upper constant temperature chamber contains liquid. A second temperature-conducting plate is located in the testing chamber, and an air guide plate is located near the second temperature-conducting plate. The air guide plate, the second temperature-conducting plate, and the inner wall of the testing chamber form a circulating air duct. The circulating air duct includes an air outlet and an air inlet. An air supply fan, a humidification device, and a dehumidification device are located at the air outlet. A vertical air outlet is located above the air supply fan, which evenly delivers the airflow blown by the air supply fan into the testing chamber. The vertical air outlet is connected to the vertical fan via an air duct. This patent has a complex structure, an overly idealistic design, and is difficult to implement. Its key feature is adjusting direct heating and cooling to secondary heat exchange to reduce the impact of direct heating and cooling on temperature fluctuations within the chamber. However, the method used involves heat conduction through double-layer heat-conducting plates, resulting in high heat loss, low efficiency, and delayed response. The constant temperature chamber is divided into upper and lower layers to differentiate between gas and liquid, increasing potential failure points and implementation difficulty. Furthermore, the lower chamber lacks circulation, making it difficult to guarantee temperature uniformity. The circulating air duct of the calibration chamber is only roughly described as a horizontal and vertical design, without specifying the fan and detailed ductwork design, thus failing to achieve uniform airflow and ensuring temperature uniformity within the chamber.

[0013] Chinese patent CN 209296542 U discloses a temperature and humidity calibration chamber, including a chamber body, a heating device (heating valve), a cooling device (cooling valve), a humidifier, a temperature sensor, a humidity sensor, and a fan. The chamber body has an outer layer, a middle layer, and an inner layer arranged sequentially from the outside in. The inner layer has a working chamber, and an exchange channel exists between the middle layer and the inner layer. The inner layer has several ventilation holes. The heating device is connected to the exchange channel via a hot air inlet duct; the heating valve is located on the hot air inlet duct. The cooling device is connected to the exchange channel via a cold air inlet duct; the cooling valve is located on the cold air inlet duct. The humidifier is connected to the working chamber via a humidifying air duct; the humidifying valve is located on the humidifying air duct. The temperature sensor and humidity sensor are located in the working chamber. The fan is used to generate circulating airflow within the exchange channel. This patent also has a complex structure, its key feature being the creation of a separate inner cavity within the conventional chamber body—the inner layer described in the patent—which serves as the final working layer. The temperature field indicators of the working layer are indirectly controlled by controlling the temperature of the middle layer. However, according to the description in the text, passive adjustments are made only through a few ventilation holes on the inner layer. Even though the diagram shows that a fan is installed in the inner layer, this would increase factors such as fan heat dissipation. In both cases, the working layer lacks a scientifically sound airflow design, resulting in an extremely unstable actual airflow field and uncontrollable airflow direction, making it difficult to guarantee temperature uniformity. Furthermore, the temperature and humidity sensors are located on the working layer, while the corresponding adjustment openings are located in the middle layer channel. The temperature field indicators between the two layers differ significantly and are uncertain, leading to problems such as excessive adjustment deviation and delayed response. Utility Model Content

[0014] The purpose of this invention is to overcome the shortcomings of the prior art and provide a structure that improves the temperature uniformity of a low-temperature calibration chamber.

[0015] To achieve the above objectives, the present invention adopts the following technical solution: A structure for improving the temperature uniformity of a low-temperature testing chamber includes an outer shell and an inner liner. The space between the outer shell and the inner liner is an insulation zone, which is equipped with a combined insulation structure. The inner liner space is divided into modular areas. The inner liner is divided into a circulating stirring zone, an air duct mixing zone, and a working test zone by a rear baffle, an upper baffle, and a lower baffle. The circulating stirring zone is located on one side of the working test zone and is connected to the working test zone. The lower end of the circulating stirring zone is connected to the air duct mixing zone, which is located at the lower part of the working test zone and on both sides of the circulating stirring zone.

[0016] A circulating fan is installed on the outside of the outer shell. The rotating shaft of the circulating fan extends laterally through the outer shell, the insulation zone and the inner liner into the circulating mixing zone. Fan blades are installed at the end of the rotating shaft. A refrigeration evaporator and a finned heater are arranged in sequence below the fan blades in the circulating mixing zone.

[0017] The air duct mixing zone includes the main air duct mixing zone located at the bottom of the working test zone and the auxiliary air duct mixing zones located on both sides of the circulating mixing zone.

[0018] The main air duct mixing zone and the auxiliary air duct mixing zone are connected.

[0019] The combined insulation structure includes a prefabricated polyurethane foam board attached to the outer surface of the inner liner, with polyurethane foaming between the polyurethane foam board and the inner wall of the outer shell.

[0020] All openings connecting the working test area to the outside world are sealed using a sealed structure.

[0021] The working test area and the circulating mixing area are separated by a rear baffle.

[0022] The rear baffle consists of a partition and an air guide shroud. The partition has a honeycomb-shaped perforated area, and the air guide shroud is installed on the outer edge of the honeycomb-shaped perforated area on the partition.

[0023] The honeycomb-shaped perforated area is smaller than the projected area of ​​the air guide shroud. This is to prevent backflow of air from the fan blades, which could affect the temperature field parameters.

[0024] The fan blades are installed at the end of the air guide shroud, which ensures smooth air intake and facilitates exhaust to the surroundings. The fan is at the end of the air guide shroud, and the air intake channel is forced along the air guide shroud, but the air is discharged outside the air guide shroud to prevent air accumulation.

[0025] Both the refrigeration evaporator and the finned heater are equipped with blades that increase the thermal contact area, thereby forcibly improving the heat exchange efficiency.

[0026] The bottom of the lower baffle is equipped with air guide vanes in different directions, which will obstruct the airflow. Some of the obstructed airflow will be guided upward through the mixing zone of the auxiliary air ducts on both sides to avoid the formation of turbulent vortices due to accumulated air, which would affect the airflow temperature exchange and thus affect the temperature uniformity inside the box.

[0027] A baffle plate is installed on the lower left side of the circulating mixing zone. Because the left side is where the evaporator coil runs, while the right side has no piping, the temperature on the left side is lower than on the right, easily leading to a temperature difference that affects the temperature uniformity within the chamber. Therefore, the baffle plate is installed to reduce the impact of the left-side piping on the airflow temperature, thereby improving temperature uniformity.

[0028] The rear baffle, upper baffle, and lower baffle are all sealed with silicone strips to ensure the consistency of the air duct and reduce the risk of poor temperature uniformity in the working test area due to leakage affecting the air duct. This measure can also improve the consistency of different batches of products and greatly improve the temperature field testing and debugging.

[0029] The lower baffle has an inclined surface at the front air outlet, with striped openings on the inclined surface and adjacent horizontal surfaces to improve airflow. Stainless steel sheets of varying widths are installed in different blocking areas at the striped openings. By adjusting these sheets, the airflow direction within the duct can be adjusted, thus regulating the uniformity of airflow within the chamber. Different openings can be sealed for different equipment based on actual test results to adapt to different operating conditions.

[0030] The inner surfaces of both sides of the inner chamber of the working test area are equipped with detachable grille supports.

[0031] A temperature sensor is installed at the center of the working test area, and a temperature protection switch is also installed at the finned heater, adding safety assurance in extreme situations. Extreme situations refer to abnormal heating of the heater, fan failure and shutdown, etc., preventing risks such as fires caused by excessive temperature. The temperature protection switch here can replace or add a temperature sensor to further improve the temperature field indicators inside the chamber.

[0032] The circulating fan and fan blades are detachable for easy maintenance. The fan speed and fan blade size and angle can be adjusted to meet different operating conditions, thereby improving the temperature uniformity inside the chamber.

[0033] During operation, the circulating fan drives the fan blades to draw air from the working test area into the circulating mixing zone. The air then passes through the refrigeration evaporator and the finned heater in sequence, and then enters the air duct mixing zone. At this point, most of the air passes through the main air duct mixing zone below, and after thorough mixing, it enters the working test area. A small portion of the air is limited by the structure and obstruction of the main air duct, and passes through the auxiliary air duct mixing zones on both sides, passing above the upper baffle and entering the working test area, thus completing the entire circulation process.

[0034] The beneficial effects of this utility model are: 1. Optimize the air duct structure design, adopt a multi-air duct design and air guide plate to ensure that the airflow evenly covers the entire box and the internal airflow distribution is uniform.

[0035] 2. Use fan blades that are well matched with the fan to ensure sufficient fan volume or air pressure, and the airflow can evenly and effectively cover the entire box.

[0036] 3. It adopts a combined insulation structure, which has stronger adaptability and excellent heat insulation performance of the box. At the same time, it adopts a sealing treatment to avoid heat loss or external heat infiltration.

[0037] 4. The evaporator is arranged in conjunction with the air duct inside the box to ensure uniform cooling.

[0038] 5. The modular design of the enclosure structure and scientific partitioning ensure good sealing between each partition through adhesive strips, preventing interference caused by leakage between different partitions, optimizing the internal structure of the enclosure and reducing airflow resistance.

[0039] 6. Reduce interference factors affecting temperature field indicators, improve uniformity between different devices, improve the consistency of temperature field indicators and test pass rate, and improve efficiency and reduce costs. Attached Figure Description

[0040] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a schematic diagram of the main structure of this utility model; Figure 3 This is a side view of the structure of this utility model; Figure 4 This is a schematic diagram of the rear baffle structure of this utility model; Among them, 1. circulating fan, 2. fan blades, 3. refrigeration evaporator, 4. finned heater, 5. rear baffle, 6. lower baffle, 7. inner liner, 8. outer shell, 9. upper baffle, 10. circulating mixing zone, 11. main air duct mixing zone, 12. working test zone, 13. auxiliary air duct mixing zone, 14. air guide hood, 15. partition. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] The structures, proportions, and sizes illustrated in the accompanying drawings are merely for illustrative purposes and to aid those skilled in the art in understanding and reading the content disclosed herein. They are not intended to limit the scope of this utility model and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of this utility model, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of this utility model. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this utility model's implementation.

[0043] like Figures 1-4 As shown, a structure for improving the temperature uniformity of a low-temperature testing chamber includes an outer shell 8 and an inner liner 7. An insulation zone exists between the outer shell 8 and the inner liner 7, and a combined insulation structure is installed within this zone. The combined insulation structure includes a prefabricated polyurethane foam board attached to the outer surface of the inner liner 7, with foam filling the space between the polyurethane foam board and the inner wall of the outer shell 8.

[0044] Considering the large surface area of ​​the low-temperature calibration chamber, direct polyurethane foaming can easily lead to chamber deformation. To avoid deformation, there are two solutions: one is to increase the board thickness and add reinforcing ribs to the chamber, which increases equipment weight and processing costs, and still cannot completely eliminate the risk of deformation; the other is to use foaming fixtures, which are costly and have complex structures and operations, affecting efficiency. This invention employs a combined insulation structure. First, prefabricated polyurethane foam boards are attached to the outer surface of the inner liner 7, and then foaming is performed. Because the foam boards evenly distribute and guide the foaming force, only simple fastening of the outer surface of the chamber is required, thus reducing the risk of foaming deformation at a lower cost. The polyurethane foaming seamlessly fills the gaps, providing reliable strength support while ensuring thermal insulation. It also offers more options for adapting to different chamber temperatures. At high temperatures, rock wool or other materials can be used to replace the polyurethane foam boards, attached to the outer surface of the inner liner 7 before foaming, ensuring temperature adaptability, insulation effect, and strength support, allowing the equipment to adapt to a wider temperature range. This excellent insulation performance reduces internal heat loss, thereby improving temperature uniformity within the enclosure. Polyurethane foam is suitable for low temperatures, while rock wool boards can be used at high temperatures, but polyurethane foam offers better insulation.

[0045] The inner liner 7 is modularly divided into zones. It is further divided into a circulating mixing zone 10, an air duct mixing zone, and a working test zone 12 by a rear baffle 5, an upper baffle 9, and a lower baffle 6. The circulating mixing zone 10 is located on one side of the working test zone 12 and is connected to it. The lower end of the circulating mixing zone 10 is connected to the air duct mixing zone, which is located at the lower part of the working test zone 12 and on both sides of the circulating mixing zone 10. The air duct mixing zone includes a main air duct mixing zone 11 located at the lower part of the working test zone 12 and auxiliary air duct mixing zones 13 located on both sides of the circulating mixing zone 10. The main air duct mixing zone 11 and the auxiliary air duct mixing zone 13 are connected.

[0046] All openings connecting the working test area 12 to the outside world are sealed with a sealed structure. For example, a double-layer sealing structure is set at the connection with the door, and foamed silicone plugs are used at the wiring to be tested, which can better ensure the sealing of the chamber. Better sealing can prevent airflow interaction between the inside and outside of the chamber, thereby improving the temperature uniformity inside the chamber.

[0047] The working test area 12 and the circulating mixing area 10 are separated by a rear baffle 5. The rear baffle 5 consists of a partition 15 and an air guide shroud 14. The partition 15 has a honeycomb-shaped perforated area, and the air guide shroud 14 is installed on the outer edge of the honeycomb-shaped perforated area on the partition 15. The honeycomb-shaped perforated area is smaller than the projected area of ​​the air guide shroud 14. The fan blades 2 correspond to the air guide shroud 14, ensuring smooth air intake while also facilitating exhaust to the surroundings.

[0048] A circulating fan 1 is installed on the outside of the outer shell 8. The rotating shaft of the circulating fan 1 extends laterally through the outer shell 8, the insulation zone and the inner liner 7 into the circulating mixing zone 10. Fan blades 2 are installed on the end of the rotating shaft. The circulating fan 1 and the fan blades 2 are detachable for easy maintenance. At the same time, the fan speed and the size and angle of the fan blades can be adjusted to meet different working conditions, thereby improving the temperature uniformity inside the chamber.

[0049] Within the circulating mixing zone 10, a refrigeration evaporator 3 and a finned heater 4 are sequentially arranged below the fan blades 2. Both the refrigeration evaporator 3 and the finned heater 4 are equipped with blades to increase the thermal contact area, thereby forcibly improving the heat exchange efficiency.

[0050] At the bottom of the circulating mixing zone 10, which is the air duct mixing zone, the main air duct mixing zone 11 is formed by passing forward through the baffle, and the auxiliary air duct mixing zones 13 are formed by passing to the left and right through the sides of the circulating mixing zone 10. Due to the limited distance between the lower baffle 6 and the inner liner 7, the bottom of the lower baffle 6 is equipped with air guide vanes in different directions. This will obstruct the airflow. Some of the obstructed airflow will be guided upward through the auxiliary air duct mixing zones 13 on both sides to avoid the formation of turbulent vortices due to accumulated air, which would affect the airflow temperature exchange and thus affect the temperature uniformity inside the chamber.

[0051] A baffle plate is installed on the lower left side of the circulating mixing zone 10. Because the left side is the piping area for the evaporator coil 3, while the right side has no piping, the temperature on the left side is lower than on the right, easily leading to a temperature difference that affects the temperature uniformity within the chamber. Therefore, the baffle plate is installed to reduce the impact of the left-side piping on the airflow temperature, thereby improving temperature uniformity.

[0052] Silicone strips are used to seal the rear baffle 5, upper baffle 9, lower baffle 6 and inner liner 7, thereby ensuring the consistency of the air duct and reducing the risk of poor temperature uniformity in the working test area 12 due to leakage affecting the air duct. This measure can also improve the consistency of different batches of products and greatly improve the temperature field testing and debugging.

[0053] The lower baffle 6 has a sloping surface at the front air outlet, with striped openings on the sloping surface and adjacent horizontal surfaces to improve airflow. Stainless steel strips of varying widths are installed in different blocking areas at the striped openings. By adjusting these strips, the airflow direction within the duct can be adjusted, achieving uniformity within the chamber. Different openings can be sealed for different equipment based on actual test results to adapt to different operating conditions.

[0054] The inner surfaces of the left and right sides of the inner liner 7 of the working test area 12 are equipped with detachable grille supports. A temperature sensor is located in the center of the working test area, and a temperature protection switch is also installed at the finned heater 4, which increases safety in extreme situations.

[0055] During operation, the circulating fan 1 drives the fan blades 2 to draw air from the working test area 12 into the circulating mixing area 10, and then through the refrigeration evaporator 3 and the finned heater 4. Finally, the air enters the air duct mixing area. At this time, most of the air passes through the main air duct mixing area 11 below and, after thorough mixing, enters the working test area 12. A small portion of the air is limited by the structure of the main air duct and obstructed, and passes through the auxiliary air duct mixing areas 13 on both sides and enters the working test area 12 above the upper baffle 9, thus completing the entire circulation process.

[0056] Although the specific embodiments of the present utility model have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present utility model. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solution of the present utility model are still within the scope of protection of the present utility model.

Claims

1. A structure for improving the temperature uniformity of a low-temperature testing chamber, characterized in that it includes an outer shell and an inner liner, with an insulation zone between the outer shell and the inner liner, a combined insulation structure provided within the insulation zone, and the inner liner space is divided into modular areas. The inner liner is divided into a circulating stirring zone, an air duct mixing zone, and a working test zone by a rear baffle, an upper baffle, and a lower baffle. The circulating stirring zone is located on one side of the working test zone and is connected to the working test zone. The lower end of the circulating stirring zone is connected to the air duct mixing zone, which is located at the lower part of the working test zone and on both sides of the circulating stirring zone.

2. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 1, characterized in that, A circulating fan is installed on the outside of the outer shell. The rotating shaft of the circulating fan extends laterally through the outer shell, the insulation zone and the inner liner into the circulating mixing zone. Fan blades are installed at the end of the rotating shaft. A refrigeration evaporator and a finned heater are arranged in sequence below the fan blades in the circulating mixing zone.

3. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 1, characterized in that, The air duct mixing zone includes a main air duct mixing zone located at the bottom of the working test zone and auxiliary air duct mixing zones located on both sides of the circulating mixing zone; the main air duct mixing zone and the auxiliary air duct mixing zone are connected.

4. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 1, characterized in that, The combined insulation structure includes a prefabricated polyurethane foam board attached to the outer surface of the inner liner, with polyurethane foam between the polyurethane foam board and the inner wall of the outer shell.

5. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 1, characterized in that, All openings connecting the working test area to the outside are sealed with a sealing structure; the rear baffle, upper baffle, and lower baffle are all sealed with silicone strips to the inner liner.

6. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 2, characterized in that, The working test area and the circulating mixing area are separated by a rear baffle; the rear baffle is composed of a partition and an air guide hood, the partition is provided with a honeycomb-shaped opening area, and the air guide hood is installed on the outer edge of the honeycomb-shaped opening area on the partition. The honeycomb-shaped opening area is smaller than the projected area of ​​the air guide cover; the fan blades are installed at the end of the air guide cover.

7. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 2, characterized in that, Both the refrigeration evaporator and the finned heater are equipped with blades to increase the thermal contact area.

8. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 1, characterized in that, The bottom of the lower baffle is provided with air guide vanes in different directions; the front air outlet of the lower baffle is provided with an inclined surface, and there are striped openings on the inclined surface and the adjacent horizontal surface.

9. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 1, characterized in that, A baffle plate is installed on the lower left side of the circulating mixing zone; detachable grid supports are installed on the inner surfaces of both sides of the inner liner of the working test zone.

10. The structure for improving the temperature uniformity of the low-temperature testing chamber as described in claim 1, characterized in that, A temperature sensor is installed at the center of the working test area, and a temperature protection switch is also provided at the fin heater.

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