Test method for maintaining air tightness during testing and impact test chamber

Abstract

The application discloses a test method for keeping air tightness during a test process, which comprises the following steps: step one, a test chamber, a high-temperature chamber and a low-temperature chamber are in a normal temperature state; step two, the high-temperature chamber is heated to 95 DEG C, the low-temperature chamber is cooled to-55 DEG C, and the test chamber is in an ambient temperature, at this time, an air conditioning box performs trace balance distribution on air in the three chambers; step three, a valve between the test chamber and the high-temperature chamber is opened, and expanded air in the test chamber enters the air conditioning box, so that the elastic silica gel cloth is inflated in a short time; step four, the valve between the test chamber and the high-temperature chamber is closed, and a valve between the test chamber and the low-temperature chamber is opened, the test chamber and the low-temperature chamber are communicated and have strong convection, the air conditioning box enters the test chamber through an air test chamber balance pipe, so that the elastic silica gel cloth is adsorbed and droops, and the air conditioning box balances air pressure in the three chambers, so that the three chambers are isolated from external air; and step six, the circulation is uninterrupted.

Description

Technical Field

[0001] This invention relates to the field of testing equipment technology, specifically to a testing method and impact test chamber that maintains airtightness during testing. Background Technology

[0002] Impact test chambers that maintain airtightness during testing, also known as "temperature-controlled airtight impact test chambers," are essential testing equipment in the metal, plastic, rubber, and electronics industries. They are used to test the structural integrity of materials or composite materials under continuous, instantaneous exposure to extremely high and low temperatures, allowing for the rapid detection of chemical changes or physical damage caused by thermal expansion and contraction. However, during rapid heating or cooling, the three chambers can instantly create negative or high pressure, allowing moisture-laden air to enter and causing frost to form on the evaporator. Therefore, we need an impact test chamber that maintains excellent sealing during testing to ensure airtightness. Summary of the Invention

[0003] The purpose of this invention is to provide a test method and impact test chamber that maintains airtightness during testing. By maintaining the balance of the three chambers through an air conditioning box, it ensures that no external air enters during the test, reduces evaporator frost formation, and increases the number of impact cycles, thereby solving the problems mentioned in the background art.

[0004] To achieve the above objectives, this invention provides a testing method for maintaining airtightness during testing, comprising the following steps: Step 1, the test chamber, high-temperature chamber, and low-temperature chamber are at room temperature; Step 2, the high-temperature chamber is heated to 95°C, while the low-temperature chamber is cooled to -55°C, and the test chamber is at ambient temperature. At this time, an air conditioning box performs a slight balance distribution of air between the three chambers; Step 3, the valve between the test chamber and the high-temperature chamber is opened, allowing them to communicate and strongly convect, and the temperature of both chambers reaches 85°C. The expanding air in the test chamber enters the air conditioning box through the test chamber balance pipe, thereby allowing the elastic silicone cloth to maintain airtightness for a short time. The internal bulge is raised, and the air conditioning box balances the air pressure in the three chambers, isolating them from the outside air. The temperature inside the test chamber is kept constant at 85℃ for a certain period of time. Step four: Close the valve between the test chamber and the high-temperature chamber, and simultaneously open the valve between the test chamber and the low-temperature chamber. The test chamber and the low-temperature chamber are interconnected and strongly convected, allowing the temperature inside the test chamber to reach -40℃. Air enters the test chamber through the air test chamber balance pipe, causing the elastic silicone cloth to be adsorbed and droop. The air conditioning box balances the air pressure in the three chambers, isolating them from the outside air. The temperature inside the test chamber is kept constant at -40℃ for a certain period of time. Step six: Continuous circulation.

[0005] An impact test chamber that maintains airtightness during testing includes a chamber body. The chamber body contains a test chamber, a high-temperature chamber, and a low-temperature chamber. The test chamber and the high-temperature chamber, and the test chamber and the low-temperature chamber, are connected by valves. During high-temperature testing, the valve between the test chamber and the high-temperature chamber is open, while the valve between the test chamber and the low-temperature chamber is closed, allowing for rapid, strong air convection between them. Similarly, during low-temperature testing, the valve between the test chamber and the low-temperature chamber is open, while the valve between the test chamber and the high-temperature chamber is closed, again allowing for rapid, strong air convection between them. The structure is existing technology and will not be described in detail here. An air conditioning box is provided on the top of the box body. The air conditioning box has an inner cavity with an upward opening. A first through hole, a second through hole, and a third through hole are respectively provided on the wall surface of the air conditioning box. The first through hole connects the inner cavity of the air conditioning box to the low temperature chamber through the low temperature chamber balance pipe. The second through hole connects the inner cavity of the air conditioning box to the test chamber through the test chamber balance pipe. The third through hole connects the inner cavity of the air conditioning box to the high temperature chamber through the high temperature chamber balance pipe. The opening of the air conditioning box is sealed with elastic silicone cloth.

[0006] Preferably, the opening of the air conditioning box is provided with a balancing component, which includes an airbag pressure plate and a locking screw. The airbag pressure plate is installed on the top of the air conditioning box by the locking screw. The airbag pressure plate presses against the surface of the elastic silicone cloth, and the elastic silicone cloth is sealed to the top of the air conditioning box by the airbag pressure plate.

[0007] Preferably, it also includes a control system, which includes a control board, a controller, and a main power supply. The controller is mounted on the control board, and the main power supply is located on the control board below the controller. The control board is mounted on the surface of the enclosure.

[0008] Preferably, temperature sensors are provided in the high-temperature chamber, the low-temperature chamber, and the test chamber, and the temperature sensors are electrically connected to the controller of the control system.

[0009] Preferably, a low-temperature chamber door is provided on one side surface of the low-temperature chamber, a high-temperature chamber door is provided on one side surface of the high-temperature chamber, and a test chamber door is provided on one side surface of the test chamber. The test chamber door is connected to the test chamber via several hinges.

[0010] Preferably, the inner wall of the test chamber door is sealed to the test chamber, a glass window is provided at the center of the surface of the test chamber door, and a door handle is provided on one side of the glass window on the surface of the test chamber door.

[0011] Preferably, an electrical box is installed inside the chamber on one side of the high-temperature chamber, a refrigeration pressure gauge is installed on one side of the electrical box, a refrigeration unit is installed on one side of the electrical box, the refrigeration unit is located below the test chamber, and a cooling water inlet and outlet are installed on one side of the refrigeration unit below the low-temperature chamber.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] This invention utilizes a combination of an air conditioning chamber, a balance pipe, and an elastic silicone cloth structure. An airbag pressure plate seals the elastic silicone cloth to the opening at the top of the air conditioning chamber, and locking screws secure the pressure plate, improving the sealing performance of the elastic silicone cloth. The air conditioning chamber is connected to the test chamber, high-temperature chamber, and low-temperature chamber via the balance pipe. During test chamber operation, the expansion and contraction of the elastic silicone cloth in the air conditioning chamber maintains balance among the three chambers, preventing external air from entering during the test, reducing evaporator frost formation, and thus increasing the number of impact cycles. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention;

[0015] Figure 2 This is a schematic diagram of the air conditioning box structure of the present invention;

[0016] Figure 3 This is a schematic diagram showing the elastic silicone cloth hanging naturally inside the air conditioning box when no test has been performed.

[0017] Figure 4 This is a schematic diagram of the elastic silicone cloth after a small amount of air enters the air conditioning box following a short-term heating process in the test chamber of this invention.

[0018] Figure 5 This is a schematic diagram of the elastic silicone cloth after a small amount of air from the air conditioning box enters the test chamber during the test chamber testing process of the present invention;

[0019] Figure 6 This is a structural diagram of an impact test chamber used in this invention to maintain airtightness during testing;

[0020] Figure 7 for Figure 6 Another perspective view;

[0021] Figure 8 A schematic diagram of the main structure of the impact test chamber to maintain airtightness during testing;

[0022] Figure 9 A top view of the impact test chamber designed to maintain airtightness during testing;

[0023] Figure 10 A side view of the impact test chamber designed to maintain airtightness during testing.

[0024] Figure 11 This is a test cycle data graph for the present invention.

[0025] In the diagram: 1. Enclosure; 2. Control system; 201. Control board; 202. Controller; 203. Main power supply; 3. Test chamber; 301. Test chamber door; 302. Glass window; 303. Door handle; 4. High-temperature chamber; 401. High-temperature chamber door; 5. Low-temperature chamber; 501. Low-temperature chamber door; 6. Air conditioning box; 7. Test chamber balance pipe; 8. High-temperature chamber balance pipe; 9. Low-temperature chamber balance pipe; 10. Electrical box; 11. Refrigeration unit; 12. Refrigeration pressure gauge; 13. Cooling water inlet and outlet; 14. Elastic silicone cloth; 15. Airbag pressure plate; 16. Locking screws. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1-11This invention provides a testing method for maintaining airtightness during testing, comprising the following steps: Step 1, the test chamber 3, high-temperature chamber 4, and low-temperature chamber 5 are at room temperature; Step 2, the high-temperature chamber 4 is heated to 95°C, while the low-temperature chamber 5 is cooled to -55°C, and the test chamber 3 is at ambient temperature. At this time, an air conditioning box performs a slight balance distribution of air between the three chambers; Step 3, the valve between the test chamber 3 and the high-temperature chamber 4 is opened, allowing them to communicate and strongly convect, and the temperature of both chambers reaches 85°C. The expanding air in the test chamber 3 enters the air conditioning box through the balance pipe of the test chamber 3, thereby causing the elastic silicone cloth to inflate in a short time. The air conditioning box balances the air pressure in the three chambers, isolating them from the outside air, and maintaining the temperature in test chamber 3 at 85℃ for a certain period of time; Step four, close the valve between test chamber 3 and high temperature chamber 4 while opening the valve between test chamber 3 and low temperature chamber 5, allowing test chamber 3 and low temperature chamber 5 to communicate and have strong convection, so that the temperature in test chamber 3 reaches -40℃. Air enters test chamber 3 through the air balance pipe in the air conditioning box, causing the elastic silicone cloth to be adsorbed and droop. The air conditioning box balances the air pressure in the three chambers, isolating them from the outside air, and maintaining the temperature in test chamber 3 at -40℃ for a certain period of time; Step six, continuous circulation. It is important to emphasize that the air conditioning chamber is used to test chamber 3 when it is subjected to intense air pressure from a sudden impact of high or low temperature air. Currently, no impact test chamber takes into account the sudden increase or decrease in air pressure within the chamber during sudden high or low temperatures, which could cause each of the three chambers to form a high or negative pressure, thus attracting outside air. The air conditioning chamber, on the other hand, regulates the airflow within the three chambers. Excess air enters the air conditioning chamber when the pressure in a chamber increases, and air enters the chamber when the pressure in a chamber decreases, thus balancing the pressure among the three chambers. This prevents the formation of negative pressure within the chambers during sudden high or low temperatures, thus avoiding the attraction of outside air. This technical solution uses an air conditioning chamber to control the pressure inside test chamber 3 and to better control the gas flow in test chamber 3, high-temperature chamber 4, and low-temperature chamber 5, improving the airtightness of the impact chamber during testing. This increases the number of impact test cycles from 50 to 500.

[0028] An impact test chamber employs a method for maintaining airtightness during testing. The chamber 1 contains a test chamber 3, a high-temperature chamber 4, and a low-temperature chamber 5. Test chambers 3 and 4, and 3 and 5, are connected via valves (not shown in the diagram). During high-temperature testing, the valve between test chambers 3 and 4 is open, while the valve between test chambers 3 and 5 is closed, allowing for rapid, strong air convection between them. Similarly, during low-temperature testing, the valve between test chambers 3 and 5 is open, while the valve between test chambers 3 and 4 is closed, again allowing for rapid, strong air convection. The structure is existing technology and will not be described in detail in this application. An air conditioning box 6 is provided on the upper part of the box body 1. The air conditioning box 6 has an inner cavity with the opening facing upward. The wall surface of the air conditioning box 6 is provided with a first through hole 61, a second through hole 62 and a third through hole 63 respectively. The first through hole 61 communicates with the low temperature chamber 5 through the low temperature chamber balance pipe 9. The second through hole 62 communicates with the test chamber 3 through the test chamber balance pipe 7. The third through hole 63 communicates with the high temperature chamber 4 through the high temperature chamber balance pipe 8. The opening of the air conditioning box 6 is sealed by elastic silicone cloth 14.

[0029] It is worth noting that the three chambers are kept in balance through the coordinated structure of the air conditioning chamber 6, the test chamber balance pipe 7, the high temperature chamber balance pipe 8, the low temperature chamber balance pipe 9, and the elastic silicone cloth 14 inside the air conditioning chamber 6. This ensures that no outside air enters during the test, reduces the frost on the evaporator, and thus increases the number of impact cycles.

[0030] Preferably, the elastic silicone cloth 14 is sealed to the edge of the opening by a balancing assembly. The balancing assembly includes an airbag pressure plate 15 and a locking screw 16. The airbag pressure plate 15 is installed on the top of the air conditioning box 6 by the locking screw 16, pressing the airbag pressure plate 15 against the surface of the elastic silicone cloth 14. The elastic silicone cloth 14 is sealed to the top of the air conditioning box 6 by the airbag pressure plate 15. The airbag pressure plate 15 is the component that presses the elastic silicone cloth 14, so that the elastic silicone cloth 14 is sealed and pressed against the top of the air conditioning box 6. The locking screw 16 is the component that fixes the airbag pressure plate 15 and ensures the sealing effect between the elastic silicone cloth 14 and the air conditioning box 6.

[0031] Specifically, the enclosure contains a control system 2, which includes a control board 201, a controller 202, and a main power supply 203. The controller 202 is mounted on the control board 201, and the main power supply 203 is located on the control board 201 below the controller 202. The control board 201 is mounted on the surface of the enclosure 1. The control board 201 is a component used to install the controller 202 and the main power supply 203. The control system 2 is electrically connected to electrical control components such as the electrical box 10 and the refrigeration unit 11.

[0032] In addition, the low-temperature chamber 5 structure also includes a low-temperature chamber door 501 located on one side surface of the low-temperature chamber 5, and the high-temperature chamber 4 structure also includes a high-temperature chamber door 401 located on one side surface of the high-temperature chamber 4. Temperature sensors are installed in the high-temperature chamber 4, low-temperature chamber 5, and test chamber 3, and the temperature sensors are electrically connected to the controller 202 of the control system 2. The independence of the high-temperature chamber 4, test chamber, and low-temperature chamber 5 expands the overall applicability. The temperature sensors can provide real-time feedback on the temperature of each temperature zone and display it in the controller 202.

[0033] Furthermore, the test chamber 3 structure also includes a test chamber door 301 located on one side surface of the test chamber 3. The test chamber door 301 is connected to the test chamber 3 via several hinges, and the inner wall of the test chamber door 301 is sealed to the test chamber 3. A glass window 302 is provided at the center of the surface of the test chamber door 301, and a door handle 303 is provided on one side of the glass window 302 on the surface of the test chamber door 301. The test chamber 3 is the testing area where tests are conducted. The glass window 302 allows for easy observation of the interior of the test chamber. The door handle 303 is a component used to control the opening and closing of the door. When the door is opened, a signal is transmitted to the controller 202, which immediately stops the equipment from operating, ensuring safe use of the equipment.

[0034] Inside the chamber 1, an electrical box 10 is located on one side of the high-temperature chamber. A refrigeration pressure gauge 12 is located on one side of the electrical box 10. A refrigeration unit 11 is located on one side of the electrical box 10, below the test chamber 3. A cooling water inlet / outlet 13 is located on one side of the refrigeration unit 11, below the low-temperature chamber 5. Hot air is heated by a heater and stored in the high-temperature chamber 4. The air is then cooled by an evaporator in conjunction with the refrigeration unit 11, and the cooled air is stored in the low-temperature chamber 5. The refrigeration unit 11 is a conventional technology in this field and will not be described in detail here.

[0035] The elastic silicone cloth 14 can be sealed to the top of the air conditioning chamber 6 by means of the airbag pressure plate 15, and the airbag pressure plate 15 is locked and fixed by the locking screw 16 to improve the sealing performance of the elastic silicone cloth 14. The air conditioning chamber 6 is connected to the test chamber 3, the high temperature chamber 4 and the low temperature chamber 5 through the balance pipe. When the test chamber is working, the expansion and contraction of the elastic silicone cloth 14 on the air conditioning chamber 6 can maintain the balance of the three chambers, ensuring that the outside air will not enter during the test, reducing the frost on the evaporator and increasing the number of impact cycles of the test chamber.

[0036] Air density varies under different temperatures and pressures. At one atmosphere, under standard conditions (0°C, 1 standard atmosphere (1 atm)), the air density is approximately 1.29 kg / m³. 3At 20℃, take 1. Therefore, due to the influence of temperature, the air density of hot air is less than that of cold air. Under normal temperature and pressure, the test chamber has good sealing properties, preventing outside air from entering. However, during the test, air expands when heated and decreases in volume when cooled, causing the sealing strip to be squeezed or moved away from the inside of the test chamber door 301. This allows the test chamber to draw air in from the outside. Adding an air conditioning box connected to the three chambers allows for self-regulation of the three chambers during the test. When the air in the three chambers is heated or cooled, the air conditioning box regulates the air in the three chambers, thus preventing the three chambers from drawing air in from the outside. Figure 5 When no test is performed, i.e., when the air in test chamber 3 is at normal temperature and pressure, the elastic silicone cloth 14 inside the air conditioning box will droop and hang down under its own weight. Figure 6 The test chamber 3 is for high-temperature testing. Under high temperature and pressure, the air molecules move more rapidly, resulting in lower air density and increased air volume (air expands due to heat). The expanded air enters the air conditioning box 6 through the test chamber balance pipe 7, causing the elastic silicone cloth 14 to inflate rapidly. Figure 7 The test chamber 3 is in a low temperature and low pressure state. The air density is high and the air volume is reduced. The air in the air conditioning box 6 enters the test chamber 3, which causes the elastic silicone cloth 14 to be adsorbed and hang down close to the bottom of the air conditioning box 6.

[0037] The airtight impact test chamber is used for multiple high and low temperature impact tests. Test chamber 3 is first lowered from 85℃ to -40℃, then raised from -40℃ to 85℃, constituting one test cycle. The sealing strip of the test chamber door 301 ensures the airtightness of test chamber 3 during testing when the chamber is not in operation. However, during testing, strong convection occurs between test chamber 3 and either the low-temperature chamber 5 or the high-temperature chamber 4. If the air inside test chamber 3 undergoes rapid thermal expansion and contraction, without an air conditioning box 6, the rapid expansion or contraction of the air inside test chamber 3 will cause the sealing strip of the test chamber door 301 to be forced open due to the increased air volume. Moisture-laden air from outside the airtight impact test chamber will enter test chamber 3 through the gap in the opened sealing strip. In the next test cycle, the air inside the low-temperature chamber 5... Increased air moisture leads to frost formation on the evaporator inside the low-temperature chamber 5. Currently, the impact test chamber, which maintains airtightness during testing, requires defrosting after approximately 50 cycles. This invention, through the air conditioning box 6, regulates the expansion or contraction of air within the test chamber 3 during rapid thermal expansion and contraction, preventing air exchange with the outside air of the impact test chamber. The sealing strip of the test chamber door 301 will not deform due to the instantaneous expansion or contraction of air within the test chamber 3. The air conditioning box structure allows for control of the internal pressure of the test chamber. It also better controls the gas flow rate within the test chamber, high-temperature chamber, and low-temperature chamber, improving airtightness during testing. This allows the number of impact test chamber cycles to increase from the original 50 consecutive cycles to 500 consecutive cycles, without requiring shutdown for defrosting during these 500 cycles.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An impact testing chamber, characterized in that: The device includes a housing (1), which contains a test chamber (3), a high-temperature chamber (4), and a low-temperature chamber (5). The test chamber (3) and the high-temperature chamber (4), and the test chamber (3) and the low-temperature chamber (5) are connected by valves. The device is characterized by having an air conditioning box (6) on top of the housing (1). The air conditioning box (6) has an upward-facing inner cavity, and the walls of the air conditioning box (6) are respectively provided with a first through hole (61), a second through hole (62), and a third through hole. The first through hole (61) connects the inner cavity of the air conditioning box (6) to the low temperature chamber (5) through the low temperature chamber balance pipe (9), the second through hole (62) connects the inner cavity of the air conditioning box (6) to the test chamber (3) through the test chamber balance pipe (7), and the third through hole (63) connects the inner cavity of the air conditioning box (6) to the high temperature chamber (4) through the high temperature chamber balance pipe (8). The opening of the air conditioning box (6) is sealed by elastic silicone cloth (14).

2. The impact testing chamber according to claim 1, characterized in that: The air conditioning box (6) has a balancing assembly on its opening. The balancing assembly includes an airbag pressure plate (15) and a locking screw (16). The airbag pressure plate (15) is installed on the top of the air conditioning box (6) by the locking screw (16). The airbag pressure plate (15) is pressed against the surface of the elastic silicone cloth (14). The elastic silicone cloth (14) is sealed to the top of the air conditioning box (6) by the airbag pressure plate (15).

3. The impact testing chamber according to claim 2, characterized in that: It also includes a control system (2), which includes a control board (201), a controller (202) and a main power supply (203). The controller (202) is mounted on the control board (201), and the main power supply (203) is located on the control board (201) below the controller (202). The control board (201) is mounted on the surface of the housing (1).

4. The impact testing chamber according to claim 3, characterized in that: Temperature sensors are provided in the high-temperature chamber (4), the low-temperature chamber (5) and the test chamber (3), and the temperature sensors are electrically connected to the controller (202) of the control system (2).

5. The impact testing chamber according to claim 1, characterized in that: The low-temperature chamber (5) has a low-temperature chamber door (501) on one side surface, the high-temperature chamber (4) has a high-temperature chamber door (401) on one side surface, and the test chamber (3) has a test chamber door (301) on one side surface. The test chamber door (301) is connected to the test chamber (3) by several hinges.

6. The impact testing chamber according to claim 5, characterized in that: The inner wall of the test chamber door (301) is sealed to the test chamber (3). A glass window (302) is provided at the center of the surface of the test chamber door (301). A door handle (303) is provided on one side of the glass window (302) on the surface of the test chamber door (301).

7. The impact testing chamber according to claim 1, characterized in that: An electrical box (10) is located inside the box (1) on one side of the high temperature chamber. A refrigeration pressure gauge (12) is located on one side of the electrical box (10). A refrigeration unit (11) is located on one side of the electrical box (10). The refrigeration unit (11) is located below the test chamber (3). A cooling water inlet and outlet (13) is located on one side of the refrigeration unit (11) below the low temperature chamber (5).

8. A test method for maintaining airtightness during testing, using the impact test chamber according to any one of claims 1-7, characterized in that: The process includes the following steps: Step 1: The test chamber (3), high temperature chamber (4), and low temperature chamber (5) are at room temperature; Step 2: The high temperature chamber (4) is heated to 95 °C, while the low temperature chamber (5) is cooled to -55 °C. The test chamber (3) is at ambient temperature. At this time, the air conditioning box (6) performs a small-scale balance distribution of the air in the three chambers (3), high temperature chamber (4), and low temperature chamber (5); Step 3: The valve between the test chamber (3) and the high temperature chamber (4) is opened to allow them to communicate and have strong convection, and the temperature of the two chambers reaches 85 °C. The air expanding in the test chamber (3) enters the air conditioning box (6) through the test chamber balance pipe (7), thereby causing the elastic silicone cloth (14) to inflate in a short time. The air conditioning box (6) balances the air pressure in the three chambers, isolating the three chambers from the outside air. 3) The internal temperature is kept constant at 85°C for a certain period of time; Step 4, close the valve between test chamber 3 and high temperature chamber 5, and open the valve between test chamber (3) and low temperature chamber (5) at the same time. Test chamber (3) and low temperature chamber (5) are interconnected and strongly convected, so that the two are interconnected and strongly convected and the temperature of the test chamber reaches -40°C. The air conditioning box (6) enters the test chamber (3) through the air test chamber balance pipe (7), so that the elastic silicone cloth (14) is adsorbed and droops. The air conditioning box (6) balances the air pressure in the three chambers, so that the three chambers are isolated from the outside air. The temperature inside the test chamber (3) is kept constant at -40°C for a certain period of time; Step 6, continuous circulation.

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