FAQs About Temperature Shock Chamber

Temperature shock testing is used to assess a product's adaptability to rapid changes in ambient temperature. It is an indispensable test item in the qualification testing of equipment design and routine testing during batch production. In some cases, it can also be used for environmental stress screening. It can be said that its frequency of application in verifying and improving the environmental adaptability of equipment is second only to vibration and high/low temperature testing.

1. What is Thermal Shock Testing?

Temperature shock testing, also known as thermal shock testing or high/low temperature shock testing, is used to assess a product's adaptability to rapid changes in ambient temperature. By simulating the environment in which a product rapidly switches between extreme high and low temperatures, it tests whether the product can withstand the stress caused by drastic temperature changes and verifies its durability, functionality, and structural integrity. The purpose of thermal shock testing includes evaluating the product's tolerance to rapid temperature changes, identifying potential defects, verifying product lifespan, and ensuring safety.

Temperature shock testing is an environmental testing method used to evaluate the durability and reliability of materials, components, or products under extreme temperature change conditions. Rapid transitions from extremely low to extremely high temperatures, or vice versa, can simulate drastic temperature changes that might occur in real-world environments, such as the dramatic temperature changes experienced by spacecraft traversing the atmosphere or the rapid warm-up of a car engine after a cold start.

Temperature shock testing is typically conducted in specialized thermal shock chambers, which consist of a high-temperature chamber, a low-temperature chamber, and a switching mechanism, enabling rapid switching between high and low temperature environments. The chamber design must ensure accurate and stable temperature control, as well as the safety of the testing process.

2. What is the purpose of temperature shock testing?

During the engineering development phase, it can be used to identify design and manufacturing defects in products; during product finalization or design qualification and mass production phases, it is used to verify the product's adaptability to temperature shock environments, providing a basis for design finalization and mass production acceptance decisions; when used as an environmental stress screening application, its purpose is to eliminate early product failures.

3. What is the typical temperature transition time for a temperature shock test?

1. For general electrical and electronic equipment, a temperature transition time of ≤3 minutes is usually required. If a two-chamber method is used, and the product size is too large to achieve the transition within 3 minutes, the transition time can be appropriately extended.

2. For non-civilian systems or equipment, the temperature transition time should be as short as possible, typically ≤1 minute.

3. For chip-level devices, the required temperature transition time is the shortest, sometimes requiring a transition time of less than 10 seconds.

4. What types of temperature shock testing equipment are available?

1. Two high and low temperature test chambers can be used. Samples are manually transferred between the two ordinary temperature test chambers, achieving a transition time of ≤3 minutes.

2. Basket-type temperature shock test chamber

A basket-type temperature shock test chamber consists of a hot chamber, a cold chamber, and a basket. The sample is placed inside the basket, and a mechanical structure moves the basket between the hot and cold chambers.

3. Damper-Type Temperature Shock Chamber

A damper-type temperature shock chamber, also known as a three-chamber temperature shock chamber, consists of a cold chamber, a hot chamber, and a test chamber. The test product is placed in the test chamber. Both the cold and hot chambers are equipped with dampers, which are automatically controlled by a program to supply hot or cold air into the test chamber. Typically, damper-type temperature shock chambers also include dampers for ambient air exchange, used to exchange the hot or cold air in the test chamber with the ambient air when switching temperatures, achieving energy savings and accelerating temperature transitions.

5. How to conduct a temperature shock test?

1. Pretreatment: Place the sample to be tested under normal test atmospheric conditions until it reaches temperature stability.

2. Initial Inspection: Compare the sample to the standard requirements. If it meets the requirements, place it directly into the high and low temperature shock test chamber.

3. Test:

- High Temperature Stage: Place the test sample in the test chamber and raise the temperature to the specified point, maintaining it for a certain period until the sample reaches temperature stability.

- Low Temperature Stage: Within 5 minutes, transfer the test sample to a low temperature test chamber pre-adjusted to -55°C, maintaining it for 1 hour or until the sample reaches temperature stability.

- Second High Temperature Stage: Within 5 minutes, transfer the test sample to a high temperature test chamber pre-adjusted to 70°C, maintaining it for 1 hour or until the sample reaches temperature stability.

- Repeat the above experimental method to complete three cycles.

4. Recovery: After removing the test sample from the test chamber, it should be recovered under normal test atmospheric conditions until the sample reaches temperature stability.

5. Post-testing: Evaluate the test results by comparing the damage level with the standards and other methods.

Precautions:

1. Ensure strict adherence to the safe operating procedures of the test chamber.

2. Closely monitor the operating status of the test chamber and the reaction of the samples during the test.

3. Select appropriate test parameters and standards according to the product type and characteristics.

6. How to calculate heat load?

According to the law of conservation of energy, the cooling capacity of our configured compressor only needs to be sufficient to remove the heat load within the enclosed space. So, what are the main components of the heat load within an enclosed space?

Based on the diagram above, the heat load mainly includes:

1. Heat load of the test chamber: The cooling capacity required to reduce the temperature from room temperature to the specified temperature;

2. Heat conduction from the insulation layer: No matter how good the insulation is, we cannot rule out the possibility of no heat leakage from the chamber, so this part of heat conduction needs to be calculated;

3. Heat leakage from doors, seams, etc.: It is impossible for the same chamber to be 100% sealed, so this part of heat leakage needs to be considered;

4. Structural load inside the chamber: The inner walls of the chamber are generally made of stainless steel or checkered plates. When the temperature inside the chamber drops to -70°C... At a temperature of -70℃, the inner steel walls also need to be cooled to -70℃, so this heat load must also be considered;

5. Equipment load inside the chamber: There may be cooling equipment inside the chamber (evaporators, steam pipes, etc.), which also need to be cooled to -70℃, and this heat load needs to be considered;

6. Heat-generating element load inside the chamber: There are fans, lighting, etc. inside the chamber, and this load also needs to be considered;

7. Air cooling load inside the chamber: The air inside the chamber needs to be cooled from room temperature to -70℃, and this load also needs to be considered.

The heat load calculation for a closed space usually requires consideration of the above components. This approach is not only applicable to the cooling capacity calculation of high and low temperature chambers, but also to the heat load calculation of other closed spaces, such as refrigerators, freezers, cold storage systems, and enthalpy difference laboratories.