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The reason why the samples of the high and low temperature test chamber can not be filled

Date: Jul 17,2021 Views: 43

high and low temperature test chamber After the test sample is put into the chamber, the channel will become narrower, which will increase the airflow speed and accelerate the heat exchange between the airflow and the tested product. This is inconsistent with the reproduction of environmental conditions, because the relevant standards stipulate that the air velocity around the test sample in the test chamber should not exceed about 1.7m/s to prevent the test sample and the surrounding atmosphere from being inconsistent with the actual heat conduction. When there is no load, the average wind speed in the test chamber is 0.6-0.8m/s, not exceeding about 1m/s. If the space to area ratio specified in the above requirements is met, the wind speed of the flow field may increase by about 50-100%, and the average extremely high wind speed is 1-1.7m/s, which meets the standard requirements. If the volume or cross-sectional area of the sample to be tested is increased without restriction during the test, the airflow wind speed during the actual test will increase to exceed the limit wind speed specified by the test standard, which will cause the validity of the test results to be doubted.

 

The accuracy index of the environmental parameters high and low temperature test chamber in the working room is the result of testing under no-load conditions. Once the product under test is placed, it will affect the uniformity of the environmental parameters in the chamber of the test chamber. The larger the space occupied by the tested product, the more serious the impact. Experimental data shows that the temperature difference between the windward side and the leeward side of the flow field can reach 3-8, and can reach more than 10in severe cases. Therefore, the requirements specified in the standard must be met as much as possible to ensure the uniformity of the environmental parameters around the tested product.

 

According to the principle of heat conduction, high and low temperature test chamber the temperature of the airflow near the wall of the chamber generally differs from the temperature of the center of the flow field by 2-3°C, and can reach 5°C at the upper and lower limits of high and low temperatures. The difference between the temperature of the chamber wall and the flow field temperature near the chamber wall is another 2-3°C, depending on the structure and material of the chamber wall. The greater the difference between the test temperature and the external atmospheric environment, the greater the above-mentioned temperature difference. The space between 150mm is not available.




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