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Reliable working volume to reproduce a true natural environment

Time:2018-01-06 Tag:Technical solution User:Sailham View:577

Climate chamber is used to simulate the true natural environment, some key factors are very important to ensure this factuality, such as raliable working volume, please see the representation below:


Air flow rate:

After being tested into the chamber to squeeze the smooth passage, narrowing the channel will lead to an increase in air flow rate. Accelerate the heat exchange between the flow and the test piece. This is inconsistent with the reproduction of environmental conditions, because the relevant standards for temperature and environmental tests require the test chamber where around the test sample, air flow rate should not exceed 1.7m / s, in order to prevent the test sample and the ambient atmosphere is not consistent with the actual heat conduction. The average wind speed in the test chamber at no-load is 0.6-0.8 m / s and not more than 1 m / s, and the wind speed of the flow field may increase when the space and area ratio specified in the two requirements are met (50~ 100)%, the average maximum wind speed is (1 ~ 1.7) m / s. If to increase the volume or windward cross-sectional area during the test, the actual test airflow speed will increase beyond the maximum wind speed specified in the test standards, the validity of the test results will be questioned.

 

Accuracy of environmental parameters:

The accuracy index of environmental parameters (such as temperature, humidity, salt spray sedimentation rate, etc.) in the working chamber of the climate chamber is the result of detection under the no-load condition. Once the test object is put into the test chamber, The uniformity of the environmental parameters will have an impact. The larger the space occupied by the test piece, the more serious this effect will be. The experimental data show that the temperature difference between the windward and leeward surfaces in the flow field can reach 3 ~ 8 and in severe cases it can be as large as 10 . Therefore, we must try to meet a, b two requirements to ensure the uniformity of the environmental parameters of the product under test.

 

Temperature difference:

According to the principle of heat conduction, the temperature of the airflow in the vicinity of the box wall usually varies from 2 to 3 ° C at the center of the flow field, and may reach 5 ° C at the upper and lower limits of the high and low temperature. The temperature difference between the chamber wall and the flow field is 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 temperature difference, therefore, (100 ~ 150mm) within the space to the chamber wall is not available.



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