The working volume of the weathering laboratory should be at least 3-5 times the volume of the tested product. The reasons for this provision are as follows:
When the tested product is placed in a climate chamber, it forces a flat channel. The narrowing of the channel will increase the air flow and increase the temperature difference between the air and the product being tested.
This is not compatible with the reproduction of environmental conditions, because of the important principles, such as the following:
a) For environmental tests related to heat, the air flow around the sample in the laboratory should not exceed 1.7 m / s to prevent the sample and the surrounding environment from creating a wrong heat wave.
b) The average wind speed in the laboratory is 0.6 to 0.8 m / s, without exceeding 1 m / s.
When the gap and area limit specified in two points a) and b) meet, the air speed of the outlet can be increased by (50 ~ 100)%. The average maximum wind speed of the heating laboratory is always (1 ~ 1.7) m / s, which meets the requirements of the standard.
If the maximum volume or height of the specimen is increased without restriction during the test, the air pressure during the actual test will increase to exceed the maximum air pressure specified in test standards, and the validity of test results.
Accurate indices of environmental parameters (such as temperature, humidity, salt spray rate, etc.) in the office of the climate house are the results of tests under no-load conditions. When the tested product is applied, it will affect the uniformity of the environmental parameters in the laboratory, and the greater the chance of the tested product, the worse the effect will be.
Good test data shows that the temperature difference between the windward and leeward output in the field flow can reach 3-8 ℃, in extreme cases, it can reach 10 ℃. Therefore, both requirements a) and b) should be met as much as possible to ensure the integrity of the environment around the tested product.
According to the principle of heat conduction, the temperature of the airflow near the house wall is usually different from the central temperature of the flow field by 2-3 ℃, and can reach 5 ℃ in the upper and lower limits of the upper temperature and bass. . The temperature of the laboratory wall of the upper and lower rooms is different from the temperature of the water flowing along the room wall by 2-3 ℃ (depending on the structure and material of the walls of the laboratory). The greater difference between the test temperature and the surrounding air, the greater the surface temperature difference. Therefore, the space at a distance of 100 to 150 mm from the wall of the laboratory is an unusable space.
