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May 31, 2021
The temperature rise and fall of our commonly used small high and low temperature environmental test chambers mainly rely on circulating flavors, condenser fans and other equipment. The resulting temperature environment contains a lot of water vapor, and when the product temperature is lower, the temperature is higher when the surface is higher. If the surface temperature of the air is lower than the dew point temperature of the air, condensation will occur, and liquid water will be produced on the lower temperature surface.
The theoretical reason for the small high and low temperature environmental test chamber is as follows: The composition of general air can be regarded as composed of three parts: dry air, water vapor and dust. Temperature is the mass of water vapor in intonation air at a certain pressure and temperature. Saturated humidity is the mass of water vapor that a unit of air can contain under this condition. In temperature supermarkets, the more water vapor can be contained in the air, the greater the saturated humidity. The ratio of humidity to saturated humidity is relative humidity. If the humidity of the air is maintained and the temperature of the air is lowered, when the temperature drops to a certain value, the partial pressure of water vapor reaches the saturation pressure corresponding to the current air temperature, and the water vapor in the air under this condition is saturated. If the air temperature is further reduced, water vapor will condense and precipitate from the air to form dewdrops. This phenomenon is called condensation
During the temperature test of the small high and low temperature environmental test box, the product condensation phenomenon is caused by the fact that when the ambient temperature in the test box rises, due to thermal inertia, the temperature of the product surface is lower than the ambient temperature. When the humid and hot ambient air encounters When the surface of the product is below the dew point, water vapor will condense on the surface to form dew drops. Moreover, if the product is sealed, when the ambient temperature in the small high and low temperature environmental test box decreases, the temperature of the inner wall of the product shell will drop faster than the temperature of the air in the cavity, and the hot and humid air in the cavity will also condense into dew drops on the inner wall of the product shell. Since most products are not completely sealed, condensation generally occurs in the heating stage. Condensation is related to the material used in the product, the size of the cavity, the rate of temperature rise and fall, and the relative humidity. The worse the heat absorption of the material, the larger the cavity, the faster the temperature rise and fall, and the greater the relative humidity, the stronger the condensation effect. As long as any one of the conditions for the occurrence of condensation is destroyed, the occurrence of condensation can be prevented. Under normal circumstances, the inherent properties such as the material used in the product, the size of the cavity, and the upper limit of temperature stability used in the test, the lower limit of temperature stability, and the rate of temperature rise and fall have been determined in advance.
The above content is the editor to share with you the reasons for condensation when the small high and low temperature environmental test box is in use.