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The process of humidification is actually to increase the partial pressure of water vapor. The initial method of humidification is to spray water onto the wall of the test chamber.
The water surface saturation pressure is controlled by controlling the water temperature. The water on the surface of the tank wall forms a large surface on which the water vapor pressure is added to the tank by means of diffusion to increase the relative humidity in the test chamber. This method appeared in the 1950s. Because the control of humidity at that time is mainly a simple switchover adjustment of the mercury-electric contact type conductivity meter, the control of the water temperature of the hot water tank with large hysteresis is poor, so the transition process of the control is long and cannot meet the alternating heat and humidity. The need for more humidification, and more importantly, when spraying the wall of the tank,
Inevitably, water droplets drip on the sample to form different degrees of contamination on the sample. At the same time, there are certain requirements for the drainage inside the tank. This method was quickly replaced by steam humidification and shallow water pan humidification. But this method still has some advantages. Although its control transition process is long, the humidity fluctuation is small after the system is stable, which is more suitable for constant damp heat test. In addition, the moisture in the humidification process does not increase the extra heat in the system. Also, when the temperature of the spray water is controlled to be lower than the point temperature required for the test, the spray water has a dehumidification effect.
Humidity is expressed in many ways. In the case of test equipment, the concept of relative humidity is often used to describe humidity. Relative humidity is defined as the ratio of the water vapor pressure in the air to the saturated vapor pressure of water at that temperature and is expressed as a percentage. It is known from the nature of water vapor saturation pressure that the saturation pressure of water vapor is only a function of temperature. It is independent of the air pressure at which water vapor can be used. Through a large number of experiments and collation, people have found a relationship between water vapor saturation pressure and temperature, which has been A large amount of measurement should be adopted by the Goffeglie formula. It is used by the current meteorological department to compile a humidity checklist.
How to humidify and dehumidify the constant temperature and humidity test chamber
How to humidify and dehumidify the constant temperature and humidity test chamber in order to realize the test conditions, it is inevitable to humidify and dehumidify the test box. This paper uses various methods in the constant temperature and humidity test chamber. Analysis, pointing out their respective strengths and weaknesses and recommended conditions.