<p> First, the constant temperature and humidity test chamber heating process
The temperature rise in the test chamber is mainly the use of high-power resistance wire. Because the temperature rise rate required by the test box is large, the temperature system of the test box is divided into two subsystems: humidification and dehumidification;
Second, the constant temperature and humidity test chamber cooling process
Cooling is cooling, the cooling mode of the test box is mechanical refrigeration and auxiliary liquid nitrogen refrigeration, mechanical refrigeration uses vapor compression refrigeration, they are mainly composed of compressor, condenser, throttling mechanism and evaporator, constant temperature and humidity test chamber if The temperature requirement of the larger cabinet is as low as -55 °C or below, and single-stage refrigeration is difficult to meet the requirements. Therefore, the cooling method of the test box generally adopts cascade cooling.
Third, constant temperature and humidity test chamber humidification process
The humidification process of the constant temperature and humidity test chamber actually increases the partial pressure of water vapor. The initial humidification method is to spray water to the wall of the constant temperature and humidity test chamber, and 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. Since 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, it is inevitable that water droplets will drip on the sample to form different degrees of contamination on the sample.
Fourth, constant temperature and humidity test chamber dehumidification process
There are two ways to dehumidify the test chamber: mechanical refrigeration dehumidification and dry dehumidification.
1. The principle of dehumidification of mechanical refrigeration dehumidification is to cool the air below the dew point temperature, so that the water vapor larger than the saturated moisture content is condensed and precipitated, thus reducing the humidity.
2. Dehumidifier of the dryer uses the air pump to pump out the air in the test chamber, and injects the dry air. At the same time, the humid air is sent to the recyclable dry for drying. After drying, it is sent to the test chamber. Dehumidification is carried out.
Most of the constant temperature and humidity test chambers now use the former dehumidification method. The latter dehumidification method requires an additional dehumidifier or chemical dehumidification to achieve a dew point temperature of 0 °C. Suitable for occasions with special requirements, but at a relatively high cost
The temperature rise in the test chamber is mainly the use of high-power resistance wire. Because the temperature rise rate required by the test box is large, the temperature system of the test box is divided into two subsystems: humidification and dehumidification;
Second, the constant temperature and humidity test chamber cooling process
Cooling is cooling, the cooling mode of the test box is mechanical refrigeration and auxiliary liquid nitrogen refrigeration, mechanical refrigeration uses vapor compression refrigeration, they are mainly composed of compressor, condenser, throttling mechanism and evaporator, constant temperature and humidity test chamber if The temperature requirement of the larger cabinet is as low as -55 °C or below, and single-stage refrigeration is difficult to meet the requirements. Therefore, the cooling method of the test box generally adopts cascade cooling.
Third, constant temperature and humidity test chamber humidification process
The humidification process of the constant temperature and humidity test chamber actually increases the partial pressure of water vapor. The initial humidification method is to spray water to the wall of the constant temperature and humidity test chamber, and 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. Since 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, it is inevitable that water droplets will drip on the sample to form different degrees of contamination on the sample.
Fourth, constant temperature and humidity test chamber dehumidification process
There are two ways to dehumidify the test chamber: mechanical refrigeration dehumidification and dry dehumidification.
1. The principle of dehumidification of mechanical refrigeration dehumidification is to cool the air below the dew point temperature, so that the water vapor larger than the saturated moisture content is condensed and precipitated, thus reducing the humidity.
2. Dehumidifier of the dryer uses the air pump to pump out the air in the test chamber, and injects the dry air. At the same time, the humid air is sent to the recyclable dry for drying. After drying, it is sent to the test chamber. Dehumidification is carried out.
Most of the constant temperature and humidity test chambers now use the former dehumidification method. The latter dehumidification method requires an additional dehumidifier or chemical dehumidification to achieve a dew point temperature of 0 °C. Suitable for occasions with special requirements, but at a relatively high cost
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