According to the survey, the current constant temperature and humidity test chamber indicators at home and abroad are basically 30% to 98% RH or 20% to 98% RH.
1. Because the relative humidity is directly related to the temperature, for the same absolute moisture content, the higher the temperature, the smaller the relative humidity, such as the absolute moisture content of 6g/kg (refers to one kilogram of dry air containing six kilograms) Water vapor), when the temperature is 30 ° C, the relative humidity is 20% RH, the temperature is 7 ° C, the relative humidity is 90% RH, when the temperature drops below 5 ° C, the relative humidity exceeds 100%, in the box will Condensation occurs.
2, low temperature and low humidity is relatively difficult to control, because the absolute moisture content at this time is very low, sometimes lower than the absolute content of the atmosphere, the need to dehumidify the air in the box, so that the air becomes Dry. The principle of cooling and dehumidification is to add a set of cooling tubes in the air pre-conditioning room of the box. When the humid air passes through the cooling tube, the relative humidity will reach 100% RH, and the cooling tube has condensation, which makes the air become drier. However, such a dehumidification method can theoretically reach a dew point temperature below zero, but when the surface temperature of the cold spot reaches 0 ° C, the water droplets on the surface of the cooling tube will freeze, thereby affecting the heat exchange, so that the dehumidification ability is lowered, and at the same time And because the box can not be absolutely sealed, the humid air in the atmosphere will seep into the box, so that the dew point temperature will rise. On the other hand, the flowing humid air only reaches a saturated state at the moment of contact with the cold pipe to fold out the water vapor. This dehumidification method makes it difficult to make the dew point temperature in the tank below 0 ° C, and the actual minimum dew point temperature is 5 ~7 ° C, dew point temperature 5 ° C corresponds to an absolute moisture content of 0.0055 g / kg, corresponding to a relative humidity of 20% RH temperature of 30 ° C. If the relative humidity reaches 20% RH when the temperature is required to be 20 ° C, the dew point temperature is -3 ° C at this time, and dehumidification is very difficult.
3, constant temperature and humidity test box to achieve high temperature, high humidity only need to spray water vapor into the air, for humidification.
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