In many practical problems, even if the absolute humidity is the same, the corresponding saturation content varies due to different temperatures, that is, the amount of moisture that can be accommodated in the air is also different. Therefore, the speed of evaporation is different. In order to represent the distance between the moisture content in the air and the saturation state, the concept of relative humidity was adopted. Relative humidity refers to the ratio of the water vapor content per cubic meter of air to the maximum allowable content at that temperature.
Since the content of water vapor is directly proportional to its partial pressure, relative humidity can also be expressed as the ratio of the partial pressure of water vapor in the air to the partial pressure of saturated water vapor at that temperature. When the moisture in the air reaches saturation, the relative humidity is 100%; The relative humidity of dry air is 0%. Therefore, the relative humidity is between 0% and 100%.
Due to the decrease of saturated vapor pressure with temperature, even if the relative humidity is 100%, the moisture content (absolute humidity) in the air varies at different temperatures. In the switching heat exchanger of the air separation device, the air temperature continuously decreases. Although the relative humidity of the air is always 100%, the absolute humidity continues to decrease, ultimately allowing all moisture in the air to precipitate, almost without moisture.
