Humidity generally represents the physical quantity of the dryness of the atmosphere. At a certain temperature and in a certain volume of air, the less water vapor it contains, the drier the air is; the more water vapor it contains, the more humid the air is. The degree of dryness and humidity of the air is called “humidity”. In this sense, physical quantities such as absolute humidity, relative humidity, comparative humidity, mixing ratio, saturation and dew point are commonly used to express it. If it expresses the weight of liquid water in wet steam as a percentage of the total weight of steam, it is called the humidity of steam.
The concept of humidity is the amount of water vapor contained in the air. There are three ways to express it:
1. Absolute humidity represents the amount of water vapor contained in each cubic meter of air, the unit is kg/m³;
2. Moisture content, indicating the amount of water vapor contained per kilogram of dry air, the unit is kg/kg*dry air;
3. Relative humidity represents the ratio of the absolute humidity in the air to the saturated absolute humidity at the same temperature. The number is a percentage, that is, within a certain period of time, the amount of water vapor contained in the air somewhere is divided by the saturated amount of water vapor at that temperature. percentage.
When the steam generator is operating, the smaller the relative humidity, the greater the distance between the air and the saturation level, so the moisture absorption capacity is stronger. This is why wet clothes can easily dry out on sunny days in winter. Dew point temperature and wet bulb temperature As mentioned earlier, water vapor in unsaturated humid air is in a superheated state.
The constant pressure formation process of superheated steam
It is divided into the following three stages: constant pressure preheating of unsaturated water, constant pressure vaporization of saturated water, and constant pressure superheating of dry saturated steam. The heat added in the constant pressure preheating stage of unsaturated water is called liquid heat; the heat added in the constant pressure vaporization stage of saturated water is called vaporization heat; the heat added in the constant pressure superheating stage of dry saturated steam is called superheat.
(1) Saturated steam: Under a certain pressure, water is heated to boiling, the saturated water begins to vaporize, and the water gradually turns into steam. At this time, the temperature of the steam is equal to the saturation temperature. The steam in this state is called saturated steam.
(2) Superheated steam continues to be heated on the basis of saturated steam. The temperature of saturated steam exceeding this pressure is superheated steam.
Post time: Oct-09-2023
