天然气中水分较少时，水分以过热蒸气状态存在。当水分逐渐增多，在一定温度下，水分只能增加至某一个

最大值，即天然气已被水蒸气所饱和，气体中的水蒸气分压也达到该温度下的最大值——饱和蒸气压。When there is little water in natural gas, the water exists in superheated vapor state. When the water gradually increases, at a certain temperature, the water can only increase to a certain maximum value, that is, the gas has been saturated by water vapor, the partial pressure of water vapor in the gas also reaches the maximum value at this temperature -- the saturated vapor pressure.