How does water precipitate in the cooler (or switching heat exchanger?

When air enters into the cooler (or switching heat exchanger) through the last stage cooler of air compressor and nitrogen water precooler, the content of water vapor in the air has reached the saturated state. After that, with the decrease of temperature, the corresponding pressure of saturated water vapor is decreasing; the content of saturated water per cubic meter of air is gradually decreasing. For example, when the temperature drops from 30℃ to-60℃, the saturated moisture content in the air changes from 30.3 g/m³Reduce to 0.011 g/m³. The extra water is precipitated on the stuffing of the cooler or the fin of the Plate-fin Heat Exchanger. At-60℃, the saturated water vapor pressure has decreased to 1.067 Pa, which can be considered as no water, so 30℃ to-60℃ is called the water precipitation area.
The "three-phase point" of water (the state of the coexistence of gas phase, liquid phase and solid phase) pressure is 0.613kPa, and the temperature is 0.01 ℃. When the partial pressure of the water vapor in the air is higher than that of the three-phase point, the air temperature reaches the saturation temperature and the water vapor is precipitated in the liquid state. Changing from gas phase to liquid phase is called "condensation" or "liquefaction ". When the partial pressure of water vapor in the air is lower than that of the three-phase point, and the air temperature reaches the saturation temperature, the water vapor is directly precipitated in the solid state, and it is called "crystallization" or "Solidification" from the gas phase to the solid phase without going through the liquid state ". The air temperature drops from 30℃ to 0℃, and the partial pressure (saturated vapor pressure) of water vapor is always higher than that of three-phase point, so the eluate in this temperature range is water drops or water membrane. When the temperature is reduced from 0℃ to-60℃, the saturated vapor pressure is lower than the pressure of three-phase point, and the precipitate of vapor is frost or snowflake-like (when the moisture content is too large, it will freeze into ice ).