Dew Point and Saturation Point in BAS

Dew Point

• Dew point is the temperature to which air must be cooled to become saturated without changing the pressure. 
• Changing the pressure affects the vapor pressure and therefore the temperature at which saturation occurs.
• Thus, the dew point temperature is determined by keeping the pressure fixed.
• Changes in pressure slightly modify the dew point temperature.
• The dew point is useful in forecasting minimum temperatures, forecasting the formation of dew and frost, and predicting fog.
• When the dew point equals the air temperature, the air is saturated and the relative humidity is %100.  
• The dew point temperature tells us nothing about how many water molecules are in the atmosphere or how close the air is to a relative humidity of 100%.

Saturation Point

• The saturation temperature is the temperature at which the refrigerant changes from a liquid state to a gas. The boiling point is the same as this. The saturation temperature of water at sea level is 212F. As pressure increases, the liquid's saturation temperature goes up.
• The saturation temperature is just the official name for the boiling point. The term “saturation” comes from the fact that it is the temperature that a liquid has to be at to boil and enter the vapor phase, based on its saturation pressure.
• At constant pressure, if you remove heat and have a vapor at its saturation temperature, it will condense and become a liquid.