FAQ

FAQ

What is the difference between atmospheric dew point and pressure dew point?

Atmospheric pressure is the pressure caused by the weight of the atmosphere. Normal atmospheric pressure is approximately 0.1013 MPa abs. When the pressure gauge of your equipment is pointing to 0.69 MPaG, the actual pressure is about 0.7913 MPa abs. The actual compression ratio can be obtained by dividing this figure by the atmospheric pressure. In this case, the ratio is 7.81:1. One cubic meter of air can hold 51.19 g/m3 of water vapor at a temperature of 40°C under normal atmospheric pressure conditions while the same amount of air can hold only 6.55 g (51.19 g/7.81) of water vapor at 0.69 MPaG pressure. As shown in this example, when pressure increases, the moisture contained in the gas compresses, making it dry.

This can be neatly summed up by the following equation:
Water content at atmospheric pressure (g/m3) / Actual compression ratio = Water content at a given pressure (g/m3)


Environment and Energy Conservation