# Properties of air and gas mixture

While studying a heat exchanger, I have encountered a hydrogen rich fluid stream (enters at 90° Celsius and exits at 120° Celsius) which has composition given in the following form:

Air Humidity/Fluid composition: 1% (2.5 bar abs)/Mass fraction of hydrogen=0.02

For the heat exchanger analysis, I need to calculate several properties of this mixture like enthalpy, specific heat.

Property reference software like Coolprop and Refprop give data for gas mixtures, but not for air-gas mixtures.

How should I start to calculate the properties of this air-gas mixture? I guess the humidity can be neglected safely because it is just 1%.

• Why exactly can you neglect humidity? Mar 27, 2022 at 16:13
• @SolarMike Honestly, I just wrote the assumption looking at only 1% value of the relative humidity which would imply a very small mole fraction of water vapour. Mar 28, 2022 at 3:51

A molar thermodynamic property $$\bar{P}$$ for a mixture containing ideal gases can generally be calculated from molar composition (mole fraction $$z_j$$) and individual component molar property $$\bar{P}_j$$ as
$$\bar{P} = \sum\ z_j\ \bar{P}_j$$