Properties & Behavior of Air:
General Properties: Air is a mixture of gasses, mainly nitrogen and oxygen. The typical composition of natural air is as follows.
Component Mass % (dry air) Volume % (dry air)
Oxygen 23.14 20.9476
Nitrogen 75.52 78.084
Argon 1.288 0.934
Carbon dioxide 0.048 0.0314
Hydrogen 0.000003 0.00005
Neon 0.00127 0.001818
Helium 0.000073 0.000524
Krypton 0.00033 0.000114
Xenon 0.000039 0.0000087
Air also contains water vapour and hard matter such as dust, microbes and pollen. These variables depend upon climatic conditions, which vary worldwide. The table therefore reflects the European average dry gas content of air, which may vary slightly in your area.The mean molecular weight of dry air is approximately 28.97.The molecular weight of water is only 18.This means that volume by volume, moist air is lighter than dry air.
The amount of energy required to heat up dry air is less than the amount to heat up the same volume of wet air. This is because of the difference in Specific Heat between dry air and water vapour.Everything has a Specific Heat. This is the amount of energy that is required to heat up a given mass of stuff compared to the amount of energy required to heat up the same mass of pure water. If we keep the pressure the same, the Specific Heat is termed Cp.
Cp for 100% water saturated air at atmospheric pressure is about 2000 Joules/kg deg K (or 2.00 kJ/kg deg K)
Cp for dry air at atmospheric pressure is 1020 Joules/kg deg K (or 1.02 kJ/kg deg K)
In real terms this means that it takes almost twice the amount of energy to heat up the water vapour in wet air, than it would take to heat up an equal number of molecules of dry air.
Temp.(°K) Temp.(°C) Specific Heat Capacity (Cp) of Dry Air
250 -23 1.0031
275 +3 1.0038
300 27 1.0049
325 52 1.0063
350 77 1.0082
375 102 1.0106
400 127 1.0135
450 177 1.0206
500 227 1.0295
Behavior of Air: Boyle’s,Charles’,General Gas,Dalton’s & Graham’s laws are sufficiently accurate for normal air in air conditioning calculations,although they are strictly correct only for the hypothetical ideal gas.
[Note:Particularly Graham’s Law, which relates to the Diffusion rate of a gas into air .Basically, a gas lighter than air will diffuse faster than one heavier than air; also, the smaller the specific gravity, the more rapid the diffusion Turbulence and temperature aid diffusion; can have stratification in quiescent air.
https://www.highratecpm.com/q2x8d20i?key=9b0eda27ebf376c2939eaffd6689ce7a
