why is the enthalpy of air same before and after adiabatic saturation?

Question

"The enthalpy of water vapour in air can be taken to be equal to the enthalpy of saturated vapour at the same temperature",says my professor.
So enthalpy is a function of temperature alone....
An adiabatic process doesnt neccesarily mean that it is isothermal.....
so unless the temperature of the air is'nt constant, how can it's enthalpy be constant?

Answer 1

Well you've answered your own question. The answer is the air temperature doesn't remain constant.

Adiabatic means no heat transfer. As the water vapor is absorbed into the air the air temperature drops. And the water temperature (bulk water, source of the vapor) also drops.

That's the way a evaporative cooling tower works.

The enthalpy of water vapor + air = the decrease in the enthalpy of the bulk water.

Answer 2

In thermodynamics, the quantity enthalpy, symbolized by H, also called heat content, is the sum of the internal energy of a thermodynamic system plus the energy associated with work done by the system on the atmosphere, which is the product of the pressure times the volume.