The air from the qanat is drawn into the tunnel at some distance away and is cooled both by contact with the cool tunnel walls / water and by the transfer of latent heat of evaporation as water evaporates into the air stream.
12.
The component of total energy transfer that accompanies the transfer of vapor into the surrounding subsystem is customarily called'latent heat of evaporation', but this use of the word heat is a quirk of customary historical language, not in strict compliance with the thermodynamic definition of transfer of energy as heat.
13.
What you need is the heat of evaporation at 298 K . If the only figure you have is for 373 K, you can adjust for the temperature difference using conservation of energy : It should take the same energy to evaporate the water at 298 K and then heat the vapor to 373 K as it should to heat the water to 373 K and evaporate it there.
