how do i calculate the energy needed to cool the air down ??

Question

a room of 70 deg fer., 50 pounds mass of air, and 10 pounds of mass of water vapor.. how do i calculate the energy needed to cool the air down to 55 deg. fer. .. plz i need help.. what equation do i use

Answer 1

A stoichiometric chart will help. You also need to know what humidity you're final state should have because the cooling involves latent as well as sensible components.

These are your calculatations.
Find the net mass of water than condenses. Remember the partial vapor pressure is different at the two temperatures, so water will condense.
Secondly find the sensible cooling required to cool down the water vapor, the liquid water, and the air to the final temperature.

Answer 2

you need the 'specific heat capacity' of the air and water vapor. If you don't have a text book giving you that, google it.
the specific heat capacity relates the amount of energy needed to change the temperature 1 degree of a certain mass of a substance. it is usually joules per (degree x gram), so you may have to convert from US to metric to do your work. Or if lucky you may find spec heat as BTU/(degree x pound).
whatever your working with your temperature change is 15 deg (convert to C..?) and you have the masses of two substances.
the eq is energy = mass x change in temp / specific heat capacity.