(dn/dt) +[(pe,iφi/ Pi) Mi]
= [(pe,oφo / Po) Mo]
dn/dt = Rate of vapor transport in moles
pe = equilibrium vapor pressure at temperature,
T and total pressure, P.
φ = humidity = (pv/pe)
pv = partial pressure of vapor in unsaturated gas
M = Rate of gas flow in moles
i = incoming flow
o= outgoing flow