ln(Hvap/Hvapo) = a1 + åai ×Tri-2×ln(1-Tr) , where the summation is from i = 2 to nTerms
Tr = T/Tc, Tc is the critical temperature, and Hvapo = 1 kJ/mol
Hvap = exp(A)×{1 - ( T / Tc )}n
Hvap/(0.001×R×Tc) = a1×t1/3 + a2×t2/3 + a3×t + a4×t2 + a5×t6
where t = 1 - T/Tc, Tc is the critical temperature, and R is the gas constant.