function cpav = CpAiravg(T)
a = 28.09;
b = 0.001965;
c = 0.000004799;
d = -0.000000001965;
Tref = 25+273.15;
CpT = a*T + b/2*T^2 + c/3*T^3 + d/4*T^4;
CpTref = a*Tref + b/2*Tref^2 + c/3*Tref^3 + d/4*Tref^4;
cpav = (CpT-CpTref)/(T-Tref);

