Estimate the residual enthalpy of propane at 120 degree C an

Estimate the residual enthalpy of propane at 120 degree C and 8 MPa.

Solution

Residual Enthalpy, H^R = H^actual - H^ideal

From P-H diagram given, we get

H^actual = H (P = 8 MPa, T = 120^oC) = 564 KJ/kg

H^ideal = H (P = 0 MPa, T = 120^oC ) = 815 KJ/kg    (At low pressure system behaves like an ideal gas)

H^R = (564 - 815) KJ/kg = -251 KJ/kg