This function calculates the liquid phase enthalpy of R134a from the state variable p (absolute pressure). It is modelled by cubic splines which are fitted with non-equidistant grid points derived from the fundamental equation of state of Tillner-Roth and Baehr (1994) and the Maxwell criteria.
It is only valid in the two-phase region (i.e., ptriple ≤ p ≤ pcrit ).