This function calculates the density and temperature of R134a from absolute pressure and specific entropy in one-phase region. The function calls the fundamental helmholtz equation of Tillner-Roth (1994) which is requiring density and temperature for input. Thus, a newton iteration is performed to determine density and temperature. The newton iteration stops if the inputs for pressure difference delp and specific entropy difference dels are larger than the actual differences derived from the newton iteration.
function dtofpsOnePhase extends Modelica.Icons.Function; input AbsolutePressure p "Pressure"; input SpecificEntropy s "Specific entropy"; input AbsolutePressure delp "Absolute iteration accuracy"; input SpecificEntropy dels "Absolute iteration accuracy"; output Density d "Density"; output Temperature T "Temperature"; output Integer error "Error flag: trouble if different from 0"; end dtofpsOnePhase;