Returns the current region (valid values: 1,2,4) for given pressure and specific enthalpy
function region_ph input Units.SI.Pressure p "pressure"; input Units.SI.SpecificEnthalpy h "specific enthalpy"; input Integer mode = 0 "mode: 0 means check, otherwise assume region=mode"; output Integer region "region (valid values: 1,2,4)"; end region_ph;