Props= LibraryFunctionLoad["CoolProp","Props",{UTF8String,UTF8String,Real,UTF8String,Real,UTF8String},Real];
Props["T","P",300,"Q",1,"R134a"]
LibraryFunctionUnload[Props]

HumidAirProps= LibraryFunctionLoad["CoolProp","HumidAirProps",{UTF8String,UTF8String,Real,UTF8String,Real,UTF8String,Real},Real];
HumidAirProps["D","T",300,"P",101.325,"R",0.5]
LibraryFunctionUnload[HumidAirProps]