(* calculation of residual enthalpy and entropy for isobutane
   using the Pitzer model for vapor (non ideal) - in the 
   text book, they have used compressibility data and calculated the
   integrals - page 213 *) 

REQUIRE "thermodynamics.a4l";

MODEL example63;
    component IS_A symbol_constant;
    component :== 'isobutane';  
    cd IS_A components_data([component],component);

    pvc IS_A Pitzer_vapor_component(P,T,cd.data[component]);
    ivc IS_A ideal_vapor_component(P,T,cd.data[component]);
    P IS_A pressure;
    T IS_A temperature;
    vivc, vpvc IS_A molar_volume;
    vresidual IS_A factor;  
    hivc, hpvc, hresidual IS_A molar_energy;
    givc, gpvc, gresidual IS_A molar_energy;
    sivc, spvc, sresidual IS_A molar_entropy; 
 
    vresidual = (pvc.v - ivc.v)/1.0{m^3/mole};
    hresidual = pvc.h - ivc.h;
    gresidual = pvc.g - ivc.g;
    sresidual = (hresidual - gresidual)/T; 

METHODS
    METHOD values;
    P.fixed := TRUE;
    P := 15.41 {bar};
    T.fixed := TRUE;
    T := 360.0 {K};
    END values;
    METHOD all;
    RUN default_all; 
    RUN values;
    END all;

END example63;