clear;
clc;
printf("\t Example 2.21\n");
                    //stefan tube experiment(pseudo steady state diffusion)

Ml=92;                       //molecular weight of toluene
T=(303);                    //temperature  in kelvin
pt=1*1.013*10^5;            //total pressure in pascal
R=8314;                    //universal gas constant
t=275*3600;                //after 275 hours the level dropped to 80mm from the top
zo=20*10^-3;              //intially liquid toluene is at 20mm from top
zt=77.5*10^-3;            //finally liquid toluene is at 80mm from top
    //air is assumed to be satgnant 
d=820;                            //density in kg/m^3
pa=(57/760)*1.0135*10^5;          //vapour pressure of toluene in at 39.4degree celcius 
cal=d/Ml;                        //conc. at length at disxtance l
ca=pt/(R*T);                    //total conc. 
xa1=pa/pt;                     //mole fraction of toluene at pt1 i.e before evaporation 
xb1=1-xa1;                    //mole fraction of air before evaporation i.e at pt1 
xb2=1;                        //mole fraction of air after evaporation i.e at pt.2
xa2=0;                        //mole fraction of toluene at point 2
xbm=(xb2-xb1)/(log(xb2/xb1));
        //t/(zt-zt0) = (xbm*cal*(zt+zo))/(2*c*(xa1-xa2)*t);
Dab=(xbm*cal*(zt^2-zo^2))/(2*ca*t*(xa1-xa2));
printf("\n the diffusivity of the mixture in stefan tube of toluene in air is :%f*10^-5 m^2/s",Dab/10^-5);
//end