Use of a correlation developed by NASA's Jet Propulsion

Laboratory in 2004.

The Correlation takes the basic form:

DAB (Large P) = DAB(Kinetic Theory)/WD,B

WD,B=1+δD,B

δD,B = c*ρr^(3/2)

c=.58 or .42 depending on fit

ρr =ρ/ρc

Example C2H4 – CO2     P=10000 kPa, T=298.2 K

First Calculate the kinetic theory Diffusivity at 1 atmosphere

restart;

dcalc(101.325,T,A:B) - start301

dcalc:=5.884*10^(-5)*m^2/s;

restart;

0.00005884 m^2/s

Calulate WD,B=1+δD,B

WDB:=1+delDB;

1 + delDB

Tcrit(B),Pcrit(B),Zcrit(B) mw(B) - start301

atm:=101.325*kPa; R:=82.0578*cm³*atm/(mol*K); P:=10000*kPa; T:=298.2*K

_{101.325 kPa}

_{8314.506585 cm^3 kPa/mol} K

10000 kPa

298.2 K

_{To calculate the molar volume, we use Van der Waals Equation of State}

_{(P+a/Vm²)(Vm-b)=RT   for CO2 a=.396 Pa*m³  and b=.00004269 m³/mol}

V:=4.38963*cm³/mol 

Pc:=7380.5*kPa; Zc:=.274; Tc:=304.2*K; MW:=44.01*g/mol

4.3893 cm^3/mol

Pc:=7380.5*kPa; Zc:=.274; Tc:=304.2*K; MW:=44.01*g/mol

7380.5 kPa

0.274

304.2 K

44.01 g/mol

Z:=P*V/(R*T);

      0.1770450523

rhor:=(P/(T*R*Z))/(Pc/(Zc*R*Tc));

21.39107224

C:=0.58

0.58

_{delDB:=c*rhor^(3/2);}

57.38215115

Finally calculate diffusivity at a high pressure:

_{DhighP:=dcalc/(1+delDB);}

0.000001007832120 m^2/s