**IdealGasMixtureProps**

IdealGasMixtureProps is an EES Procedure that will determine the specific enthalpy, entropy, viscosity and thermal conductivity of a mixture of ideal gases.

**Inputs:**

F$ a string constant or string variable that contains the names of 1 or more (up to 20) names of ideal gases that are contained in the EES property library. The names of the gases are separated with a + sign, e.g., 'CH4+C3H8'

T the temperature in the units EES is configured to work in.

P the pressure in the units EES is configured to work in. (Pressure is used only for calculation of specific entropy)

f[1..N] the mass or mole fractions of the gases represented by string F$. The sum of the values of f must add to 1.0. Supply mass fractions if EES is configured to work with specific properties on a mass basis. Otherwise, supply mole fractions.

**Outputs:**

MW The molar mass of the mixture in kg/kmol or lbm/lbmol

h the specific enthalpy of the mixture determined as the mole fraction-weighted average of the gases in the mixture. The units of h will be returned on a per unit mass basis if EES is configured to provide properties on a mass basis. Otherwise the units of h will be returned on a molar basis.

s the specific entropy of the mixture determined as the mole fraction-weighted average of the gases in the mixture plus the entropy change of mixing the gases. The units of s will be returned on a per unit mass basis if EES is configured to provide properties on a mass basis. Otherwise the units of s will be returned on a molar basis.

mu The viscosity of the gas mixture determined using the Wilke Approximation as described in Eq. 9-5.2 of Reid, Prausnitz, and Sherwood.

k The thermal conductivity of the gas mixture determined using the Mason and Saxena modification, as described in Eq. 10-6.2. of Reid, Prausnitz, and Sherwood.

**Reference:**

Reid, Prausnitz, and Sherwood, 3rd edition, McGraw-Hill, (1977).

**Note:**

IdealGasMixtureProps is not built into EES. Rather, it is an external Procedure that is loaded from the ..\USERLIB\EES_System\IdealGasmixtureProps.LIB. This file is provided in the EES installation.

**Example:**

$UnitSystem SI C kPa molar kJ

F$='CH4+C4H10'

T=20 [C]

P=101.3 [kPa]

N=2

y[1..N]=[0.697,0.303]

*Call***idealgasmixtureprops**(F$,T,P,y[1..N]: MW, h, s, mu, k)

{**Solution**

F$='CH4+C4H10'

h=-90377 [kJ/kmol]

k=0.02466 [W/m-K]

mu=0.000009313 [kg/m-s]

MW=28.79 [kg/kmol]

N=2

P=101.3 [kPa]

s=227.9 [kJ/kmol-K]

T=20 [C]}

See also: Thermophysical Functions