SequenceSpecific heat capacities of a gas mixture

Specific heat capacities of a gas mixtureAs a consequence of the Gibbs-Dalton law the internal energy of a mixture of gases is given by the Eq. 6.5

Also for a perfect gas from Eq. 2.14

Hence substituting we have

or

Eq.6.18

Specific heat capacities of a gas mixture Contd.Similarly from Eq.6.6

And from Eq.2.18

Therefore

Or

Eq.6.19

Specific heat capacities of a gas mixture Contd.From equations from 6.18 and 6.19

Using equation 2.17,

Also from equation 6.12

Specific heat capacities of a gas mixture Contd.Therefore for the mixture

The equations 2.20, 2.21 and 2.22 can be applied to a mixture of gases

Problem: The gas in an engine cylinder has a volumetric analysis of 12% CO2 , 11.5% O2 and 76.5% N2 . The temperature at the beginning of the expansion is 1000 C and the gas mixture expands reversibly through a volume ratio of 7 to 1, according to a law pv1.25=constant. Calculate the work done and the heat flow per unit mass of gas. The values of cp for the constituents averaged over the temperature are as follows: cp for CO2 = 1.271kJ/kgK; cp for O2 = 1.110 kJ/kgK; cp for N2 = 1.196 kJ/kgK.

Specific heat capacities of a gas mixture Contd.

The End