An Empirical Formula of Mean Specific Heat Capacity of Ideal Gases

Abstract

The method of formulation of tabular data of mean specific heat capacity of gases is discussed and an empirical formula to fit these data is given in this paper. A linear function of temperature is chosen as the formula to piecewise fit mean isobaric specific heat capacity data over a wide range of temperature. For seven gases including air, CO, CO 2 , O 2 , N 2 , H 2 O and SO 2 , the coefficients of the formula are regressed by means of least square method in the range of temperature 0 ℃ to 1200℃ and listed. The whole temperature interval is divided into 3 subintervals: 0 -300℃, 300 -800℃and 800 -1200℃, and fitting is done in the subintervals. The average deviations of the calculated values of the formula and reference values of mean isobaric specific heat capacity are less than 0.3% for all the gases in the temperature range from 0 to 1200℃, except CO 2 . For CO 2 , only in the subinterval of 300 ℃ to 800℃ is the average deviation 0.36%, and in other subintervals the average deviations are less than 0.3%.