A new method for the calculation of gases enthalpy

In this paper, the authors have investigated new polynomial functions for the determination of enthalpy for various gases, and for their mixtures, in ICE applications. Several polynomial functions have been investigated to determine the best matching function with respect to experimental data. Functions investigated are: exponential polynomials and logarithmic polynomials (third, fourth and fifth order). The best polynomial functions have the functional form of a V order logarithmic polynomial, and can be used in temperature ranges of practical interest. Logarithmic polynomial (LP) coefficients have been obtained by least squares matching with thermodynamic property data from the JANAF tables. Values of the specific heat have been calculated as a function of temperature, and they have been compared with experimental ones, in order to evaluate the percent error. Logarithmic polynomials (LPs) have been calculated for various gases: technical air (21% O/sub 2/), N, O, H, H/sub 2/, O/sub 2/, N/sub 2/, CO, OH, NO, CO/sub 2/ and H/sub 2/O. In literature there are many works which present mathematical functions of enthalpy vs temperature. A comparison between the polynomial functions that are present in literature and V order LP has been effected. The new LPs point out a major precision respect to the other polynomial functions, and the possibility to utilise a single LP for a wide temperature range, according to a good accuracy with experimental data.