SmoothSTF program for calculating approximation functions which approximate the standard thermodynamic functions (STF). The approximation functions are determined by coefficients that are calculated by the least square method coupled with meeting the conditions set (calculation of minimum with equality constraints). To calculate the coefficients the values of STF derivatives with respect to temperature must be available in addition to the table of STF values. The values of the derivatives are established using cubic splines and the derivative of the Lagrange interpolation polynomial. STF of individual substances are given by thermal capacity at constant pressure, entropy and enthalpy. STF are continuous and smooth in every temperature interval in which no phase transformations take place.
For calculations of processes in which chemical transformations take place, it is necessary to know the equilibrium constants of the independent chemical reactions possible in a given system. Equilibrium constants of reactions as well as the equilibrium composition of systems and their thermodynamic properties are given by the heat of formation of individual substances and by their STF.
Acknowledgement:
This paper contains the results of research work funded until the end of 2011 from Research Plan No. MSM0021630516 of the Ministry of Education, Youth and Sports of the Czech Republic, and later from the project of specific research program of Brno University of Technology No. FEKT-S-11-19.
