Przybliżenie wzorem tablic ciepła właściwego powietrza suchego

The paper presents a methods of approximation models identification of two-dimensional Lemmon thermodynamic tables of specific heat of the air in the temperature range 300 to 2000 K and pressures 0.101325 to 20 MPa. The method of least squares and minimization of the maximum deviations was used for this purpose. Considered models are linear combinations of basic functions. There are considered two-dimensional polynomials complete and incomplete higher degrees and combinations of any of basic functions. Also there is analyzed a model based on the approximation of the contour lines for p = idem and T = idem. This allowed to emerge basis functions corresponding to the nature of the approximated data. The elaborated formulas allow calculation of the specific heat at constant pressure and at constant volume value in the above ranges of pressures and temperatures with errors of no more than 0.083% of the table values.