FUNCTIONAL FORMS TO DESCRIBE THERMODYNAMIC PROPERTIES OF GASES FOR FAST CALCULATIONS

A simple way to derive physically based functional forms for approxima te description of thermodynamic properties of gases is presented. The polynomials in transformed variables obtained are intended for fast in dustrial calculations. The approach is applied on eleven thermodynamic dependencies with pairs of independent variables most frequently enco untered in turbine calculations. These functional forms were originall y derived for the description of steam properties, but they are equall y applicable to any gas in adequate region of state parameters. Approx imation function for the dependence T(h, s) of steam is presented as a n example including the values of 18 fitted parameters.