DETERMINATION OF DIFFERENCES AND RATIOS OF SPECIFIC HEATS AND CHANGE IN ENTROPY AS APPLIED TO FIVE EQUATIONS OF STATE FOR GASES

Abstract

Abstract : Presented in this report are the results of an investigation to determine analytically two thermodynamic transport properties -- difference in specific heats and the change in entropy -- as described by five independent equations of state for gases. Change in entropy and specific heats of gases are used in thermodynamics work to evaluate properties of gases undergoing change of state such as flow properties behind shocks. Change of entropy is a logical starting point for this work and where applicable properties are known at high temperatures these equations may be used. Steam was used for illustrative purposes because it is a well defined, thoroughly explored gas. The development of the equations precedes each equation in a logical, straightforward manner and ends with the desired properties in terms of known thermodynamic coordinates. Comparison of the calculated change in entropy is presented in bar-graph form for these equations of state for a real gas, superheated steam. A comparison of the difference in specific heats for these equations for the same gas is given. In both the entropy change and the difference in specific heat, good agreement is found among the five equations of state.