Determination of Thermodynamic Properties of New Refrigerants by a Simple Equation of State

Abstract

A simple extension of the Redlich-Kwong equation of state in which one of the original constants is replaced by a polynomial in powers of temperature is shown to accurately fit the p-v-T data of the new refrigerants: HCFC-123 and HFC-134a and the data of refrigerant HCFC-22. The two new refrigerants are developed to replace the thermally efficient but ozone-depleting refrigerants CFC-11 and CFC- 12, respectively. The coefficients of the polynomial extension are determined by fitting known p-v-T properties at a number of selected base points. Based on this equation of state and a specific heat relation, a simple computational procedure is used to compute the enthalpy and entropy. With only 4 terms in the polynomial extension of the equation of state, the method is shown to produce highly accurate results over a wide range of pressures and temperatures for each of the three refrigerants.