A GENERALIZED CRITICAL FLOW MODEL FOR NONIDEAL GASES

The authors present a generalized formulation for evaluating the critical flow rate of a nonideal gas characterized by the Redlich-Kwong (R-K) equation of state (EOS). The case of interest is one-dimensional isenthropic flow in a frictionless nozzle. This study seeks a generalized treatment in terms of reduced thermodynamic properties. The main focus of this paper is, therefore, to present for the first time generalized plots in a form most engineers would prefer and accurate enough for practical applications. The R-K EOS was favored due to its wide use in practice and its simple two-parameter form. In agreement with previous work by H.A. Duxbury various modifications to the ideal gas flow equations involving the use of the compressibility factor Z were found to be inaccurate when Z deviates substantially from unity.