Estimation of air specific heat ratio at elevated pressures using simple predictive tool

Over the years, considerable research effort has been expended towards evaluation of the thermophysical and transport properties of air for a wide range of temperatures. However, a relatively limited attention was oriented towards investigation of air specific heat ratios at elevated pressures. In this work, a simple predictive tool, which is easier than current available models, less complicated with fewer computations and suitable for process engineers, is presented here for the prediction of specific heat ratio of air at elevated pressures as a function of temperature and pressure using a novel and theoretically based meaningful Arrhenius-type asymptotic exponential function combined with Vandermonde matrix. The proposed method is superior owing to its accuracy and clear numerical background based on Vandermonde matrix, wherein the relevant coefficients can be retuned quickly if more data are available. The proposed correlation predicts the specific heat ratios of air for temperatures up to 1000 K, and pressures up to 1000 bar (100,000 kPa). Estimations are found to be in excellent agreement with the reliable data in the literature with average absolute deviations being less than 0.2%. The tool developed in this study can be of immense practical value for the engineers and scientists to have a quick check on the compressed air specific heat ratios at various conditions without opting for any experimental measurements. In particular, chemical and process engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions. (C) 2010 Elsevier Ltd. All rights reserved.