On the effect of friction in steady flow of dense gases in pipes

Abstract

The effect of friction in steady, one-dimensional flow of a real gas in pipes is treated in the paper, with an emphasis on the dense gas effects. In addition to the well-known fundamental derivative of gas-dynamics Γ, another derivative, defined as Γ 1 = 1 + p(∂c/∂p) T / c , is shown to play a very important role in studying these non-isentropic flows. In both of two characteristic cases of flow, isothermal and adiabatic one, pressure and density variations along the pipe are not affected by the dense gas effect, their variations being qualitatively the same as in perfect gas theory. Variations of the temperature and of the Mach number are, however, severely influenced by the dense gas effect. Perhaps the most important result from the practical point of view is that isothermal flow in the ∂ 1 < 0 region is choking-free, and that adiabatic flow in the ∂ < 0 is almost choking-free. Analytic considerations derived in the paper are supported by a number of numerical results for a van der Waals gas. © 2001 Elsevier Science Inc. All rights reserved.