Effect of thermodynamic disequilibrium on critical liquidvapor flow conditions
Abstract
In this lecture we characterize the effect of absence of unconstrained thermodynamic equilibrium and onset of a metastable state on the adiabatic flow of a mixture of liquid and its vapor through a convergentdivergent nozzle. We study steadystate flows and emphasize the relations that are present when the flow is choked. In such cases, there exists a crosssection in which the flow is critical and in which the adiabatic wave of small amplitude is stationary. More precisely, the relaxation process which results from the lack of equilibrium causes the system to be dispersive. In such circumstances, the critical velocity is equal to the frozen speed of sound, a(sub f) corresponding to (omega) (yields) (infinity). The relaxation process displaces the critical crosssection quite far downstream from the throat and places it in the divergent portion of the channel. We present the topological portrait of solutions in a suitably defined statevelocity space and discuss the potential appearance of normal and dispersed shock waves. In extreme cases, the singular point (usually a saddle) which enables the flow to become supercritical, is displaced so far that it is located outside the exit. Then, the flow velocity is everywhere subcritical (w less than a(sub f)) even though it may exceed the equilibrium speed of sound (w (approx. gt) a(sub e)) beyond a certain crosssection, and in spite of the presence of a throat.
 Publication:

Presented at the IUTAM Symposium
 Pub Date:
 1989
 Bibcode:
 1989iuta.symp.....B
 Keywords:

 ConvergentDivergent Nozzles;
 Critical Flow;
 Steady Flow;
 Thermodynamic Equilibrium;
 Vapor Phases;
 Phase Diagrams;
 Shock Waves;
 Thermodynamics;
 Thermodynamics and Statistical Physics