A TWO-PARAMETER THERMODYNAMIC METHOD FOR THE DESCRIPTION OF IRREVERSIBLE PROCESSES IN TWO-PHASE BINARY MIXTURE PARALLEL-FLOW UNITS

摘要

An actual process of a two-phase parallel-flow of a binary mixture with heat exchange to its surroundings is followed by an internal entropy production due to several kinds of irreversibilities which occur inside the flow. Such irreversibilities in actual processes provoke mass fraction deviations from equilibrium, temperature deviations between the two phases and pressure drop. In the present work the flow is assumed to be inviscid (no pressure drop) and the mass fraction and temperature deviations from equilibrium are related to mass and heat exchange delay between the two phases. Based on this criterium of "delay", a thermodynamic method is developed, according to which the determination of an actual state of the process is governed by two parameters: (i) the "degree of vapour delay" or the "degree of liquid delay" and (ii) the "degree of liquid-vapour heat exchange delay". These two parameters both confine the actual process between two extreme processes: the process of no delay (reversible-successive equilibrium states) and the process of total delay (irreversible of maximum delay). As an application of this method, the evaporation and condensation processes of NH{sub}3/H{sub}2O liquid-vapour mixture are considered, and entropy quality indices of these processes are calculated.