Singlesubstance, twophase duct flow: A unified theoretical and experimental study
Abstract
A derivation of basic conservation equations for each phase (a two fluid model) is presented. The analysis assumes onedimensional, steadystate twophase flow of a single substance in a variable crosssectional area duct of arbitrary orientation. The equations are used to examine and explain the phenomenon of slip (phases moving at different velocities). A study of choking is carried out and expressions for the critical mass flux in the presence of slip are derived. The effect of compressibility due to phase change (evaporationcondensation) on the flow states and the critical mass flux is investigated. The Mach, Reynolds and Froude numbers are identified as the most important characteristic parameters. Experimental measurements of pressure and temperature change and void fraction for adiabatic vertical flow in a circular duct are presented. The experimental points cover the full range of the flow from near flashing to choking. The effect of the characteristic parameters on the evolution of the flow is demonstrated on the basis of the experimental results and an estimate of the velocity ratio is obtained for each case examined. The measurements indicate that thermodynamic equilibrium exists in the flow except in the immediate neighborhood of flashing. The pressure evolution is dominated by hydrostatic effects in the initial region after flashing and by high acceleration in the neighborhood of choking. In the intermediate region, vicous, inertial and gravitational effects play a role of equal importance.
 Publication:

Ph.D. Thesis
 Pub Date:
 August 1986
 Bibcode:
 1986PhDT........10N
 Keywords:

 Compressibility Effects;
 Ducted Flow;
 Flow Characteristics;
 Refrigerants;
 Thermodynamic Equilibrium;
 Two Phase Flow;
 Flow Equations;
 Mach Number;
 Pressure Measurement;
 Reynolds Number;
 Temperature Measurement;
 Working Fluids;
 Fluid Mechanics and Heat Transfer