Experimental Study of Two-phase Pressure Drop in Adiabatic Tubes at Subatmospheric System Pressures

Abstract

The prediction of the frictional pressure drop in the two-phase flow has become highly crucial for the enhancement of heat transfer methodologies for various industrial applications in order to design thermal equipment efficiently. The pressure drop in the heat transfer equipment is affected by the system pressure, system geometry and working fluid. There is a dearth of literature on two-phase pressure drop in the conventional adiabatic tubes at subatmospheric system pressures. Experimental investigations on the pressure drop have been conducted at 0.25, 0.5, 0.75, and 1 bar system pressures in 1500 mm long, 8, 13.7, and 18 mm diameter adiabatic tubes. The steam at 0 – 1 vapor quality is used at 32 – 660 kg/m2s mass flux in the adiabatic tubes. The effects of tube diameter, vapor quality, mass flux and system pressure on two-phase frictional pressure drop are investigated. In the liquid-vapor flow, the pressure drop experiences a non-linear increase with changes in vapor quality. The frictional pressure drop in two-phase flow is elevated with higher vapor quality, reduced subatmospheric system pressure, increased mass flux, and a smaller tube diameter. The correlations suggested for two-phase frictional pressure drop at higher system pressure predict the pressure drop reasonably in the adiabatic tubes at subatmospheric system pressure.