Isothermal Air-Water Two-Phase Up-and Downward flows in a Vertical Capillary Tube 1st Report, Flow Pattern and Void Fraction.

Abstract

Knowledge of two-phase flow in a capillary tube is important to understand flow phenomena in narrow passages, for example, in a compact heat exchanger. The present authors have previously reported the characteristics of flow parameters such as pressure drop, and void fraction as well as flow pattern in an air-water two-phase flow in a horizontal capillary tube. In the present paper, we discuss the effect of flow direction on void fraction and flow patterns in two-phase flow in a vertical capillary tube. Two correlations relating bubble velocity with total volume flux and time-averaged void fraction with gas volume flow quality were proposed.