A Study of the Flow Characteristics of Gas-Liquid Two-Phase Flow in a Plate Heat Exchanger (Visualization and Void Fraction Measurement in a Single Channel)

Abstract

In order to clarify the gas-liquid two-phase flow characteristics in a plate heat exchanger, gas-liquid two-phase flows in simulated heat exchangers with a single channel placed in a vertical plane were visualized by a neutron radiography method. Adiabatic air-water two-phase flows and R 141 b boiling two-phase flows were visualized, and two-dimensional void fraction distributions were measured from visualized images via some image processing techniques. Moreover, total pressure loss of adiabatic airwater two-phase flows through the test section was measured, and the frictional pressure loss was calculated by using measured results of average void fraction. As a result, it was shown that the phase distributions in heat exchangers were strongly affected by the inlet configuration and the inlet conditions. In the case that the incoming flow was a gas-liquid two-phase flow, stagnant liquid at the test section inlet caused unsymmetrical phase distribution. For high gas volumetric flux, both phases tended to flow straight separately and liquid mixing in the channel with ribs was a little. It was also shows that the average void fractions and the frictional pressure loss of adiabatic air-water two-phase flows in the channel with ribs could be correlated by the drift-flux model and the L-M method, respectively.