A Study on Flow Characteristics and Heat Transfer in Countercurrent Water and Air Flows

Abstract

Flow characteristics, and the heat and mass transfer in a countercurrent annular two-phase flow in a vertical circular tube, where hot water flows downward as a film and air at room temperature flows upward, have been investigated. It is shown by the experiment that the pressure loss, and the heat and mass transfer rate in the gas phase increase due to the roughness effect of the interfacial wave. It is further shown that when the temperature of water is high, condensation of vapor occurs in the gas phase, and the heat transfer rate is enhanced by the release of latent heat accompanied by mist formation. A theoretical model based on the low Reynolds number k-ε turbulence model is proposed, where an additional production term is considered to incorporate the wave effect. The calculated results of the friction factor and the Nu and Sh numbers are compared with the experimental ones.