Interfacial condensation heat transfer of steam-water countercurrent flow in a circular pipe

Abstract

The interfacial heat transfer in a steam-water countercurrent stratified horizontal pipe was experimentally investigated for smooth and rough interfaces, with emphasis on the temperature and velocity distribution within the thick water layer (0.0175 ~ 0.0345m). Although there are several existing experimental studies on this subject, most of the existing studies were performed using a rectangular channel having large aspect ratio. Due to the great difference in flow channel geometry there is a difficulty in applying existing correlations to the flow in NPP (Nuclear Power Plant) directly. When the cross sectional area of a wide rectangular channel and that of a circular pipe are the same, the water layer of the circular channel will be much thicker than that of the wide rectangular channel for given flow rates of steam and water. In particular, when the water layer thickness is increased, the characteristics of heat, mass and momentum transport, such as the turbulent intensity and the efficiency of turbulent mixing in the interface between the steam and water which play a dominant role in the interfacial condensation heat transfer, would be changed. The present experiments have been carried out using a nearly horizontal pipe (0.02°) that has a length of 2.2m and inner diameter of 0.083m. It is shown that the velocity and temperature profiles in the water layer are different between smooth and rough interface. The velocity profile nearby the interface has been obtained by a Hot Film Anemometer. The interfacial condensation heat transfer coefficients with interfacial velocity were higher than that without interfacial velocity. Based on the present experimental data, two Nusselt number correlations were developed in terms of steam and water Reynolds numbers, and the water Jacob number; one for smooth and the other for rough interfaces. The present experimental data agree with the calculated values within ±30% for the smooth interface and ±25% for the rough interfac...