INTERFACIAL CONDENSATION FOR COUNTERCURRENT STEAM-WATER STRATIFIED SMOOTH/WAVY FLOW IN A HORIZONTAL PIPE

摘要

The main objective of the present work is to extend the previous work of Chun et al. (1999) on the interfacial condensation heat transfer in stratified smooth flow. In contrast to the previous work where only the interfacial condensation heat transfer in stratified smooth flow of steam-water has been investigated, in the present extension work both regions of stratified smooth and stratified wavy flow of steam-water are investigated. For the purpose of the present work, a few modifications of the test section and instrumentation were made to be more suitable for the investigation of interfacial condensation heat transfer at wavy flow condition. To show the difference in the heat transfer characteristics depending on the interface condition, in particular, the results obtained for both the smooth and wavy interface of steam-water stratified flow are presented and compared. A total of 174 average interfacial condensation heat transfer coefficients for a smooth interface and 105 local interfacial condensation heat transfer coefficients for a wavy interface have been obtained. The parametric effects of steam and water flow rates and the degree of subcooling on condensation heat transfer were also examined. Two empirical Nusselt number correlations, one for smooth and the other for wavy interface region, were developed based on the bulk flow properties. Comparisons of the present circular pipe data with two existing correlations developed for wide rectangular channels showed that the existing correlations underpredict Nusselt numbers for a smooth interface, whereas these existing correlations give conflicting results for stratified wavy flow.