Dryout of counter-current two-phase flow in a vertical tube

Dryout of counter-current two-phase flow is one of key issues in chemical and/or industrial systems. The aim of the present study is to provide insights into the dryout phenomena of such counter-current two-phase flow of binary gas and liquid in a vertical tube. Experimental results suggest a significant influence of the subcooling of water and the binary gas flow rate on the dryout characteristics. The observed dryout was classified into three modes, i.e., film breakdown, dryout due to flooding and dryout due to critical flooding. At the low inlet air flow rate, dryout characteristics were affected by subcooling of water. The test section was partially overheated owing to the liquid film breakdown due to the Marangoni effect. At the moderate inlet air flow rate, the dryout is induced by the reduction on the falling liquid film due to flooding. At the high gas flow rate, most of the water was carried over due to the critical flooding. In the latter two cases, there was no influence of subcooling of water on dryout. These dryout phenomena were successfully realized in the numerical simulation based on the one-dimensional heat and mass transfer model, i.e., energy balance of a heat input, a heat release rate from the heating surface and a mass transfer rate due to phase change.