水平管群内蒸発二相流の流動様式と熱伝達

抄録

An experimental investigation was performed to obtain local heat transfer coefficients of evaporating two-phase flow in horizontal tube bundles. Each test bundle consisted of 7 tubes, and tested tubes were 9 kinds of smooth and enhanced tubes. Refrigerant R113 was used as a test fluid. Flow pattern observation and a pool boiling experiment were also conducted. Obtained results were summarized as follows: 1) Corresponding flow patterns to in-tube flow were observed, but the boundaries on a flow pattern map were considerably different from those of in-tube flow. 2) Degradation in heat transfer coefficient with increasing vapor quality was observed also in a small vapor quality region, this could be explained by the flow pattern transition from stratified to wavy flow. 3) Heat transfer coefficient became smaller with increasing heat flux, excluding the nucleate boiling dominant region. 4) The vapor quality showing the maximum heat transfer coefficient at a constant mass flux was about 0.5 for all tested bundles. 5) The enhanced evaporation tube bunble showed the maximum local heat transfer coefficient throughout the experiment, however, the enhanced condenser tube bundle surpassed it in some specifc conditions of heat and mass fluxes.