小口径管で発生するフラッディングに伴うドライアウトの予測

抄録

Flooding is one of very important designing factors of actual boiling system with counter-current two-phase flow, such as a reflux condenser and a high-performance heat exchanger. Consequently, many investigations have been conducted so far, but most of those investigations have been done with large diameter tubes. Thus, flooding characteristics under a small diameter channel (I.D. < 10 mm) have not been fully understood so far. In this study, flooding experiment was conducted by using air-water system in 5 mm glass tube. As results, typical flow patterns under counter-current two-phase flow were observed, and these flow patterns could be determined by the pressure drop fluctuation and the probability density function of pressure drop. Those flow pattern transitions could be correlated with Wallis's flooding correlation, and the flooding velocity also corresponded to Wallis's flooding correlation. Moreover, on the basis on the present experimental results with adiabatic system, the dryout under counter-current two-phase flow condition has been examined. As the calculation results, two kinds of dryout , i.e. the liquid film dryout at the bottom of the tube under low mass flux condition and the critical heat flux due to the flooding at the top of the tube under high mass flux condition, have been proposed.