Characteristics of Effect of Vapor Bubble Behavior on Pressure Drop in Vertical Rectangular Narrow Channel

A visual experimental study on flow boiling in vertical rectangular narrow channel was carried out,in order to investigate the effect of vapor bubble behavior on the characteristics of pressure drop.It was found that the OSV（Onset of Significant Vapor） could emerge earlier in narrow channel than in conventional channel with identical working thermal conditions.A correlation for predicting the real vapor quality and real vapor fraction was proposed based on the experimental result.It was also found that the vapor bubble behav-ior affected the pressure drop in narrow channel significantly,and the channel was blocked easily due to the vapor cluster formed in the narrow channel;the total pressure drop,however,did not increase linearly with the increasing of outlet vapor fraction.