Study on the mechanism of Critical Heat Flux enhancement for the subcooled flow boiling in tube with internal twisted tape under non-uniform heating condition

Critical Heat Flux (CHF) of subcooled flow boiling with water in a tube with internal twisted tape under a nonuniform heating condition was experimentally investigated by direct current heating of a stainless steel tube. The boiling curve of the subcooled flow under a high heat flux was measured to confirm the characteristics of the nucleate boiling curve. The Net Vapor Generation (NVG) point almost agreed with Levy correlation. By assuming that the bubble boundary layer disrupts when the heat flux is lower than the NVG heat flux, the increasing rate of the CHF with internal twisted tape under a nonuniform heating condition was explained assuming an alternate development and disruption of bubble boundary layer. (author)