Study on the mechanism of critical heat flux enhancement for subcooled flow boiling in a tube with internal twisted tape under nonuniform heating conditions

Abstract

Critical heat flux (CHF) of subcooled flow boiling with water in a tube with an internal twisted tape under nonuniform heating conditions 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. The net vapor generation (NVG) point almost agreed with the Levy correlation. The increase of the CHF with an internal twisted tape under nonuniform heating conditions was explained by assuming an alternate development and disruption of the bubble boundary layer in which the bubble boundary layer is assumed to be disrupted when the heat flux is lower than the NVG heat flux. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(5): 293–307, 1996