Study on point of net vapor generation by neutron radiography in subcooled boiling flow along narrow rectangular channels with short heated length

摘要

Point of net vapor generation (PNVG) was investigated based on the void fraction dataset obtained by high-frame-rate neutron radiography. The test channels used in the experiment were rectangular channels heated from one side with channel gap of 3 and 5 mm, channel width of 30 mm, and heated length of 100 mm. In this study, we discuss on (1) the determination of the instantaneous and time-averaged PNVG, (2) the effects of system parameters on PNVG, (3) the applicability of existing PNVG correlations to the channel with a short heated length, and (4) the effect of the PNVG in critical heat flux (CHF) model. The following results were obtained: (a) the effects of system parameters on the thermal equilibrium quality at the PNVG were small under the present conditions, (b) existing PNVG correlations tended to underestimate the thermal equilibrium quality at the PNVG in the channel with a short heated length, and (c) the prediction accuracy of Katto's CHF model could be improved significantly by using the accurate PNVG.