Dynamic neutron radiography. New method of void fraction measurement in subcooled boiling

Dynamic neutron radiography technique was applied to measure the void fraction distribution in forced-convective subcooled-boiling flow. Measurement error on instantaneous and time-averaged void fraction was evaluated experimentally and analytically. Measurement error would be within 18% and 2% for instantaneous void fraction (measurement time is 0.89 ms), and time-averaged void fraction, respectively. Void fraction distribution of subcooled-boiling was measured using atmospheric-pressure water in rectangular channels with channel width 30 mm, heated length 100 mm, channel gap 3 mm and 5 mm, inlet water subcooling from 10 to 30K and mass velocity ranging from 240 to 2000 kg/(m2s). One-side of the channel was heated homogeneously. Instantaneous void fraction and time-averaged void fraction distribution were measured parametrically. Effects of flow parameters on void fraction were investigated. (author)