A physical model of dryout and prediction of critical heat flux in flow boiling of a saturated liquid in a channel

摘要

A physical model of dryout in flow boiling in channels is presented The model is based on the assumption that the dryout occurs when a liquid film under a vapor conglomerate evaporates completely within a residence time for the conglomerate on the heat transfer surface. Its using, in particularly, for flow boiling of saturated liquids in channels at high pressures with a great density of nucleation sites, low wall superheat, and low rates of vapor bubble growth, yielded correllations for the critical heat flux. Predictions by the proposed correlations are in good agreement with experimental data on the critical heat flux for water and nitrogen for relative pressures of P/Pcr＞0.45, mass flow rate rw of 100 to 8000 kg/(m{sup}2s), and flow quality x ＞ 0.