A procedure to predict subcooled-water-flow-boiling CHF in uniformly heated tubes for high-heat-flux applications

Abstract

A model to predict critical heat flux (CHF) for high-heat-flux subcooled flow boiling in uniformly heated tubes is proposed. The present CHF model is based on the mechanism of wall-attached bubble coalescence. To take into account the enhanced condensation due to high subcooling and high mass velocity in small-diameter tubes, a mechanistic approach is adopted to evaluate the non-equilibrium flow quality and void fraction in the subcooled water flow boiling. Comparison of the model predictions against similar to 3100 subcooled water CHF data shows relatively good agreement over a wide range of parameters that covers the operating conditions of fusion reactor components. The operating ranges of the present database cover 0.33 less than or equal to D less than or equal to 37.5 mm, 0.002 less than or equal to L less than or equal to 4 m, 0.1 less than or equal to P less than or equal to 20 MPa, 0.37 less than or equal to G less than or equal to 134 Mg/m(2) . s, 49 less than or equal to Delta h(sub, in) less than or equal to 1659 kJ/kg, -1.25 less than or equal to x(em) < 0 and 1.05 less than or equal to q(CHF) less than or equal to 276 MW/m(2).