A critical heat flux model for flow boiling in the IVR conditions

Abstract

A semi-empirical model, which is based on the CHF model developed in KAIST (Park, 2014), is developed to predict the critical heat flux (CHF) in the In Vessel Retention (IVR) configuration. The model consists of five theoretical equations describing the principal CHF variables: relative velocity, liquid velocity, micro layer thickness and the slug length. The CHF mechanism of liquid film dryout underneath slug is basically considered. Velocities of vapor and liquid are given by the Karman velocity distribution and the force balance between buoyancy and drag force. The micro layer thickness is defined by Cheung and Haddad (1997) model, based on the Helmholtz instability for the vapor stem located in the micro layer. Solution is obtained starting from seven scattered input parameters: mass flux, local quality, pressure, inclination angle, gap size, working fluid and heater material. Some assumptions are made concerning the premature CHF, the minimum length of slug and different types of the heater material and the working fluid. URANIE code, developed by Commissariat à l'Energie Atomique (CEA) is used to optimize the solution of the system. The optimization process is based on the integrated IVR-CHF database, including experimental data from KAIST, CEA (SULTAN experiments), UCSB (ULPU experiments) and MIT. For 278 experimental data, the developed CHF model has a root-mean-square (RMS) error of 14 %. The CHF predicted by the model is in good agreement with the experimental IVR-CHF database, except for the condition of high mass flux conditions (>500kg/m2s) and low inclination angle ([removed]