Abstract
Abstract
Prediction of the onset of the flow instability (OFI) in steady and transient sub-cooled flow boiling is an important consideration in the design and operation of nuclear reactors especially material test reactors (MTR). In this study, a predictive model of OFI in the MTR has been developed. The model is based on both heat balance of bubble generation and condensation and force balance for the detached bubbles at the onset of significant void (OSV). Only one coefficient involved in the proposed model is identified by experimental data that covers the wide range of MTR operating conditions. The model results are compared with results of some previous models where the present model gives the lower deviation from the experimental data. A correlation for the heat flux at OFI is also developed based on the present model. The developed correlation gives lower deviation from the experimental data than the well-known correlation of Whittle and Forgan. The model is also used to predict the OFI locus during transient where it shows good agreement with the short transient of Lee and Bankoff as well.