Critical Heat Flux (CHF) Correlations for Subcooled Water Flow Boiling at High Pressure and High Heat Flux

Abstract

The subcooled water flow boiling is beneficial for removing the high heat flux from the divertor in the fusion reactor, for which an accurate critical heat flux (CHF) correlation is necessary. Up to now, there are many CHF correlations mentioned for subcooled water flow boiling in the open literatures. However, the CHF correlations’ accuracies for the prediction of subcooled water flow boiling are not satisfactory at high heat flux and high pressure for reactor divertor. The present paper compiled 1356 CHF experimental data points from 15 independent open literatures and evaluated 10 existing CHF correlations in subcooled water flow boiling. From the evaluation, the W-2 CHF correlation performs best for the experimental CHF data in all existing critical heat flux correlations. However, the predicted mean absolute error (MAE) of the W-2 correlation is not very ideal for all database and the MAE of the W-2 correlation is from 30% to 50% for some database. In order to enhance the CHF prediction accuracy in subcooled water flow boiling at high heat flux and high pressure, the present paper developed a new CHF correlation. Compared with other existing CHF correlations, the new CHF correlation greatly enhances the prediction accuracy over a broad range of pressures and heat fluxes which are desired in the cooling of high heat flux devices, such as those in the fusion reactor divertor. The validation results show that the new correlation has a MAE of 10.05% and a root mean squared error (RMSE) of 16.61%, predicting 68.1% of the entire database within ±10% and 81.5% within ±15%. The MAE of the new CHF correlation is 7.4% less than that of the best existing one (W-2 correlation), further confirming its superior prediction accuracy and reliability. Besides, the new CHF correlation works well not only for a uniform power profile but also for a non-uniform power profile in subcooled water flow boiling at high pressure and high heat flux.