Simulation of DNB-type critical heat flux (CHF) and pressure drop in subcooled flow boiling of water for tubes with twisted tape inserts under one-sided heating conditions

Abstract

For the purpose of enhancing thresholds of nucleate boiling and ensuring working safeties for DEMO reactor, numerical analyses of the influences of twisted tapes and fluid thermal-hydraulic parameters on DNB-type CHF and pressure drops have been carried out on plain tubes and tubes with twisted tape inserts. The research campaign has been conducted following the Eulerian multiphase model and the critical heat flux boiling model based on FLUENT software. Numerical simulation methods were verified by comparing the simulation results with the experimental data. Comparisons of critical heat flux and pressure drop between experiment and computation show a good agreement, indicating that present methods are reliable for DEMO divertor design. The temperature distribution, void fraction and pressure drop for two-phase subcooled boiling water flow were obtained. The simulation results show that the DNB-type CHF can be enhanced by decreasing twist ratios or increasing tape width ratios. Compared with plain tubes, tubes with twisted tape inserts can efficiently enhance DNB-type CHF. Furthermore, the DNB-type CHF is assessed to be directly proportional to mass fluxes. The results also indicate that the pressure drops increase with increasing tape width ratios and mass fluxes, but increase with the decrease of twist ratios.