Feasibility Study of CFD Boiling Methodology for Predicting Nucleate Boiling Characteristics in a Helical Coiled Tube

Due to advantages such as larger heat transfer area, higher heat transfer efficiency, and greater thermal expansion stress, helical coiled tubes (HCTs) have been widely adopted in heat exchangers in industry, especially for nuclear power plants. The nucleate boiling heat transfer characteristics within an HCT are investigated using a multi-phase CFD boiling framework implemented and evaluated in this study. Based on the requirement of BPG (Best Practice Guideline) for the CFD applied in the nuclear safety analysis, mesh-independent calculations are performed, including of the heat transfer coefficient and wall temperature along the HCT and the void fraction and secondary flow on the cross-section of the HCT. The effects of various bubble dynamic correlations in the boiling model on the predicted results are also considered. Several previous experiments are adopted to assess the present boiling models, showing the feasibility of the present boiling CFD methodology in predicting the average nucleate boiling heat transfer coefficient along the HCT. Compared with the predicted results from the various heat transfer correlations in the subcooled and saturated nucleate boiling regions, this CFD boiling model can assess these correlations applied in HCT as well as assist in the safety analysis of system codes in selecting the appropriate boiling heat transfer correlations.