Estimating bubble interfacial heat transfer coefficient in pool boiling

Interfacial heat transfer coefficient (IHTC) is one the most deterministic factors of nucleate boiling characteristics in pool boiling. IHTC and bubble dynamics have a reciprocal effect on each other, which makes accurate estimations of IHTC even more challenging, but important for nucleate boiling studies. In this study, by considering interfacial heat resistance, micro-layer heat transfer and conjugate heat transfer, a comprehensive model that is capable of simulating phase change phenomena and IHTC has been developed and a modified form of Volume of Fluid method (VOF) is used to simulate pool boiling phenomena. In this study, three major challenges in simulating bubble dynamics and related phase change heat transfer using a VOF method have been successfully addressed to achieve more accurate simulations. First, spurious currents resulting from approximating curvature in VOF and interface diffusion have been minimized by introducing curvature smoothing and employing a simplified coupled level set volume of fluid method (S-CLSVOF). Second, simulation instability due to the concentration of source terms on the interface has been addressed by smearing source terms around the interface. Third, micro-layer thickness, which is noticeably smaller than computational cells, has been calculated based on a linear depletable micro-layer method. Effects of three-phase contact line were adopted by introducing a dynamic contact angle model and temperature variation inside the heater. The model shows great agreement with available experimental and numerical results in nucleate boiling of water and R113 in terms of bubble growth and departure rate, frequency and temperature distribution, and micro-layer thickness. The new model developed in this study simulates IHTC in two water cases and its relationship to interfacial relative velocity. (C) 2022 Elsevier B.V. All rights reserved.