Effects of contact angle schemes on pool boiling by lattice Boltzmann method

Accurate modeling of boiling heat transfer is critical for numerous engineering applications. This study employs a hybrid multiple-relaxation-time lattice Boltzmann method to systematically investigate the effects of three contact angle schemes on pool boiling. Our findings demonstrate that the three widely used contact angle schemes—the improved pseudopotential (ips), improved virtual-density (ivds), and geometric formulation (geo) schemes—can enforce desired contact angles, yet produce markedly different boiling behaviors. Near-wall fluid density at the nucleation sites is the main factor affecting the nucleation sequence, i.e., the lower liquid density at the nucleation site, the easier it is to nucleate. On the other hand, higher fluid density near the wall could enhance the heat transfer, and thus delay film boiling (extending the effective boiling range) and increase the critical heat flux (CHF). Simulations reveal that the geo scheme attains the lowest nucleation temperature at a contact angle of 45°, while the ips scheme does so at 110° Quantitative results further highlight these differences. At 45°, the maximum heat flux obtained with the geo scheme is only 66% of that with the ips scheme (ivds and ips differ by only 2%), and the Jakob number ranges for ivds and ips are identical and 2.4 times larger than that for geo. At 110°, the maximum heat fluxes with ivds and ips drop to 90% and 70% of the geo-scheme value, respectively, with their Jakob number ranges reduced to 54% and 40% of that for geo. At 90°, the three schemes exhibit nearly identical performance. Based on our systematic investigation, we think geo scheme is physically correct for boiling simulation, yet it requires further improvement for the consideration of liquid micro-layer.