Heat transfer enhancement via bubble dynamics along an inclined wall

Abstract

In this numerical study, the bubble injection effect on the heat transfer rate is investigated next to an inclined heated wall. The volume of fluid (VoF) method solver in the OpenFOAM package is extended with an energy equation and Boussinesq approximation to consider the natural convection flow. The solver is validated with several single and multiphase benchmarks, then the effect of various parameters such as wall slope angle (θ), contact angle (ϕ), bubble pair, Bond number (Bo), and bubble regimes are studied.The results show the maximum Nusselt number occurs at θ=60° where a bubble has a higher velocity than θ=[30°, 45°, 90°] and the average Nusselt number boost up 26%. While the Nusselt number is elevated in the higher Bond number (larger bubble), the studies show for the identical gas volume, the bubble pair increases the heat transfer rate more than one single large bubble. The heat transfer reduces about 9% when the contact angle increases from 0° to 120°. The intermittent contact regime has better heat transfer performance than the sliding contact regime and non-contact regime. The Nusselt number enhanced by more than 92% in this regime. The correlation for the Nusselt number based on the present study revealed that the two main influential parameters are wall slope and Bond number.