Heat transfer in falling films over vertical walls: a study of smooth vs. wavy film surfaces

Abstract

This paper presents a numerical simulation of heat transfer in falling film flow over vertical walls. The inherent instability of falling films generates surface waves and, in some cases, separation vortices, changing heat transfer between the film surface and the wall. The simulations were conducted using the OpenFOAM interFoam solver, with temperature transport equation implemented. Two scenarios were examined: a smooth film case enforced by a free-slip boundary condition at the interface, and wavy film cases generated by imposing disturbances at the inlet. The results reveal that interfacial waves have a dual impact on heat transfer. Wave-induced flow structures enhance mixing near the wall, improving local heat transfer, while thick liquid regions at wave crests reduce thermal efficiency. At Reynolds numbers 10, the smooth film exhibited higher overall heat transfer than the wavy film.

This publication is part of the R+D+I project PID2023153281OB-I00 funded by the Spanish Ministry of Science, Innovation, and Universities (MICIU/AEI/10.13039/501100011033). Y. Chen is supported by project Prep2022000005, funded by MCIN/AEI/10.13039/501100011033 and by the European Social Fund Plus (FSE+). Y. Liu holds a China Scholarship Council Studentship with the Polytechnical University of Catalonia.

Postprint (published version)