A numerical model for the thermocapillary flow and heat transfer in a thin liquid film on a microstructured wall

Abstract

PurposeThis paper aims to study thermocapillarity‐induced flow of thin liquid films covering heated horizontal walls with 2D topography.Design/methodology/approachA numerical model based on the 2D solution of heat and fluid flow within the liquid film, the gas above the film and the structured wall is developed. The full Navier‐Stokes equations are solved and coupled with the energy equation by a finite difference algorithm. The movable gas‐liquid interface is tracked by means of the volume‐of‐fluid method. The model is validated by comparison with theoretical and experimental data showing a good agreement.FindingsIt is demonstrated that convective motion within a film on a structured wall exists at any nonzero Marangoni number. The motion is caused by surface tension gradients induced by temperature differences at the gas‐liquid interface due to the spatial structure of the heated wall. These simulations predict that the maximal flow velocity is practically independent from the film thickness, and increases with increasing temperature difference between the wall and the surrounding gas. It is found that an abrupt change in wall temperature causes rupture of the liquid film. The thermocapillary convection notably enhances heat transfer in liquid films on heated structured walls.Research limitations/implicationsOur solutions are restricted to the case of periodic wall structure, and the flow is enforced to be periodic with a period equal to that of the wall.Practical implicationsThe reported results are useful for design of the heat transfer equipment.Originality/valueNew effects in thermocapillary convection are presented and studied using a developed numerical model.