Numerical investigation of the role of non‐uniform evaporation rate in initiating Marangoni convection in capillary tubes

A computational model is developed to describe convection in volatile liquids evaporating in capillary tubes. Experimental work has demonstrated the existence of such convective structures. The correlation between this convection and the phase change process has been experimentally established. Temperature distribution on the liquid‐vapour interface is considered in order to characterise the minimum of radial temperature gradient required to initiate and orientate Marangoni convection. Direct numerical simulation using finite volume approximation is used to investigate the heat and mass transfer in the liquid phase. The case of a capillary tube filled with a volatile liquid is investigated for various Marangoni numbers, to characterise heat and mass transfers under conditions close to realistic operating parameters. The simulation shows that a minimum irregularity in evaporative flux along the liquid‐vapour interface is necessary to trigger thermocapillary convection. The enhancement of heat and mass transfer by Marangoni convection is also investigated.