Controlling evaporative thermocapillary convection using external heating: An experimental investigation

An experimental study has been undertaken to investigate evaporatively driven convection underneath a meniscus (liquid–vapour interface) formed in a vertically oriented capillary tube. The evaporation process is found responsible for inducing a convection pattern in the liquid phase below the meniscus. The convective structure was revealed using a μ-PIV technique. When external heating is applied to the system, the convection pattern is altered and can be reversed depending on the relative position of the heating element with respect to the liquid–vapour interface. An IR camera was used to measure temperature gradients generated by the heater along the capillary wall and along the liquid–vapour interface. This allowed the investigation of the relation between the temperature gradients generated along the tube wall and the convection taking place in the liquid under the effect of thermocapillary stress thus generated. The present study has demonstrated that the meniscus interfacial temperature profile is key for the onset of thermocapillary convection which is observed experimentally.