Dependence of heat exchange in an evaporating liquid film in a microchannel on heater size

Heat exchange in a liquid film moving along the bottom of a microchannel is calculated on the basis of a developed three-dimensional nonstationary model of motion. The liquid moves under the action of a cocurrent gas flow in the channel, with a square heater located at its bottom. In this case, the action of all the main physical factors during their interaction is taken into account: diffusive and convective heat transfer, dependence of liquid properties on temperature, thermocapillary effect, occurrence and evolution of surface deformations, and evaporation and condensation of liquid. It is revealed that the heater size significantly affects temperature fields, surface deformations, and temperature extremes. A formula for calculating the greatest excess of the average temperature achieved on the substrate is derived.