  The evaporation from a micropillar evaporator is a problem governed by
various interfacial phenomena such as the capillarity-induced liquid flow,
thin-film evaporation intensifying near the contact lines, and
thermocapillarity-induced Marangoni flow. However, past research has not been
able to assess the effect of Marangoni flow due to the missing coupling between
cell- and device-level modeling. In this work, we develop a comprehensive model
for the evaporation from a micropillar evaporator by coupling the liquid flow
with the energy transfer in both liquid and solid domains at both cell- and
device-levels. The model is successfully validated with previous experiments.
When the Marangoni number is sufficiently high, the model identifies a sharp
reduction in the evaporator temperature attributed to the thermocapillary
convection creating circulations beneath the liquid-vapor interface, which
results in the formation of periodic reverse surface flows on the interface.
This temperature drop cannot be identified when thermocapillarity is switched
off in the model and the model's prediction substantially deviates from
experimental measurement. Therefore, the current study reveals a hitherto
unexplored role of Marangoni flow in the evaporation of water from micropillar
evaporators.
