Numerical study of conjugated heat transfer in evaporating thin-films near the contact line

The study of the mechanics of evaporating thin-films is important for improving the performance of phase-change heat transfer equipment. Various factors, including the changing profile of the thin-film with superheating and the use of small-scale and one-dimensional higher-order nonlinear governing differential equations, create difficulties for the study of the conjugated heat transfer of the thin-film and its surrounding regions. In previous studies, models of the conjugated heat transfer are simplified. The shape of the evaporating thin-film is treated as fixed, or the constant substrate temperature (CST) thin-film model is used. In this paper, a full conjugated heat transfer model, including the evaporating thin-film, the near-solid substrate and the intrinsic liquid, is proposed to study the heat transfer characteristics in the contact line region in a micro channel or a micro groove. The results show that a temperature valley value exists on the surface of the solid substrate corresponding to the peak value of the heat flow rate in the thin-film. The apparent contact angle is smaller than that of the CST model. The CST model overestimates the peak and the total heat flow rate, especially when the thermal conductivity k s of the substrate is low. For convenience in engineering applications, two simplified conjugated models are developed and evaluated by the full model. For low k s substrates, the simplified models can be used directly. Changing the thickness of the substrates affects the relative errors only slightly.