We investigate the unsteady heat transfer in harmonically excited liquid-film flows falling under the action of gravity over an electrically-heated inclined glass-substrate, by simultaneous application of planar laser-induced fluorescence (PLIF), particle image and particle tracking velocimetry (PIV/PTV), and infrared thermography (IR). These non-intrusive optical techniques allow us to recover detailed information on the film-height ( PLIF), the velocity field underneath the wavy interface (PIV/PTV), and the free-surface (gas-liquid interface) temperature (IR), with high spatial and temporal resolution. Based on these data and knowledge of the applied heat-flux and substrate temperature at the measurement location, the local and instantaneous heat-transfer coefficient (HTC) is also evaluated. Preliminary results from select flow-regions suggest significant deviations compared to expectations from equivalent steady flows.

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