Statistical investigation of the relationship between interfacial waviness and sensible heat transfer to a falling liquid film

Experiments are performed to provide an insight into the heat transfer aspects of a wavy liquid film. Local film thickness and liquid temperature are measured simultaneously using a thermal conductance thickness probe and fast response thermocouples as the wavy film falls over an electrically heated wall. Liquid temperature at a fixed distance from the wall generally increases in the thin substrate portion of the film and decreases within the large waves. Temperature shows complex excursions within the large waves due to turbulent eddies and to the relative liquid motion between the large wave and the surrounding substrate. The measurements are examined with the aid of statistical tools to investigate the relationship between film thickness and liquid temperature at various film Reynolds numbers and heat fluxes. The correlation between the two variables is stronger at higher heat fluxes compared to lower fluxes. A crossspectrum analysis shows a distinct band of dominant frequencies in the relationship between the two variables.