Determination of wave-induced fluctuations of wall temperature and convection heat transfer coefficient in the heating of a turbulent falling liquid film

Abstract

This study examines the transient thermal response of a vertical electrically-heated wall during sensible heating of a turbulent wavy film. It is shown how the wall temperature can be decomposed into two components. The first is steady and accounts for the stream-wise increase in the wall and film temperatures, and the second is periodic and corresponds to temperature fluctuations due to the film waviness. By assuming periodicity in the wall temperature fluctuation in response to large film waves, the second component is solved numerically using liquid temperature data measured across the film to define the boundary condition at the wall-liquid interface. Results show that, during the period of a large wave, the wall temperature is fairly uniform but the convection heat transfer coefficient undergoes significant fluctuation. The fluctuation amplitude of the latter decreased with increasing film Reynolds number.