Experimental investigations of fuel film evaporation with deposit formation

Highlights: • Methylnaphthalene is an appropriate test fluid to study the effects of deposit formation on heat transfer and fluid dynamics in generic experiments with practical operating conditions. • Deposit layers are wetted preferentially compared to blank surfaces. • Deposits layers are thermal barriers leading to higher wall temperatures. • Deposit mass has high thermal capacity leading to thermal delays for wetting and dewetting events. - Abstract: A new test rig has been designed to investigate the effect of carbon based deposit layer formation on the hydrodynamics and heat transfer of a thin evaporating methylnaphthalene film, which builds deposits at a hot wall under thermal stress in an oxidative environment. The liquid film is shear driven by a preconditioned air flow, spread on a foil heater (joule heating) and evaporates. With a black and white camera the hydrodynamics of the moving film is visualized, whereas the temperature field below the foil is qualitatively measured with an IR camera. Prior to conducting the measurements the foil is wetted and dried periodically multiple times to form an initial deposit layer. For the main investigations the deposit layer is removed locally. The presented recordings show a direct effect of the deposit layer on wetting and heat transfer, and thus the ongoing deposit formation. Deposit layers are preferably wetted and act as thermal barriers leading to local higher wall temperatures and thus to a reduced foil cooling.