Heat transfer mechanisms analysed by high speed video recording of metal quenching in ionic liquids and water

Abstract

To understand and control the heat transfer mechanisms of ionic liquids (ILs) as a new group of potential liquid quenching media, aluminium and steel cylinders are quenched in ionic liquids with varying water contents as well as pure water with different bath temperatures. Due to the very fast changes between the different heat transfer mechanisms, the quenching processes are recorded with a high speed video camera with up to 4000 frames per second. The videos are correlated with the temperature-time profiles of the cylinders to identify and investigate the different heat transfer mechanisms. As a result, no Leidenfrost-effect occurred in pure ionic liquids and only very short-film boiling sequences of a few 0.1 s could be identified in ionic liquid-water mixtures. Advantages, optimisations and limits of high speed video recording of quenching processes are discussed.