Multi-droplet cooling: Experimental tests on infrared-transparent media

The present work is aimed at analyzing the cooling of hot solid surfaces induced by liquid droplets. In particular, the study is focused on the comparison between the cooling effects obtained with multiple droplets and sparse spray configurations.A new, non-intrusive measurement of the transient contact temperature between impinging droplets and hot solid surfaces is used and described. An experimental apparatus was built and set up in order to approach the non-trivial problem of the measurement of a solid-liquid interface temperature after droplet impingement. The solid-liquid interface temperature was monitored from below through a transparent-to-infrared material. That material had been coated with a very thin layer of high-emissivity, opaque paint on its upper side, so that it could effectively respond to the infrared camera located below.The paper reports the main results that have been collected to date, with particular regard to the approaches used to coat the transparent solid. Some considerations are also expressed about the effectiveness of the proposed method and about the improvements that are currently being implemented to get new and more accurate interface temperature measurements.