Droplets wall interaction: Measurement of the interface temperature through infrared-transparent media

A new, non-intrusive method is proposed to measure the solid-liquid contact temperature during dropwise evaporative cooling. The droplets are deposited onto a material, BaF2, which is transparent in the infrared spectral band. The transparent tile is coated with a very thin layer of high-emissivity, opaque paint on its upper side, so that it can effectively respond to the infrared camera below. The interface temperature can thus be measured through the solid material by a thermographic camera. Tests are carried out on the black painted BaF2 disk after its optimization by mechanical machining. The experimental tests are conducted following two deposition procedures: a) multi-droplet arrays, b) sprays. The two different behaviors and the corresponding cooling results are finally compared.