Experimental analysis on the shape and evaporation of water drops on high effusivity, microfinned surfaces

A deep understanding of the behaviour of sprays is of great importance in several fields, both industrial (combustion, heat transfer, spray deposition and painting, etc.), agricultural and medical, and the study of the behaviour of single drops is a fundamental step towards the comprehension of the whole phenomenon. Focusing the attention on spray/surface heat transfer problems, the most interesting aspect is the interaction of sessile and impinging drops on solid surfaces. The description or the prediction of the drop shape parameters (height, contact angle and contact area) is a necessary pre-requisite for the thermal analysis, especially when pure evaporation is involved. This paper describes an experimental analysis on the shape and behaviour of sessile and impinging water drops on smooth and microfinned surfaces of high effusivity materials, in isothermal condition and during evaporation. Drop shape, contact angle and contact area are characterised as a function of the surface material, microfins geometry and Weber number for impinging drops. Results about the evaporation transients for sessile drops on aluminium, brass and carbon steel surfaces are presented.