Experimental analysis on the characteristics of water drops during evaporation 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 painting) 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, in particular, contact area) is a necessary pre-requisite for the thermal analysis, especially when pure evaporation is involved. The present paper refers to an experimental analysis on the shape and behaviour of sessile and impinging water drops on smooth and microfinned surfaces of medium/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, microfin geometry and Weber number for impinging drops. Preliminary results about the evaporation transients for sessile drops on aluminium and brass surfaces are presented.