Impingement dynamics of [EMIm]Ac ionic liquid drops on heated porous surfaces

•Detailed characterization of ionic liquid drops impacting on heated porous surfaces.•Increased temperature and velocity accelerate the droplet penetration.•Ionic liquid drop exhibits smaller diameter, height, and more stability than water.•Evaporation alters the relationship between residual volume and contact time. The impingement dynamics of a promising ionic liquid absorbent, namely, 1-ethyl-3-methylimidazolium acetate ([EMIm]Ac) in droplet falling film flow modes on heated porous surfaces in absorption refrigeration were investigated experimentally. The influences of impact velocity and surface temperature on the ionic liquid droplet spreading diameter, dynamic contact angle, spreading height, and residual volume against the heated porous surfaces were explored. The results indicated that the residual volume generally decreased in linear with increasing contact time at 323.15 K, while the dependence exhibited a polynomial behavior at higher heating temperatures. Compared to the impingement behaviors of deionized water droplets, such as oscillations and capillary waves were not observed in [EMIm]Ac droplets. The residual volume of the deionized water droplets varied exponentially with the contact time owing to the combined effects of the evaporation, penetration, and variation of the thermophysical properties of the droplet. Moreover, increases in the impact velocity and surface temperature enlarge the spreading diameter and accelerate the droplet penetration for the ionic liquid.