Experimental Study of Propylene Glycol–Propanetriol Binary Droplets Impact on Heated Porous Surfaces

Droplets impacting heated porous surfaces trigger a complex process involving liquid and vapor penetration, as well as the growth and rupture of internal bubbles. In the current paper, four types of sintered porous substrates with different permeability and surface roughness are used. The droplet impact process on heated porous surfaces is visualized by high-speed photography and image processing algorithms. The boiling phase transition characteristics of propylene glycol–propanetriol binary droplets impact on different heating surfaces and the variation pattern of the number and diameter of secondary droplets splashed during the boiling process were investigated. The results show that the surface properties of the porous medium and the composition of the droplet solution have a large effect on the boiling state of the droplets as well as the number and diameter of the secondary droplets. An elevated proportion of propanetriol in solution makes it difficult for droplets to penetrate porous substrates, and it is more difficult for droplets on substrates with large pore size and roughness to undergo film boiling, with more secondary droplets erupting during boiling.