Heat transfer between single cryogen droplet and epoxy skin phantom

Cryogen Spray Cooling (CSC) is an auxiliary procedure that pre-cools the epidermis during Laser Derma-tologic Surgery (LDS) to avoid non-specific epidermal thermal damage. During CSC, explosive atomization, in-flight evaporation and droplet-substrate interaction affect heat extraction from the substrate. In order to understand the heat transfer mechanism of this complex process, we first study the heat transfer between a single cryogen (R134a) droplet and an epoxy skin phantom. In a high pressure chamber, cryogen droplets are gently deposited on a skin phantom instrumented with a fast-response thin-film thermocouple. The surface temperature variations were recorded and used to calculate surface heat fluxes. Using this setup, we performed experiments to study the effect of initial surface temperature on the cooling efficiency of a cryogen droplet. The results show that the cooling effi-ciency increases with increasing initial substrate temperature