Dynamic behaviors and heat transfer of HFE-7100 droplet impingement on heated copper surfaces

Abstract

Droplet impingement is of great significance in fields such as electronic heat dissipation and spacecraft thermal management, such as flash evaporator and high-power lasers. In this work, a systematic experiment is conducted on the HFE-7100 droplet impingement on a heated copper surface to investigate the effects of surface temperature (T_s) and Weber number (We) on the dynamic behaviors and heat transfer characteristics. The results demonstrate that the droplet impact behaviors can be classified into six regimes: deposition, deposition and splitting, partial bouncing, complete bouncing, fragmentation, and splashing. When We≤85.4, the maximum spreading factor (D_max/D₀) first decreases linearly with T_s and then remains constant when T_s>100 °C, while at We≥136.7, D_max/D₀ varies with T_s in four stages due to the existence of liquid fingers and vapor layer, being independent of T_s at T_s≤50 °C and T_s>100 °C, decreasing with T_s at 50 °C<T_s≤70 °C, and increasing with T_s at 70 °C<T_s≤100 °C. The average diameter of bubbles inside the liquid film strongly depends on T_s, while the average diameter of satellite droplets is significantly affected by We. The Leidenfrost temperature of drop is in the range of 100∼110 °C. At We=273.4 and T_s=75 °C, the heat flux is the highest at 958.6 kW/m², corresponding to the shortest droplet lifetime.