Boiling heat transfer of droplet impingement on superheated concave surfaces

Abstract: A phase change spray cooling system is an important engineering application of droplet impingement on superheated surfaces due to the high rates of heat transfer that occur during the phase change process in small areas. This study employs a 3D hybrid method to numerically investigate the effect of curved concave surfaces on the hydrodynamics of droplet impact patterns and boiling heat transfer behaviour compared to rectangular-groove, rectangular-groove, and multi-concave morphologies. The hybrid method combines the D3Q19 pseudopotential multiphase lattice Boltzmann method (LBM) for simulating multiphase flows and the finite difference method for solving the heat transfer equation. It is found that the single-concave surface has superiority in improving the rates of boiling heat transfer in the boiling numbers (Bo) range of 0.0023 < Bo ? 0.03218 due to the smooth deposition of a droplet on deeper areas on the superheated surface. At higher boiling numbers (0.03218 < Bo), the multi-concave morphology demonstrated superior thermal performance due to the rebounding and bouncing of droplets away from the single-concave surface. Consequently, the thermal and hydrodynamic analysis emphasized the significance of concave surfaces in multiphase spray cooling systems. Keywords: Spray cooling., Boiling heat transfer., Multiphase pseudopotential lattice Boltzmann method., Droplet impingement., Concave morphologies.