Pressure-controlled molecular dynamics study on the heterogeneous nucleation mechanisms of dielectric fluid R1336mzz(Z)

Nucleate boiling is one of the most efficient thermal management approaches for electronic devices, where dielectric fluids are commonly utilized. However, boiling-based system often suffers from pressure fluctuations due to environmental change and two-phase flow dynamics, which in turn influences the incipience of bubble nucleation. Due to the small spatial and temporal scales involved in the early periods of nucleation, microscopic studies on pressure-related boiling heat transfer characteristics remain to be explored comprehensively. Motivated by this, non-equilibrium molecular dynamics simulations of dielectric fluid R1336mzz(Z) with heterogeneous nucleation are carried out based on mechanical pressure control method. When the heating temperature is 400 K, pressure-controlled model experiences explosive boiling phenomenon, whereas only diffusive evaporation occurs in molecular dynamics models that incorporate reflecting wall or fictitious wall at system top. This disparity originates from the reduced thermal gradient and enhanced energy dissipation of non-pressure-controlled model, where film thickness continuously decreases due to diffusive evaporation. Meanwhile, the onset of nucleate boiling is found to increase up to 1 atm and then decreases with a further raise in external pressure. The underlying mechanism can be elaborated by the variations in interfacial thermal resistance and potential energy restriction for bubble nucleation.