Comparative study of boiling behavior between liquid sodium and organic fluid under high heat flux: A molecular dynamics simulation

Abstract

Boiling characteristics of fluid is of significant importance for the efficient cooling of high-power devices, where liquid metal and low-boiling-point organic fluid are often used. In this work, the boiling heat transfer characteristics and bubble behavior of liquid sodium (Na) is numerically studied by molecular dynamics simulations, and comparison with a conventional fluid 1,1,1,2-tetrafluoroethane (R134a) is performed. In the simulation, the initial temperature of the liquid sodium is set to 600 K, the initial thickness is 8 nm, and the surface superheat of the solid substrate is 1000 K. The results indicate that, compared to R134a, during the nucleate boiling stage, liquid sodium exhibits a longer duration of nucleate boiling, accompanied by more vigorous bubble motion within the liquid film. The heat flux of liquid Na is three orders higher in magnitude than that of R134a. For liquid sodium, total thermal resistance (Rtot) at the onset of nucleate boiling (ONB) is 2.28 × 10−11 K‧m2/W, while for R134a, Rtot at ONB is 7.15 × 10−7 K‧m2/W. During explosive boiling, there are noticeable bubbles generation within liquid film of Na, while there are no bubbles inside the liquid film of R134a. Liquid-vapor phase transition involves a competition between kinetic energy and potential energy. For liquid sodium, there exists a critical range of the total energy that triggers the phase transition.