Effects of the wall temperature on the boiling process and the molecular dynamics behavior of the liquid hydrogen on a flat aluminum wall

Abstract

Understanding the nucleation mechanism and boiling heat transfer characteristics of liquid hydrogen is a key issue in the development of liquid hydrogen storage systems. However, the current methods of experimental and mesoscopic or macroscopic scale continuous flow simulations suffer from the problems of large study scales and undetermined initial boundary conditions. The purpose of this study is to reveal the bubble nucleation mechanism and bubble development process of liquid hydrogen on the surface of heating plate at the molecular scale, and to investigate the effect of different heating plate temperature on bubble growth, during thin film boiling. In this research, molecular dynamics simulation is used to combine molecular position distribution with energy analysis and explain the molecular behavior. The effect of heating temperature on different phase transition stages of liquid hydrogen is also investigated by varying the heating surface temperature. In this study, the bubble nucleation, bubble development and merging of liquid hydrogen on the heating surface were successfully observed. It is shown that increasing the heating temperature has a small effect on the bubble growth rate and liquid layer thickness in the nucleation boiling stage, and mainly affects the gas film growth rate in the film boiling stage. The bubbles are extremely unstable at the initial stage of generation. Within 1 fs of the first appearance of bubbles, which are associated with random micro-pits caused by thermal motion of solid atoms, bubbles move on the surface of the heating plate. This study found a phenomenon that bubbles firstly generated and then disappeared. This paper provides a new idea for the nucleation mechanism and boiling heat transfer study of liquid hydrogen. Moreover, it provides a solution to the problems of liquid hydrogen phase change research.