Molecular Dynamics Study On Boiling Heat Transfer Of Ultra-thin Water Film On MoS₂ Substrate

As a typical transition metal sulfide?TMDs?,layered molybdenum disulfide?MoS₂?has graphene-like crystal structure and special mechanical,electrical,optical and thermal properties,and is expected to be widely used in integrated circuits and micro-nano electromechanical systems.However,the study of liquid boiling heat transfer by using MoS₂ as a heat transfer substrate has not been publicly reported.In this thesis,the molecular dynamics?MD?methods are used to study the evaporation and boiling phenomenon of the liquid water film on the superheated layered MoS₂substrate.The aim of the study is to explore the interaction between water molecules and layered MoS₂ during evaporation and boiling,as well as related heat transfer characteristics.The main work of this thesis is as follows:First of all,this thesis introduces the research background and international research status of micro-nanoscale boiling heat transfer,and summarizes the structure and properties of MoS₂,especially the thermal characteristics.After that,the basic theories and correlative mechanisms of boiling heat transfer and wettability are introduced.Meanwhile,some related methods used for the study of boiling heat transfer are analyzed,and the relevant parameters and setting methods of molecular dynamics method used in this thesis are introduced.Then,the modeling process of the ultra-thin water film boiling system is described in detail,including the modeling of two phase?1T and 2H phase?MoS₂ substrates,the selection of the water model and the modeling of the liquid water films.The parameters used in the simulation are selected,focusing on the selection of potential functions of MoS₂ and water molecules.Finally,the boiling heat transfer process of ultra-thin water film on MoS₂ substrate are simulated by using MD method,and the results are analyzed by qualitative phase transition locus of water and quantitative thermodynamic quantities?temperature,pressure,number density,net evaporation number,and heat flux?.The boiling heat transfer characteristics and the effect of different conditions on the boiling results are analyzed.The results show that the heat transfer effect of 2H phase MoS₂ substrate is slightly better than that of 1T phase.Besides,high substrates superheated temperature and larger temperature gradient within the water film along the z-axis can promote the occurrence of explosive boiling of the liquid water film and increase the phase change rate.Good wetting characteristics of solid-liquid interface can improve the heat transfer efficiency of phase transition,and the effect of solid-liquid interface interaction on boiling results is greater than that of heat source temperature when the superheat degree is low.Through the study of this thesis,the interaction and heat transfer mechanism between MoS₂ and water molecules are explored,which will provide useful references and basis to the design of heat-dissipation devices and systems of MoS₂ and surface steam cleaning of the devices.