Molecular Dynamic Simulation of Evaporative Heat Transfer on Graphene Coated Silicon Substrate for Electronics Cooling

摘要

Traditional heat dissipation methods based on single phase air or liquid cooling are reaching their limits for keeping the functional unit at a sufficiently low temperature with an ultra-high heat flux $( gt 1mathrm {k}mathrm {W}/mathrm {c}mathrm {m}^{2})^{1-2}$. Twophase cooling such as thin film evaporation, owing to the large amount of latent heat in the phase change process, can effectively remove large amounts of heat while maintaining a small temperature difference across the heat transport system. As the evaporating liquid becomes sufficient thin, the surface characteristics such as interfacial thermal resistance become important parameters affecting the heat and mass transport during thin-film evaporation. This resistance is induced by the acoustic mismatch between the solid and liquid molecules, which impedes for heat propagating across the interface 3–4. Besides, based on the fundamental theory behind interfacial thermal resistance, the heat exchange across the solid-liquid interface is a strong function of the affinity between the two phases, i.e., the surface wettability. In general, it is expected that interfacial thermal resistance is positively related to the contact angle of the working fluid on the solid substrate. However, it remains unclear if the surface wettability has a direct impact on evaporative transport behavior from a thin liquid film. More importantly, we still lack a general description of the change in interfacial resistance with surface wettability and how such resistance can affect the thin-film evaporative transport. Understanding the relationship between interfacial thermal resistance, surface wettability, and evaporation behavior is important for evaluating the evaporative transport rate on different surfaces and designing rational nanocoatings to enhance evaporative heat transfer.