Molecular dynamics study of enhanced thermal transport from nano-engineered solid liquid interfaces

Abstract

The efficiency in modern technologies and green energy solutions has boiled down to a thermal engineering problem on the nanoscale. Due to the magnitudes of the thermal mean free paths approaching or overpassing typical length scales in nanomaterials, the thermal transport across interfaces can dictate the overall thermal resistance in nanosystems. However, the fundamental mechanisms driving these electron and phonon interactions at nanoscale interfaces are difficult to predict and control since the thermal boundary conductance across interfaces is intimately related to the characteristics of the interface such as structure, bonding, geometry, etc., in addition to the fundamental atomistic properties of the materials comprising the interface itself. Thus, the study of thermal transport across different solid-liquid interfaces is important to understand different natural systems and to manipulate thermal transport in different engineering systems. This thesis focuses on the indispensable understanding of thermal transport across solid-liquid interfaces having different surface modifications. The study centered in modeling thermal transport across the nanoscale interfaces. As continuum approximation is not applicable for the nanoscale phenomena, molecular dynamics (MD) simulation is used to explore the mechanism of thermal transport at the nanometer scale interfaces. MD simulation with simplified molecular model was employed in this study. Several interfacial geometric parameters that are generally disregarded in macro scale phenomena has been investigated to quantify the thermal enhancement in different interfacial conditions. From the simulation results it was observed that the presence of the nanostructures increases the surface wettability, solid-liquid contact area and decreases the interfacial thermal resistance which increase the thermal transportation from the solid surface to the liquid surface resulting in higher evaporation rate. On the other hand, the nanoparticles enhance the thermal transport from solid surface to liquid and thus evaporation becomes faster compared to the molecular level flat surface and the effect was intensified with the size and number of the particles. However, different scenario was observed for the rough surface. When nanoparticles get trapped between the clearance of the surface roughness it decreases thermal transport from solid to liquid layer but when nanoparticles rests on top of the nanostructures it enhances thermal transport as observed for the molecular level flat surface