Date of Award

1-1-2012

Document Type

Campus Access Dissertation

Department

Mechanical Engineering

First Advisor

Jamil A Khan

Second Advisor

Chen Li

Abstract

Liquid molecules located at the interfacial region behave differently than they do in the bulk. These interfacial liquid molecules play a very crucial role in heat transfer from solid to liquid, especially when the system dimension shrinks to the nanoscale range. Behavior of these interfacial liquid molecules depends on the characteristics of the interface. All the interfaces have different characteristics that can be tailored precisely with the aid of advanced manufacturing technology. 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, e.g. thermal management of micro/nano electronics, energy conversion devices, micro/nano fluidics devices, energy storage system, drug delivery, and to understand different biological systems. The present work focuses on the fundamental understanding of thermal transport across solid-liquid interfaces having different characteristics and exploration of techniques to manipulate these interfaces for different thermal devices. The study starts by 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. With the aid of MD simulation, several interfacial geometric parameters are investigated. It was found that solid-liquid interaction strength plays a dominating role in interfacial heat transfer; additionally the role of interfacial

nanostructure's length was also found to be significant. Distribution, shape and density of the nanostructures also influence the energy transfer but the effect is of less extent.

One useful application of the nanoscale interface engineering is in thermal management of microelectronics. The insight obtained from the MD simulations in this study is extended into experimental diagnostics of convective heat transfer performance of microchannel with integration of nano- engineered interfaces. Interface characteristics of the microchannel are modified with three different types of nanostructures: CuNWs, Cu-Al2O3 nanocomposite and Al2O3 nanoparticles. Experimental results reveal that interfacial nanostructures positively affect Critical Heat Flux (CHF) irrespective of the type of nanostructures. Whereas Heat Transfer Coefficient (HTC) may increase or decrease depending on the type of nanostructures.


In the last part of this study, a low cost simulation approach is outlined to evaluate system level application of a conceptual thermal system considering micro/nano engineered interfaces.

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