Molecular dynamics study of nanoscale heat transfer at liquid-solid interfaces (LSIs)

Date
2012-09-26
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Abstract
Phonons, or lattice vibrations, are the primary thermal energy carriers in dielectric solids. At liquid-solid interfaces (LSIs), there is a considerable mismatch in the vibrational properties between the two phases. Consequently, during heat transfer across LSIs, the transmission of phonons is impeded. This gives rise to a temperature drop that is proportional to what is termed as the Kapitza resistance(RLSI). The present work examines various important aspects of nanoscale heat transfer across LSIs. This is accomplished computationally using the Molecular Dynamics (MD) method, in which the two phases are treated at the atomic scale. First, the effect of the solid surface geometry is investigated in light of advancements in nanopatterning. It is found that the surface atomic structure can be tailored to significantly reduce RLSI, by simultaneously influencing two key factors: (i) the interaction energy between liquid and solid atoms at the LSI, and (ii) the vibrational characteristics of the nanopatterned surfaces. The second study focuses on the effects of system pressure on RLSI for wetting (W), and nonwetting (NW) surfaces, respectively. It is demonstrated that, in contrast to the W surfaces, the system pressure has a strong effect on lowering RLSI for the NW surfaces. For the pressure range considered, it is concluded that the central cause of this behavior is the relative increase in adsorbed liquid density accompanying the pressure increase. In the third part of the thesis, the aim is shifted towards carbon nanotubes (CNTs). Using a novel technique, a spectral analysis for the frequency dependence of thermal energy exchange at CNT LSIs is conducted. The results confirm the notion of thermal coupling between a CNT and its surrounding liquid being limited to the low frequency range. The CNT inner high-to-low frequency heat transfer is a limiting factor that results in a high RLSI. More importantly, the findings provide evidence of the origin of a heat transfer 'bottle-neck' within the CNT. This could provide new avenues for improving RLSI in CNTs.
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Engineering--Mechanical
Citation
Issa, K. (2012). Molecular dynamics study of nanoscale heat transfer at liquid-solid interfaces (LSIs) (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26985