Role of Thermal Interaction Between Aggregated Particles in Thermal Conductivity Enhancement of Nanofluids

Abstract

This study investigates the role of thermalinteraction (TI) between aggregated particles (APs) on the enhanced thermal conductivity of nanofluids. With the assumption of configurations of linear chainlike aggregates in the direction transverse to the thermal flux, twodimensional heat conduction is considered for estimation of the effective thermal conductivity of regular arrays, which is separated into three components, namely, no thermalinteraction (NTI) effect, longitudinal thermalinteraction (LTI) effect, and transverse thermalinteraction (TTI) effect. We have obtained a solution to the 1D confine case of APs, and a thermal analysis is carried out for different confine systems to investigate their relatively quantitative assessments of thermal contribution to the enhanced effective thermal conductivity using the firstorder approximation. We show that these effects are represented as a function of د• (where د• is the volume fraction of APs) for engineering purposes. It is also found that TI contribution to the enhanced thermal conduction reaches up to around 87.5% when APs contact with each other and that TTI has an important role in the range 0.3785 ≤ د•â€‰â‰¤â€‰0.7031 due to the confine effect of fieldvariation caused by transversely bidirectional thermalinteractions. When د•â€‰> 0.7031, LTI effect again plays key role in heat conduction in nanofluid systems owing to closed packing of APs. Consequently, to achieve energyefficient heat transfer nanofluids that are required in many industrial applications, both APs' distribution configuration and APs' volume fraction have to be considered in the thermal analysis of nanofluids.