This study investigates the role of thermal-interaction (TI) between aggregated particles (APs) on the enhanced thermal conductivity of nanofluids. With the assumption of configurations of linear chain-like aggregates in the direction transverse to the thermal flux, two-dimensional heat conduction is considered for estimation of the effective thermal conductivity of regular arrays, which is separated into three components, namely, no thermal-interaction (NTI) effect, longitudinal thermal-interaction (LTI) effect, and transverse thermal-interaction (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 first-order approximation. We show that these effects are represented as a function of ϕ (where ϕ 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 ≤ ϕ ≤ 0.7031 due to the confine effect of field-variation caused by transversely bidirectional thermal-interactions. When ϕ > 0.7031, LTI effect again plays key role in heat conduction in nanofluid systems owing to closed packing of APs. Consequently, to achieve energy-efficient 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.
Role of Thermal-Interaction Between Aggregated Particles in Thermal Conductivity Enhancement of Nanofluids
School of Mechanical and Aerospace Engineering,
Seoul National University,
Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received September 24, 2011; final manuscript received October 3, 2012; published online February 8, 2013. Assoc. Editor: Patrick E. Phelan.
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Jin, J. S., and Lee, J. S. (February 8, 2013). "Role of Thermal-Interaction Between Aggregated Particles in Thermal Conductivity Enhancement of Nanofluids." ASME. J. Heat Transfer. March 2013; 135(3): 034501. https://doi.org/10.1115/1.4022995
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