A molecular dynamic simulation of the influence of linear aggregations on heat flux direction on the thermal conductivity of nanofluids

Abstract

To reveal abnormal enhancement of thermal conductivity of nanofluids, molecular dynamics simulation is employed to investigate effects of included angle and nanoparticles size arrangement on thermal conductivity of Cu/Ar nanofluids. Included angle θ ranged from 0 to 90°, and six types of size arrangements are designed using combinations of r 1 and r 2 of Cu nanoparticles of 11 Å and 8.48 Å, 10.5 Å and 9.45 Å. Results demonstrated by reducing θ from 90° to 0°, thermal conductivity improved from 0.165 to 0.184 W . m −1 ·K −1 as actual heat flux distance increasing. Moreover, larger Cu nanoparticles on either side attracted more Ar atoms to form a denser interfacial layer, creating a compact heat flux channel to transfer more heat. The optimum thermal conductivity is at θ = 0° and Type 1 (two larger Cu radius r 1 = 10.5 Å on either side and two smaller radius r 2 = 9.45 Å in the middle). • Abnormal enhancement of thermal conductivity was revealed from microscopic view. • Effect of included angle of linear aggregations on thermal conductivity was conducted. • Particle size arrangement on thermal conductivity was comparatively investigated. • Optimum thermal conductivity was obtained to guide design of nanofluids.