Modeling of anisotropic thermal conductivity of ferrofluids

Abstract

In the present study, we propose a new thermal conductivity model for ferrofluids using the aggregation structure of magnetic nanoparticles under external magnetic field. According to this model, in the presence of an external magnetic field, the total ferrofluid volume consists of two parts: a volume with aggregated magnetic nanoparticles - chainlike clusters and a volume with non-aggregated uniformly dispersed nanoparticles. It has been shown that with increasing the external magnetic field the degree of aggregation increases proportionally to the magnetic field strength. It has been proven that the thermal conductivity of ferrofluids along the magnetic field direction is higher than in the perpendicular direction, due to the increased contribution of aggregated magnetic nanoparticles with a magnetic field. The predictions of the proposed model of anisotropic thermal conductivity for ferrofluids were compared with the available experimental data and a good correlation was achieved.

Graphical Abstract

Keywords:

• Ferrofluid
• nanofluid
• nanoparticles
• thermal conductivity
• aggregation

Additional information

Funding

This work did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.