Finite Element Modeling of Heat Transfer in a Nanofluid Filled Transformer

In order to investigate the heat transfer characteristics of transformer oil containing nanoparticles, an electric-thermal-fluidic analysis using the FEM is carried out in this paper. The temperature and velocity distribution of oil and density of nanoparticles in a nanofluid filled transformer under natural and forced convections are obtained. The results show that generally the heat transfer efficiency is better under the forced convection. In addition, the distribution of nanoparticles in the oil depends on the temperature and velocity of the oil. This indicates that the local density and electrophoresis of nanoparticles must be considered for nanofluid application in transformers because of their potential influence on the temperature and velocity of the oil. Therefore, improvement of the simulation model taking into account of the local density of nanoparticles using the effective thermal conductivity had been carried out. Furthermore, electrophoretic force term had been implemented in Navier-Stokes equation, whereas the effective dielectric permeability was obtained by a homogenization technique using FEM.