The development of mathematical modeling for nanofluid as a porous media in heat transfer technology

Abstract

Nanofluids as combinations of nanoparticles and base fluids are introduced to be used as working mediums in heat transfer and thermal fluid technologies. The solid parts or nanoparticles have high thermal conductivity property and can enhance overall heat transfer properties when they are mixed with the base fluids which have low thermal conductivity. In the nanofluid-flow field, the nanoparticles could be assumed to be distributed uniformly throughout the base fluid, this flow could also be presumed as the nanofluid flow through the uniform porous media (the solid parts) with nanofluid properties. The current work presented the developed mathematical model of the nanofluid flow; Al2O3 nanoparticles and water flow, as the steady fluid flow with the nanofluid properties through the porous medium with the Al2O3 properties. The simulated nanofluid flow was under fully developed laminar flow conditions through a rectangular pipe. The governing equations written in terms of the 3-D dimensionless variables were solved through the developed in-house program by using the finite volume method with the SIMPLE algorithm. Effects of the porous media characteristics; porosity, thermal conductivity and permeability, on accuracies of simulated results were investigated when the porosity value of 0.98 was considered to be equal to the nanofluid volume fraction of 0.02; as a synopsis relationship between the porosity and the volume fraction. The mixing thermal conductivity model; Yu and Choi model coupled with Maxwell model, was applied to be the thermal conductivity model of the porous media part. From the comparisons between the simulated and experimental results, the assumed relationships between the porosity and the volume fraction could be proved to be gratified and implied that the nanoparticles were distributed uniformly throughout the fluid and the nanofluid flow could be taken as the fluid with the nanofluid properties flowing through the porous media as well. The current developed model using the mixing thermal conductivity model with the porous media assumption could improve the model performance and supported its excellent potential in the nanofluid simulation as the fluid flow through the porous media.