Numerical investigation of the effect of nanoparticle sedimentation on the thermal behavior of cavities with different cross-sectional shapes

Abstract

In this paper, the thermal behavior of nanofluids was numerically simulated during nanoparticle sedimentation. A new solver was developed in the open-source framework, i.e. openFoam, using the finite volume method by combining appropriate solvers. Free convection flow was transiently modeled using this solver during the second phases (nanoparticles) sedimentation. A relative velocity term from the Vesilind relation was added to the momentum equation to model the sedimentation. Boussinesq and Maiga’s relations were used to calculate the density changes with temperature and effective conductivity, respectively. Simulations were performed for square, triangular, and circular cross-sections with the same hydraulic diameter at three different Rayleigh numbers. In addition, the changes in Nusselt number over time and the distribution of nanoparticles under different conditions were studied. The results showed that the formation of the sediment layers at the bottom of the enclosure reduced the streamlines and decreased natural convection and rotational flow. In addition, it contributed to conductive heat transfer, leading to a rapid decrease in the Nusselt number of cavities. Moreover, by increasing the Rayleigh number, the square, and triangular cross sections had the highest and lowest heat transfer, respectively.

Keywords

• transient flow
• free convection
• nanoparticles sedimentation
• openfoam
• cross-section