Abstract
The objective of current research was to investigate the fluid flow properties and features of heat transfer by natural convection in a rectangular enclosure containing a hybrid nanofluid and equipped with multiple isothermal heat source devices mounted on the left vertical side wall and the opposite side was subjected to isothermal cooling. The heat sources used are protruding heaters where two, three, and four heaters are used. The upper and lower boundary walls in addition to the spaces between heat sources of enclosure were kept insulated. Effective characteristics of hybrid water-based Cu-Al2O3 nanofluid, including its density, specific heat, and coefficient of thermal expansion, were modelled using mixture theory. Also, the thermal conductivity and effective viscosity were modelled using Brinkmann and M-G models respectively. Mass, momentum, and energy conservation equations describing the system were formulated employing a 2-dimensional model and computationally solved applying the finite element technique via the Galerkin method. Results were presented for a wide range of pertinent factors (103 ≤ Ra ≤ 106) and volume fraction (Vol.% concentration) of nanoparticles of (0 ≤ ϕ ≤ 0.10). The influence of Rayleigh number, volume percentage of nanoparticles, and heat sources (number or geometry) were investigated. The current model results were verified by comparing with data existing in literature. The findings demonstrated that higher mean Nusselt number was obtained as Rayleigh number and vol% concentration of nanoparticles increased. Correlation formulae are derived for the Nusselt number of each heater, considering the hybrid nanoparticles’ volume percentage and Rayleigh number.
