Abstract
This paper reports a numerical study of mixed convection in a square enclosure, filled with a mixture of water and different types of nanoparticles. The upper and the bottom walls of the cavity are thermally insulated, while the remaining walls are mobile and differentially heated. In order to solve the general coupled equations, a computer code based on the finite volume method is used and it has been validated after a comparison between the present results and those of the literature. To make clear the effects of the governing parameters on the fluid flow and heat transfer inside the square, a wide range of the Richardson number, taken as 0.01 to 100, and the nanoparticles volume fraction, taken from 0 to 10%, is investigated. The phenomenon is analyzed through streamlines and isotherm plots with a special attention to the Nusselt number. The obtained results show that the mean Nusselt number is an increasing function of the decrease Richardson number, and increases with increasing values of the nanoparticles volume fraction, and far from the natural convection mode, higher heat transfer is noted with Ag-water nanofluid. At the end, useful correlations predicting heat transfer rate as a function of the solid volume fraction are proposed for each value of the Richardson number, which predict the numerical results within ±0.02%.
Highlights
Heat convection of nanofluids, which are a mixture of nanoparticles in a base fluid such as water and oil, has been recently an active field of research since they are used to improve heat transfer
The aim of the present paper is to examine the combined natural-forced convection heat transfer within this kind of cavities, filled with a nanofluid to predict, the effects of the governing parameters such the Richardson number and the nanoparticles volume fraction on the fluid motion and heat transfer as well
– The heat transfer acts as a decreasing function with the increase Richardson number
Summary
Heat convection of nanofluids, which are a mixture of nanoparticles in a base fluid such as water and oil, has been recently an active field of research since they are used to improve heat transfer. Compared to other techniques for enhancing heat transfer in practical applications, nanofluids have the advantage of behaving like pure fluids because of the nanometric size of introduced solid particles. They are used as heat transfer fluids for various applications, such as advanced nuclear systems or micro/mini channel heat sinks, electronic equipment such power transistors, printed wiring boards and chip packages mounted on computer mother boards. The aim of the present paper is to examine the combined natural-forced convection heat transfer within this kind of cavities, filled with a nanofluid to predict, the effects of the governing parameters such the Richardson number and the nanoparticles volume fraction on the fluid motion and heat transfer as well. The use of the latter, Cu (or Ag), is considered in this investigation
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