Appraising conjugate heat transfer, heatlines visualization and entropy generation of Ag-MgO/H₂O hybrid nanofluid in a partitioned medium

Abstract

Purpose

This paper aims to perform the lattice Boltzmann simulation of conjugate natural convection heat transfer, heat flow visualization via heatlines approach and entropy generation in a partitioned medium filled with Ag-MgO (15-85%)/water.

Design/methodology/approach

The lattice Boltzmann method (LBM) is used to predict the dynamic and thermal behaviors. Experimental correlations for dynamic viscosity and thermal conductivity versus solid volume fraction are used. The study is conducted for the ranges of Rayleigh number 10³ ≤ Ra ≤ 10⁶, the partitioner thickness 0.01 ≤ δ ≤ 0.9, its position 0.15 ≤ X_s ≤ 0.85 and the hybrid nano-suspensions volume fraction 0% ≤ ϕ ≤ 2%.

Findings

The effects of varying of controlling parameters on the convective flow patterns, temperature contours, heat transfers, the heatlines and the entropy generation are presented. It has been found that the maximum rate of heat transfer enhancement occurs for low Ra numbers (10³) and is close to 13.52%. The solid thickness d and its horizontal position X_s have a substantial influence on the heat transfer rate, flow structure, heatline, total entropy generation and Bejan number. Besides, the maximum heat transfer is detected for high Ra and δ ≈ 1 and the percentage of augmentation is equal to 65.55% for ϕ = 2%. According to the horizontal position, the heat transfer remains invariant for Ra = 10³ and takes a maximum value near the active walls for Ra ≥ 10⁴. The total entropy generation increases with Ra and decreases with ϕ for Ra = 10⁶. The increase of ϕ from 0 to 2% leads to a reduction in close to 40.76%. For this value of Ra, the entropy is the maximum for δ = 0.4 and X_s = 0.35 and X_s = 0.65%. Moreover, as the Ra increases the Bejan number undergoes a decrease. The Bejan number is the maximum for Ra = 10³ independently to δ and X_s. The superior thermal performance manifests at low Ra and high value of δ independently to the positions of the conducting body.

Originality/value

The originality of this paper is to analyze the hybrid nano-additive effects on the two-dimensional conjugate natural convection in a partitioned medium using the LBM. The experimental correlations used for the effective thermal conductivity and dynamic viscosity give credibility to our study. Different approaches such as heatlines and entropy generation are used.

Citation

Ferhi, M. and Djebali, R. (2020), "Appraising conjugate heat transfer, heatlines visualization and entropy generation of Ag-MgO/H₂O hybrid nanofluid in a partitioned medium", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 30 No. 10, pp. 4529-4562. https://doi.org/10.1108/HFF-10-2019-0749