Lattice Boltzmann simulation of free convection in nanofluid filled cavity with partially active walls - Entropy generation and heatline visualization

Abstract

Purpose: The lattice Boltzmann simulation of natural convection heat transfer in cavities included with active hot and cold walls at the side walls and internal hot and cold obstacles has been performed. Design/methodology/approach: The cavity is filled with DWCNTs-water nanofluid. Different approaches such as local and total entropy generation, local and average Nusselt number and heatline visualization are employed to analyze the natural convection heat transfer. The cavity is filled with DWCNTs-water nanofluid which it’s thermal conductivity and dynamic viscosity are measured experimentally at different solid volume fractions of 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, and 0.5% and a temperature range of 300 to 340 (K). Findings: Two sets of correlations for these parameters based on temperature and solid volume fraction developed and used in the numerical simulations. The influences of different governing parameters such as Rayleigh number, solid volume fraction and different arrangements of active walls on the fluid flow, heat transfer and entropy generation are presented, comprehensively. It is found that the different arrangements of active walls have pronounced influence on the flow structure and heat transfer performance. Furthermore, the Nusselt number has direct relationship with Rayleigh number and solid volume fraction. On the other hand, the total entropy generation has direct and reverse relationship with Rayleigh number and solid volume fraction, respectively. Originality/value: The originality of this work is to analyze the two-dimensional natural convection using lattice Boltzmann method and different approaches like entropy generation and heatline visualization.