Natural convection analysis by entropy generation and heat line visualization using lattice Boltzmann method in nanofluid filled cavity included with internal heaters Empirical thermo-physical properties

Abstract

The natural convection heat transfer analysis is performed by different approaches such as heat line visualization, total and local entropy generation, average and local Nusseltnumber using lattice Boltzmann numerical method in nanofluid-filled cavity with partially heated and cooled walls in cluded by internal heaters. The cavity is filled withDWCNTs-water nanofluid which its thermal conductivity and dynamic viscosity are measured experimentally at different solid volume fractions of 0.01%,0.02%,0.05%,0.1%,0.2%,and0.5% and a temperature range of 300–340(K). Two sets of correlations for theses parameters based on temperature are developed and used in the numerical simulations. The sidewalls of cavity are cooled uniformly, two partially hot and cold surf aces at the bottom and top walls are located, respectively. The internal heaters are heated uniformly as well. The influences of different governing parameters such different arrangements of internal heaters, different concentrations of nanofluid and Rayleigh numbers on the fluidflow, temperature filed, average and local Nusseltnumber, total and local entropy generation and heat lines are presented. The results show that the arrangements of the internal heaters have pronounced effects on the fluid flow, heat transfer performance and entropy generation. Furthermore, the Nusseltnumber 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.