Natural convection in nanofluid enclosure under magnetic field: Entropy generation and economic analysis

Abstract

This study investigates the unsteady natural convection and entropy generation under the effects of magnetic field and baffles inside a nanofluid filled E-shaped enclosure. The nanofluid flow is driven by time-varying sidewall temperature and is partitioned by baffles. Multiple factors are discussed, including the enclosure aspect ratio (0.2 ≤ AR ≤ 0.7), nanofluid volume fractions (0 ≤ ϕ ≤ 0.1), Hartmann numbers (0 ≤ Ha ≤ 80), frequency of time-varying side wall temperature (0.01 ≤ ω ≤ 0.1), baffle locations (0 ≤ d ≤ 0.4) and length (0 ≤ l ≤ 0.4). An economic analysis is conducted to show the nanofluid cost of enhancing thermal transfer and reducing entropy generation. The modelling results show that increasing aspect ratio and nanofluid volume fraction enhance the thermal transfer behavior, while the magnetic field suppresses the nanofluid natural convection. Total entropy generation monotonically decreases with the increasing nanofluid volume fraction and Hartmann number. Installing baffles into horizontal walls can boost the thermal transfer behavior and decrease the total entropy generation. The economic analysis shows that increasing the nanofluid volume fraction can effectively improve the thermal economy, and this improvement increases with magnetic intensity.