Eur. Phys. J. Plus (2018) 133: 486
https://doi.org/10.1140/epjp/i2018-12278-4

Regular Article

Effect of horizontal and vertical elliptic baffles inside an enclosure on the mixed convection of a MWCNTs-water nanofluid and its entropy generation

¹ Young Researchers and Elite Club, Arak Branch, Islamic Azad University, Arak, Iran
² Department of Mechanical Engineering, University of Kashan, Kashan, Iran
³ Sustainable Management of Natural Resources and Environment Research Group, Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City, Vietnam
⁴ Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

^* e-mail: marjan.goodarzi@tdtu.edu.vn

Received: 24 June 2018
Accepted: 25 September 2018
Published online: 29 November 2018

Abstract

In the present study, the effect of horizontal and vertical elliptic baffles on the flow, heat transfer and entropy generation of a MWCNTs-water nanofluid was investigated. Experimental data were used to calculate the viscosity and thermal conductivity of the nanofluid at different temperatures and volume fractions. A square enclosure with a central elliptic baffle was numerically studied. The elliptic baffle was located in two horizontal and vertical positions. The hot baffle was at temperature T_h and the walls of the enclosure, except for the lower insulated wall, were at temperature T_c. A FORTRAN code based on the finite volume method and SIMPLER algorithm was used to analyze mixed convection. Nanoparticle volume fractions of 0, 0.002, 0.004, 0.008, and 0.01 at Richardson numbers of 0.01, 0.1, 1 and 100 at a constant Grashof number of 10⁴ were studied. Horizontal placement of thermal baffle led to a higher heat transfer rate, which is more favorable in terms of heat exchange. The entropy generation values in the horizontal position were higher than the vertical position. The highest mean Nusselt number and total entropy generation were 7.9 and 20.4, respectively. For the horizontal placement, the highest mean Nusselt number happens at a volume fraction of 0.01 and a Richardson number of 0.01. Studies often focus on higher heat transfer rates. However, a horizontal baffle is more favorable than the vertical position considering that the greatest difference in the total entropy generation is about 8%.