Regular Article

Study of mixed convection in closed enclosure with a ceiling fan^★

¹ LTPMP Laboratory, Faculty of Mechanical and Proceeding Engineering, University of Sciences and Technology Houari Boumediene, Algiers, Algeria
² LMT/ENS-Cachan/CNRS/Université Paris Saclay, 61 av. du Prés. Wilson, 94235 Cachan, France

^* e-mail: ameziani.de@gmail.com

Received: 26 February 2019
Received in final form: 20 April 2019
Accepted: 23 April 2019
Published online: 21 June 2019

Abstract

This paper presents a numerical study of heat transfer by convection in a square cavity. The vertical walls of the cavity are differentially heated and the horizontal ones are considered adiabatic. A fan is placed in the middle of the cavity and releases a jet down. Numerical simulation was performed using the lattice Boltzmann method to show the flow patterns and the heat flux depending on the Rayleigh number (thermal convection intensity) and the Reynolds number (fan-driven flow intensity). A parametric study was performed presenting the influence of Reynolds number (20 ≤ Re ≤ 500), Rayleigh number (10 ≤ Ra ≤ 10⁶) and the fan position (0.2 ≤ H_F ≤ 0.8). In forced convection mode, the flow structure has been mapped according to the position and the power of the fan. Three structures have emerged: two symmetrical cells, four symmetrical cells and asymmetrical structure. It has been observed that the heat transfer rate increases with the rise of Reynolds number and the reduction of the distance of the fan position from the ceiling. For the latter one, an unfavorable evolution of Nusselt number is observed for Ra > 10⁴.