Effect of heat conducting thick wall on pure mixed convection in a lid-driven trapezoidal cavity filled with water-Al_2O_3 nanofluid

摘要

The present numerical study deals with the effect of different heat conducting thick bottom wall materials on mixed convection inside a lid-driven trapezoidal cavity filled with nanofluid. The top wall of the cavity is considered as isothermal cold surface, and is moving at a constant speed in its own plane. The solid bottom wall is heated whose lower surface temperature is varied sinusoidally, and three different materials such as glass fiber, plexiglas and dry concrete are selected as heat conducting thick wall. The cavity is filled with water-Al_2O_3 nanofluid. The non-dimensional Navier-Stokes and the thermal energy equations are used as governing equations for this problem, and finite element method is used to solve those equations. Numerical simulation is performed in pure mixed convection regime by varying parameters such as Reynolds and Grashof numbers simultaneously within the range of 0.1 ≤ Re ≤ 2×10~4 and 10~(-2) ≤ Gr ≤ 4×10~8, and thus the Richardson number is maintained as unity. The influence of working fluid (both pure fluid and nanofluid) on the average Nusselt number of the top surface of the thick bottom wall is observed for different heat conducting materials. Results show that the materials of the thick wall with high thermal conductivity demonstrate better performance in convection dominated regime than those with low thermal conductivity.