The present work aims to investigate the nanofluid flow and heat transfer during natural convection phenomenon. The thermal lattice Boltzmann is utilized to simulate the natural convection problem, and the related modifications for the curved boundary conditions are applied to the LBM. The considered configuration is a rectangular cavity with a sinusoidal wall included with several internal active pipes. The cavity is filled with Al2O3-EG, and the thermo-physical properties including thermal conductivity and dynamic viscosity are measured experimentally using KD2 PRO thermal properties analyzer and Brookfield viscometer of Brookfield, respectively. The numerical simulations are coupled with experimental data using derived correlations for nanofluid at different temperatures and volume fractions. The Rayleigh number (10(3) < Ra < 10(6)), volume fraction of Al2O3-EG (0 < phi < 0.8) and thermal arrangements of internal bodies are the governing parameters in this study. The effects of mentioned parameters on the flow structure, temperature distribution, local/total entropy generation and heat transfer rate are presented. (C) 2019 Published by Elsevier B.V.