In this numerical study, natural flowand heat transfer of nanofluids with Al2O3, TiO2, Cu and CNT nanoparticles in a vertical channelwith dimpled fins at Rayleigh number (Ra) of Ra= 3.25 x 10(7) to Ra= 1 x 10(8) are investigated by using the finite volume method. The obtained results revealed that, using CNT in volumefractions of 2% and 4% leads to significant heat transfer and at phi = 6%, using TiO2 nanoparticles has a great effect on Nu number enhancement. Also, using solid nanoparticles in base fluid causes more uniform heat transfer distribution, especially in areas close to heated surface and by adding more volume fraction in base fluid, temperature level reduces. In general, according to temperature contours, reduction of wall temperature depends on the increase of Ra and volume fraction and the type of solid nanoparticles. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Co., Ltd. All rights reserved.