Natural convection of hybrid nanofluids inside a partitioned porous cavity for application in solar power plants Rasul Mohebbi 1 · S. A. M. Mehryan 2 · Mohsen Izadi 3 · Omid Mahian 4,5 Received: 23 August 2018 / Accepted: 8 January 2019 © Akadémiai Kiadó, Budapest, Hungary 2019 Abstract The present article deals with the CFD simulation of natural convection heat transfer of a hybrid nanofluid in an inverted T- shaped cavity partitioned and saturated by two different types of porous media. Suspensions of organic and inorganic nanoparticles, i.e., MWCNTs and Fe 3 O 4 , in water were selected as the working fluid. The macroscopic conservation equations for the flow field and heat transfer were modeled via volume averaging the microscopic equations inside porous media over a representative elementary volume. The effects of many parameters were investigated. The parameters included the Rayleigh number (Ra = 103–106), porosity coefficient ratio of two porous media (ε r =0.5–1.8), volume fraction of the dispersed nanoparticles (u =0–0.003), Richardson number (Ri =0.1–20), Darcy number ratio of two porous media (Dar = 0.01, 1, 100) and thermal conductivity ratio of two porous media (k r = 0.2, 0.4, 1, 5). The results showed that, with an increase in the Rayleigh number, porosity ratio and Darcy number ratio and decrease in the thermal conductivity ratio, the averaged Nusselt number increased. & Rasul Mohebbi Rasul_mohebbi@du.ac.ir & Mohsen Izadi Izadi.m@lu.ac.ir 1 School of Engineering, Damghan University, P. O. Box 3671641167, Damghan, Iran 2 Young Researchers and Elite Club, Yasooj Branch, Islamic Azad University, Yasooj, Iran 3 Mechanical Engineering Department, Faculty of Engineering, Lorestan University, Khorramabad, Iran 4 School of Chemical Engineering and Technology, Xi’an Jiaotong University, Xi’an 710049, Shaanxi, China 5 Center for Advanced Technologies, Ferdowsi University of Mashhad, Mashhad, Iran 123 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-019-08019-9