  Citation: Ba, T.L.; Gróf, G.; Odhiambo, V.O.; Wongwises, S.; Szilágyi, I.M. A CFD Study on Heat Transfer Performance of SiO 2 -TiO 2 Nanofluids under Turbulent Flow. Nanomaterials 2022, 12, 299. https:// doi.org/10.3390/nano12030299 Academic Editors: Ali Ahmadian, Massimiliano Ferrara, Abdon Atangana and Soheil Salahshour Received: 12 November 2021 Accepted: 11 January 2022 Published: 18 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). nanomaterials Article A CFD Study on Heat Transfer Performance of SiO 2 -TiO 2 Nanofluids under Turbulent Flow Thong Le Ba 1, * , Gyula Gróf 2 , Vincent Otieno Odhiambo 1 , Somchai Wongwises 3,4 and Imre Miklós Szilágyi 1, * 1 Department of Inorganic and Analytical Chemistry, Faculty of Chemical Technology and Biotechnology, Budapest University of Technology and Economics, Muegyetem rakpart 3, 1111 Budapest, Hungary; vincent.odhiambo@mail.bme.hu 2 Center for Energy Research, Konkoly-Thege Miklós út 29-33, 1121 Budapest, Hungary; grof.gyula@ek-cer.hu 3 Department of Mechanical Engineering, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Bangmod, Bangkok 10140, Thailand; somchai.won@kmutt.ac.th 4 National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand * Correspondence: kenty9x@gmail.com (T.L.B.); szilagyi.imre.miklos@vbk.bme.hu (I.M.S.) Abstract: A CFD model was performed with commercial software through the adoption of the finite volume method and a SIMPLE algorithm. SiO 2 -P25 particles were added to water/ethylene glycol as a base fluid. The result is considered a new hybrid nanofluid (HN) for investigating heat transfer (HT). The volume concentrations were 0.5, 1.0, and 1.5%. The Reynolds number was in the range of 5000–17,000. The heat flux (HF) was 7955 W/m 2 , and the wall temperature was 340.15 K. The numerical experiments were performed strictly following the rules that one should follow in HT experiments. This is important because many studies related to nanofluid HT overlook these details. The empirical correlations that contain the friction factor perform better with higher Reynolds numbers than the correlations based only on Reynolds and Prandtl numbers. When temperature differences are moderate, researchers may consider using constant properties to lower computational costs, as they may give results that are similar to temperature-dependent ones. Compared with previous research, our simulation results are in agreement with the experiments in real time. Keywords: nanofluids; ANSYS; CFD; turbulent 1. Introduction Common liquids such as water, ethylene glycol, thermal oil, etc., are used in HT devices for different industrial applications. In the last few years, many studies have improved the HT to maintain more suitable HT in different thermal systems [1,2]. The hybrid nanofluid is a novel fluid with a hybrid nanofluid for high thermal conductivity (k) and stability. Much research has been conducted on HT through a tube with different nanofluids [3,4]. Hussein et al. investigated the impact of the cross area on HT and friction [5]. They found that, compared with circular and elliptical pipes, flat pipes have a notable increment of HT and pressure drop (PD). Additionally, they studied the augmentation of forced convection HT in an automotive cooling system [6]. In many studies, researchers have combined different nanomaterials to obtain novel composites with better properties [7,8] and nanofluids with higher HT efficiency [9–14]. Suresh et al. [15] synthesised Cu-Al 2 O 3 /water hybrid nanofluids with 0.1 and 2 vol% via a two-step method. Nanofluids’ k and viscosity (μ) increased with an increase in concentration growth. Madhesh et al. [16] studied the HT of Cu-Ti/water hybrid nanofluids with 0.1–1.0 vol%; they observed that the convective HT coefficient was maximum, with 48.4%, at 0.7 vol%. Nanomaterials 2022, 12, 299. https://doi.org/10.3390/nano12030299 https://www.mdpi.com/journal/nanomaterials