Vol.:(0123456789) 1 3 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-020-09639-2 Experimental and numerical investigation of heat enhancement using a hybrid nanofuid of copper oxide/alumina nanoparticles in water Robert Dakota Plant 1  · Gregory K. Hodgson 2  · Stefania Impellizzeri 2  · M. Ziad Saghir 1 Received: 18 February 2020 / Accepted: 24 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020 Abstract The following work experimentally and numerically investigated the thermal performance of a hybrid nanofuid, prepared by decorating a nanostructured aluminum oxide support with copper oxide nanostructures, in a fow system of porous open- cell foam metals. The porous medium was comprised of 6061-T6 aluminum with a porosity of 0.91 and a permeability of 9.54788 × 10 −7  m 2 . Experiments were performed under variable heat fux, using a hybrid nanofuid consisting of a 0.1 mass% aqueous solution of CuO@Al 2 O 3 nanocomposite particles 28 ± 11 nm in size. Thermal performance was evaluated with respect to the Nusselt number and the index of performance with pressure. Remarkably, the implementation of a copper oxide/alumina nanocomposite with the use of porously flled channels resulted in signifcant thermal enhancement (6–11%) relative to commercial alumina nanofuid, despite a total copper concentration of only 0.0001 mass% in the hybrid nanofuid. Increased performance is attributed to a combination of ultralow copper content and the approach to hybrid nanofuid design. Specifcally, a small amount of copper signifcantly increased the local Nusselt number, indicative of superior heat extraction. At the same time, a numerical model of the system was also developed and agreed with experimental measurements within an error of 5%. Numerical results predicted a slightly higher pressure drop for the hybrid nanofuid, but also showed higher absolute pressures for the hybrid fuid all along the channel in the three-channel confguration. Simulation also produced an interesting discrepancy between the performances of the hybrid nanofuid as a function of heat fux, possibly related to dif- ferent channel pressures inherent to the two heat sink models under investigation. This could point to a heightened pressure sensitivity of the thermal properties of hybrid nanofuids as well as a greater need to consider experimental design in the comparison of heat enhancement across nanofuidic systems. In terms of material design, decorating alumina nanoparticles with copper nanoparticles rather than mixing two individual nanostructured components appears to have been a benefcial strategy. The photochemical methodology used to prepare the nanocomposite material may also have improved thermal performance by yielding smaller (< 5 nm) copper oxide nanoparticles and provided access to the synergistic properties of a true nanocomposite material. This study demonstrates that heat enhancement by nanofuids can be achieved using a much smaller amount of copper than previously described in the literature and further highlights that synthetic methodology and material characterization can have a dramatic impact upon the performance of applied nanocomposite materials. Addition- ally, this work delivers a practical example of how progressive nanofunctionalization of materials can enhance thermal functionality of nanofuids. Keywords Nanofuid · Nanocomposite · Hybrid fuid · Porous media · Forced convection · Navier–Stokes formulation · Darcy–Brinkman model Introduction Recent research into the use of nanofuids has achieved remarkable performance improvements in heat trans- fer applications. Indeed, nanofuids ofer the opportunity to obtain thermal enhancement with very few negative impacts upon the net cost and efciency of operating fow systems. The more recent emergence of hybrid nanofuids * M. Ziad Saghir zsaghir@ryerson.ca 1 Department of Mechanical Engineering, Ryerson University, Toronto, Canada 2 Department of Chemistry and Biology, Ryerson University, Toronto, Canada