The current study uses the multi-physics COMSOL software and the Darcy–Brinkman–Forchheimer model with a porosity of ε = 0.4 to conduct a numerical study on heat transfer by Cu-TiO2/EG hybrid nano-fluid inside a porous annulus between a zigzagged triangle and different cylinders and under the influence of an inclined magnetic field. The effect of numerous factors is detailed, including Rayleigh number (103 ≤ Ra ≤ 106), Hartmann number (0 ≤ Ha ≤ 100), volume percent of the nano-fluid (0.02 ≤ ϕ ≤ 0.08), and the rotating speed of the cylinder (−4000 ≤ w ≤ 4000). Except for the Hartmann number, which decelerates the flow rate, each of these parameters has a positive impact on the thermal transmission rate.

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Nano-fluid applications span such a broad range of topics in the practical field that they demand their own review articles. In this review paper, the use of magnetic fields, porous media, and Nano-fluids in different heat transfer applications is discussed mainly in the solar thermal field. It has been proven that the employment of these techniques provides significant enhancement results for convective flows especially when they are combined, also the mathematical equations used to model this type of flow are summarized. In addition, different studies reported that the geometrical parameters of the enclosures can also effect the flow. In this context, recently scholars maintained many investigations on complex shaped cavities and their impact on heat transfer. These studies showed promising results for the use of this type of geometries especially for the trapezoidal ones. As reviewed in this paper, trapezoidal geometries and their properties strongly effect the convective flow in a great way leading to considerable enhancement. Overall, this review aims to present an insightful vision on different heat transfer improvement techniques and values the use of these methods in trapezoidal geometries for solar heat transfer applications.

Phase change materials (PCMs) proved to be valuable and drew the attention of numerous scientists striving to establish novel techniques to minimize energy consumption and expand heat storage; yet a number of challenges hampered their research. This paper provides an overall overview on how to overcome those constraints by adapting nano-enhanced phase change materials, the motivation behind their investigation, their advantages, area of applications, and their impact on thermal management and storage equipment. Recent computational and experimental studies have revealed that nanoparticles are extremely useful in terms of improving the thermo-physical properties of PCMs, allowing nano-PCMs, mainly nano-paraffin, to have a major positive influence on thermal concepts at the economical, ecological, and effectiveness levels. In this context, nano-enhanced PCMs are now able to store and release large amounts of heat in short intervals of time, which is relevant to thermal storage systems and contributes to augmenting and boosting their efficiency. It also improves the thermal performance of cooling and heating systems in buildings and regulates the operating temperature of PV systems, electronic components, and batteries.