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The newest class of heat transfer improvement is accomplished by using hybrid Nano-fluids. Therefore, the heat transfer and pressure drop of a mixture of Iron oxide (Fe3O4) and Magnesium oxide (MgO) nanoparticles suspended into the base fluid under a turbulent regime through a plain and wavy tube are computed employing commercial software ANSYS Fluent. A mixture of Fe3O4 and MgO nanoparticles in pure water is considered a brand-new type of hybrid Nano-fluid for boosting heat transfer. The simulation procedures were performed utilizing the single and multiphase (mixture) approaches at Reynolds number in the range of (3,916 - 31,331) and volume concentrations range of (0.5% ≤ φ ≤ 2%). The plain and wavy walls are subjected to a constant heat flux of 18,189 W/m2, and the flow is presumed as fully developed. The computed outcomes are validated with the correlation equations and experimental data of literature. The outcomes demonstrate that boosting the nanoadditives fraction leads to a remarkable improvement of heat transfer and hydrothermal performance indicator (HPI) of MgO-Fe3O4 /H2O Hybrid Nano-fluid through the considered tubes compared with the conventional base fluid. However, the increment is slightly higher with a wavy wall tube than with the plain one. Moreover, new correlations were suggested for specific water-based hybrid Nano-fluid volume concentrations.

Nano-fluids are produced by combining one or more nano-particles in a base-fluid. Nano-fluids, especially hybrid nano-fluids, have better thermal conductivities than simple liquids. The results of various articles demonstrated that various parameters such as nano-particles size, their volume fraction, temperature, aspect ratio, base-fluid, nano inclusions, additive, and pH affect nano-fluid thermal conductivity. In this paper, the effect of these parameters is reviewed by considering experimental works performed on thermal conductivity. Since thermal conductivity is measured by researchers experimentally, it is also important for researchers to understand the effect of nano-particles on humans and the environment. Thus, in this article, published articles in this field are reviewed and the effect of nano-particles on human and environment are investigated. The results of these articles indicated that nano-particles can endanger human health and can have irreversible effects on human health. The nano-particles also have a devastating effect on the environment and can affect the water, soil, and animals. • Nanofluids discovery has had an important impact on heat transfer. • Reviewing Brownian motion and Clustering phenomena found in nanofluids. • Reviewing effect of temperature and concentration of nanoparticles on fluids thermal conductivity. • Assessment of effect of pH values, size and shape of nanoparticles on thermal conductivity. [ABSTRACT FROM AUTHOR]