Definition of Nanofluids

Introduction

In his original study, Choi (Hamilton & Crosser, 1962) used nanoparticles to improve the thermal conductivity of several materials (base fluids). Nanomaterial is defined as a mixture of normal fluids and nanoparticles. These nanoparticles may be found in a variety of shapes, including spherical, rod-like, or tubular structures, rectangular blocks, and spheres. In order to improve heat transmission, nanofluids are acknowledged as an alternative to traditional fluids. By dispersing nanoparticles with diameters approximately 100 nm in the base fluid, this class of fluids is produced. As the basis fluid in nanoparticles, substances such engine oil (EO), ethylene glycol (EG), kerosene oil, blood, water, polymer, etc are being used Due to its widespread use in a variety of sciences and businesses. Metallic (Cu, Ag, Si), non-metallic, oxide (CuO, Al₂O₃) nanoparticles have recently attracted lot of interest. The idea of developing a more efficient heat transfer fluid by Hamilton and crosser (1962), was first tested by dispersing micro-sized particles in the base fluid. Interesting work was done to understand the application and thermophysical properties of nanofluids by Devarjan et al. (2018) and Esfahani et al. (2018). Advanced heat transfer fluids known as hybrid nanofluids are made by fusing nanoparticles with conventional base fluids. These very small nanoparticles have a high heat conductivity. They greatly enhance the fluid's capacity for heat transmission when disseminated inside a base fluid. Due to their improved thermal performance, hybrid nanofluids are being studied and used in a variety of industrial and scientific applications. HyNFs is actually made by placing two several nanoparticles, with the same or different size, in a common fluid. Hayat and Nadeem (2017) in their study about the increase of heat transfer by HyNF concluded that even with heat generation, radiation and chemical reaction, the heat transfer of hybrid nanofluid is more than ordinary nanofluid. Thermal analysis for hybrid nanofluid (Al₂O₃–Cu) from behind a cylinder exposed to magnetic field was investigated by Alharbi et al. (2019). In accord with Suresh et al. (2011) the heat conduction characteristics of HyNFs intensify practically linearly with increasing nanoparticle volume concentration. New research on the characteristics of THyNFs has been conducted (Cakmak et al., 2020; Parekh, 2014). Manjunatha et al. (2022) investigated the properties of the THyNF (Tio₂+sio₂+Al₂O₃/H₂O) such as 𝜌, k and 𝜌C_p and presented a model for a THyNF to increase the heat transfer pace. in this study, the THyNFs was discovered to have higher thermal conductivity than HyNFs. According to research by Afridi et al. (2019) on the generation of entropy in the flow of HyNF over a flat surface with heat loss, HyNF creates less entropy than regular nanofluid. Ternary hybrid nanoparticles are nanostructures made up of three unique materials or components that provide a flexible platform for integrating varied features. Researchers employ diverse materials, such as metals, semiconductors, or polymers, to develop nanoparticles with increased capabilities, making them useful in domains such as nanotechnology, materials science, and medicine for adapting materials and devices to particular applications. Awan et al. (2023) examines the Ellis hybrid nanofluid flow model with magnetic, Darcy-Forchheimer, and nonlinear thermal radiation effects over the stretched cylinder from a theoretical and computational perspective. The findings of their study demonstrated that greater Darcy-Forchheimer inputs and magnetic parameters result in a reduction in the speed characteristics of mono and hybrid nanofluids. In the world of engineering, heat transfer from a coated surface in a porous medium through which a non-Newtonian hybrid nanofluid flows is of enormous practical significance. The steady free convection flow of a non-Newtonian hybrid nanofluid in a saturated porous media characterized by Forschheimer's extended Darcy law was numerically solved and presented by Sahu et al. (2022). Their research's findings demonstrate that, depending on whether inertia is present or absent, the cross hybrid nanofluid velocity exhibits opposing responses to the Weisenberg number and porosity parameter augmentation. The ternary hybrid nanofluid has the largest surface effect. Furthermore, the ternary hybrid nanofluid has a quicker rate of heat transmission than both hybrid and ordinary nanofluids. Abbas et al. (2022) have studied the hybrid nanofluid flow from a permeable curved surface with nonlinear tension. The findings demonstrate that hybrid nanofluids transmit heat at a slower pace than basic nanofluids. Alharbi et al. (2019). explored the flow of an electroconductive incompressible ternary hybrid nanofluid with heat conduction in a boundary layer including metallic nanoparticles and magnetic induction effects across an extended cylinder. They also underlined that the variety of ternary hybrid NPs improves the thermophysical properties of the base fluid substantially. On an unstable spinning disk, Acharya et al. (2022) investigated the entropy generation of HyNF GO+Fe₃O₄/H₂O. The results show that for increasing magnetic field values, entropy generation increases, but for radiation and nanoparticle concentration, the opposite is true, and the HyNF has lower entropy generation than the normal nanofluid.