**1. Introduction**

Water, ethylene glycol and mineral oils are traditional heat transfer fluids with low thermal conductivities which may restrict their effectiveness in many industrial domains such as chemical processing, generation of power, air conditioning systems, microelectronics and transportation. Solid particle suspensions and fluids have a strong ability to enhance heat transfer. One may classify particles in a number of ways including metallic, non-metallic and polymeric. However, there are issues that arise when industries use macro-sized suspensions such as heat transfer erosion and flow channel blockage owing to poor suspension stability and a gradual but steady decrease in pressure. Therefore, researchers and engineers have been hammering away to conquer this fundamental barrier by dispersing particles as small as millimeters or micrometers in liquids since Maxwell (1873). Large particles quickly settle in fluids which is an issue. Extended surface technology has reached its limits in thermal management system designs; thus, innovations that might increase interest in which nanofluids are nanotechnological heat transfer fluids. Nanofluids are suited for engineering applications and have various benefits over convectional suspensions which include improved stability, high thermal conductivity and negligible pressure loss. Thus, nanofluid technology will emerge as a promising and interesting field of study in the twenty-first century [1–9].

**Citation:** Abbas, I.; Hasnain, S.; Alatawi, N.A.; Saqib, M.; Mashat, D.S. Thermal Radiation Energy Performance on Stagnation-Point Flow in the Presence of Base Fluids Ethylene Glycol and Water over Stretching Sheet with Slip Boundary Condition. *Energies* **2022**, *15*, 7965. https://doi.org/10.3390/en15217965

Academic Editors: Gabriela Huminic, Eleftheria C. Pyrgioti, Ioannis F. Gonos and Diaa-Eldin A. Mansour

Received: 10 September 2022 Accepted: 7 October 2022 Published: 27 October 2022

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**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/).

Flow and heat transfer caused by the stretching sheet is a prominent process in many industrial applications, such as metallic sheet cooling, crystal growth in cooling baths, plastics and rubber sheets manufacturing, paper and glass fiber production, and the eviction of polymer and metals. Although enhancement of thermal and electrical conductivity can be achieved by using metallic particles was first proposed by Maxwell (1873), Choi learned from his work with micrometer-sized particle and fiber suspensions in the 1980s in which traditional particles in micro-channel flow passages are unusable [9–11]. However, advancements in nanotechnology can process and manufacture materials with average crystal-lite sizes below 50 nm. Thermal conductivity is key to developing energy-efficient heat transfer fluids. Because of the growing level of competitiveness on a worldwide scale, a number of different sectors are in desperate need of innovative heat transfer fluids that have much greater thermal conductivities than those that are already on the market [12]. In recent years, several studies have investigated the nanofluids boundary layer flow across a stretched surface using a wide range of metal and oxide nanoparticles [13–17]. Using a reworked version of Buongiorno's model with verified thermo-physical correlations which examine the impact of Darcy–Forchheimer and Lorentz forces on radiative alumina-water nanofluid flows across a slippery curved geometry subject to numerous convective restrictions [18]. Later on, Saima et al. [19] used a finite volume method, a numerical approach to study micropolar nanofluids flow through a lid-driven cavity. The development of innovative hybrid 2*D*-3*D* graphene oxide diamond micro composite polyimide films to alleviate electrical and thermal conduction. It is believed to be a useful option for the thermal dissipation of the electronic components of electric machines as a result of its high and outstanding thermal conductivity [20]. A numerical investigation for two-dimensional Sutterby fluid flow which is bounded at a stagnation point with an inclined magnetic field and thermal radiation was conducted by Sabir et al. [21]. Meanwhile, another computational approach was performed on stagnation point pseudo-plastic nano-liquid flow towards a flexible Riga sheet by Azad et al. [22]. The stagnation-point flow of an incompressible non-Newtonian fluid over a non-isothermal stretching sheet is investigated by Rashidi et al. [23]. Baag et al. [24] investigated numerical methods into the flow of MHD micro-polar fluids toward a stagnation point on a vertical surface with a heat source and a chemical reaction.

In light of this, a comparison study was carried out on the flow with velocity and thermal boundary layers (BL) of Al2O3 and *γ*-Al2O3 nanofluids along various base fluids across a stretching sheet. We have been successful in developing a conjuncture between stagnation-point flow and nanofluids flow over the stretching sheet with slip boundary conditions, by the numerical technique. Models of viscosity and thermal conductivity are developed from data through experiments. For Al2O3, Maxwell's thermal conductivity with radiation and Brinkman viscosity models are used in nanofluids flow. Therefore, this is a comparative new study and its contribution to the existing body of research will be significant.
