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This paper presents a numerical investigation of the natural convection in an inclined rectangular enclosure with a baffle filled with Cu/water and then with Al2O3/water nanofluids using the finite difference method for tracking the thermal behavior within it versus the baffle length. The horizontal enclosure walls are assumed to be adiabatic, while the vertical ones are supposed to be a differentially heated. A thin horizontal baffle was attached to its left sidewall and is assumed to be cold. The flow and thermal fields are computed, respectively, for various values of Rayleigh number (103 ≤ Ra ≤ 105), inclination angle (0° ≤ ∅ ≤ 60°), baffle length (0.25 ≤ Lb ≤ 0.5), solid volume fraction (0.02 ≤ ϕ ≤ 0.06), and aspect ratio (1 ≤ AR ≤ 2). It was found that as the Rayleigh number, solid volume fraction, baffle length, and aspect ratio increase, an enhancement in the intensity of fluid flow in the enclosure was observed. In comparison, it reduces when the inclination angle increases. Moreover, it was found that the local Nusselt number (Nuc) enhances with the rise in Rayleigh number and the solid volume fraction. In contrast, it reduces with the increase in the aspect ratio and the inclination angle. [ABSTRACT FROM AUTHOR]

This work aims to enhance the heat transfer of a small prototype linear Fresnel reflector by using rGO-Co 3 O 4 /water hybrid nanofluids at a location in Blida region, in Algeria. Hybrid nanofluids, with varying concentrations (0.05, 0.10, and 0.20 wt%) and temperatures (20–60 °C), are prepared. For 0.2 wt % of rGO-Co 3 O 4 nanofluids, the viscosity and density increased by 70.83%, and 0.47%, respectively, while the specific heat decreased by 0.17% at a temperature of 60 °C over the base fluid data. The receiver pipe energy balance equations are solved using MATLAB software. With the use of 0.2 wt% of hybrid nanofluid, the mean thermal efficiency enhanced by 2.75%–31.95%, the mean exergy efficiency improved by 23.67%–2.27%, and the mean temperature increased by 9.42 °C, while, the receiver pipe temperature decreased by 2.69 °C. In addition, the mean heat transfer coefficient, mean thermal conductivity, Nusselt number, and the performance evaluation criteria were improved by using rGO-Co 3 O 4 /water nanofluid at 0.2 wt % by 309.67%, 19.31%, 254.75%, and 240.92%, respectively, while the mean entropy generation and electrical energy consumption decreased by 59.48% and 20.30%, respectively, as the CO 2 emission mitigation was 253.94 kg. Image 1 • Stable rGo-Co 3 O 4 /Water hybrid nanofluids with excellent thermal properties was experimentally obtained. • Thermal conductivity increased by 19.14% at 0.2 wt% for 60 °C using hybrid nanofluids. • Thermal behavior of hybrid nanofluids was investigated in a small LFR. • LFR thermal efficiency enhanced by 2.75%–31.95% using rGo-Co 3 O 4 /Water with 0.20 wt %. • Mean performance evaluation criteria using rGo-Co 3 O 4 /Water with 0.20 wt % enhanced by 240.92%. [ABSTRACT FROM AUTHOR]

In this study industrial grade Multi-walled carbon nanotubes (MWCNTs) nanoparticles dispersed in distilled water (DW) are investigated to evaluate its impact on the thermal behavior of linear Fresnel solar reflector technology. The stability and thermophysical properties of the MWCNTs/DW nanofluids are obtained experimentally. Stable nanofluids that showed higher thermal conductivity compared to DW were obtained. Thermal conductivity (TC) of the nanofluids increased by 3%, 6% and 7% for the volume fractions of 0.05%, 0.1% and 0.3% at 25 °C, respectively. TC also increased with the increase in temperature (i.e. 11% for 0.3% volume fraction at 70 °C). A one-dimensional model is developed to evaluate the transient behavior of the nanofluid within the linear solar reflector. Matlab code based on the finite difference method is developed to solve the energy balance equations at the different components of the studied solar collector. The numerical model is then validated with experimental results, where a maximum experimental thermal efficiency of 29.205% at 14:00 is achieved. MWCNTs/DW nanofluid with 0.3% volume fraction has the highest thermal efficiency of 33.81% and the highest PEC value as well as the lowest entropy generation. • Small linear Fresnel reflector has been manufactured and experimentally tested. • The maximum experimental thermal efficiency of DW is equal to 29.205%. • Stability and thermophysical properties of the MWCNTs/DW nanofluids are obtained. • Thermal conductivity of the nanofluids increased with the increasing volume fractions. • Highest thermal efficiency of 33.81% was obtained for MWCNTs/DW nanofluid. [ABSTRACT FROM AUTHOR]

The present study is a 4E (Energy, Exergy, Economic, and Environmental) analysis of a nanofluid-based parabolic trough collector (PTC) which is conducted with a developed model in MATLAB. MXene (Ti 3 C 2) nanoparticles were added to the silicon oil at weight concentrations of 0.05, 0.08, and 0.1%. The result was the important enhancement of the thermal conductivity of the nanofluid on the rand of 70%–89% for the highest concentration. According to the results, the PTC's optical efficiency was estimated at 79%, while thermal and exergy efficiencies of 74.71% and 22.44% with 0.10 wt% concentration were recorded on July 17, 2019. It is found that the MXene based silicone oil can reduce the system's cost by 0.021 M$ and enhance the energy gained by 1.51% at 0.10 wt% concentration compared to pure oil. Also, the annual CO 2 mitigation from the energy side varies from 2.25 to 2.30-ton CO 2 /year, while the annual environmental gain ranged between 32.73 and 33.28 $/year and 9.065 to 9.102 $/year for the energy and exergy studies respectively. [Display omitted] • A nanofluid-based parabolic trough collector is studied with MXene. • The collector thermal efficiency enhancement is found up to 1.1%. • For the day July 17, 2019, the exergy efficiency was improved from 0.07% to 15.16%. • For energy analysis, the annual CO 2 mitigation varies from 2.26 to 2.30 ton CO 2. • The environmental gain from the energy analysis varies from 32.73 to 33.28 $/year. [ABSTRACT FROM AUTHOR]