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This work aims to enhance the heat transfer of a small prototype linear Fresnel reflector by using rGO-Co3O4/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-Co3O4 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-Co3O4/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 CO2 emission mitigation was 253.94 kg.

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.

In this paper, the design process steps of a conventional solar parabolic trough with large rim angle are presented. The various parameters which intervene to obtain the suitable parabolic trough form of the concentrator are applied. Through an experimental characterization, the real focal distance and the focal zone size of the designed concentrator have been determined and compared with those calculated theoretically. Then, its concentration ratio is evaluated and the focused solar flux at the focal zone along the absorber tube is calculated using Soltrace code. It should be noted that the wind speed effect was not taken into account in the experimental tests which are conducted under a solar irradiation of 970 W/m2 and a receiver inclination angle of 36° which corresponds to the experimentation site latitude.

In this paper, an experimental and analytical study of various parameters which affected the thermal efficiency as well as total heat loss of solar cylindrical cavity receiver for solar dish is presented. The downward facing receiver having a depth of 20 cm, inner diameter of 10 cm and 19 helically turns of copper tube thermally insulated has been designed. The wind speed effect was not taken into account in the experimental tests which are conducted under a solar irradiation of 957 W/m2 and a receiver inclination angle of 36° which corresponds to the experimentation site latitude. The developed analytical model is based in its structure on the different Nusselt number correlations suggested to evaluate the convective and radiative heat losses through the cylindrical cavity. Then, the model makes it possible to predict the total heat loss in order to determine the receiver thermal efficiency under a given inclination angle. The experimental and analytical thermal efficiency estimations agree reasonably well with a maximum deviation of about 12%.