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Recently, research and development on progressive and efficient hydrogen production methods has been paid lots of attention due to carbon-free feature of hydrogen. Application of nanoparticles to enhance an integrated solar-based hydrogen production unit is suggested and investigated in this work. The integrated plant consists of parabolic trough collectors coupled with a Kalina cycle for electricity generation to be consumed in a polymer electrolyte membrane electrolyzer for hydrogen production. The system performance is apprised for nanofluid as the heat transfer media for solar collectors and is compared with the pure basefluid case. Thermal model for parabolic trough collectors as well as thermodynamic models for Kalina cycle and electrolyzer are developed and validated. Also, thermo physical properties of nanofluid is assessed based on volume fraction of the nanoparticles. Parametric analyses are implemented for system performance assessment in which influence of design variables related to solar collectors, nanoparticels as well as the Kalina cycle are appraised. The effect on the hydrogen rate and solar-to-hydrogen exergy efficiency of design variables are comprehensively examined and discussed. According to the obtained results, the η e x , S T H is found to be 9.19% for the case with basefluid (without nanoparticles), whereas it can be improved to 9.63% with employment of 5% volume fraction of CuO nanoparticles. Such an efficiency improvement is due to the increment of hydrogen production from 0.669 kg/h to 0.702 kg/h using CuO-based nanofluid. • Effect of nanoparticles are evaluated in a PTC unit applied for hydrogen production. • Kalina cycle and PEM electrolyzer is used for electricity and hydrogen production. • Thermal and exergetic evaluations are carried out for performance investigation. • The CuO is found as the best nanoparticle among the three considered types. • Performance enhancement of around 5% is found with nanoparticle incorporation. [ABSTRACT FROM AUTHOR]

Response surface methodology (RSM) is used in this study to optimize the thermal characteristics of single graphene nanoplatelets and hybrid nanofluids utilizing the miscellaneous design model. The nanofluids comprise graphene nanoplatelets and graphene nanoplatelets/cellulose nanocrystal nanoparticles in the base fluid of ethylene glycol and water (60:40). Using response surface methodology (RSM) based on central composite design (CCD) and mini tab 20 standard statistical software, the impact of temperature, volume concentration, and type of nanofluid is used to construct an empirical mathematical formula. Analysis of variance (ANOVA) is applied to determine that the developed empirical mathematical analysis is relevant. For the purpose of developing the equations, 32 experiments are conducted for second-order polynomial to the specified outputs such as thermal conductivity and viscosity. Predicted estimates and the experimental data are found to be in reasonable arrangement. In additional words, the models could expect more than 85% of thermal conductivity and viscosity fluctuations of the nanofluid, indicating that the model is accurate. Optimal thermal conductivity and viscosity values are 0.4962 W/m-K and 2.6191 cP, respectively, from the results of the optimization plot. The critical parameters are 50 °C, 0.0254%, and the category factorial is GNP/CNC, and the relevant parameters are volume concentration, temperature, and kind of nanofluid. From the results plot, the composite is 0.8371. The validation results of the model during testing indicate the capability of predicting the optimal experimental conditions. [ABSTRACT FROM AUTHOR]

• 3D analysis of a PVT collector with water/silver nanofluid coolant is assessed. • Absorber tubes with the plain, ribbed, and porous-ribbed walls are investigated. • Effect of reynolds number and nanoparticle concentration on the result are assessed. • Among the examined absorber tubes, porous-ribbed absorber has the best performance. This paper deals with 3D numerical analysis and optimization of a Photovoltaic thermal (PVT) collector with water/silver nanofluid (NF) coolant. Three different absorber tubes with the plain wall, ribbed, and porous-ribbed configurations were investigated considering four Re numbers (500–2000) and four nanoparticle concentration (φ) of between 0 and 2%. The results indicated that the application of porous-ribbed absorber tube at Re numbers of 500–2000 enhances the overall efficiency of the PVT (η overall) by 28–32% and 30–32% higher than that are obtained for the plain and ribbed configurations, respectively. Within the studied range of Re (500–2000), the T PV in PVT with the porous-ribbed tube is nearly 1.19–0.95% and 0.94–0.85% lower than that with the plain and ribbed tubes, respectively. In addition, the escalation of Re from 500 to 2000 leads to reduce T PV by 0.81%, 0.66%, and 0.52% for the plain, ribbed, and porous-ribbed configurations, respectively. The increase in φ from 0 to 2% increases pressure drop inside three studied tubes by 41%, and also decreases T PV by 0.18%, 0.16%, and 0.06% in the plain, ribbed, and porous-ribbed configurations, respectively. [ABSTRACT FROM AUTHOR]

The usability of water based GO-TiO 2 -Fe 3 O 4 ternary nanofluid in a photovoltaic/thermal (PV/T) collector from both energy and exergy perspectives is inspected in the present experimental study. The effect of nanoadditive mixing ratio (σ = 1:1:1, 1:2:1, 1:1:2, and 2:1:1), nanofluid mass flow rate ( m ˙ n f = 20, 40, 60 and 80 kg h−1) and nanoparticle volume concentration (φ = 0%, 0.25%, 0.5% and 1%) on the outcomes is investigated. The results revealed that the nanofluid with σ = 1:1:1 has the best performance from both energy and exergy viewpoints. Among the examined cases, the maximum overall energy and exergy efficiencies were 88.23 and 15.36%, respectively, both belonging to the case of σ = 1:1:1, m ˙ n f = 80 kg h−1, and φ = 1%. Finally, it was found that m ˙ n f and φ have an escalating effect on both the overall energy and exergy efficiencies. • Energetic and exergetic performances of a nanofluid-based PV/T unit are assessed. • The unit is equipped with a sheet-and-serpentine tube collector. • Water based GO-TiO 2 -Fe 3 O 4 ternary nanofluid is considered as coolant. • Nanofluid with mixing ratio of 1:1:1 has the best energy and exergy performances. • The highest overall energy and exergy efficiencies were equal to 88.23% and 15.36%. [ABSTRACT FROM AUTHOR]