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• Rheological behavior of hydraulic oil HLP 68 based ternary nanofluid is examined. • The considered nanoparticles are Fe 3 O 4 , TiO 2 , and GO. • Effect of volume fraction, mixing ratio and temperature on the results is studied. • All the examined nanofluids have a Newtonian behavior. • The highest and lowest viscosities respectively belong to MR of 1:1:1 and 2:1:1. Considering the importance of hydraulic oils in various tasks, such as lubrication and cooling, this study evaluated the feasibility of improving the efficiency of hydraulic systems by modifying the thermophysical properties and rheological behavior of base hydraulic oil. The rheological behavior of the hydraulic oil HLP 68 as a base fluid in the presence of a novel ternary combination of iron oxide (Fe 3 O 4), titanium dioxide (TiO 2), and graphene oxide (GO) as nano-additives were evaluated experimentally in a wide range of solid volume fractions (VFs) (0 to 1%), nanomaterial mixing ratios (MRs) (1:1:1, 2:1:1, 1:2:1 and 1:1:2), and temperatures (15 to 65 °C). Analysis of changes in dynamic viscosity versus shear rate for all MRs revealed that the THNFs have a Newtonian behavior. It was found that the highest increase in base fluid viscosity in the presence of a 1% VF of GO: Fe 3 O 4 : TiO 2 is 345%, 1821%, 1763%, and 1990% for MRs of 1:1:1, 1:1:2, 1:2:1, and 2:1:1, respectively, which occurs at a temperature of 15 °C. Also, the maximum increase in viscosity with temperature reduction from 65 °C to 15 °C for the MRs of 1:1:1, 1:1:2, 1:2:1, and 2:1:1 was found to be 66%, 75%, 60%, and 70%, respectively, which occurs at the highest solid VF. In addition, an algorithm for optimizing the structure/training parameters of the subtractive clustering-based ANFIS system as a leading regression technique in machine learning was developed. [Display omitted] [ABSTRACT FROM AUTHOR]

By combining photovoltaic panels that are able to convert solar energy into electricity with solar collectors that are able to convert solar energy into heat, photovoltaic/thermal hybrid collectors (PTHCs) are invented. In these systems, solar energy is simultaneously converted into electricity and heat, and they have a better performance than separate photovoltaic panels and solar collectors. For this reason, improving the performance of these systems has always been the focus of researchers. The present numerical research is devoted to the investigation of the effect of using a rotary propeller type turbulator in a concentrating PTHC (CPTHC) on the energy and exergy features of the collector. The results are compared with the data belonging to the cases without a turbulator and with a stationary turbulator. The effect of Reynolds number (R e) and rotational speed of the turbulator (ω) on the results is investigated. Water is considered as the working fluid of the CPTHC, and its flow is carried out in a turbulent regime. Among the three investigated cases, the best and worst performance belonged to the CPTHCs with a rotary turbulator and without a turbulator, respectively. The results showed that the rise of ω from 0 to 10000 rpm results in a growth in the thermal energy efficiency, total energy efficiency and thermal exergy efficiency by 75.47%–90.17%, 115.80%–130.78% and 0.75%–0.87%, respectively. Additionally, it was explored that the rise of ω entails an ascending-descending trend in the useful electrical power, first law electrical efficiency, second law electrical efficiency and second law total efficiency of the CPTHC, and the maximum value of these parameters occurs at ω = 5000 rpm. The highest total energy efficiency, which was equal to 130.78%, belonged to the case of R e = 20000 and ω = 10000 rpm, while the highest exergy efficiency was equal to 17.24% and belonged to the case of R e = 20000 and ω = 5000 rpm. [ABSTRACT FROM AUTHOR]

• Numerical study of using ultrasonic wave for thermal management of CPUs. • Totally 31 scenarios are examined by altering location and number of transducers. • Impact of Reynolds number and transducer frequency on the outcomes are assessed. • Case with transducers at ceiling and lateral walls (case#27) has the highest PEC. • The maximum PEC belongs to the case#27 and occurs at Re = 1000 for F = 30 kHz. The suitable thermal management of electrical devices leads to their reliable operation and durability. The present study investigates the application of ultrasonic surface vibration in a pin–fin heatsink to improve hydrothermal performance. To this end, a totally 31 scenarios were examined by altering the location of the vibrating transducers at four lateral walls and the top plate of the heatsink. The numerical calculations were performed within Reynolds number (Re) ranges of 500–2000 and frequency magnitude (F) of 15–30 kHz. Our results showed that the heatsink with three transducers at the top plate and two lateral adjacent walls (near and the opposite side of the inlet), namely case#27, exhibits the highest heat transfer coefficient and performance evaluation criteria (PEC) of 1.38 over the base case without transducers (WOT) at Re = 2000 and F = 30 among the studied cases. In addition, case#27 has its highest heat transfer coefficient and pressure drop (Δ P) at Re = 2000, while its maximum PEC is obtained as 1.78 at Re = 1000 for F = 30 kHz over the base case without vibration. Moreover, the maximum heat transfer coefficient and the lowest Δ P for case#27 at Re = 2000 were obtained at = 25 kHz. In such a case, the PEC was obtained as 1.06 over the base case. [ABSTRACT FROM AUTHOR]

A comparative study is performed to assess a hybrid building integrated photovoltaic/thermal (BIPV/T) system and earth-air heat exchanger (EAHE) in comparison with individual BIPV/T and EAHE systems. Different systems are examined based on energy, exergy, environmental, exergoeconomic, and enviroeconomic analysis. The hybrid system is able to increase/decrease the outdoor air temperature in winter/summer and produce electricity. A parametric study is also performed to inspect the impact of geometrical and operational metrics on the exergoeconomic and enviroeconomic parameters of the hybrid system. The outcomes revealed that the hybrid device produces higher annual total thermal and electrical energies by almost 10.1% and 935.6% compared with the BIPV/T and EAHE systems, respectively. In addition, it was found that the hybrid system produces 3.2% less annual total thermal and electrical exergy compared with the BIPV/T unit. While the hybrid system's enviroeconomic parameter was 3.2% less than the BIPV/T unit, its exergoeconomic parameter was 51% higher than that for the BIPV/T system. The case study analysis indicated that the exergoeconomic parameter increases by enhancing the air mass flow rate and EAHE length. Furthermore, it was found that the enviroeconomic parameter increases for a higher length and width of the BIPV/T system. • 5E analysis of hybrid BIPV/T-EAHE system compared with the individual systems. • Performing a case study to evaluate the effective parameters on the hybrid unit. • 10.1% and 935.6% higher annual useful energy compared with BIPV/T and EAHE systems. • Higher exergoeconomic parameter by 51% compared with the BIPV/T system. • Lower enviroeconomic parameter by 3.2% compared with the BIPV/T system. [ABSTRACT FROM AUTHOR]

• Rheological behaviour of polyethylene glycol-carbon dot nanofluid is examined. • Effect of shear rate, nanoparticle concentration and temperature are assessed. • A predictive model is developed for estimating the viscosity of the nanofluid. • The nanofluid shows a non-Newtonian behavior. • The UKF-ANN scheme was adopted for accurate estimation of the nanofluid viscosity. In the present study, the polyethylene glycol 200 (PEG200)-based nanofluid containing carbon dot (CD) nanoparticles was synthesized, and its rheological behavior at different temperatures and nanoparticle concentrations (φ) was investigated. The values considered for φ were 0%, 1% and 3% and 7% the values considered for temperature were 20, 30, 40, 50 and 60 °C. It was observed that the PEG200 has a Newtonian behavior, and the nanofluid has a non-Newtonian behavior which is amplified with increasing temperature. Also, a decreasing and increasing trend of viscosity was observed with temperature and φ. As another novelty of this research, a robust novel artificial neural network (ANN) model integrated with an unscented Kalman filter (UKF-ANN) was presented for accurate estimation of the viscosity of the PEG-CD nanofluid based on φ , temperature, and shear rate as the input features. Besides, two efficient data-driven approaches, including classical perceptron ANN (MLP) and response surface methodology (RSM) were developed to examine and evaluate the robustness of UKF-ANN model. The statistical and infographic assessment indicated that the UKF-ANN outperformed the MLP and RSM, respectively. [ABSTRACT FROM AUTHOR]

• Effect of nanoparticle shape on entropy generation in a heat sink is examined. • Simulations are conducted for both laminar and turbulent flow. • Spherical particles have the most insignificant impact on entropy generation. • Thermal entropy generation is reduced up to 43% by using platelet shaped particles. • Platelet nanoparticles increase frictional entropy generation up to 6.32 folds. Entropy generation characteristics of different nanoparticle shapes are explored considering a nanofluid-cooled helical heat sink system for both laminar and turbulent flow regimes. For each flow regime, four different Reynolds numbers are considered, ranging from Re =500 to 20,000. Five different particle shapes (spherical, bricks, blades, cylindrical and platelets) are included for this comparative study, and their thermal, frictional, and total entropy generation characteristics are evaluated for four different nanoparticle volume concentrations (ϕ =0.5, 1.0, 1.5, and 2.0%), and the outcomes are compared to the base fluid case (ϕ =0%) as well as a comparison is considered among the investigated nanoparticles. Obtained results revealed that in the turbulent flow regime, the thermal entropy generation tends to decrease with increasing particle volume fraction, and the highest decrements are obtained for platelet shape (43%). The frictional entropy generation shows an opposite trend, and the platelet nanoparticles yield the highest increment, around 6.32 folds in both laminar and turbulent flow. In both flow regimes, the spherical particles have the smallest impact on the entropy generation among the examined ones. In addition to that, increment in Re results in a decrement in the thermal entropy generation, while it causes a remarkable increase in the frictional entropy generation. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, 1.7 MHz ultrasonic and thermoelectric generators (TEGs) are used to cool down a photovoltaic (PV) module and improve its performance. The PV module is placed on a rectangular enclosure equipped with five ultrasonic piezoelectrics, which produce cold vapor of water inside the enclosure. The hot side of TEGs is attached to the rear surface of the PV module and their left side is cooled using water cold steam generated by ultrasonic piezoelectrics. The outcomes revealed that when the cooling system is not used, T s,ave increases to about 62.81 °C in the steady-state condition, while by using just the TEGs and just ultrasonic (H = 1.5 cm), the T s,ave is reached 55.4 °C and 52.3 °C, respectively. The hybrid cooling system of TEGs and ultrasonic reduced the T s,ave to 48.1 °C and increased its output power by 25.7%. By using the proposed cooling system, considering the impact of H on the temperature uniformity of the PV module represents that H = 0.75 cm is an efficient value to achieve high power output. In addition, the electrical efficiency of the PV module at the more efficient condition boosts from 8.61% to 12.46% compared to the non-cooling system. [ABSTRACT FROM AUTHOR]

• Nanoparticle shape effect is examined for laminar and turbulent regimes. • Nanoparticle shape has a remarkable impact on thermal performance of heat sink. • Platelet shaped nanoparticles are the most beneficial in laminar and turbulent regime. • Spherical particles are the least beneficial for thermal performance. • CHTC is improved up to 25% and 22.5% with platelets in laminar and turbulent flow, respectively. This study is motivated by the impacts of nanoparticle shapes on flow and heat transfer characteristics in a microchannel helical heat sink for cooling of electronics in both laminar and turbulent flow regimes. Therefore, effects of five different nanoparticle shapes (platelet, cylindrical, blade, brick and spherical) at five different volume fractions (ϕ = 0, 0.5, 1.0, 1.5, 2.0%) and at eight different Reynolds numbers corresponding to laminar and turbulent flow regimes (Re = 500–20,000) are investigated using finite volume method with two-phase mixture approach for nanofluids. Various performance parameters related with the first law of thermodynamics are considered. It was found that nanofluid utilization remarkably improves heat transfer along with causing an increment in pumping power. Furthermore, it was revealed that these variations in the parameters strongly depend on the utilized nanoparticle shape, and the platelet shaped particles were the most advantageous. They improved convective heat transfer coefficient up to 25% in laminar and up to 22.5% in turbulent flow regimes compared to base fluid. However, they increased pumping power up to 6.3-folds both in laminar and turbulent flow regimes. On the other hand, spherical particles yielded the least enhancement in convective heat transfer coefficient, which can reach up to 3.7% in laminar, and 1.8% in turbulent flow. Nevertheless, they slightly increase pumping power, which maximally reaches up to around 8%. Yet, the performance evaluation criteria showed that the heat transfer improvement effect of platelet shaped particles is more dominant over the increment effect in pumping power, which makes them favourable for applications. [Display omitted]. [ABSTRACT FROM AUTHOR]

The chief goal of this survey is about comprehensively examine a photovoltaic-thermal (PVT) system with a sheet-and-sinusoidal serpentine tube collector (PVT-S) experimentally from the perspective of energy, exergy and entropy generation. The results are compared with those of the PV module deprived of cooling and the PVT unit accompanied by a sheet-and-plain serpentine pipe collector (PVT-P). A water based nanofluid (NF) containing magnetite nanoadditives is considered as a coolant. The effects of volume concentration of nanoadditives (ϕ), NF mass flow rate ( m ˙ n f ), amplitude of the sinusoidal serpentine tube (a), and wavelength of the sinusoidal serpentine tube (w) on the performance metrics of the PVT unit are considered. The outcomes declared that the combined use of sinusoidal serpentine tube and NF leads to augmentation of energetic and exergetic performances of the PVT unit. According to the results, the first-law thermal, electrical and overall efficiencies of the PVT-S unit are 20.67–30.63%, 1.94–2.32% and 8.83–18.28% bigger than those of the PVT-P unit, respectively. In addition, the second-law thermal, electrical and overall efficiencies of the PVT-S unit are 10.56–26.68%, 1.94–2.32% and 2.44–4.57% greater than those of the PVT-P unit, respectively. Moreover, it was demonstrated that the increase of ϕ and m ˙ n f and the decrease of w result in an increment of performance features of the studied PVT units. Furthermore, it was found that among the entire the items considered in the survey, the best energetic and exergetic performances and the lowest entropy generation rate belongs to the NF-based PVT-S unit at ϕ = 2%, m ˙ n f = 80 kg/h, a = 5 mm and w = 60 mm. • Energetic and exergetic performances of a nanofluid-based PVT unit are assessed. • The unit is equipped with a sheet-and-sinusoidal serpentine tube collector. • Aqueous suspension of magnetite nanoparticles is considered as coolant. • Energetic and exergetic performance of the unit intensify with boosting ϕ and m ˙ n f . • The best performance of the unit occurs at a = 5 mm and w = 60 mm. [ABSTRACT FROM AUTHOR]

This experimental study is conducted to explore the rheological behavior of magnetite-water ferrofluid in the attendance of an external magnetic field (MF). Tetramethylammonium hydroxide is used as surfactant to increase the stability of prepared ferrofluids. The impacts of MF strength (0–480 G) and volume concentration of nanoparticles (0.3–1.5%) on the outcomes are examined. It was found that as the shear rate increases, the viscosity decreases sharply and then tends to a fixed number and therefore, the magnetite-water has non-Newtonian pseudoplastic behavior. It was also found that the application of the MF both increases the viscosity and enhances the non-Newtonian behavior of the ferrofluid. Moreover, it was found that the rise of nanoparticle concentration (φ) leads to the increase of ferrofluid viscosity. Then, the artificial neural network is applied to develop a prediction model for the rheological behavior of water- magnetite ferrofluid in both the absence and attendance of an external MF based on the obtained experimental data. The outcomes revealed that the developed models are capable of predicting the outputs in the absence and attendance of an external MF with R 2 value of 0.9772 and 0.9692. Unlabelled Image • Preparation of water-magnetite ferrofluid using coprecipitation method • Examination of dynamic viscosity of samples under a constant magnetic field strength • As the shear rate increases, the viscosity decreases sharply and then tends to a fixed number. • Applying magnetic field increases viscosity and non-Newtonian behavior of the ferrofluid. • A predictive model is developed for estimating the viscosity of the nanofluid. [ABSTRACT FROM AUTHOR]

• Evaluating effects of sonication time on thermal conductivity of Fe 3 O 4 -liquid paraffin nanofluid. • The sonication process is performed at seven temperatures in the range of 20 to 90 °C. • An excessive increase in sonication time can impair nanofluid stability. • Optimal sonication time is 3 h for this nanofluid. • Optimal sonication time is not a function of the temperature and nanoparticles volume fraction. In this study, the duration of sonication efficacy on the thermal conductivity of Fe 3 O 4 -liquid paraffin nanofluid is investigated. The nanofluid is produced at 0.005, 0.01, 0.015, 0.02, 0.025 and 0.03 vol concentrations by applying two-step method. The sonication process is performed in a temperature range of 20–90 °C. The duration of sonication seems to have two important effects: On the one hand, increasing the duration of sonication breaks the nanoparticles clusters, hence distributes the nanoparticles more uniformly which in turn rises thermal conductivity. On the other hand, an excessive increase in the duration of sonication can impair nanofluid stability. The results of experimental tests proved that the optimal duration of sonication is 3 h. The optimal duration of sonication is not dependent on the nanoparticles volume fraction (φ) and temperature. It was found that at the highest temperature and φ (90 °C , 0.03), the greatest thermal conductivity enhancement (28.49%) is obtained. In contrast, at the lowest temperature and φ (20 °C , 0.005) the lowest thermal conductivity enhancement was obtained (2.82%). [ABSTRACT FROM AUTHOR]

This study aimed at improving the performance of engine oil (SAE50) by adding zinc oxide nanoparticles. First, the microstructure of nanoparticles was studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). After confirming the microstructure of nanoparticles, a two-step method was used to prepare the engine oil/zinc oxide nanolubricant. The nanolubricant remained stable without any sedimentation for more than 5 weeks in static mode. Different volume fractions of the nanolubricant were prepared and the rheological behavior and nanofluid viscosity were studied in the range of 25 to 65 °C and, additionally, the cloud, freezing and flash points were measured. According to the results of dynamic light scattering (DLS) test, the nanoparticles in the base nanofluid had an average diameter of 55 nm. The viscosity increased with increasing concentration up to 25.3% relative to the base fluid. The viscosity of the nanolubricant decreased with increasing temperature. An accurate relation was proposed based on different temperatures and nanofluid volume fractions to calculate the nanofluid viscosity. The cloud, freezing and flash points were improved respectively by 22.2, 19.4 and 7.2% at the highest concentration, indicating the reasonable performance of nanoparticles. Unlabelled Image • Improving the performance of engine oil by adding zinc oxide nanoparticles • Measuring the rheological behavior, cloud, freezing and flash points • The viscosity increased with increasing concentration up to 25.3% relative to the base fluid. • The cloud, freezing and flash points were improved respectively by 22.2, 19.4 and 7.2%. • The nanofluid is a good alternative to the engine oil base fluid in practical systems. [ABSTRACT FROM AUTHOR]

Having a reliable approximation of heating load (HL) and cooling load (CL) is a substantial task for evaluating the energy performance of buildings (EPB). Also, the appearance of soft computing techniques has made many traditional methods antiquated. Thus, the main effort of this study was to evaluate the capability of several learning methods for appraising the HL and CL of a residential building. To this end, a proper dataset consisting of eight influential factors was provided. To simplify the problem, we executed feature validity by using a correlation-based feature subset selection (CfsSubsetEval) technique. The results of this process showed that wall area, overall height, orientation and glazing area have the most significant impact on the HL and CL simulation. After preparing the suitable dataset, sixteen learning methods namely, elastic net (EN), Gaussian process regression (GPR), least median of squares regression (LMSR), multiple linear regression (MLR), multi-layer perceptron regression (MPR), multi-layer perceptron (MLP), radial basis function regression (RBFR), sequential minimal optimization regression (SMOR), functions XNV, lazy K-star, lazy LWL, rules decision table (RDT), M5Rules, alternating model tree (AMT), directional path consistency (DPC), and Random Forest (RF) were developed in Weka environment to forecast the HL and CL variables. Referring to the results, it was concluded that RF, lazy K-star, RDT and AMT outperform other predictive models. Also, comparing the results with the results of the previous studies showed that the applied feature reduction not only did not disturb the learning process but also has enhanced the performance of models. Also, due to the excellent accuracy of the MLP, a formula was derived from the optimized structure of it to predict the HL and CL variables. • This research focuses on preference learning and feature validity. • Sixteen machine learning and regression methods are evaluated to realize this problem. • Our findings show that random forest, lazy outperform other predictive models. [ABSTRACT FROM AUTHOR]

In this study, the rheological behavior of ethylene glycol (EG)-graphene nanosheet nanofluid is examined experimentally. The impacts of mass concentration of nanoparticles (0–5%), temperature (5–65 ° C) and shear rate (0–90 1 s) on the dynamic viscosity of EG-graphene nanofluid are examined. The obtained results showed that incorporating graphene nanoparticles into EG causes fluid behavior to change from Newtonian to power-law non-Newtonian. In addition, it was found that the dynamic viscosity of EG-graphene nanofluid augments by boosting nanoparticle concentration and decreasing temperature. Moreover, the regression technique is utilized to develop predictive correlations of consistency-index and power-law index of the power-law model. The results demonstrated that the R-squared value for the obtained correlations for consistency index and power-law index are 0.925and 0.982, respectively. Unlabelled Image • Rheological behaviour of EG-graphene nanofluid is evaluated experimentally. • Effects of nanoparticle concentration and temperature on the results are assessed. • Correlations are developed to predict the consistency index and power-law index. • The EG-graphene nanofluid follows the Newtonian and non-Newtonian behaviour. • R2 for the obtained correlations for m and n are respectively 0.925 and 0.982. [ABSTRACT FROM AUTHOR]

• Effects of oscillating magnetic field on thermal-conductivity of two ferro-fluids. • Water-Fe 3 O 4 and water-Fe 3 O 4 /CNT ferro-fluids are considered. • Comparing the results of oscillating and constant magnetic fields. • Ascending-descending trend of thermal-conductivity in the constant magnetic field. • Increasing the thermal-conductivity by applying an oscillating magnetic field. The aim of this experimental assessment is to examine the influence of an oscillating magnetic field on the thermal-conductivity of a water-Fe 3 O 4 and water-Fe 3 O 4 /CNT ferro-fluids. Magnetic field is created by an electromagnet composed of a core made of ferrite and two copper windings. The impacts of magnetic field strength and frequency are also examined and the findings are compared with those of the constant magnetic field. The outcomes revealed that the pattern of thermal-conductivity in the attendance of a constant magnetic field is initially ascending and then descending. In addition, it was found that the descending trend of the thermal-conductivity can be prevented by using an oscillating magnetic field. Moreover, the results depicted that the most effective oscillating magnetic field has a frequency equal to the inverse of one minute less than time to reach the highest thermal-conductivity in the attendance of constant magnetic field. According to the results, the highest increase in the average thermal-conductivity of the water-Fe 3 O 4 and water-Fe 3 O 4 /CNT ferro-fluids in the attendance of an oscillating magnetic field of 700 Gauss in comparison to the case of a constant magnetic field of 700 Gauss, is respectively 22.62 and 24.25%. [ABSTRACT FROM AUTHOR]

• Predicting the energetic performance of a BIPVT system using ANN, ANFIS and GA. • Definition of PEC to examine the overall performance of the BIPVT system. • Better performance of ANN model compared with the GA and ANFIS. The main motivation of this study is to evaluate and compare the efficacy of three computational intelligence approaches, namely artificial neural network (ANN), genetic programming (GP), and adaptive neuro-fuzzy inference system (ANFIS) in predicting the energetic performance of a building integrated photovoltaic thermal (BIPVT) system. This system is capable of cooling PV panels by ventilation/exhaust air in winter/summer and generating electricity. A performance evaluation criterion (P E C) is defined in this study to examine the overall performance of the considered BIPVT system. Then, the mentioned methods are used to identify a relationship between the input and output parameters of the system. The parameter P E C is considered as the essential output of the system, while the input parameters are the length, width, and depth of the duct underneath the PV panels and air mass flow rate. To evaluate the accuracy of produced outputs, two statistical indices of R2 and RMSE are used. As a result, all models presented excellent performance where the ANN model could slightly perform better performance compared to GP and ANFIS. Finally, the equations belonging to ANN and GP models are derived, and the GP presents a more suitable formula, due to its simplicity of use, simplicity of concept, and robustness. [ABSTRACT FROM AUTHOR]

Due to their rapid commercialisation, Photovoltaic (PV) systems are considered the foundation of present and future renewable energy. Nonetheless, the full potential of this technology has yet to be realised because of several challenges. Consequently, effective solutions are critical for achieving high solar PV performance. This work aims to consolidate and provide a unique global review of pioneering recent studies on the most influential factors affecting solar PV performance. Four driven parameters are emphasised: dust/soil, tilt angle, temperature, and humidity. Regional, national and international experiments performed indoor, outdoor and at the laboratory, real-scale studies and numerical simulation dealing with PV performance challenges and potential routes for improvement and optimisation are reported. The review included studies from across the world, including the Middle East, Africa, the Asia Pacific, America and Europe. The figures and detailed tables with pertinent information on the key subject are provided. The studies suggest that the dust can reduce PV efficiency by up to 24 %. Adjusting PV module alignment up to five times a year can enhance energy yield by 3.63 %. The efficiency drops by 0.05 %/°C, with the temperature increase from 25 °C to 45 °C causing an efficiency drop of up to 20.22 %. This paper provides a comprehensive analysis of the thermal management, economic implications, environmental impact, and disposal concerns associated with end-of-life PV modules, highlighting the need for effective regulations to address emerging challenges. Finally, this work can be used as a pertinent guide for communities working in the field of solar PV involving researchers, industrialists and policymakers in the design, sizing, application and commercialisation of high-performance PV technologies and systems. • Dust accumulation lowers the performance efficiency of the photovoltaic (PV) module by up to 40 %. • The power and efficiency of the PV module are reduced by 0.5 % and 0.05 % for every 1 °C rise in ambient temperature. • The optimum tilt angle of the module is determined by mathematical analysis and empirical correlations. • The maximum output of the PV module declined by 34.22 % for the increase in relative humidity by 50.15 %. • Degradation of the PV modules is expedited up to 23 times in highly humid conditions. [ABSTRACT FROM AUTHOR]

In this experimental research, the laminar forced convection of water–magnetite nanofluid (NF) in a horizontal twisted tube (TT) is examined under a rotating magnetic field (MF). The findings are compared with those of the plain tube (PT). The influence of nanoadditive concentration (φ ), Reynolds number (Re), twist pitch (P) and MF arrangement on the heat transfer, friction factor and overall thermohydraulic features of NF is assessed. The MF consists of two magnets that rotate around the tube. For each of the magnets, three modes of clockwise rotation, counterclockwise rotation and without rotation are considered. The findings showed that the combined use of TT and rotating MF entails an increase in the overall thermohydraulic features of water–magnetite NF. In addition, it was found that the overall thermohydraulic features of NF augment with boosting φ , while they decline with boosting P and Re. Moreover, it was revealed that the best thermohydraulic features of the water–magnetite NF belonged to the case of φ = 2%, Re = 500 and P = 10 mm in the presence of a rotating magnetic field resulting from the clockwise rotation of the first magnet and the counterclockwise rotation of the second magnet. [ABSTRACT FROM AUTHOR]

• The presence of PCMs reduces temperature fluctuations and heat transfer to the room. • Performing sensitivity analysis for HTR based on variation in properties. • Thermal conductivity of PCM plays most significant role in selecting the appropriate PCM. • For equal thermal conductivity, closer melting point to room temperature is preferred. • When PCM is closer to the exterior, a larger portion of it melts, HTR is greater. Passive latent heat thermal energy storage approach incorporating phase change materials (PCM) is a brilliant technique to tackle high energy consumption issue in buildings. This paper investigated the thermal performance of the conventional walls of buildings in Isfahan, Iran with the inclusion of thirteen different phase change materials. The studied base wall was composed of plaster (2 cm), clay brick (15 cm), and cement (3 cm). The effect of PCM position inside the wall on the heat transfer was assessed in two scenarios, namely: close to the interior and close to exterior. The nonlinear governing equations were solved using the finite volume method. The results show that the performance of PCM-based wall is strongly influenced by the thermal conductivity, phase-change enthalpy and melting temperature of PCM. A PCM can more efficiently reduce the heat transfer to the interior space in case it has a lower thermal conductivity, has a higher latent heat of phase-change, and its phase-change temperature is closer to the room temperature. Moreover, the thermal conductivity has priority over other PCM thermophysical properties. The lower PCM thermal conductivity leads to transfer the lower amount of heat to the interior space. A two-fold increase in the thickness of the PCM leads to less than a twofold reduction in the heat transfer. Among the studied PCMs, the heat transfer reduction by Enerciel 22 was within the range 15.6–47.6%, while this range was 2–7.8% for CaC l 2. 6 H 2 O. [ABSTRACT FROM AUTHOR]

This numerical study aims to focus on the effect of difference between the inlet temperatures of working fluids on the hydrothermal characteristics of a counter-current minichannel hairpin heat exchanger. The water flows in the annulus side and the water based hybrid nano-fluid containing Fe 3 O 4 and carbon nanotubes (CNTs) passes through the tube side of heat exchanger. Temperature-dependent thermal conductivity and viscosity are considered for the non-Newtonian hybrid nano-fluid. The effects of Fe 3 O 4 and CNT volume fractions as well as the Reynolds number on the performance metrics of the heat exchanger are also assessed. The results revealed that the increase of difference between the inlet temperatures of working fluids leads to the augmentation of heat transfer rate, overall heat transfer coefficient (except at Reynolds number of 500), heat exchanger effectiveness and PEC; while the pumping power diminishes with the increase of inlet water temperature. Unlabelled Image • A hybrid nanofluid containing coated CNT/Fe 3 O 4 nanoadditives is prepared. • Variable thermal conductivity and viscosity are employed. • Effect of inlet temperature are assessed on the hydrothermal aspects of a hairpin heat exchanger. • Merit of using nano-fluid in the heat exchanger is higher at higher inlet temperatures. [ABSTRACT FROM AUTHOR]

• Simulation of nanofluid in a heat exchanger equipped with twisted tape using a two-phase mixture model. • Studying effect of nanofluid and twisted tape on the thermal performance of heat exchanger. • Evaluating effect of material type of twisted tape on heat transfer and pressure drop in the heat exchanger. • The use of twisted tape improved the Nusselt number up to 22%. • Alumina nanoparticles increased heat transfer and pressure drop up to 30% and 40%, respectively. The present study dealt with the numerical simulation of nanofluid flow in a double tube heat exchanger equipped with twisted tape. Alumina/water nanofluid and pure water are considered to be working fluids. A two-phase mixture model was employed for nanofluid flow simulation. The effect of nanofluid and twisted tape on the hydrodynamic and thermal performance of the heat exchanger was studied. Next, the focus was placed on the effect of the surface roughness (material type) of twisted tape on heat transfer and pressure drop in the heat exchanger. The results are presented as the temperature distribution, velocity field, Nusselt number, and pressure drop for various Reynolds numbers, nanofluid concentrations, pitch ratios, and tape insert materials. The results revealed that the use of twisted tape improved the Nusselt number up to 22%; also, adding alumina particles to water augmented heat transfer up to 30% and increased pressure drop up to 40%. Tapes with more roughness provided heat transfer enhancement of up to 16%, whereas the friction factor increased up to 21%. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Phase change material (PCM)-based heat sinks can offer reliable and effective thermal management (TM) solutions for increasingly sophisticated applications. A critical aspect of such heat sinks is determining how long it takes them to reach a set-point temperature. However, no generalised method exists in the literature that can predict and interpret the thermal performance of a wide range of PCM–porous media-integrated heat sinks. In this regard, this study examines the heat transfer characteristics of PCM-based heat sinks integrated with various metallic foams through experimental and deep learning (DL) techniques. The experiments are performed for transient TM analysis of various PCM-based heat sinks. Diverse variables, including foam porosity (0.95–0.97), PCM fraction (0.6–0.8), heat flux (0.8–2.4 kW/m2), foam materials (Fe–Ni alloy, Ni and copper) and PCM type (RT-35HC, RT-44HC, RT-54HC and paraffin wax), are investigated in this study. The experimental data are fed to the optimal DL model using the Bayesian surrogate model-tuned hyperparameters. Utilising a correlation analysis, as exemplified by the heat map and correlation plot, in conjunction with explainable artificial intelligence, it has been deduced that the thermal performance of the heat sink is principally influenced by factors such as PCM type, PCM fraction, foam material, foam porosity, and heat flux. Comparing the model's predicted data with the empirical findings, a good agreement was observed. Specifically, the mean absolute error (MAE) for the anticipated temperature and gradient registered at 0.0438 and 0.0054, whilst the mean square error (MSE) manifested values of 0.0579 and 0.0087, respectively. The proposed model can accurately assess the heat sink's thermal performance (correlation coefficient, R2 = 0.99) for various PCM types, fractions, foam materials, applied heat flux and foam porosity. [Display omitted] [ABSTRACT FROM AUTHOR]

In recent years utilizing nanoparticles in black paint (nano-paint) of solar desalination absorbers has become a topic growing interest. However, in most of studies, only the effect of using different types of nanoparticles brought into the spotlight, while in those limited studies that discussed on optimum concentration of nanoparticles, the results were controversial and not conclusive. Herein, an experimental study to find the optimum concentration of nanoparticles (silver, 1–5%) in solar absorbers in summer, spring and autumn with/without reflectors was conducted. To find the optimum concentration, performance of the systems from different viewpoints including energetic, exergetic, economic, productivity, exergoeconomic, energy-matrices, and environmental (amount of CO 2 /SO 2 /NO emission/reduction) analysis for each season and thorough its lifetime was examined thoroughly. Ascribe the highly variable of parameters; two Matlab codes have been developed to precisely calculate the economic and exergoeconomic parameters for different scenarios. The results showed that increasing the nanoparticle concentration to 5% from an economic viewpoint was reasonable just in summer, while for autumn and spring, 2.5% was optimum. The same was valid for productivity and exergy analysis. Importantly, the embodied energy of nanoparticles for the first time considered in calculation to obtain more accurate results in terms of environmental analysis and energy-matrices. Finally, it was concluded that even though using 5% nanoparticle in limited cases led to better results, the 2.5% concentration with reflector was optimum for all seasons and through the lifetime. This work would be a cornerstone for future researches in the context of using nano-paint in solar absorbers. [Display omitted] • Optimum concentration of nanoparticle in solar absorber in autumn, spring and summer. • Productivity, energy, exergy, economic, environmental, exergoeconomic, energy-matrices consider as criteria assessment. • Improvements for nanoparticle at 1%–2.5% is higher than 2.5%–5% for all seasons. • Negative effect on increasing nanoparticle from 2.5% to 5% in autumn and spring observed. • Although 5% in limited cases has better results, 2.5% regarding all criteria proposed for real-world applications. [ABSTRACT FROM AUTHOR]

Generally, Montazer Ghaem Combined Cycle Power Plant (MGCCPP) is equipped with natural draft dry cooling towers (NDDCT) and its performance strongly depends on environmental conditions such as wind speed. Thus, the present study aims to evaluate the effects of wind blowing on the cooling towers (CTs) efficiency and propose methods to improve their performance. It can help increase plant efficiency and decrease energy loss, which leads to cleaner production. For this purpose, the cycle of MGCCPP is modeled simultaneously using CFD and energy-exergy analyses for the first time. Moreover, the effect of windbreak walls (WBWs) on CT performance and CCPP are addressed. The results of CFD analyses are used to recognize the behavior of the towers in different wind speeds and deriving heat rejection. Based on obtained results, using the WBW in the prevailing wind leads to about 6.5 MW excess power in each unit. According to the economic analysis, the payback period of the three proposed plans is 14, 15.5, and 16 months, which is fully justified. • Three NDDCTs s are modeled using CFD analyses. • All the cycle equipment are modeled using EES. • Wind break walls are used to reduce the wind effects. • 3E (Energy, Exergy and Economical) analyze is done for the plant. • The payback period of the three proposed plans is 14, 15.5, and 16 months. [ABSTRACT FROM AUTHOR]

• Different dome heights and enclosure inclinations are considered. • Dome shape influences the flow circulations in a way to improve convection. • Nu can be augmented by up to 25% using dome shaped enclosures instead of rectangular or square. • For bottom-heating case (θ =90°), impact of the dome shape is more prominent. • D45 has the lowest entropy generation rate for all investigated parameters. Flow structure is an essential aspect for the intensity of natural convective heat transfer in enclosures. Improvements in the enclosure geometry affecting the flow structure can increase the natural convective heat transfer performance. As the dome shaped walls can change the flow direction in a way to improve the flow circulations and natural convection, the present work numerically investigates laminar flow and natural convective heat transfer of air in dome shaped enclosures with three different dome inclinations. The dome shape can be designed for such enclosures by either filleting the corners of a rectangular cavity or replacing one of the adiabatic walls of a square cavity with a dome shaped wall. Therefore, the impact of dome shape utilization is analyzed from these two perspectives by separately considering the rectangular and square enclosures as reference cases. To broaden the investigation for various circumstances, three different Rayleigh numbers and four different cavity inclination angles are considered. Furthermore, the non-dimensional entropy generation rates are computed for each enclosure to evaluate their performance in terms of second law of thermodynamics. The results show that the dome shape wall significantly changes the flow structure by providing a smoother circulation, which facilitates more intensified convection currents by directing the hot fluid to the colder region of the enclosure, hence, establishing a more effective natural convective heat transfer. The computed results reveal that the mean Nusselt number can be augmented up to 22.5 and 25.0% by the utilization of dome shaped enclosure compared to the equivalent rectangular and square enclosures, respectively. The impact of the dome is dependent on the cavity inclination and generally decreases as Ra increases. Besides, the dome shaped enclosure codified by D45 gives the lowest entropy generation value. [Display omitted] [ABSTRACT FROM AUTHOR]

• The naturally cooled baffled U-shaped cavity is examined under the magnetic field. • The power-law non-Newtonian water-Fe 3 O 4 nanofluid is considered as coolant. • The average Nu rises with boosting aspect ratio and nanoparticle volume fraction. • The impact of n and Ra on average Nu is significant only for Ra =106. • The effect of Ha and n on average Nu is considerable only for the cases where Ha <30. This numerical work examines the impact of an external magnetic field on the hydrothermal aspects of natural convection of a power-law non-Newtonian nanofluid inside a baffled U-shape enclosure. The enclosure is heated from the bottom and cooled from the baffles while the other walls are thermally insulated. Sinusoidal profile is chosen to describe the temperature distribution along the bottom wall. A comprehensive analysis is conducted to study the influence of pertinent parameters including Rayleigh number (Ra), Hartmann number (Ha), nanoparticle volume fraction (ϕ), aspect ratio of cold baffles (AR), inclination angle, and power-law index (n) on the flow and heat transfer characteristics in detail by using Galerkin finite element method. The obtained results show that the impact of n on the Nusselt number (Nu) is considerable for Ra =106 and inappreciable below this value. The influence of n and Ha on the heat transfer is significant when Ha is smaller than 30. For Ha <30, there is a threshold value of nanoparticle after which the rise of n augments heat transfer, which is 5% for AR =0.4 and 7% for AR =0.6. The analysis of heat transfer and fluid flow in open cavities is important because of the diverse applications in thermal engineering. In this work, magnetic field, non-Newtonian power-law nanofluid, and sinusoidal heat flux are used to improve the performance of a naturally cooled U-shape cavity. It was found that the cooling performance of cavity augments with the rise of aspect ratio, nanoparticle volume fraction, Rayleigh number, while it reduces with boosting Hartmann number. Finally, it was revealed that the best cooling performance of cavity occurs at Ra =106, Ha= 0, ϕ =5% and AR =0.6 Image, graphical abstract [ABSTRACT FROM AUTHOR]

In this study, the effects of incorporating MWCNTs nanoparticles on paraffin liquid-based viscosity behavior were examined. Viscosity of the prepared samples of MWCNTs-liquid paraffin is measured within the temperature of 5–65 °C at volume fractions of 0.005, 0.01, 0.05, 0.1, 0.5, 1 and 5%. Experiment results showed that nanofluid of MWCNTs-liquid paraffin should be characterized as a fluid with non-Newtonian behavior (shear-thinning). The behavior of the consistency index is such that it tends to decrease with increasing temperature and decreasing volume fraction. It was observed that with increasing volume fraction or temperature, fluid behavior deviates more from Newtonian behavior (decreasing power-law index). Temperature and volume fraction are two important and effective parameters on nanofluid viscosity. Increasing the temperature strengthens the effect of the volume fraction on the viscosity, but increasing the volume fraction weakens the effect of temperature on the viscosity. Due to the increase in volume fraction, the maximum intensification in viscosity was calculated to be 12.66%. Finally, two correlations were derived to calculate the consistency index and power-law index, respectively. • Dispersing MWCNTs in paraffin liquid-based and examining its rheological behavior • Preforming stability analysis by means of zeta potential test • MWCNT-liquid paraffin is non-Newtonian fluid with shear-thinning behavior. • Consistency index decreases with increasing temperature and decreasing volume fraction. • With increasing volume fraction, or temperature power-law index decreased. [ABSTRACT FROM AUTHOR]

This paper presents exergo-economic and enviro-economic assessment of a novel building integrated photovoltaic thermal-compound sensible rotary heat exchanger (BIPVT-SRHX) system. The innovative BIPVT-SRHX system preheats/precools the outdoor air in winter/summer and generates electric power. The performance of the system are analyzed from the energy/exergy viewpoints for Kermanshah, Iran climatic conditions. Then, the multi-objective genetic algorithm (MOGA) optimization is used to optimize to determine the optimum values of geometric and operating parameters in order to maximize the annual average exergo-economic and enviro-economic aspects of the system. The considered geometric and operating parameters include the length, width and depth of the air channel located underneath the PV modules, the air mass flow rate, and the diameter, rotational velocity and length of the SRHX. Moreover, the annual performance of the optimized and non-optimized BIPVT-SRHX systems are compared. The results showed that the annual average exergo-economic and enviro-economic aspects of the optimized BIPVT-SRHX system are 0.0076 $/annum and 246.9 kWh/$, respectively. Furthermore, it was found that the annual average enviro-economic aspect, annual average exergo-economic aspect, and yearly sum of CO 2 mitigation of the optimized BIPVT-SRHX system are respectively 36.8%, 23.1% and 37.7% higher than the non-optimized system. • An innovative exhaust air energy recovery system consisting of a BIPVT and a SRHX. •Pre-heating/pre-cooling ambient air in winter/summer and producing electricity. •Genetic algorithm-based multi-objective optimization approach for BIPVT-SRHX system. •Optimization leads to a 36.8% increase in annual average enviroeconomic parameter. •Optimization leads to a 23.1% increase in annual average exergoeconomic parameter. [ABSTRACT FROM AUTHOR]