Performance Of Solar Collector Research Articles

Numerical investigation of the overall thermal and thermodynamic performance of a high concentration ratio parabolic trough solar collector with a novel modified twisted tape insert using supercritical CO2 as the working fluid

Supercritical CO2 (sCO2) is favoured as the next-generation working fluid for advanced high-temperature and high-concentration ratio parabolic trough solar collectors (PTSC) due to the fluid’s low cost, availability and thermal stability at high temperatures. However, the lower thermal transport properties of sCO2 compared to conventional working fluids necessitate heat transfer enhancement of receivers using sCO2. In this study, a combined and extensively validated approach using Monte-Carlo ray tracing for optical analysis and computational fluid dynamics (CFD) for thermal and thermodynamic analysis were used to investigate the overall thermal and thermodynamic performance of a high concentration ratio sCO2-based PTSC with a modified twisted tape (MTT) inserts in the receiver. MTT inserts with twist ratios in the range of 2.0 to 4.0 and width ratios in the range of 0.75 to 0.95 were investigated. Results show enhancement of the heat transfer performance by up to 73% and thermal efficiency by 6%, and reduction of the receiver heat losses and circumferential temperature gradients when the MTT inserts are used. In addition to presenting results using the first law of thermodynamics, this study also considered the second law of thermodynamics by evaluating the entropy generation rates due to heat transfer and fluid friction irreversibilities. Results showed that the use of MTT inserts caused a reduction in the total entropy generation rates, with the lowest irreversibility occurring at a Reynolds number of 1,650,000 for a twist ratio of 2.0 and width ratio of 0.95.

The effect of adding hybrid nanoparticles (Al2O3–TiO2) on the performance of parabolic trough solar collectors using different thermal oils and molten salts

Enhancing the operational efficiency of parabolic trough solar collector (PTSC) systems is key to the advancement of solar energy technologies that enhance power generation sustainability. In the quest for efficient, environmentally friendly energy sources, solar energy systems have been a major focus of both researchers and industry. Adding hybrid nanoparticles (Al2O3–TiO2) to different base fluids of thermal oil or molten salts and then simulating the PTSC's energetic and exergetic performance is pivotal to efficiency enhancement. The focus of this paper will be on three thermal oils Syltherm-800, Therminol VP-1, and Therminol 75 that are used as base fluids with the addition of hybrid nanoparticles. Molten salts such as Solar Salt, Hitec, and HitecXL, which are considered different base fluid types, are also simulated with the same hybrid nanoparticle combination. The inlet temperature is found to be a determining factor in the choice of the base fluid. Inlet temperatures in the range of 300–650 K for thermal oils with the addition of Al2O3–TiO2 have improved the thermal and exergy efficiency of the PTSC by approximately 0.99 % and 0.59 %, respectively. Therminol VP-1/Al2O3–TiO2 has the highest average thermal efficiency among other thermal oils, with an average percentage of 71.68 %, while Syltherm-800/Al2O3–TiO2 has recorded the highest exergy efficiency of 24.1 %. At higher inlet temperatures above 500 K mixing Al2O3–TiO2 with molten salts has increased both energetic and exergetic PTSC performance by approximately 0.60 %. Solar Salt/Al2O3–TiO2 has the highest average thermal and exergy efficiency of 61.8 % and 36.1 %, respectively.

Exergy, exergoeconomic, and exergoenvironmental analyses of novel solar- and biomass-driven trigeneration system integrated with organic Rankine cycle

This study proposes a combined cooling, heating, and power (CCHP) system driven by biomass and solar energy integrated with an organic Rankine cycle (ORC). Its exergy, exergoeconomic, and exergoenvironmental performances are investigated. First, the thermodynamic parameters of each material and energy flow for the proposed CCHP system are simulated using Aspen Plus. Second, the exergy and exergoeconomic performances of the system are investigated, and an exergoenvironmental analysis of the system is performed. The results show that the unit exergy costs (UEC) of domestic hot water, electricity generated by an internal combustion engine (ICE) and the ORC, and chilled/heated water under summer/winter conditions are 2.742/2.742, 6.713/6.629, 12.930/12.930, and 27.100/12.530 MW/MW, respectively, with corresponding unit exergoeconomic costs (UEEC) of 41.11/41.11, 124.40/139.20, 181.80/181.80, and 507.10/302.60 USD/MWh, respectively. Meanwhile, the corresponding environmental impact rates per exergy unit are 0.616/0.616, 2.988/3.023, 0.030/0.030, and 6.567/3.072 mPts/MJ, respectively. The results highlight the urgency to prioritize improvements to the solar collector performance to reduce the UEC of electricity generated by the ORC. The absorption chiller/heater, heat exchanger, and ICE exhibit significant potential for enhancing their exergoeconomic performance. Additionally, the gasifier, ICE, and ORC can be optimized to mitigate their environmental impact with relatively minimal exertion.

Thermo-economic analysis of organic Rankine cycle using a new two-stage solar collector with nanofluids

The flat plate collector (FPC) has a low economic cost, while the parabolic trough collector (PTC) has a high heat collection temperature. To reduce costs, improve efficiency, and promote the use of solar energy, this study proposes a new two-stage solar collector that couples FPC and PTC. The main objective of this paper is to verify the performance of this two-stage solar collector when containing nanofluids. This collector drives the organic Rankine cycle (ORC) with four nanoparticles (Cu, CuO, TiO2, and Al2O3) in the oil heat transfer fluid. The FPC outlet temperature in the two-stage solar collector is optimized, the exergy of ORC is analyzed, and the economics of the new system using nanofluid are calculated and compared with those of the new system without nanofluid. Results show that Cu-oil outperforms the other nanofluids in terms of heat transfer. At a rated output power of 5 kW, the new two-stage solar collector with 5 % Cu-oil can reduce economic costs by 6.8 % compared with a single PTC. Meanwhile, the ORC with a two-stage solar collector using 5 % Cu-oil reduces the economic costs by 5.7 % compared with the ORC equipped with PTC without nanofluid. The new system has a minimum payback period of 17.3 years, and increasing the output power of the ORC is beneficial for reducing the investment payback period of the system.

Experimental Study of Hybrid Photovoltaic (PV/T) Thermal Solar Collector with Air Cooling for Domestic Use: A Thermal and Electrical Performances Evaluation

Photovoltaic-thermal (PV/T) collectors convert solar energy into both electrical and thermal energy. This conversion enables the cooling of solar cells while also allowing the produced thermal energy to be used to heat water or space. A hybrid solar panel converts the heat emitted by photovoltaic cells into a transfer fluid (liquid or air), enhancing PV cell efficiency while also producing useful solar heat for household hot water or heating. The heated air extracted from the PV/T collector can be used as a heat source for the building. The paper presents a baffle-based collector for a photovoltaic/thermal system (PVT) to increase output from the system using solar power by comparison with a PVT system without baffles, and its electrical and thermal performance are analysed with the experimental results. Baffles are a solution for optimizing the performance of flat plate solar collectors, which often have low performance. Three typical days from the March 2022 season were chosen and presented as part of this study. For the experiments, two fans were used for air extraction in the PV/T collector, with three speeds chosen: 0.02804 m3/s, 0.0082 m3/s, and 0.016 m3/s, respectively. The variation in thermal and electrical efficiencies of PV/T solar collectors has been calculated for the three tests of March 3, 4, and 5, 2022. The results indicated that the thermal and electrical efficiencies of the PV/T collector were on average 86% and about 9%, respectively, and the thermal efficiency improved by 22% compared with a PV/T collector without baffles in the absorber.

Assessing performance of an external compound parabolic concentrator solar collector with cascaded latent heat thermal storage

AbstractThis study presents quantitative results of charging experiments conducted on cascaded thermal energy storage system (CTESS) integrated with external compound parabolic concentrator solar collector (XCPCSC). Increasing mass flow rate in 2‐stage CTESS integrated with XCPCSC resulted in a 30% reduction in initiation time of phase change materials (PCMs) during charging, with a higher mass flow rate of 0.025 kg/s. However, due to disparate melting point temperatures of PCMs, phase transition in the two‐stage CTESS did not occur simultaneously, leading to poor heat transfer rates within the CTESS. To address this, study extended number of phases from two to three, resulting in a 1.5‐fold increase in rate of heat transfer compared to 2‐stage PCM system. The simultaneous melting processes at various stages in the CTESS maximized energy absorption, leading to a 25% increase in system efficiency. Notably, the values of energy stored efficiency and over‐all efficiency reached their peak values of 95% and 60%, respectively, between t = 12.00 h and t = 13.00 h. This time period also saw a significant increase in collector efficiency to 72%. These quantitative findings highlight importance of mass flow rate and PCM arrangement in achieving efficient heat transfer and system performance in a CTESS integrated with XCPCSC.

Numerical study of parabolic trough solar collector’s thermo-hydraulic performance using CuO and Al2O3 nanofluids

The current study aims to boost the thermal and hydraulic performance of a parabolic trough solar collector by modifying the absorber tube with a porous obstacle insertion. The research investigates how porous media and nanoparticles together influence the system's thermal performance, considering factors like outlet temperature, average Nusselt number, average friction factor, thermal performance factor, and thermal efficiency at different mass flow rates. To achieve better thermal performance, the base fluid, water, is substituted with Copper Oxide (CuO)-water and Aluminum Oxide (Al2O3)-water nanofluids at concentrations ranging from 3% to 7% by volume. The experiments are conducted at 800–1000 W.m-2 heat flux on the outside tube surface. The finite element method discretizes the governing equations for 3-D fluid flow simulations conducted in COMSOL Multiphysics 6.1 software. The simulation is carried out considering four altered rates of mass flow, ranging from 0.015 kg.s−1 to 0.060 kg.s−1. The findings show that at a Reynolds number of 1428 and a 7% volume concentration, the maximum thermal performance factor recorded is 1.97 and 1.99 for Al2O3 and CuO nanofluids, respectively. Additionally, the absorber tube achieves maximum thermal efficiency of up to 77.93% and 79.03%. Also, the augmentation in the average Nusselt number ratio is 26.27% and 36.74% when using Al2O3 and CuO nanofluids, respectively, with the tube height-to-diameter ratio (h/D) set at 0.42. The average friction factor ratio was reduced by 2.9% using CuO nanofluids compared to Al2O3 nanofluids. Thermal efficiency was enhanced by 7.2% using a porous obstacle insert in the parabolic trough solar collector system compared to a non-porous system.

Study of the enhancement in the performance of a hybrid flat plate solar collector using water and air as working fluids

AbstractA hybrid flat solar collector was manufactured from basic materials to combine the effects of both water and air solar heaters. The reason is to increase the amount of heat delivered to water by doubling the heat sources, one from the direct beam of sun and the other from the hot air delivered by the air solar heater. In addition, the flow of water inside the solar heater is made in a thin layer so that much heat can be gained by water per unit time. The outlet hot air of the solar air heater enters air ducts that pass through the solar water heater. With a constant water flowrate of 0.0167 kg/s, three different air velocities (1.7, 2.1, and 2.4 m/s) were applied to determine the optimum air velocity that results in the maximum outlet water temperature and the maximum removal factor FR for the solar water heater. The experiment was run from 10:00 a.m. to 2:00 p.m. every day during June 2023 and the data was recorded every 15 min. The data obtained from the experiment showed that the lowest air speed (1.7 m/s) results in the highest outlet water temperature (63°C) and heat removal factor FR (0.74).

Enhancing Parabolic Trough Solar Collector Efficiency through Absorber Tube Rotation: A Computational Study

This work uses CFD simulations to examine how absorber tube rotation affects parabolic trough solar collector performance, including output temperature, thermal efficiency, and surface temperature distribution. Simulation results are closely matched to experimental data, with variances ranging from 0.54% to 4.63%. It examines how mass flow rates (0.01 kg/s, 0.015 kg/s, and 0.02 kg/s) and input temperatures (32°C to 38°C) affect system performance in stationary and rotational modes at 1 and 2 rpm. Tube rotation considerably improves thermal mixing in the heat transfer fluid (HTF), resulting in more equal temperature distribution and possibly improved heat transfer efficiency. Increased rotational speed causes complicated dynamics that slightly impair thermal efficiency due to centrifugal forces affecting fluid flow patterns. The study shows that thermal efficiency peaks in the morning, emphasizing the importance of climatic and operational factors on collector performance. DOI: https://doi.org/10.52783/pst.276

Correlation study of thermal charging, discharging, and efficiency of graphene oxide-reinforced paraffin wax for thermal energy storage system

Nanocomposites, produced through mechanical blending, serve to enhance thermal performance of heat exchangers, solar collectors, and photovoltaic-thermal systems. This work employs an experimental methodology to assess the thermal charging (TC) and thermal discharging (TDC) of a composite generated by mixing graphene oxide (GO) and paraffin wax. TC and TDC of the GO-reinforced paraffin wax-based phase change material (PCM) have been examined across different flow rates (0.375, 0.75, and 1.5 L/min) and concentrations of GO (ranging from 0.25 to 1.00 vol%). The results exhibit a direct correlation between TC, TDC and efficiency, and reaction parameters (flow rate and volume concentration of GO). The experimental and predicted values of TCs, TDCs, and efficiencies fell ±15% (for TC and TDC), and ±9% for thermal efficiency, demonstrating a satisfactory level of agreement. This holds a practical application and valuable predictive tool for estimating TC, TDC, and thermal efficiency on known flow rates and concentrations of GO in wax-based PCMs.

Performance analysis and machine learning algorithms of parabolic trough solar collectors using Al2O3-MWCNT as a hybrid nanofluid

The critical importance of developing solar energy technologies for sustainable power generation places a high priority on the crucial efforts to optimize the performance of parabolic trough solar collector (PTSC) systems. This study focuses on optimizing the volume frictions of the hybrid nanofluids (1% Al2O3− 2% MWCNT/Syltherm-800, 1.5% Al2O3− 1.5% MWCNT/Syltherm-800, and 2% Al2O3− 1% MWCNT/Syltherm-800) in order to attain the most effective performance of the PTSC system. A mathematical model to investigate the PTSC performance under various volume concentrations is developed. Furthermore, this study trained three machine learning models (Decision Tree, Support Vector Machine, and Artificial Neural Network) using the generated data from the developed mathematical model to predict the PTSC outlet temperature more quickly, with the goal of achieving higher accuracy with fewer inputs. The findings of this study indicate that the PTSC system exhibits higher thermal efficiency when utilizing a combination of 2% Al2O3 and 1% MWCNT/Syltherm-800, with an average thermal efficiency of 70.54%. Moreover, the Artificial Neural Network (ANN) was the most accurate model out of the three. It performed remarkably well, showing an astounding R2 value of 99.99%, a mean absolute percentage error (MAPE) of 4.8x10−5, a root mean square error (RSME) of 0.012, and a mean absolute error (MAE) of 0.0057.

Innovative new solar parabolic trough collector enhanced by corrugated receiver surface with PCM and turbulator inside

A solar trough parabolic collector (STPC) has a reflecting surface that is curved into the shape of a parabola. An implementation study on solar trough parabolic collector thermal performance with four different volumetric flow rate values showing the effect of the Reynolds number with multiple passive enhancement approaches was applied tothe solar collector. The first approach is to use a corrugated copper receiver tube, which increases the collector solar heat absorbed by increasing the receiver tube surface area and turbulence. The second enhancement method was done using paraffin wax PCM (phase change material). Phase change material is used as an athermal storage material for heat absorbed by the collector, increasing the outlet water temperature through the night while slightly affecting the day water outlet temperature. By applying this approach, the solar trough parabolic collector enhances the heat transfer rate by around 40 % for all the volumetric flow rates adopted in this work. The third solar trough parabolic collector enhancing method was done by adding a turbulator twisted tape inside the corrugated receiver copper tube. This approach method increases the solar trough parabolic collector performance by around 35 % for all selected volumetric flow rate values. Adopting the three enhancing techniques on solar trough parabolic collector increased the overall thermal efficiency to approximately 85 %. The solar trough parabolic collector heat transfer coefficient, pressure drop, and friction factor were also investigated. A comparison study with previous works was also adopted in this work, which proves a superior thermal performance of the Innovative solar trough parabolic collector of this work over the earlier studies work.

Effects of nanoparticle shape factor on radiative ternary hybrid nanofluid flow over a wedge in presence of induced magnetic field

PurposeSeveral graphs, streamlines, isotherms and 3D plots are illustrated to enlighten the noteworthy fallouts of the investigation. Embedding flow factors for velocity, induced magnetic field and temperature have been determined using parametric analysis.Design/methodology/approachTernary hybrid nanofluids has outstanding hydrothermal performance compared to classical mono nanofluids and hybrid nanofluids owing to the presence of triple tiny metallic particles. Ternary hybrid nanofluids are considered as most promising candidates in solar energy, heat exchangers, electronics cooling, automotive cooling, nuclear reactors, automobile, aerospace, biomedical devices, food processing etc. In this work, a ternary hybrid nanofluid flow that contains metallic nanoparticles over a wedge under the prevalence of solar radiating heat, induced magnetic field and the shape factor of nanoparticles is considered. A ternary hybrid nanofluid is synthesized by dispersing iron oxide (Fe3O4), silver (Ag) and magnesium oxide (MgO) nanoparticles in a water (H2O) base fluid. By employing similarity transformations, we can convert the governing equations into ordinary differential equations and then solve numerically by using the Runge–Kutta–Fehlberg approach.FindingsThere is no fund for the research work.Social implicationsThis kind of study may be used to improve the performance of solar collectors, solar energy and solar cells.Originality/valueThis investigation unfolds the hydrothermal changes of radiative water-based Fe3O4-Ag-MgO-H2O ternary hybrid nanofluidic transport past a static and moving wedge in the presence of solar radiating heating and induced magnetic fields. The shape factor of nanoparticles has been considered in this study.

Thermal performance and experimental analysis of stainless steel flat plate solar collector with full-flow channels

The thermal performance of a flat plate solar collector (FPSC) is a critical indicator that depends on the environment, operational parameters, and dimensions. This study examines the impact of size on thermal performance improvement mechanisms. Firstly, numerical simulation models are introduced as the foundation for optimization research. This involves analyzing the flow resistance of microchannels and defining their structural parameters. Furthermore, experimental tests were conducted on a stainless steel flat plate solar collector (S/S FPSC) with the best design parameters to validate the accuracy of the mathematical model during the design phase. The results indicate that increasing the width of the microchannel and the height of corrugations can effectively enhance the thermal performance of the S/S FPSC. The momentary efficiency is projected to reach a remarkable 86.10% under ideal circumstances. Additionally, a mathematical expression was proposed to establish the relationship between the surrounding conditions and the momentary efficiency of the S/S FPSC. Moreover, the microchannel comprises S/S material, maintaining a homogeneous temperature distribution to maximize heat absorption. The use of stainless steel also extends the lifespan of the FPSC.

Green Engineering with Nanofluids: Elevating Energy Efficiency and Sustainability

Colloidal suspensions of nanoparticles in a base fluid, known as nanofluids, have gained attention as a promising green technology with a lot of promise to address issues with sustainability and energy efficiency in a variety of industries. The main features and uses of nanofluids as a sustainable solution are summarized in this paper. Due to their high thermal conductivity and high surface area to volume ratio, nanoparticles give off exceptional thermal and heat transmission capabilities. They are a desirable option for boosting the effectiveness of heat exchange systems, such as refrigeration, air conditioning, and cooling in electronic equipment, due to their improved qualities. Higher heat transfer rates and lower energy consumption can be achieved by using nanofluids as coolants or heat transfer fluids, which lowers greenhouse gas emissions and energy expenditures. Nanofluids have also found use in the realm of renewable energy, where they can improve the performance of geothermal and solar thermal collectors. The capture and conversion of renewable energy sources can be greatly enhanced by using nanofluids as working fluids in these systems, helping to create a greener and more sustainable energy landscape. Additionally, environmental cleanup and pollution management could benefit from the use of nanofluids. They are appropriate for uses including wastewater treatment, oil spill cleanup, and air purification because of their special features that allow for effective heat transfer and pollutant absorption. Furthermore, nanofluids can significantly contribute to lowering the amount of water and energy used in industrial operations, thus advancing sustainability objectives. The numerous uses of nanofluids as a green technology are highlighted in this paper, with an emphasis on their potential to improve energy efficiency, lessen environmental impact, and contribute to a more sustainable future. As this area of study and development develops, nanofluids will be in a position to play a crucial part in resolving the urgent problems of our day.

Investigative analysis of the influence of diverse fin configurations on the performance of a dual pass solar air collector

This study conducts a thorough investigation into the thermal performance of the double pass solar air collector, with a specific focus on the effects of three distinct fin configurations: parallel, vertical, and opposed. It is significant as it delves into the realm of solar air heating efficiency, a critical component in the broader application of solar energy technologies. Utilizing the geometric details and experimental findings, this study broadens its scope by examining a range of mass flow rates, specifically 0.0036 kg/s, 0.0110 kg/s, 0.0146 kg/s, and 0.0183 kg/s. Such an approach allows for a comprehensive understanding of the double pass solar air collector’s performance across diverse operational scenarios. The methodology is Computational Fluid Dynamics, which facilitates an in-depth analysis of temperature and velocity contours in both XY and YZ planes of the double pass solar air collector. The results of this study indicate that the parallel fin configuration significantly enhances heat transfer, evidenced by notable temperature increases, especially at the lower end of the mass flow rate spectrum. Conversely, while vertical and opposed fins result in greater pressure drops, they do not proportionally increase the temperature in a similar manner to parallel fins. The study concludes with a strong recommendation for the incorporation of parallel fins in future double pass solar air collector designs, particularly in situations where lower mass flow rates are predominant. This study contributes significantly to both the theoretical and practical aspects of solar collector efficiency, offering valuable insights for the development of more effective solar heating solutions.

Green synthesized clove-treated carbon nanotubes/titanium dioxide hybrid nanofluids for enhancing flat-plate solar collector performance

Green synthesizing carbon-based hybrid nanofluids has the potential to drive innovation in both renewable energy technologies and nanomaterial applications. In this regard, the current experimental work focuses on enhancing the thermal performance of flat-plate solar collectors (FPSCs) using working fluids made of nanocomposite materials via an eco-friendly technique (clove). Conventional methods of synthesizing nanofluids frequently involve using hazardous chemicals, raising concerns about the environment and human health. This experimental work examined the energy efficiency, exergy efficiency, and hydrothermal performance of FPSC using clove-treated carbon nanotubes/titanium dioxide (CT-MWCNTs/TiO2) nanocomposites by the ratio of (60 % to 40 %) dispersed in distilled water (DW). The test conditions were in the following ranges: hybrid nanofluid in different weight concentrations (0.025, 0.05, 0.075, and 0.1 wt%), different flow rates (0.3, 0.6, 0.9, and 1.2 L/min), heat flux intensities (400, 600, 800, and 1000 W/m2) and inlet temperature (30, 35, 40, 45 °C). The experimental results revealed that, the maximum enhancement in the energy efficiency (20.6 %) and exergy efficiency (22.9 %) were achieved at 0.1 wt% and 1.2 L/min, relative to the base fluid. In addition, the solar collector size was reduced by 20.5 % due to using a hybrid nanofluid. To conclude, the hybrid nanofluid outperformed the mono nanofluids regarding overall thermal evaluations. The novel hybrid nanofluids generally showed promising results for managing and conserving energy applications.

Studying the Improvement of Solar Collector Mechanism with Phase Change Materials

This study delves into the integration of phase change materials (PCM) in solar thermal collector systems to address this challenge. By incorporating nano encapsulated PCMs, researchers have mitigated concerns surrounding PCM leakage, revolutionizing the potential of solar collector systems to elevate energy efficiency, diminish carbon emissions, and yield manifold benefits. This article comprehensively investigates the design and utilization of solar phase change energy storage devices and examines the transformative impact of employing nano-coated phase change materials (Nano capsules) to augment solar collector performance. The integration of paraffin-based PCM and the insulation of the collector system have been crucial in optimizing heat retention and operational efficacy. The composition of the PCM involves a balanced blend of octadecane phase-change particles and water as the base fluid, designed to maximize thermal performance. Analysis of the experimental findings demonstrates the dynamic thermal behavior of the nano encapsulated phase change material, revealing distinctive temperature profiles about fluid dynamics and absorbent characteristics. Notably, the study emphasizes the nuanced trade-offs associated with the conductivity and melting temperature of the Nano encapsulated PCM, yielding valuable insights into energy storage capacity limitations and thermal performance variations throughout diurnal cycles. Central to the investigation, the optimal nanoparticle proportion is elucidated, shedding light on its pivotal role in modulating PCM performance. Furthermore, findings underscore the complex interplay between nanoparticle volume fraction and thermal fluid temperature, providing critical perspectives on optimizing PCM-enhanced solar collector systems.

Thermal performance of a flat-plate solar collector using elliptical riser tubes and magnesium oxide nanofluid

In this research, a solar flat plate collector with a rectangular geometry with elliptical risers has was studied experimentally. The collector was designed and built by the authors and the studies and tests were based on the ASHRAE standard and were done in the south of Iran. Thermal performance for water fluid and magnesium oxide nanofluid was performed in different discharges and atmospheric conditions. Studies were performed based on the type of fluid including ordinary water and nanofluid of water-magnesium oxide with a concentration of 1% and the environmental conditions of the test site as well as the fluid flow. The results showed that using nanofluid increases the collector efficiency in all conditions, especially at higher flow rates of the working fluid. Also, the maximum efficiency obtained in the best conditions for water is about 62.7% and for water-magnesium oxide nanofluid is approximately 82.3%.

Analysis of radiative mixed convective heat transfer for non-Newtonian fluid with heat generation/absorption phenomena

The current work consists of investigating the heat generation/absorption and non-linear thermal radiation effects for two-dimensional mixed convective bi-viscosity fluid flow inside the C-shaped enclosure with uniformly heated left and linearly heated top and bottom walls. The physical flow problem is governed by applying the constitutive laws of bi-viscosity model, conservation of mass, momentum and energy balance equations. The governing non-linear coupled partial differential equations is transformed into the algebraic nonlinear system by using Galerkin's finite-element technique after eradicating the pressure terms via the penalty method, and then the Newton–Raphson technique is used to solve it. It is noted that at a low value of [Formula: see text] (which gives the high plasticity of the bi-viscosity liquid), only the primary circulations with intensity [Formula: see text] appeared, but at a high value of [Formula: see text] decreased the plasticity which caused enhanced buoyancy-driven that generate also the secondary bowls with intensity [Formula: see text] inside the enclosure. The heat transfer rate increased [Formula: see text] by an increase in the Reynolds number from [Formula: see text] to [Formula: see text]. The findings of this study will play a role in improving the thermal performance of microelectronic devices, cooling systems, food processing, solar collectors, and high performance boilers by tracing the energy transport trajectories through heatlines.