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Nanofluids (NFs) have emerged as a revolutionary medium for enhancing heat transfer, with magnetohydrodynamics (MHD) gaining particular attention for its potential to improve system efficiency. Despite this growing interest, a critical gap remains in understanding the combined impact of Fe3O4 and its hybrid nanofluids under magnetic fields, especially in turbulent and transition flow regimes of internal forced convection. This review offers an in-depth exploration of MHD-NF internal forced convection, addressing key aspects such as magnetic field dynamics, nanoparticle clustering, stability, dispersion, flow control, and responsive rheology. Leveraging a comprehensive bibliographic analysis of 100 experimental studies from 2010 to the 2024, along with data from the Scopus® database, this work highlights how optimized nanofluid volume concentrations, magnetic field intensities, and frequencies significantly enhance heat transfer coefficients. The findings underscore that both magnetic field strength and nanoparticle concentration critically influence particle motion, flow patterns, entropy generation, thermal performance, and pressure drops, offering new insights into system design. The versatility of MHD-NF systems presents promising applications in fields ranging from advanced cooling technologies to solar thermal systems and material processing. Furthermore, this review addresses ongoing debates on the efficacy of alternating versus constant magnetic fields, advocating for customized magnetic field configurations to unlock the full potential of MHD-enhanced heat transfer. This work not only identifies existing gaps but also lays the foundation for future breakthroughs in magnetically influenced nanofluid systems.

Nanofluids have emerged as a transformative cooling solutions that offer substantial improvements in various engineering applications that require enhanced heat transfer. This review comprehensively analyses the latest research advances, technological progress, and regulatory considerations associated with nanofluids. Beginning with an overview of nanofluid properties, composition, and preparation methods, we highlight their roles in enhancing heat transfer. Detailed examinations of experimental studies and numerical simulations have revealed their effectiveness in applications such as automobile radiators, electronic cooling, turbine blade cooling, and solar PV-thermal systems. Health and safety considerations were addressed by discussing nanoparticle toxicity, biocompatibility, and environmental impacts, along with occupational health hazards and recommended safety measures. We scrutinized the regulatory landscape and identified challenges and gaps in frameworks across Africa, Asia, North America, and the European Union. A bibliographic analysis of the progress in nanofluid applications for heat transfer provides insights into the research trends, publication dynamics, and key contributors. This review concludes with future research prospects and potential applications of nanofluids, emphasizing the need for innovation and regulatory oversight. This review underscores technological and scientific advancements while stressing the importance of safety protocols and robust regulatory frameworks for sustainable nanofluid technologies.

Applying a magnetic field to influence convective flow of ferrofluids has become an efficient method for enhancing heat transfer in thermal systems, particularly in straight tubes. This study investigates the heat transfer properties of Fe₃O₄/TiO₂ nanofluids within a heated copper tube under varied magnetic field strengths and waveforms. Optimal magnetic field conditions were determined at 4 V and 60 Hz across all waveform types, as higher frequencies and voltages increased magnetic field intensity, thereby reducing heat transfer rates. Magnetic waveforms exerted differential influences on pressure drop, indicating varied nanoparticle alignment and turbulence levels, impacting fluid flow dynamics and viscosity. Higher nanoparticle concentration (0.1% vol) correlated with increased pressure drops across sine, square, and triangular waveforms, suggesting heightened flow resistance and potential nanoparticle agglomeration, thus reducing thermal efficiency. Conversely, lower concentrations exhibited enhanced thermal performance due to improved nanoparticle dispersion and reduced thermal resistance. At 0.1% vol, heat transfer enhancement without a magnetic field was 16.5%. The introduction of magnetic field waveforms attenuated this enhancement: 15.3% (sine), 13.26% (square), and 12.59% (triangular). Conversely, at lower volume fractions, heat transfer enhancements with magnetic fields exceeded those without at 0.05% vol, enhancements were 20.92% (sine), 21.3% (square), and 21.34% (triangular); at 0.025% vol, enhancements were 22.07% (sine), 22.3% (square), and 21.32% (triangular); at 0.0125% vol, enhancements were 27.87% (sine), 28.21% (square), and 26.74% (triangular); and at 0.0065% vol, enhancements were 22.24% (sine), 22.3% (square), and 24.49% (triangular).

Effective thermal management is crucial for optimum performance and energy conservation in energy-intensive industries and power systems. This study explores the influence of TiO2-water nanofluids on enhancing heat transfer during impinging jet-cooling of a heated copper surface, both under transient and steady-state cooling conditions. TiO2-water nanofluids, with volume fractions (0.025 vol% ≤ ɸ ≤ 1 vol%), were prepared, characterized, and utilized in the investigation. The experimental setup involved a dimensionless nozzle-to-target gap (H/D = 4) and Reynolds number (10000

Hot cylinders within the cavity can find diverse thermal applications, ranging from electronic devices and heat exchangers to solar systems, nuclear reactors, and the thermal design of passive cooling systems. Consequently, considering the use of phase change materials (PCM) close to hot cylinders emerges as a viable method for both cooling and storing thermal energy. In this work, two hot cylinders are arranged vertically and horizontally in the nano-enhanced phase change material (NePCM) trapezoidal enclosure with varying angles. The novelty of the current study lies in the fact that no prior research has explored the impact of hot cylinders arrangement on the melting process of a NePCM within a trapezoidal cavity, considering various inclination angles. The fixed grid, adaptive mesh refinement, and enthalpy-porosity method are used to model the melting flow. The numerical results indicate that the trapezoidal enclosure with vertically arranged hot cylinders exhibits better thermal performance than the other configuration. It is also found that the full melting time for both arrangements is minimum when the angle of the trapezoidal enclosure is γ=+40°. The reduction in full melting times for the vertical and horizontal arrangements of this angle are 25.3% and 29.6%, respectively, compared to the trapezoidal enclosure with γ=0.0°. Moreover, the NePCM with the graphite nanoplatelets (GNPs) of φ=1.0% has the shortest melting time for 0.0%≤φ≤3.0%. As future research, further exploration into the complexities of non-Newtonian NePCM flow can be pursued. Additionally, there is potential to explore modifying the cylinders' geometry into elliptical forms, encompassing a range of aspect ratios.

Nowadays, phase change materials are widespread in different engineering applications including cooling of electronics, thermal performance in building elements, heat exchangers, and many more. It is critical to gain thorough comprehension on phase change material behavior. The present research aims to numerically simulate phase change material in a heat storage unit having two isothermal elliptical elements. The formulated partial differential equations have been solved by the finite element technique taking into account the enthalpy-porosity approach and adaptive mesh refinement technique. The developed computational code has been validated using numerical and experimental data from the literature. The influence of the aspect ratios of the two elliptical cylinders on the melting phenomenon has been scrutinized, and the most efficient shapes have been identified. It has been found that more intensive melting occurs when the aspect ratios of the upper and lower cylinders are ARu = 0.25 and ARl = 4.0, with a reduction of 18.45 % in the melting time compared to the case with ARu = ARl = 1.0. Furthermore, the case with ARu = 1.0 and ARl = 0.5 shows the longest melting time, with an increase of 0.6 % in the melting time compared to the case with ARu = ARl = 1.0.

Abstract This study delves into an extensive investigation of the thermophysical properties and heat transfer efficacy of a hybrid nanofluid incorporating graphene nanoplatelets and γ-Al2O3 nanoparticles dispersed in deionised water. The nanofluids were characterised for their viscosity (µ), thermal conductivity (λ), and electrical conductivity (σ) over a 15–40 °C temperature range for varying nanoparticle loading (0.1–0.4 vol%). The experimental results revealed notable enhancements in µ, λ, and σ with increasing nanoparticle concentration, while µ decreased at elevated temperatures as λ and σ increased. At the highest concentration (0.4 vol%), µ increased by 21.74%, while λ and σ exhibited peak enhancements of 17.82% and 393.36% at 40 °C. An Adaptive Neuro-fuzzy Inference System (ANFIS) model was devised to enhance predictive precision by meticulously optimising the number of membership functions (MFs) and input MF type. The ANFIS architecture that exhibited the most remarkable agreement with the experimental data for µ, λ, and σ was found to utilise the Product of Sigmas, Difference of Sigmas, and Generalized Bell MFs, respectively, with corresponding input MF numbers being 2–3, 3–2, and 3–2. The optimal ANFIS model for µ, λ, and σ exhibits a higher prediction accuracy with an R2 value of 0.99965, 0.99424 and 0.99995, respectively. The Figure of Merit analysis using Mouromtseff Number identified an optimal nanoparticle concentration range of 0.1–0.2 vol% for enhanced heat transfer performance with a reasonable µ increase. This range guides practitioners in utilising hybrid nanofluids effectively while managing potential drawbacks.

Ceria-based H2O/CO2-splitting solar-driven thermochemical cycle produces hydrogen or syngas. Thermal optimization of solar thermochemical reactor (STCR) improves the solar-to-fuel conversion efficiency. This research presents two conceptual designs and thermal modelling of RPC-ceria-based STCR cavities to attain the optimal operating conditions for CeO2 reduction step. Presented hybrid geometries consisting of cylindrical–hemispherical and conical frustum–hemispherical structures. The focal point was positioned at x = 0, -10 mm, and -20 mm from the aperture to examine the flux distribution in both solar reactor configurations. Case-1 with 2 milliradian S.E (slope error) yields a 27% greater solar flux than case-1 with 4 milliradians S.E, despite the 4 milliradian S.E produces an elevated temperature in the reactor cavity. The mean temperature in the reactive porous region was most significant for case-2 (x = -10 mm) with 4 mrad S.E for model-2, reaching 1966 K and 2008 K radially and axially, respectively. In case-2 (x = -10 mm) for 4 mrad S.E, model-1 attained 1720 K. The efficiency analysis shows that the highest conversion efficiency value was obtained to be 7.95% for case-1 with 4 milliradian S.E.

Exhaust gases from the smelting furnace have high temperature and mass flow rate, and there is huge potential to use them for energy-related purposes such as electricity generation, cooling and heating. Utilization of the gases for energy-related purposes would lead to fuel savings and emissions reduction. To use this potential, it is necessary to design proper systems and cycles and apply a heat recovery unit. Several technologies are useable for heat recovery depending on the characteristics of exhaust gases, such as their mass flow rate, temperature and compositions. Due to the higher potential of combined heating, cooling and power (CCHP) generation systems compared with the systems with a single output, a CCHP is designed and investigated in the present study by consideration of the specifications of the exhaust gases. The applied system in this study comprises a Supercritical CO2 (SCO2) cycle, heat exchanger and single-stage absorption chiller for simultaneous heating, cooling and power production. Engineering Equation Solver (EES) is employed to model the proposed system by considering the properties of the flows and characteristics of the components. To get deep insight into the effective parameters on the outputs of the designed system, the impact of three factors, namely the mass flow rate of the gases, the effectiveness of heat exchanger and temperature of exhaust gases, are analyzed and investigated by the implementation of sensitivity analysis. As one of the main conclusions, it is found that an increment in the mass flow rate of exhaust gases from 30 kg/s to 70 kg/s causes augmentation in the power generation from 2037 kW to 4754 kW. Furthermore, exergy analysis is carried out, and it is found that an increase in the temperature or mass flow rate of exhaust gases or a decrease in the effectiveness of heat exchangers would lead to decrement in the exergy efficiency of the system. According to the performed sensitivity analysis, the mass flow rate of exhaust gases has the most remarkable influence on the heating and cycle-generated power among the considered factors.

In this research, we conduct a computational investigation into the mixed convection flow of copper/water nanofluids (NFs) within a rectangular cavity, utilizing the Lattice Boltzmann Method (LBM). The cavity is uniquely configured with five high-temperature obstructions (HOBs), and we vary their dimensions and positions to evaluate Nusselt numbers (Nu) across a range of Richardson numbers (Ri). The three walls of the cavity, excluding the moveable top wall, are thermally insulated, while the latter is maintained at a lower temperature. A constant magnetic field (MCF) exerts influence within the cavity, with Ri spanning from 0.01 to 100, HOBs ranging from 0.1 to 0.5, and HOBs at the bottom wall spanning from 0.25 to 0.4. This numerical investigation is executed using a customized in-house code, focusing on examining heat transfer (HTR) dynamics within the cavity. Our findings reveal that augmenting the height of the HOBs and positioning them closer to the cold wall significantly enhances the average Nusselt number (Nuav). Conversely, an increase in Ri leads to a reduction in Nuav on the cold wall. Specifically, the most notable enhancement, with a 66.7 % increase in Nuav, occurs at Ri = 0.01 when HOBs are elevated from 0.1 to 0.5. On the other hand, an increment in Ri from 0.01 to 100 results in a 79.4 % reduction in Nuav. Furthermore, elevating the HOBs from 0.25 to 0.4 produces a substantial 44.3 % increase in Nuav.

The advent of nanotechnology has spurred the development and utilization of nanomaterials and nanofluids in solar energy research. This paper presents for the first time a bibliometric analysis of scientific publications on nanofluid application to solar energy research. Data sourced from the Scopus® database covering 15 years were employed in this study. Network analyses of the participating organizations and countries, citations of documents and sources, and co-occurrence of author keywords were performed using VOS viewer® software. The result showed that 1630 articles consisting majorly of journals (76.4%) were published with the year 2021 recording 23.48% of the total publications. Engineering (922 articles) emerged as the subject of study with the most published articles. The results revealed that China and the University of Malaya with the highest number of publications were the most productive country and organization, respectively. The work of Ghasemi H. published in 2014 was the leading paper with 1049 citations while “Solar Energy” was the leading journal with 5456 citations. The most used keyword was “Nanofluid”. Research hotspots focused on the optical and thermal properties of different nanofluids and their application in solar energy devices. Development of green and novel nanoparticles and base fluids, deployment of thermal enhancement techniques, and increased studies on hybrid nanofluids and solar still are future research undertakings. The compendium of findings herein is expected to benefit the solar energy research community and serve as the catalyst for future studies in this regard.

Considering solar gain through the window (SGW), this study investigated the effects of installing shading on cooling load. Approving energy analysis for the base building (without shading), the cooling, heating, and annual energy demand were calculated. The best window angle and the best shading projection were obtained using the genetic algorithm. For the yearly minimum energy demand scenario, it was found that the window should be placed in the south direction, accompanied by the shading project with a maximum length of 20 cm. The results of the genetic algorithm revealed that for windows at the angle of 75–90°, the positive shading effects on annual energy demand become maximum. In this case, the shading reduces the yearly energy consumption by 3.1 %. The optimization showed that the shades have the best results for reducing the cold load for windows that are located in the azimuth angle between 135 and 180 °.

This study delves into the interplay between magnetic fields, heat transfer, and fluid behavior within a 3D mini-channel. Exploring the effects of a magnetic field on a hybrid nanofluid (Fe3O4–TiO2) under varying intensities (1000–2000 Gauss) and positions. Using numerical simulations (finite volume method), key parameters like Nusselt number (Nu), Friction factor (f), and Thermal Enhancement Factor (TEF) have been analyzed to uncover how magnetic fields and nanofluids interact in complex geometries. Results showed that the application of a magnetic field significantly enhanced heat transfer performance, with a maximum Nusselt number enhancement of 230%. Moreover, it was shown that greater magnetic field intensities were associated with elevated friction factors, whereas friction factors exhibited a declining trend as Reynolds numbers increased. The thermal enhancement factor initially increased with Reynolds numbers, but declined after reaching a peak. However, higher magnetic field strengths mitigated this decline, intensifying heat transfer enhancement effects reaching a maximum of 2.18 at 2000G magnetic field. These findings provide quantitative insights into the effectiveness of magnetic fields in enhancing heat transfer in Fe3O4–TiO2 hybrid nanofluids.

In industrial and energy systems, precise temperature control is indispensable. This study investigates the impact of hybrid nanofluids and certain jet hydrodynamic effects on enhancing the cooling efficiency on a heated copper surface. γ-Al2O3-MWCNT/water hybrid nanofluids consisting of Aluminum oxide (Al2O3) and Multi-Walled Carbon Nanotube (MWCNT) in de-ionized water with a mixing ratio of 60:40 was prepared and characterized. Nanofluid volume fraction (0.05 vol% ≤ Φ ≤ 0.3 vol%) and jet hydrodynamic parameters; dimensionless jet-to-target gap (1 ≤ β ≤ 5), dimensionless jet diameter (0.05 ≤ Ⴋ ≤ 0.17), and Reynolds number (8000

This article discusses the behavior of specific dispersive waves to new (3+1)-dimensional Hirota bilinear equation (3D-HBE). The 3D-HBE is used as a governing equation for the propagation of waves in fluid dynamics. The Hirota bilinear method (HBM) is successfully applied together with various test strategies for securing a class of results in the forms of lump-periodic, breather-type, and two-wave solutions. Solitons for nonlinear partial differential equations (NLPDEs) can be identified via the well-known mathematical methodology known as the Hirota method. However, this requires for bilinearization of nonlinear PDEs. The method employed provides a comprehensive explanation of NLPDEs by extracting and also generating innovative exact solutions by merging the outcomes of various procedures. To further illustrate the impact of the parameters, we also include a few numerical visualizations of the results. These findings validate the usefulness of the used method in improving the nonlinear dynamical behavior of selected systems. These results are used to illustrate the physical properties of lump solutions and the collision-related components of various nonlinear physical processes. The outcomes demonstrate the efficiency, rapidity, simplicity, and adaptability of the applied algorithm.

The present paper investigates the magnetohydrodynamics Casson fluid flow with porous medium. The Cu-water nanofluid is used to investigate further analytical results. Thermal radiation is considered along with the Cattaneo-Christov heat flux model and then solved analytically, then expresses the closed forms analytical solution in terms of two variables of hypergeometric function. The special form of Appell hypergeometric solutions are closed form of analytical solutions. The results of normalized shear stress at the wall and temperature profile, and rate of heat flux can be analyzed with suitable parameters, Viz., relaxation time parameter, Prandtl number, Radiation parameter, Magnetic parameter, and so on. The newness of the current work's novelty is to explain a solution to issues with stretching sheets on the basis of Appell hypergeometric form and also investigation takes place on a time relaxation parameter. The shear stress fηη0 is also calculated analytically. This problem has many industrial applications and engineering processes, namely glass-fiber production, extrusion of rubber sheets and so on. Finding that an increase in the thermal relaxation parameter and Prandtl number keeps the fluid temperature constant is the primary physical application.

In this study a 2D cubic chamber model filled with paraffin is analyzed with and without the inclusion of magnetic Fe3O4 nanoparticles at concentrations of 0.5, 1, 1.5 and 2 wt%, and an external magnetic field of intensities 0.005, 0.01, 0.015 and 0.02 T. It is ascertained that adding magnetic nanoparticles leads the horizontal temperature gradient to be reduced owing to increments in thermal conductivity. Additionally, this feature is found to be accelerated by applying an external magnetic field, which shapes highly conductive cluster formations of nanoparticles. However, since the increase in nanoparticle concentration and magnetic intensity increases the composite viscosity, there is an optimum configuration while applying both schemes. As such, the addition of 1 wt% nanoparticles provides the best results, as the melting time is reduced up to 25% compared to pure paraffin. Meanwhile, the melting time of a 1 wt% nanoparticle-containing phase change material (PCM) in the presence of an external magnetic field is improved up to 24% compared to the case with no external magnetic field. Also, the heat transfer coefficient of a 1 wt% nanoparticle-containing PCM both with and without an external magnetic field is also staggeringly enhanced compared to pure paraffin. Good correspondence with experimental data was achieved.

Abstract This research is mainly aimed at investigating the numerical modeling of thermal‐hydraulic and exergy efficiencies of parabolic trough solar collectors (P‐SCs) filled with magnetic hybrid nanofluid. The k‐epsilon turbulence, S2S, and mixture models were used to simulate the turbulence equations, radiation, and two‐phase nanofluid, respectively. The experiments were run using magnetic nanofluid in Reynolds numbers of 5000‐20 000, the volume fractions of 1%‐3%, and the ratios of pitch (ROPs) of 1, 2, and 3 of the combined turbulator. According to the results, there is a significant increase in average Nusselt number (Nu) and pressure drop (ΔP) with increasing Reynolds number, nano‐additive concentration, and ROP. Moreover, the use of the hybrid magnetic turbulator and hybrid nanofluid increased the thermal performance of the P‐SC. It was also found that the Reynolds number of 20 000 and volume fraction of 3% of nanoparticles resulted in the optimal exergy efficiency mode in using a hybrid turbulator.

Abstract Nanofluids are great heat transfer carriers for collecting thermal energy in solar thermal applications. In the present study, a theoretical study of single‐slope solar still (passive type) has been carried out by incorporating CuO, Al2O3, Ag, Fe2O3, and SiC‐water nanofluids at different volume concentrations (0.02, 0.05, 0.08, 0.12, and 0.2). This analysis has been carried out with an optimum water depth of 0.02m as obtained from the experimental and theoretical studies. In order to validate the model, the experiments were conducted on solar still and then performance of still was compared. The analytical expression of the characteristic equation using Runga‐Kutta ODE, for passive single slope solar still was found to be in good agreement with experiments carried out in Patiala, India. The total deviation for both experimental and theoretical distillate output of a still for a day was found to be 12.24%. Daily production for Al2O3‐water‐based nanofluid was found to be (14.22%) higher than simple solar still without nanofluid, followed by CuO (10.82%), Ag (8.11%), Fe2O3 (7.63%) and SiC (7.61%).

This article performs a numerical study on a transient solar still (SOST) by utilizing a variable heat flux using COMSOL software. A phase change material (PCM) layer with a thickness of 10–50 mm is placed at the bottom of the desalination. Some aluminum nanoparticles are added to the water in the water desalination, and the two-phase method is used to simulate this part of the desalination water. Other variables include the angle of the glass that changes from 10 to 45⁰ and the heat transfer coefficient (HTFC) on the glass that varies from 5 to 300 W/m2. The effect of these variables on the average PCM temperature (T-PCM), PCM volume fraction (VOF-PCM), average moisture (AV-MO) temperature, and AV-MO concentration is examined in 12 h. The simulations are done using the finite element method (FEM). The results demonstrate that the average temperature and VOF-PCM, AV-MO concentration, and AV-MO temperature are enhanced from morning to noon and decreased from noon to evening. An increment in the thickness of PCM causes the VOF-PCM in desalination water to reduce by 35%. An enhancement in the glass angle reduces the average temperature of PCM, especially in the morning and afternoon. The change in PCM thickness, especially in the evening, significantly enhances the AV-MO temperature.

Abstract Solar photovoltaic (PV) power is emerging as one of the most viable renewable energy sources. The recent enhancements in the integration of renewable energy sources into the power grid create a dire need for reliable solar power forecasting techniques. In this paper, a new long‐term solar PV power forecasting approach using long short‐term memory (LSTM) model with Nadam optimizer is presented. The LSTM model performs better with the time‐series data as it persists information of more time steps. The experimental models are realized on a 250.25 kW installed capacity solar PV power system located at MANIT Bhopal, Madhya Pradesh, India. The proposed model is compared with two time‐series models and eight neural network models using LSTM with different optimizers. The obtained results using LSTM with Nadam optimizer present a significant improvement in the forecasting accuracy of 30.56% over autoregressive integrated moving average, 47.48% over seasonal autoregressive integrated moving average, and 1.35%, 1.43%, 3.51%, 4.88%, 11.84%, 50.69%, and 58.29% over models using RMSprop, Adam, Adamax, SGD, Adagrad, Adadelta, and Ftrl optimizer, respectively. The experimental results prove that the proposed methodology is more conclusive for solar PV power forecasting and can be employed for enhanced system planning and management.

Abstract The use of different energy storage materials can have a high effect on the water productivity of solar desalination. This study evaluates the impact of magnetic powders on modified solar still (MPSS) performance and compares the results with conventional solar still (CSS). Black iron oxide magnetic powder was selected to increase solar radiation absorption. The black iron magnetic powder simultaneously acts as a thermal storage material and a porous absorber medium. The thermal energy stored in the magnetic powder improved the performance of the MPSS during peak solar irradiation hours, resulting in higher productivity. The results showed that the thermal performance of MPSS was higher than CSS. The MPSS exhibited a 39.8% higher evaporative and 14.5% higher convective heat transfer rate compared with CSS. Results showed that the cumulative water productivity of MPSS was 31.2% greater than CSS. Also, the energy and exergy efficiencies of MPSS were improved by 18.9% and 19.04%, respectively, compared with CSS. Moreover, the predicted payback period in MPSS and CSS were 3.2 and 4.3 months. Additionally, the CO2 reduction of MPSS was improved by approximately 45.53% compared with that of CSS. The results also showed that the exergoeconomic parameter of MPSS and CSS with energy base was equal to 33.1 and 24.56 kWh/$, respectively.

Abstract Compression ignition (CI) engines have good performance but more exhaust emissions. Dual fuel (DF) engines have better performance and lower emissions compared to CI mode. Also, the scarcity of fossil fuels made the researchers to find alternative fuels to power CI engines. Therefore, the present work aims to use hydrogen (H2) and honne oil biodiesel (BHO) to investigate the performance of CI engines in DF mode. Also, it aims to compare the performance of CI engines in various DF modes, namely induction, manifold injection, and port injection. First, the CI engine was fuelled completely by diesel fuel and BHO. The data were gathered when the engine ran at a constant engine speed of 1500 rpm and at 80% load. Second, the CI engine was operated in various DF modes and data were generated. CI engine operation in DF mode was smooth with biodiesel and H2. The brake thermal efficiency (BTE) of 32% and 31.1% was reported with diesel and biodiesel, respectively, for manifold injection due to low energy content and high viscosity of biodiesel. These values were higher than CI mode and other DF modes. Fuel substitution percentage for DF manifold injection was 60% and 57% with diesel and biodiesel, respectively. Smoke, hydrocarbon (HC), and carbon monoxide (CO) emissions were lower than conventional mode, but a reverse trend was observed for oxides of nitrogen (NOx) emissions. Heat release rate (HRR) and peak pressure (PP) were higher than conventional mode due to the fast combustion rate of hydrogen. The shortest ignition delay (ID) period was noticed for traditional diesel fuel, but it was longer for BHO biodiesel due to its higher viscosity and lower cetane number. On the contrary, the presence of hydrogen led to an increment in the combustion duration (CD) owing to the scarcity of oxygen in CD. Consequently, the paper clearly showed that the injection way of hydrogen plays a respectable role in the engine characteristics.

This paper presents reliability, availability, and maintainability (RAM) analysis framework for evaluating the performance of a circulation system of water (WCS) used in a coal-fired power plant (CFPP). The performance of WCS is evaluated using a reliability block diagram (RBD), fault tree analysis (FTA), and Markov birth–death probabilistic approach. In this work, the system under study consists of five subsystems connected in series and parallel configuration namely condensate extraction pump (CEP), low-pressure feed water heater (LPH), deaerator (DR), boiler feed pump (BFP), high-pressure feed water heater (HPH). The reliability block diagram (RBD) and fault tree approach (FTA) have been employed for the performance evaluation of WCS. The Markov probabilistic approach based simulation model is developed. The transition diagram of the proposed model represented several states with full working capacity, reduced capacity, and failed state. The ranking of critical equipment is decided on the basis of criticality level of equipment. The study results revealed that the boiler feed pump affects the system availability at most, while the failure of deaerator affects it least. The availability of the system is optimized using the particle swarm optimization method. The optimized availability parameter (TBF, TTR) based modified maintenance strategy is recommended to enhance the availability of the plant system. The optimized failure rate and repair rate parameters of the subsystem are used to suggest a suitable maintenance strategy for the water circulation system of the thermal power plant. The proposed RAM framework helps the decision-makers to plan the maintenance activity as per the criticality level of subsystems and allocate the resources accordingly.

Utilizing latent heat thermal energy storage (LHTES) units shows promise as a potential solution for bridging the gap between energy supply and demand. While an LHTES unit benefits from the latent heat of the high-capacity phase change material (PCM) and experiences only minor temperature variations, the low thermal conductivity of PCMs hinders the rapid adoption of LHTES units by the market. In this regard, the current work aims to investigate the thermal behavior of a semi-cylindrical LHTES unit with various copper fin configurations (including horizontal, inclined, and vertical fins) on the melting flow. The novelty of this research lies in the fact that no prior studies have delved into the impact of various fin structures on the thermal performance of a semi-cylindrical LHTES system. The nano-enhanced phase change material (NePCM) fills the void within the unit. The warm water enters the semicircular channel and transfers a portion of its thermal energy to the solid NePCM through the copper separators. It is found that the system experiences the highest charging capability when the fins are mounted horizontally and close to the adiabatic upper wall. Moreover, the presence of dispersed graphite nanoplatelets (GNPs) inside the pure PCM increases the charging power and temperature of the LHTES unit.

Heat and flow pattern of a vertical free jet impinging on a hot disk were numerically investigated. A cylinder with various thicknesses and materials exposed simultaneously to uniform heat flux on one side and a free impinging jet on the other side is simulated by ANSYS Fluent 19.3. For simulations, the thermal boundary condition on the hot surface might differ due to the nature of the heat flow. The Volume of Fluid (VOF) approach is used to model the free jet heat transfer and fluid dynamics with the presence of air, while only the energy equation is solved in the cylinder. Heatline equation is solved to reveal the heat flow direction and effects of different geometry conditions. The maximum heat flux of 2.5 MW/m2 was obtained at the edge of stagnation region for hot target made of copper, while the value was 1.5 MW/m2 when the material was combined with stainless steel. However, the general thermal and hydrodynamic features of the jet flow were not influenced. It means that hot object condition may only affect the balance between heat flux and temperature, and the ideal uniform heat flux on the impinging wall may not be achieved in any experimental conditions.

The turbulent convective thermal transfer in channel heat exchangers (CHEs) is studied numerically via the CFD (Computational Fluid Dynamics) method. Deflectors are inserted on the hot bottom walls of the heat channel to enhance the hydrothermal characteristics. Various shapes of in-line deflectors are considered, namely: rectangular (a/b = 0.00), cascaded rectangular-triangular (a/b = 0.25, 0.50, and 0.75), and triangular (a/b = 1.00) shapes. From the obtained results, the inclusion of in-line deflectors with a/b = 0.75 has given the most significant thermal enhancement factor, which was higher than that for a/b = 0.00, 0.25, 0.50, and 1.00 by about 5.36, 5.06, 67.27, and 3.88%, respectively. Also, the in-line cascaded deflector’ case (a/b = 0.75) shows an increase in the enhancement factor (η) from 4 to 15.44% over the cases of one deflector (corrugated, rectangular, triangular, trapezoidal, arc, (+), S, 45° V, 45° W, T, Γ, and ε-shaped) or two deflectors (staggered corrugated). This highlights the effectiveness of in-line cascaded rectangular-triangular deflectors with a/b = 0.75 in improving the performance of the proposed exchanger for the conditions adopted.

This work computationally explores the two-phase flow of nanofluids and their thermal energy transport coefficients in 3D diamond-shaped cavities with square-shaped barriers having reducing dimensions. Materials with two emissivity values, $ \varepsilon=0.3 $ and 0.9, have been considered to investigate the effect of the radiation thermal energy transport coefficient while the hot side is maintained at 400 or 500 K. Two values of the Rayleigh number, Ra = 106 and 108, are used for the study. Cu nanoparticles (NPs) with an average size of 25 nm have been used at a concentration of 0.01–0.05% in the base fluid. The temperature gradients and thermal energy transport coefficient characteristics are enhanced by raising the volume concentration of nanoparticles, but the streamlines do not alter substantially. By increasing Ra, the thermal energy transport coefficient rate is further augmented. It is also found that increasing the Ra and volume concentration of NPs results in enhanced heat transfer inside a cavity, while a change in the emissivity coefficient has no significant impact on the thermal and flow characteristics of the nanofluid. For each case, there is an optimum NP volume fraction for each model that leads to the highest Nusselt number.

The present work investigates heat transfer through natural convection using a series of experiments and computational modeling using Computational Fluid Dynamics (CFD) simulations in a one-meter bundle pipe with three internal pipes. The exact complex geometry is modeled where the flow channel is reduced through a spiral groove attached to a rod inside the internal tubes which was challenging compared to the flow in circular pipes in previous studies. To support the computational modeling investigations, convective heat transfer analysis is also studied through experiments with water as the production and heating fluids. Further, simulations are carried out with water-crude oil and aqueous ethylene glycol-water as the heating mediums and production fluids, respectively. Based on the heat transfer rates estimated from experimental data and CFD simulation results for the respective tubes, a modification to an existing Nusselt number is proposed for the range of temperature and flow rates used in the experiments. The proposed model, Nui = Prim Rain, was validated against experimental data and a good agreement with R2 values of more than 0.94 was achieved.

The study focused on the impact of concentration and temperature on the electrical conductivity, viscosity, and thermal conductivity of GNP/Fe2O3 hybrid nanofluids. The study found that nanofluids have better electrical conductivity, viscosity, and thermal conductivity than water. The electrical conductivity and thermal conductivity increase linearly with concentration for a constant temperature. However, the nanofluid’s viscosity increases with the addition of the hybrid nanoparticles and decreases as the temperature increases. Furthermore, the study shows that the thermal conductivity of the nanofluid is enhanced with increased addition of hybrid nanoparticles in the base fluid and that the thermal conductivity ratio increases with increased addition of nanoparticles. Overall, the results suggest that GNP/Fe2O3 hybrid nanofluids could be used in various industrial applications to improve the heat transfer and energy efficiency of systems.

Advancements in technology related to energy systems, such as heat exchangers, electronics, and batteries, are associated with the generation of high heat fluxes which requires appropriate thermal management. Presently, conventional thermal fluids have found limited application owing to low thermal conductivity (TC). The need for more efficient fluids has become apparent leading to the development of nanofluids as advanced thermal fluids. Nanofluid synthesis by suspending nano-size materials into conventional thermal fluids to improve thermal properties has been extensively studied. TC is a pivotal property to the utilization of nanofluids in various applications as it is strongly related to improved efficiency and thermal performance. Numerous studies have been conducted on the TC of nanofluids using diverse nanoparticles and base fluids. Different values of TC enhancement have been recorded which depend on various factors, such as nanoparticles size, shape and type, base fluid and surfactant type, temperature, etc. This paper attempts to conduct a state-of-the-art review of the TC enhancement of metal oxide nanofluids owing to the wide attention, chemical stability, low density, and oxidation resistance associated with this type of nanofluid. TC and TC enhancements of metal oxide nanofluids are presented and discussed herein. The influence of several parameters (temperature, volume/weight concentration, nano-size, sonication, shape, surfactants, base fluids, alignment, TC measurement techniques, and mixing ratio (for hybrid nanofluid)) on the TC of metal oil nanofluids have been reviewed. This paper serves as a frontier in the review of the effect of alignment, electric field, and green nanofluid on TC. In addition, the mechanisms/physics behind TC enhancement and techniques for TC measurement have been discussed. Results show that the TC enhancement of metal oxide nanofluids is affected by the aforementioned parameters with temperature and nanoparticle concentration contributing the most. TC of these nanofluids is observed to be actively enhanced using electric and magnetic fields with the former requiring more intense studies. The formulation of green nanofluids and base fluids as sustainable and future thermal fluids is recommended.

Thermal photovoltaic systems are used to harness solar energy to generate electricity and thermal at the same time. In this technology, electrical efficiency is very low compared to thermal efficiency; as the cell surface temperature rises, the electrical efficiency decreases, so one of the ways to achieve high efficiency is exergy analysis. Exergy analysis of a process or system shows how much of the ability to perform the work or input exergy has been consumed by that process or system. In this research, an ordinary thermal photovoltaic panel with air cooling has been examined for exergy. To do this, it has identified the effective performance variables from a mechanical point of view, which are inlet air temperature, inlet air flow, and length (number of modules that are connected in series). The effect of changing each of the variables based on Saveh weather conditions has been simulated using MATLAB software. The results show that the exergy efficiency of the panel decreases with the inlet air temperature increasing. It was also observed that the optimal airflow is 0012 (kg/s) and will have the highest efficiency per 8.8 m length.

This paper presents a failure analysis conducted in 7175 aluminum alloy compressor impellers used in olefin units which operate at 34500 rpm to compress gas in the process. Some characterizations such as chemical composition, microstructure, and hardness tests were conducted to obtain a detailed evaluation of the base alloy. Furthermore, a finite element method and a 3D point cloud data technique have used to determine critical stress points on the surface of impellers. The finite element result showed the root of blades has significant stress concentration. Moreover, the formed cyclic tension has led to a fatigue phenomenon in the root of the blade, so near this location, the local strain accumulation was visible in 3D points cloud data. The fractography results showed that the mode of crack progression and the fractured surface would change by changing the stress mode. In addition, CFD modeling for investigating the effect of flow hydrodynamics on the HP and LP compressor blades is analyzed. The results revealed that the maximum pressure of gas stream for the rotor speed of 34500 had taken place in the area of a blade that already breakdown took place, and the changes of pressure, stress, and temperature gradients of flow in the HP compressor were significantly higher than the LP compressor.

Today, the use of renewable energy is increasing day by day. The most susceptible to renewable energy is biomass energy because it depends directly on the size of the population and does not have the problems of other renewable energies such as lack of access day and night and constant change throughout the year. For this reason, animal solid waste has been used in the research to supply electrical energy to the study area. In this regard, the amount of animal waste is considered as a source of biomass input energy. HOMER software was used to simulate the system under study. To better compare the competitiveness of this energy, photovoltaic systems and wind turbines have been used as different scenarios of electrical energy production in the study area. The results of scenario analysis showed that in all designed systems, the highest amount of energy production was in July and was related to the hottest season of the year. Among hybrid systems, the biomass system has a higher priority than other systems due to the minimum cost of energy production and total net present cost (NPC). The amount of exhaust gas from the biomass system reached 53.5 kg/yr and the biomass-wind and biomass-wind-solar systems reached 52.5 kg/yr and 52.2 kg/yr, respectively. The surplus generated electricity also increases from 2.91% to 6.65% from the biomass-wind system to the biomass-with-solar system.

In this research, the CRDI engine characteristics were analyzed with the aid of exhaust gas recirculation rate (EGR) adoption fueled with ethanol blends. The test fuels were the various blends with ethanol, such as (10% of ethanol + 90% of diesel) E10D90 (20% of ethanol + 80% of diesel), E20D80, and (30% of ethanol + 70% of diesel) E30D70. From the results, it was revealed that performance characteristics were reduced when using a higher concentration of the alcohols mixed with diesel fuel. The blend E30D70 showed that brake thermal efficiency (BTE) without EGR drops by 3.8%, increased by 9.14% of BSFC, a 9.25% decrease in oxides of nitrogen emissions, and slightly decreased CO and HC emissions compared to baseline diesel operation at 60% load condition. The blend E10D90 with 20% EGR shows the highest BTE of 8.87% when compared with base fuel, due to proper fuel mixture taking place in the inlet manifold. The results indicate that the engine runs smoothly, and E30D70 has chosen an optimum blend. A further experiment was performed using E30D70 with different rates of exhaust gas recirculation system. The addition of exhaust gas recirculation with E30D70 in the common rail diesel engine exhibits oxides of nitrogen emission, but in contrast, it was noticed to have inferior performance characteristics and drastically decreased HC and CO emissions. The hydrocarbon emission decreased E10D90, E20D80, and E30D70 at 60% load condition by 21.42%, 37.38%, and 48.76%, respectively. The blends E10D90, E20D80, and E30D70 decreased carbon dioxide by 7.9%, 30.08%, and 31.98%, respectively. The maximum reduction of NOx emission was observed at about 51.06% at an EGR rate of 20% with E30D70.

The acceleration of global warming is primarily attributable to nonrenewable energy sources such as conventional fossil fuels. The primary source of energy for the automobile sector is petroleum products. Petroleum fuel is depleting daily, and its use produces a significant amount of greenhouse emissions. Biofuels would be a viable alternative to petroleum fuels, but a redesign of the engine would be required for complete substitution. The use of CNG in SI engines is not new, but it has not yet been implemented in CI engines. This is due to the fuel having a greater octane rating. The sole use of CNG in a CI engine results in knocking and excessive vibration. This study utilizes CNG under dual-fuel conditions when delivered through the intake manifold. In a dual-fuel mode, compressed natural gas (CNG) is utilized as the secondary fuel and a blend of 90% tamanu methyl ester and 10% ethanol (TMEE10) is used as the primary fuel. The injection pressure (IP) of the primary fuel changes between 200 and 240 bar, while the CNG induction rate is kept constant at 0.17 kg/h. The main combustion process is governed by the injection pressure of the pilot fuel. It could be affecting factors such as the vaporization characteristics of the fuel, the homogeneity of the mixture, and the ignition delay. Originally, tamanu methyl ester (TME) and diesel were used as base fuels in the investigation. As a result of its inherent oxygen content, TME emits more NOx than diesel. The addition of 10% ethanol to TME (TMEE10) marginally reduces NOx emissions in a CI mode because of its high latent heat of vaporization characteristics. Under peak load conditions, NOx emissions of TMEE10 are 6.2% lower than those of neat TME in the CI mode. Furthermore, the experiment was conducted using TMEE10 as the primary fuel and CNG as the secondary fuel. In the dual-fuel mode, the TMEE10 blend showed higher combustion, resulting in an increase in performance and a significant decrease in emission characteristics. As a result of the CNG’s high-energy value and rapid burning rate, the brake thermal efficiency (BTE) of TMEE10 improves to 29.09% compared to 27.09% for neat TME. In the dual-fuel mode of TMEE10 with 20.2% CNG energy sharing, the greatest reduction in fuel consumption was 2.9%. TMEE10 with CNG induction emits 7.8%, 12.5%, and 15.5% less HC, CO, and smoke, respectively, than TME operation.

The paper investigates the heat transfer performance of distilled water (DW) and ethylene glycol-DW mixture (EG-DW) based aluminum and magnesium sulfate nanofluids and their hybrid nanofluids in a radiator. Mono and hybrid nanofluids at 0.05% and 1% volume fractions with Malay Apple (Syzygium Malaccense) extract were formulated and run in the experimental set up at 0.4 kg/s. The heat transfer performances of DW, EG-DW, mono, and hybrid nanofluids were determined using Nusselt number (Nu), heat transfer rate (Q˙) and coefficient (h), effectiveness (ε), heat transfer (Q), Prandtl number (Pr). An increment in the volume fraction was found to enhance Q˙, h, Nu, Q, Pr, and ε. The maximum heat transfer performance was obtained using mono (Mg/DW (Q = 2.26 kW and Nu = 175), Al/EG-DW (Q = 6.57 kW and Nu = 462)) and hybrid (Mg–Al/DW (Q = 10.06 kW and Nu = 348)) nanofluids. In comparison with the corresponding base fluid, maximum heat transfer enhancements of 13.9%, 306.7%, and 493.9% were obtained for Mg/DW, Mg–Al/DW, and Al/EG-DW nanofluids, respectively. This remarkable heat transfer enhancement obtained can be related to the presence of the Malay Apple (Syzygium Malaccense) extract. These novel nanofluids appeared to be suitable candidates for radiator cooling.

This paper simulates a simple solar panel and the solar panel with a cooling system. The present paper aims to perform an economic and exergy study of PV and PVT 250 W and to compare the return on investment for the operating conditions in China. PVT working fluid is MgO/water nanofluid. PVT cooling system includes a special arrangement of copper tubes placed at its bottom, which cools the panel and produces hot water. COMSOL Multiphysics software and finite element method are employed for numerical analysis and simulation of solar panels. An in-house code is MATLAB code and meteorological data from China are used for economic analysis. The variables include the volume percentage of nanoparticles that is between 0 and 1% and the volume flow rate from 0.5 to 4 lit/min. The results of this study show that enhancing the nanofluid flow in the cooling system makes the panel cooler and reduces the amount of exergy output. The addition of nanoparticles, especially at low nanofluid flow rates, enhances the exergy output. The trend of changes in exergy efficiency with the variations of volume percentage of nanoparticles and volume flow rate is similar to that of the exergy output. The results demonstrate that an increment in the flow rate from 0.5 to 4 lit/min reduces the efficiency by 2.03%. Adding 1% nanoparticles increases the exergy efficiency by 0.45% at a volume flow rate of 0.5 lit/min. The economic analysis of the solar panel shows that the investment recovery is 6 years for PV and 4 years for PVT.

In this paper, the turbulent flow of a nanofluid in a channel is simulated in the presence of a pin-fin heatsink. Pin fins have different shapes, including hexagonal, circular, square, and triangular that are considered in two different arrangements. Constant heat flux is applied to the heatsink from its bottom due to the operation of an electronic chip. The nanoparticles suspended in water are alumina, which are in different shapes such as blades, bricks, cylinders, and plates. Their shape effect is investigated. The nanofluid enters the channel at a constant velocity in the range of 1–3 m/s and a constant volume percentage of 2%, and exits after cooling the pin-fin heatsink. The standard k-ε turbulence model is used to model turbulent flow, and the SIMPLEC method is employed to linearize the equations. The variables include fin type, fin arrangement, nanoparticle shape, and nanofluid velocity. Their effect on the maximum and average heatsink temperature and pressure drop (ΔP) is studied. The results show that increasing the velocity leads to a reduction in heatsink temperature, and the use of brick-shaped nanoparticles and circular fin results in the best cooling performance. Also, the use of circular fin and brick nanoparticles requires less ΔP than other cases.

In this paper, the entropy generation (EGen) and exergy of a solar collector (SC) with alumina/ethylene glycol-water (50:50) nanofluid (NFs) flow are calculated. The tubes and the absorber plate of the collector are made of copper and steel, and the results of both materials are compared. Tubes with hexagonal cross section are considered. Nanoparticles (NPs) with four different shapes of platelet, brick, blade, and cylinder are considered, and their effect is evaluated. Volume fraction (ϕ) changes in the range of 0–4%, and mass flow rate varies from 0.25 to 1 kg/s. These parameters as well as the material of collector tubes and the shape of NPs are the variables of this study and their effect on fluid frictional entropy generation (Sg,ff), thermal entropy generation (Sg,th), total entropy generation (Sg,tot), exergy output (Exout), and exergy loss (Exloss) is examined. Proposed relationships and an in-house code in MATLAB software are used for analysis. The results demonstrated that the use of copper tube leads to smaller amounts of Sg,ff, and Sg,tot than steel tube. Besides, the Exout for cooper tubes is higher than that for steel ones. An increment in the flow rate enhances Sg,tot. Increasing the fluid mass flow rate from 0.25 to 1 kg/s increases the values of Sg,tot 7.9 and 8.4 times for the steel and copper collectors, respectively. The addition of NPs reduces Sg,th but enhances Sg,ff at high values of ϕ. The addition of 4% of all shapes NPs intensifies the magnitudes of Exout and Exloss.

In this numerical work, the cooling performance of water–Al2O3 nanofluid (NF) in a novel microchannel heat sink with wavy walls (WMH-S) is investigated. The focus of this article is on the effect of NP diameter on the cooling efficiency of the heat sink. The heat sink has four inlets and four outlets, and it receives a constant heat flux from the bottom. CATIA and CAMSOL software were used to design the model and simulate the NF flow and heat transfer, respectively. The effects of the Reynolds number (Re) and volume percentage of nanoparticles (Fi) on the outcomes are investigated. One of the most significant results of this work was the reduction in the maximum and average temperatures of the H-S by increasing both the Re and Fi. In addition, the lowest Tmax and pumping power belong to the state of low NP diameter and higher Fi. The addition of nanoparticles reduces the heat sink maximum temperature by 3.8 and 2.5% at the Reynolds numbers of 300 and 1800, respectively. Furthermore, the highest figure of merit (FOM) was approximately 1.25, which occurred at Re=1800 and Fi = 5%. Eventually, it was revealed that the best performance of the WMH-S was observed in the case of Re=807.87, volume percentage of 0.0437%, and NP diameter of 20 nm.

This paper presents the simulations of the cooling system of a battery pack (BTPC) consisting of lithium-ion (LIN) plate batteries. The BTPC includes six battery cells (BTCL) in two rows with three BTCLs, which are placed in a channel with one inlet and two outlets. The laminar and steady airflow flows in the channel. Phase-change material (PCM)-filled rectangular cubic enclosures enclose every BTCL. Transiently adjusting the cavity aspect ratio (AR) every 6000 s is how this investigation is conducted. For four values of AR, the values of the PCM volume percentage surrounding each BTCL in the BTPC, and the temperature of each BTCL are calculated. The simulations are performed using the FEM and COMSOL software. The results demonstrate that the maximum changes in temperature of the battery (TOB) pack by changing the AR occur when the TOB pack is reduced. The maximum temperature reduction at this time is 1.88 °C which occurs between AR2 and AR4 at 720 s. The maximum temperature corresponds to AR3 and AR4 and the minimum one is related to AR1 and AR2. From 1260 to 3500 s, the effect of AR on PCM volume fraction is maximal. The value of solid PCM for AR1 and AR2 is higher than that for AR3 and AR4 at different times. Additionally, an increment in the value of the AR enhances the amount of channel pressure drop by 14%.

In response to the issues of environment, climate, and human health coupled with the growing demand for energy due to increasing population and technological advancement, the concept of sustainable and renewable energy is presently receiving unprecedented attention. To achieve these feats, energy savings and efficiency are crucial in terms of the development of energy-efficient devices and thermal fluids. Limitations associated with the use of conventional thermal fluids led to the discovery of energy-efficient fluids called “nanofluids, which are established to be better than conventional thermal fluids. The current research progress on nanofluids has led to the development of the advanced nanofluids coined “hybrid nanofluids” (HNFs) found to possess superior thermal-optical properties than conventional thermal fluids and nanofluids. This paper experimentally explored the published works on the application of HNFs as thermal transport media in solar energy collectors and thermal energy storage. The performance of hybrid nano-coolants and nano-thermal energy storage materials has been critically reviewed based on the stability, types of hybrid nanoparticles (HNPs) and mixing ratios, types of base fluids, nano-size of HNPs, thermal and optical properties, flow, photothermal property, functionalization of HNPs, magnetic field intensity, and orientation, and φ, subject to solar and thermal energy storage applications. Various HNFs engaged in different applications were observed to save energy and increase efficiency. The HNF-based media performed better than the mono nanofluid counterparts with complementary performance when the mixing ratios were optimized. In line with these applications, further experimental studies coupled with the influence of magnetic and electric fields on their performances were research gaps to be filled in the future. Green HNPs and base fluids are future biomaterials for HNF formulation to provide sustainable, low-cost, and efficient thermal transport and energy storage media.

Here, hydrodynamic features of laminar forced nanofluid flow between two parallel plates are numerically investigated, and the results are mathematically discussed. The conventional understanding of developing flow in the entrance region of internal flows is based on the idea that boundary layers start forming at the inlet and merge at some point just before the fully developed section. However, because of the consideration of mass and flow conservation, the entire conception is required to be detailed with appropriate criteria according to the numerical simulations. Hence, nanofluid flow between two parallel plates is solved by ANSYS Fluent 19.3 for laminar forced in an isothermal condition. Two major criteria are studied to find the location of the boundary layer merging points: vorticity and velocity gradient in a direction perpendicular to the flow. The former presents the influential area of wall shear stress, and the latter is the direct infusion of the boundary layer induced by the solid walls. Vorticity for an irrotational flow is obtained by calculating the curl of the velocity. It is found that the merging points for the hydrodynamic boundary layers are considered before the fully developed region. For the first time, in this study, the results of various Reynolds numbers are collected, and correlations are proposed to predict the length of the boundary layer merging location by using a regression analysis of the data.

The application of nanofluids for enhancing the heat transfer rate is widely used in various heat exchanger applications. The selection of oil as the base to prepare nanofluids significantly enhances the thermal performance, due to its high heat carrying capacity as compared to conventional base fluid. A review is performed of various heat exchanger conduits having base fluid as nanoparticles with oil. It is reported that the heat transfer rate of a heat exchanger is significantly increased with the use of oil-based nanofluids. The rate of heat transfer depends on the type of nanoparticle, its concentration and diameter, the base fluid, as well as factors like the mixture of more than two nanoparticles (hybrid nanofluids) and stability. A review is also performed of the thermal performance of the different nanofluids analyzed by various investigators. The heat transfer system reviewed in this work includes triangular, square, and circular conduits, as well as rib surface conduits. The review of various applications viz. solar thermal systems, heat exchangers, refrigerators, and engines, is carried out where the inclusion of the oil base is used. It is reported that the amalgamation of the nanomaterial with the oil as base fluid is a prolific technique to enhance thermal performance. The performance of the reviewed research work is comparatively analyzed for different aspects viz. thermal oil, mineral oil, hybrid, and conventional nanoparticles, concentration of nanoparticles, etc. The novelty of the present work is the determination of the effective performing oil-based nanofluid in various applications, to figure out the selection of specific mineral oil, thermal oil, nanoparticle concentration, and hybrid nanofluids.

Engineering applications including food processing, wastewater treatment, home heating, commercial heating, and institutional heating successfully use unglazed transpired solar collectors (UTCs). Trapping of solar energy is the prime goal of developing an unglazed transpired solar collector. The UTC is usually developed in and around the walls of the building and absorbs the solar energy to heat the air. One of the key challenges faced by the UTC designer is the prediction of performance and its warranty under uncertain operating conditions of flow variables. Some of the flow features are the velocity distribution, plate temperature, exit temperature and perforation location. The objective of the present study was to establish correlations among these flow features and demonstrate a method of predicting the performance of the UTC. Hence, a correlation matrix was generated from the dataset prepared after solving the airflow over a perforated flat UTC. Further, both strong and weak correlations of flow features were captured through Pearson’s correlation coefficient. A comparison between the outcomes from a linear regression model and that of computational simulation was showcased. The performance probability for the UTC was interlinked with correlation matrix data. The Monte Carlo simulation was used to predict the performance from random values of the flow parameters. The study showed that the difference between the free stream value of temperature and the value of temperature inside the UTC’s chamber varied between 15 and 20 °C. The probability of achieving system efficiency greater than 35% was 55.2%. This has raised the hope of recommending the UTC for drying and heating where the required temperature differential is within 20 °C.

In this article, alumina/water nanofluid (NF) flow in a heatsink (H-S) with wavy microchannels (W-MCs) is simulated. The H-S is made of aluminum containing four similar parts. Each part has an inlet and outlet. Constant heat flux is applied on the bottom of the H-S. The study is based on two-phase (T-P) mixture and single-phase (S-P) models to determine the difference between these two types of simulations. FLUENT software and the control volume method were used for simulations. The volume control method is employed to solve equations. The effective variables include the volume fraction 0 < φ < 5% of alumina and Reynolds number (Re) 300 < Re < 1800. The maximum H-S bottom temperature, the required amount of pumping power (PP), the temperature uniformity, and the heat resistance of the H-S are the outputs studied to simulate the S-P and T-P models. The results show that the use of the T-P model has less error in comparison with the experimental data than the S-P model. An increment in the Re and φ reduces the maximum temperature (M-T) of the H-S. The S-P model, especially at a higher value of φ, leads to a lower M-T value than the T-P model. The S-P model shows a 0.5% greater decrease than the T-P model at the Reynolds number of 300 by enhancing the volume percentage of nanoparticles (NPs) from 1 to 5%. Temperature uniformity is improved with Re and φ. The reduction of H-S thermal resistance with Re and φ is the result of this study. Adding NPs to water, especially at higher amounts of φ, enhances the required PP. The T-P model predicts higher PP than the S-P one, especially at a high value of φ. The T-P model shows 4% more PP than the S-P model at Re = 30 and a volume fraction of 4%.

This paper investigates the thermophysical properties and heat transfer performance of graphene nanoplatelet (GNP) and alumina hybrid nanofluids at different mixing ratios. The electrical conductivity and viscosity of the nanofluids were obtained at temperatures between 15–55°C. The thermal conductivity was measured at temperatures between 20–40°C. The natural convection properties, including Nusselt number, Rayleigh number, and heat transfer coefficient, were experimentally obtained at different temperature gradients (20, 25, 30, and 35°C) in a rectangular cavity. The Mouromtseff number was used to theoretically estimate all the nanofluids’ forced convective performance at temperatures between 20–40°C. The results indicated that the thermal conductivity and viscosity of water are increased with the hybrid nanomaterial. On the other hand, the viscosity and thermal conductivity of the hybrid nanofluids are lesser than that of mono-GNP nanofluids. Notwithstanding, of all the hybrid nanofluids, GNP-alumina hybrid nanofluid with a mixing ratio of 50:50 and 75:25 were found to have the highest thermal conductivity and viscosity, enhancing thermal conductivity by 4.23% and increasing viscosity by 15.79%, compared to water. Further, the addition of the hybrid nanomaterials improved the natural convective performance of water while it deteriorates with mono-GNP. The maximum augmentation of 6.44 and 10.48% were obtained for Nuaverage and haverage of GNP-Alumina (50:50) hybrid nanofluid compared to water, respectively. This study shows that hybrid nanofluids are more effective for heat transfer than water and mono-GNP nanofluid.

The study aimed to enhance the heat transport by improving the hydrodynamic structure of the system by changing and restructuring the duct's internal geometry. Modern fins, of the shape ‘V’, have been proposed with different dimensions, and they are periodically arranged over the duct surfaces. The most important steps of this research are the change in the V-fin attack-angle (40°–80°), length (Hb/2, 3Hb/4, Hb, 5Hb/4 and 3Hb/2), and separation length (Ds/2, 3Ds/4, Ds and 5Ds/4), as well as the flow rate (6 × 103–3 × 104). The study yielded an optimum case for a 40-degree attack-angle, with a factor of thermal enhancement of 2.163 for the highest value of Reynolds number. On the other hand, improving the length of the V-fins or decreasing in the space between them, increases the flow strength by enlarging the recycling cells, which reflects on the hydrodynamic behavior, and changes the heat transfer. The presence of this new model of fins also highlights a hydrothermal improvement ranging between 1.196 and 23.779 percent compared to the previously indicated models, reflecting the effectiveness of the new system of solar heat exchangers with air V-finned ducts.

The impact of presence of nano-scale particles inside a flow between two flat plates which known as Poiseuille flow is numerically analyzed. Nanofluids have been investigated in the past few years mainly by considering the heat transfer aspect in a fully developed section of internal flows, rather than detailing the hydrodynamic and thermal developing viewpoint of nanofluid. In other words, this research will focus on the fundamental understanding of developing nanoparticles flows in hydrodynamic and thermal boundary layers in the entrance region. Therefore, flow between two flat plates is numerically studied here by injecting and tracking nanoparticles from inlet to outlet of the channel. The flow is kept in the laminar regime with uniform heat flux applied on the plates. ANSYS Fluent 19.3 is used to numerically solve the continuity and momentum equations, as well as discrete phase modeling for particles. The results showed three major stages in vorticity development in the entrance region. It was found that Brownian motion plays an important role in nanoparticles migration, and close to the wall with the involvement of Thermophoresis. Also, nanoparticles can deviate from flow layers after merging boundary layers.