بحوث سكوبس — م.د. محمود شاكر حسن

The study of bubble growth and collapse is of great significance in the context of sustainability due to its influence on numerous energy-related processes and technologies. Understanding the dynamics of bubble behavior is vital for optimising heat transfer efficiency, which has an energetic role in improving the performance of sustainable systems such as nuclear reactors, thermal inkjet printing, and nucleate boiling. Indeed, researchers can progress strategies to enhance the efficiency of these technologies by analysing the parameters influencing bubble growth and collapse, which can lead to reduced energy consumption and environmental impact. Although several theoretical models and experimental investigations have been achieved in the past to inspect bubble growth and collapse, a thorough review and critical assessment of the studies conducted have not yet been achieved. This review aims to provide a comprehensive understanding of the relationship between bubble dynamics and sustainability, highlighting the potential for further research and development in this area. Specifically, the scope and limitations of past research on bubble growth and collapse is conducted to fill this gap in the open literature. The review covers both numerical and experimental studies of bubble growth and collapse in a wide set of innovative industrial applications including nuclear reactors, thermal inkjet printing, nucleate boiling, hydrodynamic erosion, and ultrasonic and medicinal therapy. The current review also attempts to illustrate and evaluate the numerical methods used and underlines the most relevant results from the studies that were looked at in order to provide researchers with a clear picture of the growth and collapse of bubbles in different applications. The results give a precise understanding of the dynamics of bubble growth and collapse and the related temperature change and cumulative heat transmission from the thermal boundary layer. Additionally, it has been demonstrated that simulation-based models can effectively predict transport coefficients. However, the review observes a number of limitations of the past research on bubble growth and collapse. Due to numerical instability, very little work with respect to dynamic modelling has been carried out on the mechanisms of bubble collapse. Accordingly, a number of recommendations are made for the improvement of heat transmission during bubble growth and collapse. Specifically, future criteria for the highest heat transmission will demand more precise experimental and numerical approaches. © 2024 by the authors.

This research evaluates the performance of a solar panel under the influence of dust deposition and explores methods to enhance its efficiency. The panel's cooling system incorporates a wavy duct design fitted with V-shaped fins, and the working fluid—water—is augmented with nanoparticles to improve heat transfer. Lorentz force is applied in the y-axis direction to regulate the flow of the ferrofluid, a mixture of water and magnetic nanoparticles. The simulation involves modeling various layers of the panel to account for heat conduction, including the heat generated by solar irradiation. The study reports the electrical efficiency (ηPV) and thermal efficiency (ηth) under different operational parameters. The application of a higher Hartmann number (Ha) results in a cooler panel and warmer nanofluid at the outlet. However, the presence of dust significantly diminishes the positive effects of the magnetic field on both efficiency metrics, particularly reducing ηPV by 10.22 %. As the Hartmann number increases, the temperature across the silicon layer decreases, and the uniformity of the isotherms improves by approximately 5.2 %. When the Hartmann number is set to 95, an increase in dust levels leads to a reduction of 25.33 % in ηPV and 9.82 % in ηth. Additionally, the work finds that the impact of the (ϕ) on both ηPV and ηth is significantly greater at a higher inlet velocity (Vin = 0.093), being 3.96 and 2.7 times greater, respectively, compared to a lower velocity (Vin = 0.018). © 2025 The Authors

As the world deals with climate change and the need for sustainable solutions, harnessing renewable energy sources like solar power becomes progressively decisive. This research intends to inspect the potential of evacuated tube solar collectors for providing hot water in domestic settings, concentrating on the specific context of Baghdad, Iraq. In this regard, this research examines and evaluates the DHWS's (domestic hot water system) thermal performance using T∗sol Valentin software. The system consists of an evacuated tube solar collector (Con-solar TUBO 12 with an active area 5.33 m2) and a solar tank with 0.5 m3. The examination is conducted under the weather conditions of Baghdad-Iraq between 30th April to 1st October 2023, while considering various tilt angles of (30 °, 40° and 50°). The performance indicators under investigation include the outlet temperature, energy production, collector efficiency and the electricity consumption. The simulation findings show that the proposed system can meet the households hot water requirements. In more details, the maximum outlet temperature of the evacuated tube solar collector is registered to be around 51oC in April 2023 at 30° tilt angle. However, the maximum annual electricity energy is 33 kWh in December, the total E solar -DHWS radiation of 330 kWh in March and collector efficiency is estimated to be 42% in January at the same angle. Furthermore, the tilt angle 50° has enabled to acquisition of the maximum solar energy contribution of 2552 kWh in DHWS, which is equivalent to 98.7% from the total energy consumption. © Published under licence by IOP Publishing Ltd.

In this study, a photovoltaic (PV) system was enhanced through the combination of a cooling duct utilizing a nanofluid composed of water and Al₂O₃ nanoparticles, aimed at optimizing thermal regulation and improving electrical efficiency. A novel approach was introduced by systematically examining the effects of channel cross-sectional shapes and fin arrangements on heat dissipation. Using a single-phase simulation model, the thermal performance of the nanofluid was evaluated across various nanoparticle shapes, providing new insights into the relationship between geometry and nanofluid cooling efficacy. The results demonstrated that altering the cross-sectional shape generally reduced thermal performance, but strategic fin configurations significantly enhanced heat transfer. The optimal design, featuring eight shorter fins arranged around an eight-lobed pipe, resulted in a 4.3 % improvement in thermal performance. Additionally, blade-shaped nanoparticles were identified as the most effective, enhancing heat absorption by 1.15 % compared to pure water. This research presents the first combination of advanced nanofluid cooling with a detailed analysis of geometric factors (cross-section and fin design) in PV systems. The findings provide practical guidelines for improving heat management in PV cells, ultimately leading to increased electrical efficiency and an extended operational lifespan. These insights hold promising implications for the design of more efficient solar energy systems and could inform future thermal management solutions in renewable energy applications. © 2024

This study investigates the efficacy of applying a Lorentz force to improve the efficiency of a photovoltaic-thermal (PVT) system featuring a finned duct, while also addressing challenges associated with dust accumulation. The magnetic field helps to prevent nanoparticle aggregation, enhancing the cooling process. The use of a finned duct combined with a nanofluid as the cooling medium efficiently dissipates excess heat from the silicon layer. Dust accumulation on the glass layer reduces transmissivity, negatively impacting system performance. The magnetic field's interaction with the nanoparticles enhances convective cooling of the upper layer, leading to an overall improvement in performance. Increased pumping power results in higher cooling rates, with improvements of approximately 3.48 % in thermal efficiency (ηth), 75.01 % in thermoelectric generator efficiency (ηTEG), and 39.37 % in photovoltaic efficiency (ηPV). An increase in the Hartmann number (Ha) improves ηth by about 1.87 %, with corresponding enhancements in electrical performance components. A higher concentration of ferrofluid further boosts performance, with the effect being roughly 1.7 times more significant in the absence of MHD compared to when Ha = 97. Dust presence decreases ηth, ηTEG, and ηPV by approximately 9.39 %, 8.55 %, and 25.77 %, respectively. Furthermore, the presence of Ha diminishes the influence of Vin on ηth by around 1.33 %. © 2024 The Authors

In this investigation, Galerkin technique was utilized as a reliable method for simulating transient phenomena, to model the unsteady discharging process. The use of an adaptive grid further bolsters the reliability of the numerical simulation, a feature substantiated in the subsequent sections. The study centers on two pivotal factors: the powder diameter (dp) and their concentration (ϕ). With rise in ϕ, there is a significant 41.2% enrichment in the discharging rate. Significantly, the incorporation of nanotechnology has proven to be a game changer, resulting in a notable 41.2% improvement in the discharging rate. The effect of dp is interesting, demonstrating a dual impact on freezing time—initially decreasing by 19.95% and later increasing by 49.18%. © Akadémiai Kiadó, Budapest, Hungary 2024.

In current work, the productivity of a photovoltaic thermal (PVT) unit impacted by dust accumulation was improved using magnetic force. The magnetic force was implemented to a cooling duct with Y-shaped fins, while solar irradiation was included as heat sources in the equations. Dust effects were simulated by adjusting the optical properties. The addition of a thermoelectric generator (TEG) layer boosted the electrical output. The cooling fluid was a homogeneous water and iron oxide mixture. Dust accumulation led to a 9.3 % drop in thermal performance, but the use of magnetic force enhanced electrical efficiency. Higher concentrations of additives improved system performance, with a maximum gain of 15.88 % at the highest inlet velocity (Vinlet). Increasing Vinlet further improved thermal efficiency (ηth) by 10.96 %, photovoltaic efficiency (ηPV) by 1.16 %, and thermoelectric efficiency (ηTE) by 33.53 %. Moreover, the application of Lorentz force increased isothermal uniformity by approximately 5.91 % © 2024 The Authors

An innovative approach to optimizing cold storage in elliptic containers has been pioneered by integrating tree-shaped fins and diverse nanoparticle shapes into the water. The use of a finite element method, deliberately excluding the velocity term, distinguishes this work and allows for a focused exploration of the efficacy of these elements on the unsteady freezing. Addressing a research gap in the understanding of such processes within elliptic containers, especially in conjunction with tree-shaped fins, a holistic approach is taken compared to prior publications. The increase in “m" correlates with a significant 6.98 % decrease in the freezing period, reducing the process time from 335s to 245.23s with the inclusion of nano-powders. The outputs showed that incorporating powders decline the freezing time about 26.79 %. © 2024 The Authors

The current article studies the improvement of the discharging rate in cold storage systems by modifying the tank configuration and incorporating additives. Specifically, the study inspects how varying the diameter (dp) and fraction (ϕ) of nano-powders affects the process duration. The governing equations, derived under the assumption of negligible slip velocity of nanoparticles and convection terms, were solved using the Galerkin method. The computational grid was modified owing to location of the ice front, and unsteady terms were discretized using an unconditionally stable approach. The results indicate that initially, increasing dp decreases the process duration by approximately 20.01 %, but further increases in dp lead to a 49.53 % rise in the duration. As the process time increases, the amount of ice produced also increases, with nanoparticle loading resulting in a significantly higher ice yield. Specifically, the incorporation of nanoparticles enhances the storage rate by approximately 41.37 %. © 2024 The Authors

The intensification of freezing rates through the incorporation of nano-sized powders and fins through a cold storage unit was examined. The Galerkin method with special meshing was utilized to solve equations, which were based on the supposition of conduction mode dominance. Additives of varying diameters (dp) and three different concentration levels (ϕ) were implemented. The findings are presented through ice front visualization, contour plots, and scalar curves. The computational code demonstrated high accuracy during the validation phase. The results reveal that as the dp increases, the solidification time initially drops by approximately 20 %, then subsequently increases by about 49.45 %. The optimal solidification time of 2951.17 s was achieved with medium-sized powders. Furthermore, an intensification in (ϕ) leads to a significant decrement in freezing time by about 41.43 %, with the most pronounced effect observed for nano-powders with dp = 40 nm. © 2024 The Authors

In order to determine the environmental and economic implications of H2, cooling and distillation water production powered by reforming cycle, both environmental and economic factors must be examined. Therefore, this study propose, evaluate, and optimize a novel poly-generation plant driven by reforming cycle that integrates an organic flash cycle, a two-phase ejector, a thermoelectric generator, and a reverse osmosis unit. The proposed scheme is subjected to a thorough analysis from multiple perspectives, including exergy, energy, sustainability, environmental, thermoeconomic, and economic perspectives. Parametric studies assess the effect of functional parameters on plant performance. It is observed that a rise in reactor temperature leads to a diminution in H2 production. Nevertheless, this augmentation in temperature has a beneficial impact on both the inlet temperature and the mass flow rate of the subsystem. Subsequently, the heat transfer process is effectively augmented due to this increment in temperature and mass flow rate. Thus, purified water production and cooling within the system are augmented. The alteration in the rate of methanol molarity has a substantial impact on the net present value, which is abridged to 3.258 million dollars. Furthermore, the payback period is elongated to 8.979 years. As a consequence of this optimization procedure, an optimal solution is attained. This solution displays an impressive energy efficiency of 62.99% and a payback period of 2.902 years. © 2024 The Institution of Chemical Engineers

In current article, a numerical technique was engaged to simulate the cold storage process. To accelerate this process, the enclosure was fitted with fins, and water was mixed with nanoparticles. These nanoparticles, varying in shape and concentration, were extensively analyzed in the results section. The Galerkin method was used and an adaptive technique generated the mesh, with unsteady terms discretized using an implicit approach. It was determined that velocity terms had a negligible effect and were thus omitted. Model verification demonstrated good accuracy, confirming its reliability. The results reveal interesting insights into the impact of shape factor on freezing, showing that an increase in shape factor can boost the freezing rate by around 10.74 %. Besides, the substantial impact of nano-powders on freezing was highlighted. The freezing time for water was 9383.64 s, while the nanofluid case required only 6316.1 s, marking a substantial 32.69 % reduction in freezing time with nanoparticles. This research emphasizes the importance of numerical techniques in modeling cold storage processes, particularly regarding nanoparticles and shape factors. The findings highlight the potential for optimizing cold storage systems to improve efficiency and reduce energy consumption. © 2024

In the current articles, a numerical approach is developed to analyze the unsteady freezing process within a wavy container embedded with porous foam. The incorporation of porous foam, along with the addition of nanoparticles and radiative cooling, significantly accelerates the solidification process. These methods enhance thermal conduction within the system, which in turn improves the efficiency of cold energy storage, making them highly beneficial for applications requiring rapid cooling. The governing equations are derived by incorporating source terms related to the freezing, and the Galerkin technique is employed to solve these equations. The use of an adaptive grid technique ensures accurate representation of the moving solid–liquid interface, or ice front, during the simulation. Validation results demonstrate excellent agreement with experimental data, underscoring the importance of using adaptive meshing in capturing the transient dynamics of the freezing process. The findings reveal that the insertion of porous foam declines the needed time about 81.14%, significantly boosting the overall efficiency of the system. Furthermore, the utilizing nano-powders decline freezing time about 6.87%. Additionally, incorporating radiative cooling into the system further speeds up the freezing process by around 10.86%. These improvements highlight the combined benefits of using porous materials, nanotechnology, and radiative cooling for optimizing cold energy storage systems. The reduction in freezing time demonstrated in this study, particularly the 81.14% improvement with porous foam insertion, represents a noteworthy step forward in cold energy storage technology. © Akadémiai Kiadó, Budapest, Hungary 2024.

The process of roughing surfaces by sandblasting before the coating is essential to obtain consistently high tensile strength between coating and substrate, for carbon-deposit elimination, and to remove some flaws such as piston cracks and minor chips in the top crown. This work aims to investigate the effect of sandblasting pressure and alumina volume on the roughness of the AK12MMgN alloy substrate and the roughness of the deposited galvanic plasma modification (GPM) coatings after blast cleaning, and the adhesion strength of these coatings. Many technological factors, such as grain size, pressure and time of blasting, distance to the abrasive, angle of blasting, and the hardness of the surface parts subjected to blasting, determine the magnitude and nature of surface roughness. Thus, the sandblasting process must be controlled appropriately in order to obtain a high GPM coating with a high coating-to-substrate adhesion value. More importantly, the process parameters must be optimized. The results indicate the importance of the roughness of the base after sandblasting of the AK12MMgN alloy and the roughness of the subsequently applied coatings in determining the bond strength value. © 2024, Scibulcom Ltd.. All rights reserved.

Moving towards a sustainable future requires modernized and economic energy production, especially in the context of current policy incentives. In the present paper, a new integrated process using flue gas leaving a power plant is projected and studied. The proposed process consists of a carbon dioxide (CO2) capture unit (CCU), a water electrolyzer unit (WEU) for renewable hydrogen production, a power generation unit (PGU), a heat generation unit (HGU), and a methanol production unit (MPU). The designed structure has low CO2 emission, low production cost, and high thermodynamic efficiency. This process is simulated using Aspen HYSYS. The simulation results show that the methanol production in this process is equal to 606,228 ton/year (methanol with a purity above 99% mole), and according to the environmental analysis, the intensity of CO2 emission is 0.61 [Formula presented], which is lower compared to that of bi- and tr-reforming processes. The results indicate that the overall exergy and energy efficiencies of the proposed process are 71.97% and 56.74%, respectively. Thermodynamic analysis determines that the exergy destruction intensity of this process is equal to 29.54 [Formula presented], and the highest destruction happens in the CCU (62.38%). It is also found that the exergy efficiency of the CCU, MPU, WEU, HGU, and PGU is 97%, 92%, 93%, 48%, and 53%, respectively. The exergy analysis exhibits that the coefficient of effectiveness (ψi) in the CCU is high (equals 85.89%), so it is the main factor in increasing the second law efficiency of the proposed process. Finally, according to the economic analysis, it is determined that the total annual cost and the total production cost of methanol in the presented structure respectively are 31,479,267 $ and 0.52 [Formula presented], which compared to similar technologies based on renewable energy is lower by 64.86%. It is suggested to use this sustainable production mode to promote economic production in some pilot projects or high-tech parks. © 2023

In this paper, an integrated process for coproduction of methanol (122500 [Formula presented]), desalinated water (40.56 [Formula presented]), and oxygen (13420 [Formula presented]) using landfill gas upgrading is presented. The process embraces negative carbon dioxide (CO2) emission framework, high thermodynamic efficiency, and low product cost. The proposed process consists of nine subsystems, which are utilized for heat recovery in addition to production of electricity and desalinated water. Results showed that the total energy and exergy efficiencies of the trigeneration system are 59.19% and 48%, respectively. According to the conducted analysis, the total exergy destruction rate equals 973291 kW in which the biogas upgrading unit has an 80% contribution. In addition, it is demonstrated that the combustor of the biogas upgrading unit is responsible for 57.96% of the total exergy destruction rate. Moreover, the sensitivity analysis illustrates that the increase in the [Formula presented] ratio is an important factor in increasing the carbon efficiency and total energy efficiency, and decreasing the CO2 emission. From the environmental perspective, it is deduced that the total net emission of the proposed process is −0.6773 [Formula presented], which is significantly lower than other methanol production technologies. Economic analysis is performed for the integrated structure and its results showed that the total annual cost and methanol production cost rate are 124,660,373 $ and 0.124 [Formula presented], respectively. This value is 91.68% lower than the renewable methanol production technology. © 2023

Thermal management of microelectronic circuits will be one of the most difficult challenges facing engineering processes in the near future. High operating temperatures in these devices can degrade the reliability of the components and reduce their life. Therefore, effective cooling technologies that can disperse the significant heat load from the surface of microelectronic equipment are required. An appropriate microchannel heat sink (MCHS) system with optimized geometry can be one of the reliable choices. In the current work, an artificial neural network (ANN) is exerted to optimize the geometry of a finned-MCHS. The distance of fins from the inlet in the second row (l), the distance of fins from the side walls in the first and third rows (t), and the angle of hexagons (θ) are the input parameters. According to the obtained results, the ANN model with a coefficient of determination of 0.999 performed well in predicting the Nusselt number (Nu) and pressure drop (ΔP). Among the investigated input parameters, the variations of the parameter of t affected the thermal and hydrodynamic properties of the device noticeably. Besides, the ANN model suggested that when the optimum values of input parameters (i.e., l = 7.636 mm, t = 4 mm, and θ = 140) are used for the hexagonal fins inside a microchannel, the maximum relative efficiency index of 1.491 can be acquired. © 2023 The Authors

The present study aims to simulate and design a near-Zero Energy neighborhood in one of the most significant industrial cities for reducing greenhouse gas emissions. For this building, biomass wastes are used for energy production, and also energy storage is provided using a battery pack system. Additionally, the Fanger model is used to assess the passengers' thermal comfort, and information on hot water usage is given. The transient performance of the aforementioned building is tested for one year using TRNSYS software, which was employed for this simulation. Wind turbines are considered electricity generators for this building, and any extra energy generated is stored in a battery pack for usage when the wind speed is insufficient and electricity is needed. Hot water is created using a biomass waste system and is kept in a hot water tank after being burned using a burner. A humidifier is utilized to ventilate the building, and a heat pump provides both the building's heating and cooling needs. The produced hot water is used to supply the residents' hot water. In addition, The Fanger model is considered and used for the assessment of occupants' thermal comfort. Matlab software is a powerful software used for this task. According to the findings, a wind turbine with a 6 kW generation capacity may supply the building's power needs while also charging the batteries beyond their initial capacity, and the building will have zero energy. Additionally, biomass fuel is used to give the building the required water which should be hot. On average, 200 g of biomass and biofuel are used per hour to maintain this temperature. © 2023

Misalignment is one of the most common challenges that the normal operation of journal bearings faces. This type of problem may be the result of a wide range of reasons, such as bearing wear, shaft deformation, and errors related to the manufacturing and installation process. The main undesirable consequences of the misalignment, such as pressure rise and lubricant film reduction, are concentrated on the bearing edges. Therefore, chamfering the bearing edges reduces such misalignment-related drawbacks. This work presents a novel numerical solution to the problem of finite-length journal bearing considering edge chamfering. This solution involves the determination of the levels of lubricant layer thickness and pressure distribution in addition to the journal trajectory under impact load with the related stability limits. The finite difference method is used in this solution, and the equations of motion are also solved numerically using the Runge–Kutta method. The Results of this novel analysis show that chamfering the bearing edges increases the film thickness and reduces pressure spikes associated with the system operation under the case of 3D misalignment. Furthermore, the chamfered bearing shows a wide stability range under impact loads, where the normal bearing is unstable as the critical speed increases by 26.98%, which has positive consequences on the journal’s trajectory. © 2023 by the authors.