The negative environmental and economic impacts of fossil fuels have made it essential to meet energy supply from renewable energy sources, especially in recent years. Among renewable energy sources, the popularity of solar energy is increasing day by day due to its ease of application and short payback periods. One of the common solar energy applications is rooftop solar energy systems. In this study, a grid-connected rooftop solar energy application was simulated using PVsyst software, utilizing the electricity consumption data of a textile manufacturing factory with a closed area of 5,000 m2 in the Gaziosmanpa & scedil;a neighborhood of Ankara province and considering its geographical location. Taking into account array losses, DC cabling, and system losses, the performance ratio was found to be 77.73%. It has been calculated that 1,002,928 kWh/year of electricity can be generated with the system installed at the facility, which consumes a total of 674,099 kWh/year of electricity. Considering the inflation data of the last two years, with an annual inflation rate of 30% and taking electricity generation into account, it has been determined that the profit to be obtained from the system after 20 years will be 36,406,905 USD. As a result of the environmental impact analysis of the system, it has been calculated that a total of 12,362.1 tons of CO2 emissions can be prevented during the 30-year operational period.
Representative Elementary Unit (REU) simplification has become a standard approach for CFD modeling of structured packings; however, its reliability in predicting dry pressure drop remains a critical yet underexplored issue. In particular, the sensitivity of hydraulic performance to internal geometric parameters is often overlooked in the current literature. This study addresses this gap by calibrating an REU model for Mellapak 500.Y against the semi-empirical correlation of Stichlmair et al. (1989) and experimental data from Tsai (2010). Singlephase simulations were conducted using the SST k-omega turbulence model over a gas-load range of 0.72-4.32 Pa-0.5. Grid independence was established at 0.53 million cells per REU. A domain-sensitivity analysis using one, four, and six REUs yielded deviations below 10%, confirming that a single-unit domain provides sufficient accuracy for dry-flow calibration. The results show that the nominal 2.00 mm sheet spacing leads to substantial underprediction of pressure drop, whereas an effective spacing of 0.24 mm brings the CFD predictions into agreement with Tsai's measurements within a +/- 20% error band and consistent with the Stichlmair correlation across the operating window. These findings identify the effective sheet spacing as the dominant geometric calibration parameter and provide a reproducible, computationally efficient baseline REU for subsequent hydrodynamics simulations in Mellapak 500.Y.
This study employs computational fluid dynamics (CFD) to investigate the heat transfer performance of a shell-and-tube heat exchanger featuring a specially arranged tube bundle, in which no heat-exchange tubes are installed within the circular region at the center of the bundle. Taking the diameter of the tube-free region as a key parameter, a coupled thermo-hydraulic model of the heat exchanger is established to analyze the effects of the tube-free region on flow resistance, heat transfer intensity, and heat transfer uniformity. The results show that the shell-side fluid can participate in heat exchange within the tube-free region, which contributes to the homogenization of heat transfer within the tube bundle. As the tube-free region expands, the degree of heat transfer uniformity increases; however, the overall heat transfer intensity decreases due to the reduction in effective heat transfer area. For the heat exchanger investigated in this study, when the diameter of the tube-free region increases from 140 mm to 440 mm, the shell-side heat transfer coeffi-cient decreases by 22.1%, whereas the heat transfer uniformity improves by 77.1%. A comprehensive performance evaluation based on the TOPSIS decision-making method indicates that a tube-free region diameter of 300 mm provides a favorable balance be-tween flow and heat transfer performance. Under this operating condition, the shell-side pressure drop is 74.95 kPa, the shell-side heat transfer coefficient reaches 8441.03 W/(m2 & centerdot;K), and the relative standard deviation of the tube-side outlet temperature is 0.00969.
The current study investigates heat transfer improvement in a backward-facing step configuration using an inclined flexible fin, through numerical simulation based on the Finite Element Method (FEM). The influence of the position of the flexible fin on thermal and fluid dynamic performance is examined using forced convection of air as the working fluid. The heat transfer characteristics are studied for different Reynolds numbers (Re between 50 and 200) and Cauchy numbers (Ca from 10-8 to 10-4) at three positions (P1, P2, P3) in the channel, with a constant Prandtl number of Pr = 0.71. The results show an enhancement in heat transfer, with the best performance occurring at a Reynolds number of 200 and a Cauchy number of Ca = 10-8, corresponding to the most rigid fin. Specifically, when the fin is located closer to the step, a remarkable 40% increase in the Nusselt number is observed compared to the case without a fin. Additionally, the paper highlights the influence of flow separation and the interaction of recirculation zones with the elastic characteristics of the fin on convective heat transfer. These findings demonstrate the potential of elastic fins as an effective strategy for passive heat transfer enhancement in compact thermal systems.
In the pursuit of ensuring the long-term viability of residential areas, sustainability emerges as a pivotal element to be considered. During the planning phase of a residential area, it is imperative to assess energy use and daylighting potential from a sustainability perspective. In order to elucidate the impact of layout designs on these critical factors, a standardized and replicable reference case was chosen as a model. An alternative residential floor plan was created and analyzed across four different settlement configurations and building envelope improvement scenarios. The effects of the layout scenarios on energy consumption, daylighting performance and illuminance level are evaluated. According to the results, it was found that linear building planning prevents overheating by shading each other, and the enhancement of the thermal transmittance coefficient (u-value) of the building envelope reduces energy consumption. In addition, sufficient distance between the blocks optimizes the use of solar energy and reduces the need for heating.
Piezoelectric energy harvesting is crucial for providing power to systems where conventional power sources are unavailable. In this study, a novel wake-driven energy harvesting concept is proposed by exploiting vortex-induced vibrations generated downstream of semi-circular bluff body cylinders using piezoelectric film transducers. Flow visualization experiments are conducted to characterize the wake topology behind the bluff bodies. Bluff bodies with various length-to-diameter ratios are systematically investigated to examine the influence of geometric parameters on wake dynamics Based on the flow visualization results, piezoelectric film transducers are positioned at various streamwise distances and mounting orientations to evaluate their interaction with the unsteady wake of these various bluff bodies. Energy harvesting experiments for all configurations are performed by connecting the transducers to an input capacitor. The time-dependent charging behaviour is recorded to assess the energy output of each configuration. The models showing the best results are connected to the output capacitor, and their charging performance is measured. The experimental results demonstrate that optimized configurations yield average output capacitor voltages of 2.41 V and 2.84 V for different orientation and distances. The findings reveal a strong correlation between flow topology and energy generation. Moreover, both bluff body geometry and the spatial placement and orientation of the piezoelectric transducers play a critical role in maximizing energy output. This study highlights the potential of this approach for enabling self-sufficient energy generation in remote areas with promising applications in low-power off-grid systems.
In recent years, with the depletion of energy resources, studies on the use of renewable and clean energy sources have increased rapidly. The use of renewable energy sources is particularly prominent in the construction sector, which has a high energy consumption. This study examines the energy performance of Building-Integrated Photovoltaic (BIPV) systems applied to different fa & ccedil;ade designs in a prototype office building in the Mediterranean climate, specifically designed for renewable energy use in buildings. Four different PV fa & ccedil;ade design scenarios were determined for the prototype building, and energy performance analyses were conducted using the DesignBuilder simulation program. In this context, energy performance values such as Energy Coverage Ratio (ECR) and Self-Consumption Ratio (SCR) of the scenarios were compared. As a result of the comparison, the S2 inclined PV fa & ccedil;ade demonstrated the highest ECR (42.92%) and the lowest SCR (70.9%). The findings show that facade designs and the application of PV systems are important elements in determining the building energy performance and can meet a significant portion of the energy consumption. The study contributes to the evaluation of energy performance arising from differences in PV system applications in fa & ccedil;ade designs during the building's preliminary design process.
Application of nano-fluids in machining is becoming increasingly common due to their convenient thermo-physical properties. Previous studies indicate that adding Al2O3, MWCNT or TiO2 nano-particles into base fluids improves properties like density, viscosity, and thermal conductivity. This experimental study investigates the impact of addition of these nanoparticles at concentrations of 0.5%, 1%, and 1.5% into a boron mineral oil-water mixture. This research was carried out in three stages: Nano-fluid preparation, determination of thermophysical properties, and machining experiments on Ti-6Al-4V alloy. Results showed that increasing nano-particle concentration led to a consistent rise in fluid density at 24.5 degrees C. However, similar trends were not observed for dynamic viscosity and thermal conductivity, which began to decline beyond 1% concentration and this situation was attributed to precipitation and sedimentation showing fluid instability. Furthermore, the use of nano-fluids significantly marked down temperature at the tool-workpiece interface. For instance, usage of 0.5% MWCNT reduced interface temperature by approximately 18%, in degrees C unit, and improved surface finish by around 25%. Besides, higher concentrations resulted in increased interface temperature and surface roughness due to particle deposition. The study concluded that nanofluids only with optimal concentrations improve machining performance, as with excessive amounts degrade the performance -a finding supported by SEM images of the cutting inserts.
The examination of carbon dioxide capture systems is motivated by growing apprehensions regarding global greenhouse gas emissions as a viable method for mitigating climate change. This study examines the extraction of carbon dioxide (CO2) from the Bismayah Power Plant in Baghdad, Iraq. The system consists of six stages, each generating 750 MW, resulting in a total power output of 4500 MW, and utilizes a natural gas combined cycle system. The impact of carbon capture on plant efficiency and power generation is under investigation. The postcombustion method, reliant on the absorption and adsorption capabilities of amines, is recognized as one of the most prevalent techniques owing to its high efficiency in carbon capture. The research utilized Thermo-flow and Aspen HYSYS 14 software (R) for analysis. The study concluded that the average carbon dioxide release to the ocean from the plant is 2.26 Mt CO2 per year for each stage. The estimated total quantity of released CO2 is approximately 14 Mt CO2 per year. The incorporation of a carbon capture unit, achieving a capture efficiency of 90%, will lead to a 14% reduction in the overall efficiency of combined cycle power production, culminating in a net power decrease of 13.6%. This method has the potential to reduce annual carbon dioxide emissions to 0.22 Mt CO2 per year. The emissions associated with electricity production are 40.6 grams of CO2 per kilowatt-hour (g CO2/kWh) with carbon capture and 376.85 g CO2/kWh without it.
Solar air heaters (SAHs) are essential for sustainable thermal energy applications, yet their efficiency is often limited by poor internal heat transfer and significant thermal losses. Evacuated tube solar air heaters (ETSAHs) offer improved insulation but require internal modifications to enhance convective heat transfer. This study experimentally investigates the thermal and exergetic performance of a novel double pass evacuated tube solar air heater with copper tube (DPETSAHCT). The present work focuses on improving heat transfer performance while limiting the pressure drop in ETSAH systems. Experiments were conducted under outdoor conditions in Coimbatore, India, across mass flow rates ranging from 10 to 50 kg/h. Performance parameters including outlet temperature, heat gain, thermal efficiency, effective efficiency, pressure drop and exergy efficiency were evaluated. The DPETSAH-CT achieved a maximum outlet air temperature of 110.1 degrees C at 10 kg/h. The highest useful heat gain was 663.8 W at 50 kg/h. Thermal efficiency increased with flow rate, peaking at 40.1%. The system exhibited an effective efficiency of 39.2% and a maximum exergy efficiency of 1.21%. The integration of copper tubes as internal flow guides significantly enhances heat transfer while maintaining manageable pressure drops. The DPETSAHCT design presents a viable, energy-efficient solution for medium-temperature air heating applications, contributing to reduced operational costs and environmental impact.
This study investigates the interplay between geometric spacing, thermal boundary conditions, and three-dimensional flow structures on heat transfer and aerodynamic performance in tandem finite circular cylinders. Two finite circular cylinders of diameter D and aspect ratio AR=3 placed vertically on the bottom wall (ground plane) of the computational domain are subjected to uniform external flow resulting in a Re=20000. The distance between the cylinders S was varied as S=D, 2D, 4D. The turbulence model SST k-omega is employed to solve the governing equations. First, a numerical verification study was conducted to determine the most suitable turbulence model and grid configuration using a single 3D cylinder for which benchmark data are available in the literature. Subsequently, the flow field is simulated for two cylinders arranged in a tandem configuration. As a significant new contribution to the literature, the primary turbulence and flow characteristics across the computational domain and on each cylinder surface are systematically identified and presented in tabular form. The heat transfer performance over isothermal cylinders is evaluated using the mean and local Nusselt number distributions, providing insights for design optimization. While no K & aacute;rm & aacute;n vortex street forms at S/D=1 due to irregular vortex shedding, a stable K & aacute;rm & aacute;n vortex street is observed atS/D=4. In terms of heat transfer, the highest performance is observed at S/D=1 for the upstream cylinder and atS/D=4 for the downstream cylinder. For the upstream cylinder, the average Nusselt number decreases by 13.9% from S/D=1 to S/D=2 and increases by 3.6% from S/D=2 to S/D=4. For the downstream cylinder, the average Nusselt number decreases by 12.6% from S/D=1 to S/D=2 and increases by 19.1% from S/D=2 to S/D=4.
The high-temperature behavior of CEM I cement paste was investigated using TG-DTG/DSC, BET, XRD, SEM, and FTIR analyses to evaluate the structural and chemical modifications occurring between 25 and 1000 degrees C under air atmosphere. The degradation profiles from TG-DTG/DSC experiments revealed three distinct regions: (i) dehydration of the C-S-H gel and pore water, (ii) dehydroxylation of portlandite, and (iii) decarbonation of calcite. Characteristic temperatures for each degradation step were determined, and kinetic parameters were calculated using the Ortega method. Accordingly, the activation energy of Region 1 was determined to be 42.92 kJ/mol. For Region 2, the activation energy was calculated as 151.82 kJ/mol, while in Region 3 it was found to be 152.11 kJ/mol. BET analysis indicated extensive cracking of the micropore structure, while XRD, SEM, FTIR analysis provided insights into phase transformations and microstructural evolution in pastes exposed to elevated temperatures. Also, the effect of heating rate on the thermal degradation of the cement paste was investigated by using DSC data. It was observed that as the heating rate increased, the degradations shifted towards higher temperatures. These findings contribute to a better understanding of the thermal stability and degradation mechanisms of cementitious materials under fire conditions.
Many design parameters influence the energy demand of buildings. While research on building energy performance typically emphasizes physical design parameters and the technical characteristics of buildings, the behavior, actions, duration, and intensity of use by occupants are also critical factors impacting energy performance. Buildings should be constructed with functions aligned to the intended actions within spaces, ensuring user needs are considered during the design process. In this study, the variation in building energy performance was analyzed based on 9 different building functions and 3 climate types. Building energy models were developed using the BIM-BES methodology, and energy simulations were conducted using DesignBuilder software. The simulation results were analyzed through graphs, and energy performance characteristics were compared. Regression analyses were performed in Excel to explore the linear relationship between energy performance and occupant-related parameters, while correlation matrices were prepared and analyzed in Python. The findings revealed energy differences exceeding 80% due to variations in climate parameters and building functions. These results highlight the importance of context-specific design and demonstrate, through numerical data, the necessity of user-centered approaches to improve building energy performance.
Peltier modules are thermoelectric devices that convert electric energy to thermal energy. The cost of the cooling process by the module depends on the size of the module. The number of modules is vital in deciding the system's performance. A Peltier module has a high value of the coefficient of performance (COP) for the applied electrical power. The module finds many applications because of its compact size, eco-friendly nature, high durability, noise and vibration-free operation, and low maintenance. Despite these advantages, the Peltier module faces constraints for large-scale applications. This work presents a computational analysis of the temperature distribution of a fluid volume surrounded by four Peltier modules using COMSOL Multiphysics software. Nine different cuboids with multiple Peltier modules are analyzed. The temperature distribution as a function of time is presented. A Machine learning algorithm is developed to predict the temperature of the fluid for varying cuboid sizes surrounded by Peltier modules. The developed machine learning model can predict the average temperature of the fluid domain with an accuracy of 97% for any given Peltier size, fluid volume, applied current, and time.
Electric vehicles (EVs) have emerged as a critical solution to reducing greenhouse gas (GHG) emissions in the transportation sector. However, the effectiveness and sustainability of EVs are closely tied to the performance and environmental impact of lithium ion batteries (LIBs). This study provides an in-depth exploration of LIB technologies, focusing on battery thermal management systems (BTMSs), recycling processes, and the environmental consequences of large-scale battery deployment. We compare different battery types, including lithium-ion, nickel-metal hydride, lead-acid, and metal-air batteries, presenting their advantages, limitations, and sustainability metrics in a comprehensive table. Furthermore, this work investigates a variety of cooling methods, air, liquid, phase change material (PCM), and thermoelectric systems, highlighting their effects on battery lifespan, efficiency, and safety. The analysis extends to the environmental impacts of LIB production and disposal, exploring recycling technologies like pyrometallurgical, hydrometallurgical, and direct recycling processes. By integrating intelligent cooling systems and addressing challenges in waste management, this research bridges a crucial gap in the literature, offering innovative solutions to enhance LIB efficiency, longevity, and sustainability in EV applications.
This study presents ChemEqT, a computational tool for calculating chemical equilibrium compositions and adiabatic flame temperatures in multicomponent fuel-air mixtures. The unified framework integrates Gibbs free energy minimization and the element potential method, enabling users to select the numerical strategy most appropriate for their application. The objective is to simplify the complexity of equilibrium combustion analysis while ensuring accuracy and computational efficiency. The performance of ChemEqT is validated through three representative case studies. In the first case, simulations of a propane-air mixtures involving 10 species yielded adiabatic flame temperature predictions with a maximum deviation of 0.32% and molar species deviations below 0.77% for CO2. The second case examines methane-air mixtures enriched with hydrogen, using 52 species, where the maximum deviation was under 0.04%. The third case involves adiabtic flame temperature predictions for 10 different fuel-air mixtures, with deviations below 0.146% for C3H6-air. These results confirm ChemEqT as a reliable and efficient tool for equilibrium-based combustion analysis, with strong potential for integration into broader energy system simulations. The accuracy and modularity of ChemEqT distinguish it from conventional solvers and make it a valuable asset for researchers working in the fields of combustion and energy systems.
This study compares the heating efficiency of the Solar Energy-powered Embedded Pipe Envelope System (SEPES) in various building envelope locations using a novel simulation model developed with TRNSYS. The evaluation includes indoor air temperature, inlet and outlet water temperatures in walls, internal surface temperatures of envelopes, and heating energy consumption across six different SEPES installations. Key findings include: 1) SEPES significantly improves indoor temperatures during cold winters in Harbin, with ceiling installations increasing temperatures by up to 8.4 degrees C, and strategic placements optimizing warmth and energy efficiency; 2) Water temperature in SEPES pipes indicates heating capacity, with the highest temperatures in east and west wall installations; 3) Ceiling-embedded pipes perform best in blocking heat loss, with surface temperatures ranging from 7.42 degrees C to 11.59 degrees C; 4) SEPES installations significantly reduce daily heat loads, with ceiling installations achieving the highest energy-saving rate of 49.7% and an 8.9-year payback period. 5) Installing SEPES in as many building envelope structures as possible can maximize the use of solar radiation to resist thermal insulation loads.
This study proposes a novel method for evaluating energy and exergy performance in active solar water heating systems. It introduces new dimensionless energy and exergy efficiency numbers (EV, EVeX) and solar utilization energy and exergetic ratios (F, FeX) derived from the equations of the F-chart method, which are used to resize the system. Annual and seasonal variations of energy and exergy efficiencies for both the collector and the entire system, depending on their dimensionless numbers are analyzed and presented graphically. The findings reveal that as the dimensionless number of EV and EVeX varies inversely proportional to the energy and exergy efficiency of the system. The system achieves a moderate energy efficiency (F = 0.57 with a 10 m2 necessary collector area) and a relatively high exergy efficiency (FeX = 0.71), indicating significant potential for usable work. While larger collector areas enhance solar and exergetic utilization, they reduce the dimensionless efficiency indicators. The study finds that collector areas between 3 and 4 m2 strike an optimal balance, whereas a collector size of 8 m2 is recommended for maximizing solar utilization.
In this study, a water-source heat pump system was designed, manufactured, and experimentally investigated for space heating applications, with R-134a serving as the working refrigerant. The energy, exergy, and life cycle climate performances of two different systems were evaluated. The first system employed conventional POE oil as the compressor lubricant, while the second system used a nanolubricant, referred to as POE + Al2O3 nanofluid, formulated by adding 1 wt.% Al2O3 nanoparticles to the POE oil. The heat pump was tested under source water temperatures of 10 oC, 11 oC, and 12 oC. Within this scope, both the heating energy and exergy performances of the heat pump unit and the entire system, as well as their life cycle climate performances, were experimentally compared. The results indicate that the addition of Al2O3 nanoparticles increased the compressor power consumption by 1.62-3,0%. However, the heating energy performance of the heat pump unit decreased by 7.1-8.4%, and the overall system performance dropped by 12.5-22.8%. On the other hand, while the nanoparticle additive enhanced the exergy performance of the heat pump unit by 7-40%, it reduced the overall system exergy performance by 12.5-25%. Additionally, the Al2O3 additive improved the life cycle climate performance by 0.6-3.6%.
