Energy
R. Shafaghat; M. Fallahi; B. Alizadeh Kharkeshi; M. Yousefifard
Abstract
This paper has experimentally investigated the performance of a dual-chamber oscillating water columns (OWC) imposed on Caspian Sea wave’s characteristics. Experimental runs were performed for three water draft depths of 10, 15, and 20 cm and eight wave frequencies ranging from 0.4 to 0.7 Hz. Also, ...
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This paper has experimentally investigated the performance of a dual-chamber oscillating water columns (OWC) imposed on Caspian Sea wave’s characteristics. Experimental runs were performed for three water draft depths of 10, 15, and 20 cm and eight wave frequencies ranging from 0.4 to 0.7 Hz. Also, if the converter consists of only one chamber, the power generated was 75W; however, by placing the second chamber serial behind the first chamber, the converter power increased to 116 watts (55% improvements). The results showed that if the frequency of the incident wave is not in the natural frequency range, the converter performs is better at the lowest water draft depth (10 cm). Whereas if the frequency of the incident wave is in the natural frequency range, the converter will have the best performance at the maximum water draft depth (20 cm). As the power generated at a water draft depth of 10 cm increased by 3.8% compared to a water draft depth of 20 cm. But within the natural frequency range and by resonance, the power produced at a depth of 20 cm is 27.3% more than the power generated at a depth of 10 cm.
Energy
S. A. Shourehdeli; K. Mobini; A. Asakereh
Abstract
A number of isentropic coefficients are used in the one-dimensional models which predict ejector performance at critical mode. Some of these coefficients have considerable effects on accuracy of the model. These coefficients depend on geometry, working fluid and operating conditions; but, they are usually ...
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A number of isentropic coefficients are used in the one-dimensional models which predict ejector performance at critical mode. Some of these coefficients have considerable effects on accuracy of the model. These coefficients depend on geometry, working fluid and operating conditions; but, they are usually taken constants or are presented as functions of geometry and working condition based on a specific experiment. In this work, the idea of using the flow parameters to determine these coefficients is introduced and has been analyzed. For this purpose, four models with different formulations are employed. The fluid has been considered as a real gas; hence, the models which are based on the ideal gas assumption are modified. The experimental data related to some ejectors with different geometries, working fluids and working conditions have been used. Using the empirical data, correlations between some of the isentropic coefficients and the flow parameters are developed for some models. Using these correlations, entrainment ratios are calculated with the maximum relative error of 35%, while in most cases the maximum relative error is about 10%. However, errors are acceptable since the empirical data are extracted from a vast range of different geometrical and operational conditions.
Energy
M. Mahmoudi; H. Farzan; E. Hasan Zaim
Abstract
Asphalt materials commonly have high absorption coefficients, and their surface temperature reaches as high as 80 oC during daytime hours since their surfaces are exposed to solar radiation for long periods. Hence, asphalt pavements can easily be converted to solar air heaters (SAHs) to collect solar ...
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Asphalt materials commonly have high absorption coefficients, and their surface temperature reaches as high as 80 oC during daytime hours since their surfaces are exposed to solar radiation for long periods. Hence, asphalt pavements can easily be converted to solar air heaters (SAHs) to collect solar energy. Even though asphalt materials have low thermal conductivity, resulting in a weak convection heat exchange rate between the flowing air and asphalt surface. The current experimental study analyzes utilizing aluminum shavings as asphalt coating materials to improve SAHs’ thermal performance. To this aim, a serpentine SAH prototype was constructed, and several sensors were utilized to monitor its dynamic thermal response. Black-painted aluminum shavings were utilized as coating materials to improve the convective heat exchange rate and increase the roughness of the absorber surface. Two scenarios were considered, including the uncoated absorber plate and coated one with 0.2 kg aluminum shavings. The experiments were carried out for two air mass flow rates of 0.02 kg/s and 0.03 kg/s under field conditions. Based on the air mass flow rate, the coated absorber reaches higher temperatures, approximately 5 oC to 9 oC, than the uncoated one. The acquired results illustrate that the coated SAH has nearly 4 oC to 5 oC higher maximum exhaust air temperature; hence, the coating strategy improves the thermal efficiency by 24.75% and 44% in two air mass flow rates of 0.02 kg/s and 0.03 kg/s, respectively.
Water Resources Engineering
P. E. Omuku; C. C. Odidika; A. E. Ozukwe; K. O. Iwuozor
Abstract
The objective of this study was to evaluate comparatively the effects of different brands of corrugated roofing sheets on rainwater utilized within Awka metropolis. Different physicochemical parameters were assessed in the rain water harvested using established standard laboratory procedures. The rain ...
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The objective of this study was to evaluate comparatively the effects of different brands of corrugated roofing sheets on rainwater utilized within Awka metropolis. Different physicochemical parameters were assessed in the rain water harvested using established standard laboratory procedures. The rain water was harvested directly (control) and also collected after passing through the different brands of corrugated roofing sheets (samples). The results showed no appreciable effects on the physical appearance, observable odour, or taste of the water samples compared to the control sample. However, at 30 °C, there were minor changes in the pH. The amount of suspended solids (SS) in mg/100ml, total solids (TS), and total dissolved solids (TDS) found in each of the samples, including the control sample, did not vary. This showed that the corrugated roofing sheet has no significant effect on the SS, TS, and TDS of the rain water harvested within the study area. Iron, zinc, and chloride ions followed a similar trend as SS, with Fe and Zn occurring at non-detectable limits of the instrumentation, while the levels of Cl- ion (3mg/100ml) did not vary in all the samples, including the control sample. The results revealed that corrugated roofing sheets affect the total alkalinity and methyl orange alkalinity of the harvested rain water in the study area greatly but had no impact on their physical appearance.
Environment
H. Tamadon Ghareghie; M. Yazdi; D. Yousefi Kebria; H. Aminirad
Abstract
Soil contamination is considered a controversial issue in most countries. Nowadays, it is important to clearly understand how pollutants influence the soil from different sources. Today, hydrocarbons are one of the most important sources of soil contaminants, which is considered as a fundamental issue ...
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Soil contamination is considered a controversial issue in most countries. Nowadays, it is important to clearly understand how pollutants influence the soil from different sources. Today, hydrocarbons are one of the most important sources of soil contaminants, which is considered as a fundamental issue at the global level. The current study aims to analyze and model the effect of simultaneous parameters (time and concentration) of phenols and naphthalene with different percentages (10, 15, 20 and 25%) together with the amount of bentonite in fine-grained sandy soil. The designed experiments made use of response surface methodology (RSM) and Design-Expert software to carry out a computer-based simulation. According to the proposed model, the amount of bentonite is most affected by the permeability of the soil. The obtained results also showed that the permeability significantly decreases in the light of increasing the percentage of phenol and naphthalene coupled with the amount of bentonite and the age of contamination. On average, an 80% reduction of permeability was observed in contaminated soil, which was found in the soil contaminated with naphthalene. According to the results of the synergistic effects of time, the considerable impacts of both the percentage of hydrocarbon pollutants and the amount of bentonite on the reduction of permeability are quite evident.
Chemical Engineering
A. Mohammadi
Abstract
Semiclathrate hydrate formers such as tetra-n-butylammonium bromide (TBAB), chloride (TBAC) and fluoride (TBAF) are promising compounds that mild the thermodynamic conditions of gas hydrates, considerably. The Clausius-Clapeyron equation is employed in this manuscript to calculate the dissociation enthalpies ...
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Semiclathrate hydrate formers such as tetra-n-butylammonium bromide (TBAB), chloride (TBAC) and fluoride (TBAF) are promising compounds that mild the thermodynamic conditions of gas hydrates, considerably. The Clausius-Clapeyron equation is employed in this manuscript to calculate the dissociation enthalpies of methane/carbon dioxide/nitrogen + TBAF semiclathrate hydrates. A 460 cm3 stirred batch reactor was used to measure the phase equilibria of gas + TBAF semiclathrate hydrates at various concentrations of tetra-n-butylammonium fluoride. The dissociation P-T data were obtained using an isochoric pressure-search method in the temperature range of 275.15 to 304.7 K and the pressure range of 0.53 to 10.24 MPa at 0.0 - 0.4482 mass fraction of TBAF. Investigating the obtained dissociation data showed that the addition of TBAF to the solution increases the amount of dissociation enthalpy of semiclathrate hydrates per mole of the hydrated gas. Increasing the mass fraction of tetra-n-butylammonium fluoride, showed a straight relation with the amount of dissociation enthalpy per mole of hydrated gas.
Energy
S. A. Gandjalikhan Nassab
Abstract
This paper deals with the development of compound parabolic collectors (CPCs), utilizing a partial glass sheet adjacent to the absorber plate for the purpose of performance improvement. The collector under study has a parabolic shape, whose cavity is filled with air and the turbulent natural convection ...
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This paper deals with the development of compound parabolic collectors (CPCs), utilizing a partial glass sheet adjacent to the absorber plate for the purpose of performance improvement. The collector under study has a parabolic shape, whose cavity is filled with air and the turbulent natural convection takes place because of the air density gradient. The main goal is the reduction of heat losses by keeping away the high-temperature region near to the absorber from the main recirculaetd convection airflow by installation of a separating glass sheet. The conservations of mass, momentum and energy as the set of governing equations for the steady and turbulent free convection airflow in the CPC’s cavity and the Laplace equation for computation of temperature distributions in solid parts including the glass cover, absorber plate, and glass sheet were numerically solved by the finite element method. The COMSOL Multiphysics software was used for the present simulation. For the computation of turbulent stress and heat flux, the κ-ε turbulence model was employed. An attempt was made to investigate the installation of a fully transparent glass sheet near the absorber plate on the thermal behavior of the studied CPC. It is expected that this factor leads to lowering the heat losses from boundary surfaces, especially from the glass cover. Numerical findings showed about a 24% increase in the efficiency of studied test cases because of the installed glass sheet. Comparison between the theoretical findings with experiment shows good consistency.
Chemical Engineering
M. R. Maraki; H. Tagimalek; B. Pasoodeh
Abstract
The copper/aluminum composite is very important and practical due to its light weight, optimal thermal and electrical conductivity. The high weight resistance ratio, along with its inherent properties, makes it attractive for new applications. In this regard, the use of composites with high mechanical ...
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The copper/aluminum composite is very important and practical due to its light weight, optimal thermal and electrical conductivity. The high weight resistance ratio, along with its inherent properties, makes it attractive for new applications. In this regard, the use of composites with high mechanical properties has significantly increased. In this research, 5000 series aluminum and pure copper samples in 1st, 2nd, 3rd, and 4th passes have been subjected to friction stir welding (FSW) and then the mechanical and metallurgical properties of the welded samples have been compared with the original samples. In order to further study the results of tensile tests, metallography and microhardness tests have been performed. Microstructural evaluation of welded samples showed that the mixing zone of the samples was determined by combining aluminum and copper layers. The results showed an increase in yield strength in the welding zone and ultimately an improvement in hardness and ultimate strength in the weld zone compared to the prototype. Compared to stretched samples, the greater the distance from the nugget weld, the less the improvement in mechanical properties and microhardness. By changing the parameters and increasing the inlet temperature, the mixing and uniform dispersion of the particles is performed more appropriately and ultimately increases the tensile strength. Finally, in the research, experimental data were modeled using fuzzy logic method and considering that the presented model was obtained in two indices R-Sq (pred) and R-Sq (adj), 96 and 99%, respectively. The comparison between the experimental data and the model data indicated an acceptable error in the experimental data.
Environment
M. O. Ezugwu; F. O. Akhimien; Z. Y. Hamza
Abstract
Characterization and quantification of solid waste in Equity girls hostel blocks, Igbinedion University Okada was carried out to provide data for waste management strategy in the University. The waste survey was done for 3 months by collecting generated wastes from various rooms on a daily basis excluding ...
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Characterization and quantification of solid waste in Equity girls hostel blocks, Igbinedion University Okada was carried out to provide data for waste management strategy in the University. The waste survey was done for 3 months by collecting generated wastes from various rooms on a daily basis excluding Sundays. The collected wastes were segregated and sorted into their various constituents and weighed using an automatic weighing scale. Waste per capita per head was also determined by estimating the total number of students/population in the study area. Identified wastes constituents were plastics, paper, glass, bottles, organic wastes, etc. The total amount of waste recorded was 1605.65kg for 3 months. Organic wastes recorded the highest amount of wastes generated with a total of 304.542kg (19%) followed by glass/bottles recorded as 250.993kg (16%). Waste per capita per day was estimated as 0.045kg. From the wastes stream, some wastes were identified as reusable and recyclable which can generate income for the university when properly handled and it will indirectly aid in decreasing the volume and amount of wastes to be disposed. Organic wastes have been identified to constitute the highest amount of waste in the waste stream. These organic wastes are degradable and can be utilized for crop production and agricultural purposes which invariably contribute to waste stream reduction. Adopting efficient waste mangement strategy will create wealth, reduce pollution and demand on raw materials, and provide a greener environment.
Energy
M. Esmaeili Shayan; M. R. Hayati; G. Najafi; S. Esmaeili Shayan
Abstract
Energy democracy policymakers pay attention to planning to the formation of energy markets and exchanges of energy regions, diversification of energy resources, especially renewable resources, and global challenges due to greenhouse gas emissions. Over the introduction of concepts related to sustainable ...
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Energy democracy policymakers pay attention to planning to the formation of energy markets and exchanges of energy regions, diversification of energy resources, especially renewable resources, and global challenges due to greenhouse gas emissions. Over the introduction of concepts related to sustainable development, energy planning at the international level finds its place and goals in the direction of sustainable development, i.e., economic, social, environmental, and institutional dimensions. Energy democracy designs equations of great powers over energy with the aims of Resist, Reclaim, Restructure. This research focuses on free governments and energy democracy and the integration of priorities and methods to improve energy policy and analysis. No one policy instrument in isolation significantly impacts the energy democracy agenda. instead, all policies are essential for increasing this aim. They created new policy tools, supporting efforts to end fossil fuel dependence and connecting them to renewable energy. This research provides a starting point for improving the visibility of the energy democracy movement and constructing appropriate policies for different renewable energy transition options.
Energy
A. H. Shiravi; M. Firoozzadeh
Abstract
Nowadays, the world is moving toward using renewable and sustainable energy sources, as much as possible. Photovoltaic (PV) technology is one of the most popular alternatives. PVs are widely used to supply electricity for pumping systems to irrigate the farmlands. It has been proved by many scholars ...
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Nowadays, the world is moving toward using renewable and sustainable energy sources, as much as possible. Photovoltaic (PV) technology is one of the most popular alternatives. PVs are widely used to supply electricity for pumping systems to irrigate the farmlands. It has been proved by many scholars that PV cell temperature is a crucial factor in cell’s efficiency. In this study, a novel arrangement of a PV/pumping system has been considered, in order to enhance the pumping performance. To make it feasible, a small part of the pumped water is directed to a box-type passage at the backside of the PV module, and then connect to the water pipe and drain to the farmland. Two various flow rates of 5 and 10 L/min were tested. The results showed two proposed cases have a bit difference in their outputs. Accordingly, the temperature of modified cases did not pass beyond 36°C while, the temperature of the conventional module reaches to 72°C. This temperature reduction leads to about 50% higher electrical efficiency. From the output power point of view, more than 45% increase was observed. Also, an environment evaluation is performed and it was found that the present improvement can reduce emission of 34.57 tons CO2, annually.
