Energy
N. Tayari; M. Nikpour
Abstract
New designing techniques have been used recently in design phases of buildings to adapt human thermal comfort. Due to wide range of energy consumption within a building, it is impossible to make a proper decision about the impact of different energy efficiency strategies without simulation tools. Architects ...
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New designing techniques have been used recently in design phases of buildings to adapt human thermal comfort. Due to wide range of energy consumption within a building, it is impossible to make a proper decision about the impact of different energy efficiency strategies without simulation tools. Architects need to understand the accuracy and precision of simulation software to use them as valuable tools to predict energy consumption. This research aims to investigate the validity of DesignBuilder simulation software by using the actual traditional house in terms of heat gain. In this study, the comparative method was used to determine the differences in heat gain in a traditional courtyard house in Kerman that was simulated using DesignBuilder software and measured experimentally. This study also reveals that the difference between simulation results and empirical measurement is not more than 10%. It can be concluded that DesignBuilder has enough validity to calculate the amount of heat gain in the rooms adjacent to courtyards.
Energy
F. Chabane; N. Moummi; C. Toumi; S. Boultif; A. Hecini
Abstract
This study aimed to compare global solar radiation on the horizontal area between two models of Chabane Foued and M.Capderou. The model of Chabane has been interested in pollution factors such as TL (turbidity), BE (Angstraon), and the chemical components of the air such as WV, O3, CH4, CO, CO2, and ...
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This study aimed to compare global solar radiation on the horizontal area between two models of Chabane Foued and M.Capderou. The model of Chabane has been interested in pollution factors such as TL (turbidity), BE (Angstraon), and the chemical components of the air such as WV, O3, CH4, CO, CO2, and the especial part the new pollution factor such as hbeam, kbeam, and kdiffuse, which all influenced onto solar radiation, and the model of Capderou has been used the atmospheric disturbance to calculate the direct and diffuse components of radiation received on a plane, while the constituents of the atmosphere (absorption and diffusion) can be expressed by disturbance factors, which is very necessary to determine irradiation In the clear sky. The results reveal a significant difference between the two models with approximated curves. The difference between the models probably returns to the nature of the geographic site which the authors used and injected into the models.
Energy
M. Esmaeili Shayan; M. R. Hayati
Abstract
Having kilometers of asphalt road, yet with this heat going to waste, an attempt has been made in this research to extract the road's renewable energy heat. The purpose of the experiment is to compare the energy and exergy efficiency of various materials of asphalt solar water heaters (ASWH), as well ...
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Having kilometers of asphalt road, yet with this heat going to waste, an attempt has been made in this research to extract the road's renewable energy heat. The purpose of the experiment is to compare the energy and exergy efficiency of various materials of asphalt solar water heaters (ASWH), as well as heat transmission through the water tube and how friction affects exergy destruction. The water flow rate of one ASWH was 0.01 kg/s, while that of the other was 0.02 kg/s. Each ASWH has an area of 0.5 square meters. The copper tube is buried 10 mm deep in the asphalt. 15 degrees is the angle of inclination. The results indicate that the energy and exergy efficiencies are reasonably high for the water flow rate of 0.02 kg/s. Depending on the water flow rate, asphalt temperature, and sunlight intensity, the energy and exergy efficiencies changed from 32% to 65% and 5.8% to 16%, respectively. The water flow rate is an essential parameter for estimating the internal convective heat transfer coefficient and Reynolds number in order to calculate the friction factor in the copper tube based on internal convection heat transfer. In contrast, the friction factor is a consequence of the pressure loss and exergy degradation induced by friction.
Energy
A. Yousefi; R. Shafaghat; M. Beykani; A. Aghajani Afghan; S. T. Seyyed Mostafa
Abstract
Surface piercing propellers are special supercavitation propellers operating at free surface. These propellers are designed to have the best performance at the highest speed. The geometric parameters of the number of blades and the pitch ratio will significantly impact the critical advance coefficient ...
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Surface piercing propellers are special supercavitation propellers operating at free surface. These propellers are designed to have the best performance at the highest speed. The geometric parameters of the number of blades and the pitch ratio will significantly impact the critical advance coefficient range, ventilation and consequently the hydrodynamic performance of the propeller. Therefore, in this paper, the effect of two crucial parameters of pitch ratio and number of blades were experimentally studied in free surface water tunnel. After calibration and evaluation of uncertainty, two 5-bladed propellers with same section profile and pitch ratio of 1.5 and 1.4 used to investigate effect of pitch ratio. The results of two 5-blade and 6-blade propellers with same section profile and pitch ratio of 1.4 were compared. The immersion ratio was 40%, and the shaft inclination angle was zero. Results showed that increasing the pitch ratio increased the thrust and torque coefficients by 30%; while increasing the critical advance coefficient. Consequently that has led to the development of a full ventilation range and improved hydrodynamic performance of the propeller. In addition, by increasing the number of blades, at values greater than the critical advance coefficient, the thrust and torque coefficients were increased by 10%. However, the critical advanced coefficient changes were negligible. Comparing the results in the three-dimensional contours showed that with the change in the number of blades, by increasing the pitch ratio, the critical advance coefficient increased; which led to a further increase in efficiency.
Energy
A. Amini; N. M. Nouri
Abstract
The Surface-Piercing propeller blades move in and out of the water with each rotation to reduce the immersion depth from the free surface to the shaft axis . The main challenge facing surface piercing propellers, however, is their lower efficiency at lower advance velocity, compared to other propulsion ...
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The Surface-Piercing propeller blades move in and out of the water with each rotation to reduce the immersion depth from the free surface to the shaft axis . The main challenge facing surface piercing propellers, however, is their lower efficiency at lower advance velocity, compared to other propulsion systems. To improve the performance of the propeller, an aeration mechanism was used at low advance velocities so that air was blown to the surface behind the propeller. Experimental studies were carried out on a propeller model in the Hydrotech laboratory of the Iran University of Science and Technology, and the effect of the injected air velocity ratio was evaluated at different immersion ratios. Based on the results obtained, it was concluded that an increase in the injected air velocity ratio could only promote thrust enhancement under specific conditions. For immersion ratios of 0.85 and more, as well as advance coefficients of 0.6 and more, a change in the velocity ratio of the injected air could not lead to an improvement in thrust. The best performance was identified with an immersion ratio of 0.4 and an advance coefficient of 0.4, while thrust performance at below or above of this condition declined .
Energy
H. Eskandari
Abstract
Agriculture is a system exhibiting high levels of energy consumption. Thus, energy analysis is crucial for improving the energy efficiency of agricultural systems. In this research, the input energy of an irrigated wheat production system, including seeds, machinery, fertilizer, irrigation, electricity, ...
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Agriculture is a system exhibiting high levels of energy consumption. Thus, energy analysis is crucial for improving the energy efficiency of agricultural systems. In this research, the input energy of an irrigated wheat production system, including seeds, machinery, fertilizer, irrigation, electricity, diesel fuel and human labour, were determined and thereby the net output energy, energy efficiency and energy productivity were calculated for energetic system evaluation. For reaching this goal, 110 farmers were asked to complete the questionnaires in which cultivation information such as machinery, diesel fuel, grain produced per hectare, cultivation method, the method and the duration of water supply, workers, chemical materials which were used for plant treatment. The results showed that the total input energy for producing irrigated wheat was 42,481 MJ.ha-1. Energy efficiency was achieved as 1.56, suggesting that the total output energy of the system was more than the input energy. The net output energy, indicating the rate of obtained net energy from the system, was 23,819 MJ.ha-1. Electricity and fertilizer were the inputs consuming the most energy in an irrigated wheat production system, in which 41% and 31% of the total consumed energy were devoted to electricity and fertilizer, respectively. Therefore, the appropriate management of electricity and fertilizer through advanced methods of irrigation and the precise calculation of plants’ required nutrient elements can result in the improvement of the energy efficiency of the system. Reducing seed bed preparing operations (decrease diesel fuel consumption) may also increase the energy efficiency of the wheat production system
Energy
S. Prem Kumar; G. Kumar
Abstract
In solar drying, the moisture content of a product is reduced through the use of sunlight. Solar drying is practiced since civilization for the drying of crops. The dried crop has a longer shelf life and requires less storage space. For crop drying, hot air is required in the moderate temperature range ...
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In solar drying, the moisture content of a product is reduced through the use of sunlight. Solar drying is practiced since civilization for the drying of crops. The dried crop has a longer shelf life and requires less storage space. For crop drying, hot air is required in the moderate temperature range of 40 to 75℃. Solar dryer makes it possible to obtain better product quality. Over the past 20 years, numerous experimental projects have been carried out in the field of solar dryers. Most conventional dryers are not able to operate continuously during the off sunshine time. However, attempts were made to develop uninterrupted solar drying systems by incorporating an energy storage facility and a hybrid mode of operation. Sensible and latent heat storage methods are widely used to store solar energy. Heat storage materials store energy in the form of heat during sunshine and release it whenever it is required. Biogas backup, Chemical heat pump, Photo Voltaic, and Fluidized bed methods were integrated with solar dryers for uninterrupted operation. In this article, the discussion is made about different dryers. Also, the challenges and scope in the area of the solar dryer are highlighted.
Energy
R. Aghagolzadeh Silakhor; O. Jahanian; B. Alizadeh Kharkeshi
Abstract
Using cogeneration systems is a great way to tackle fossil fuel consumption problems. This paper introduces a Combined Cooling Heating Power (CCHP) system to recover the waste heat of an RK215 heavy diesel engine as a prime mover. Therefore the CCHP system consists of Internal Combustion Engine (RK215), ...
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Using cogeneration systems is a great way to tackle fossil fuel consumption problems. This paper introduces a Combined Cooling Heating Power (CCHP) system to recover the waste heat of an RK215 heavy diesel engine as a prime mover. Therefore the CCHP system consists of Internal Combustion Engine (RK215), a heat storage tank, and an absorption chiller. Also, the system has been studied in four modes: CCHP, CHP, CCP, and single generation. The waste heat ratio has changed due to a y factor, and the effect of this different parameter, such as the start of fuel injection and exhaust gas heat, on the system's efficiency by considering first and second laws of thermodynamic in different operating modes has been investigated. The system's highest energy and exergy efficiency in CCHP mode is equal to 50.46 and 30.8%, respectively. According to the result, as the CCHPs cooling load to the absorption chiller increases, the performance also rises. Also, the system’s carbon dioxide emissions reduction has been studied. The results showed that using different modes for waste heat recovery can reduce carbon dioxide by up to 30% approximately for different modes. Also, the fuel energy saving ratio (FESR) has been investigated, and the results showed that systems in CCHP, CHP, and CCP modes could have FESR approximately equal to 21%.
Energy
F. Najjari Seresht; A. Hakimi Oskui; S. Salkhi; E. Imani
Abstract
The building envelope is one of the most influential factors in energy consumption. Therefore, optimizing the facade of the building with new technologies is one of the most effective passive solutions to provide thermal comfort. The purpose of this research is to design a composite facade, which according ...
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The building envelope is one of the most influential factors in energy consumption. Therefore, optimizing the facade of the building with new technologies is one of the most effective passive solutions to provide thermal comfort. The purpose of this research is to design a composite facade, which according to the two main driving forces; the pressure difference caused by the heat flow (air flow and wind force) and the insulation of the air, for a residential building with a typical plan of Yazd in the hot and dry climate of Iran. That can be used to reduce the heating and cooling load of the building. For this purpose, firstly, the effect of two types of two-skin facades - floor-to-floor and all-over two-skin facades - compared to the model without two-skin facades in cooling and heating energy consumption throughout the year was modeled and analyzed with Design Builder version 6.1 software. The results of the constructions show the possibility of reducing about 60% of cooling energy through the creation of air conditioning and 26% of heating energy through the creation of thermal insulation in the residential building simulation model throughout the year by means of two combined shells. The findings of this research lead to the creation of more efficient energy solutions by creating innovation and combining new technologies according to climatic conditions.
Energy
N. Tayari; M. Nikpour
Abstract
Most of the spaces in contemporary houses in Iran cannot achieve enough daylight during daytime. Daylight utilization has a significant impact on decreasing energy consumption in residential buildings. Residents are deprived of natural daylight when there is no attention to the design based on daylight. ...
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Most of the spaces in contemporary houses in Iran cannot achieve enough daylight during daytime. Daylight utilization has a significant impact on decreasing energy consumption in residential buildings. Residents are deprived of natural daylight when there is no attention to the design based on daylight. Iranian traditional architects use practical and straightforward methods in constructing courtyards houses to provide comfort conditions in unique rooms in courtyard houses in terms of daylight quality. In this research, the daylight quality of five separate rooms around the courtyard of Yazdanpanah's house was investigated through an experimental method. Average work plane illuminance and uniformity ratio were calculated in these rooms of the house in Kerman city, located in Iran's hot and dry climate. Findings of this research demonstrated that all rooms surrounding the courtyard of traditional houses have the ability to achieve work plane illuminance of more than acceptable value. Among all rooms around the central courtyard, one room facing the south direction achieves more than 500 Lux work plane illuminance. The amount of uniformity in this room is acceptable with more than 0.5 on most of the days in a year. The findings of this research could be used to design more comfortable rooms in contemporary houses in terms of daylight quality by creating central courtyards.
Energy
L. H. Pratomo; L. A. Matthias
Abstract
Renewable energy is energy that can be used indefinitely. As a result, renewable energy sources such as solar photovoltaics developed. Conventional converters, typically used to connect the microgrid to the battery, only change the voltage. To link the microgrid to the battery, bidirectional converters ...
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Renewable energy is energy that can be used indefinitely. As a result, renewable energy sources such as solar photovoltaics developed. Conventional converters, typically used to connect the microgrid to the battery, only change the voltage. To link the microgrid to the battery, bidirectional converters are required. A bidirectional converter is available in a variety of configurations. The control structure is highly sophisticated to obtain a satisfactory output. This article proposes a bidirectional DC-DC buck-boost converter for controlling current in DC microgrids, solar systems, and loads. A bidirectional DC-DC Buck-Boost converter is required to transmit and receive energy from the battery to the DC microgrid. When voltage is sent to the DC microgrid, the battery voltage is reduced. Otherwise, the charging voltage is increased when a battery is charged by voltage. This converter produces a better output voltage than an AC-DC Buck-Boost Converter, and its switching frequency is double that of typical converters. The modified DC-DC converter has the simplest form and the advantage of having the highest responsiveness.
Energy
S. Bagheri; S. A. A. Oloomi; S. A. A. Mirjalily; A. Zare-Shahabadi
Abstract
The phenomenon of nuclear boiling has always been recognized suitable for heat transfer between different boiling regimes. Study on boiling is considered as a new field which meets different research and industrial needs such as heat transfer in nuclear reactors, cooling units, rocket motors, electronic ...
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The phenomenon of nuclear boiling has always been recognized suitable for heat transfer between different boiling regimes. Study on boiling is considered as a new field which meets different research and industrial needs such as heat transfer in nuclear reactors, cooling units, rocket motors, electronic equipment cooling, batteries, etc. In this study, a chamber with immiscible fluid, water, steam, and air, having a side wall with uniform heat flux has been studied in 3D. To do so, we first considered the prediction of the heat flux interval for which the boiling occurs in the form of nuclear boiling. In this study, two-phase fluid volume (VOF) approach was used for modelling boiling on the vertical wall and two-phase flow. In this research, Ansys software package was used for numerical modelling and numerical simulation. Distribution of the velocity field follows more uniform pattern in dimensionless heights less than 0.9. In this study, bubbles are only present near a wall with heat flux that has a lower Rayleigh number. Also, existence of these bubbles on the wall, which prevents fluid infiltration, affects vortices caused by natural convection. However, the general and uniform patterns of vortices remain unchanged in most part of the fluid, which is because of the limited amount of bubbles near the wall with heat flux. Natural convection increases the height of fluid inside the chamber, which leads to the formation of stronger vortices at a dimensionless height of 0.9 that has a high Raleigh number due to high heat flux. In this case, the continuous use of heat flux gives rise to the production of bubbles over time.
Energy
P. A. Ayoubi; M. E. Yazdi; I. Harsini
Abstract
The development of models that predict power production of wind farms (WFs) by considering the interacting wakes is important; because wakes of the turbines exert a significant influence on power production of turbines, and hence on the layout of wind turbines in WFs. Thus, the purpose of present study ...
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The development of models that predict power production of wind farms (WFs) by considering the interacting wakes is important; because wakes of the turbines exert a significant influence on power production of turbines, and hence on the layout of wind turbines in WFs. Thus, the purpose of present study was to provide an innovative analytical method for the prediction of power generation of the WFs that have a flat terrain and are consisted of horizontal-axis wind turbines (HAWTs) with the same hub height. The methodology employed utilized an analytical Gaussian model of HAWT wake to develop an analytical model that calculates the effective wind velocity acting on the downstream HAWT(s), which is further used for reading its generated power from the turbine’s catalog; thus, providing the generated power of the WF as the output. The results of presented model were validated by the field measurements data of Horns Rev WF and also were compared to two analytical models for predicting the generated power. The results were compared with two numerical simulations of the literature, and the output data of three commercial software. Moreover, the error analysis revealed that the presented model mostly showed superior accuracy in predicting the field measurements data.
Energy
S. Abbasi; S. Esmailzadeh Vali
Abstract
In this study, the simultaneous effect of suction and blowing on the boundary layer and the effect of control parameters on the flow separation from a NACA 0012 airfoil is numerically analyzed. Reynolds number is considered 500000 , and the shear stress transport (SST) k-w turbulence model is used to ...
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In this study, the simultaneous effect of suction and blowing on the boundary layer and the effect of control parameters on the flow separation from a NACA 0012 airfoil is numerically analyzed. Reynolds number is considered 500000 , and the shear stress transport (SST) k-w turbulence model is used to estimate eddy viscosity. The airfoil is supposed to be 2-D. To validate the numerical results, they were compared with reported experiments. In the flow control by simultaneous suction and blowing, the location of the suction jet was 0.1 of the airfoil chord from the fixed leading edge, and that of the blowing jet was 0.5, 0.7, and 0.9 of the airfoil chord from the leading edge. When the blowing location is at 0.5 of the airfoil chord, better results are observed than I n; other locations. An increase in suction jet velocity increases the lift-drag ratio between 22% and 55%. Also, increasing the blowing jet velocity increases this ratio between 43% and 55%. Horizontal blowing has the most negligible effect on improving aerodynamic characteristics. Based on the results, at the angle of attack of 16°, blowing is most effective in the flow control at with an approximate velocity of half the free stream velocity. In this condition, vertical suction has the best effect , and the lift-drag ratio will increase by 76%.
Energy
F. O. Aweda; T. K. Samson
Abstract
This current study was conducted on rainfall and air temperature data obtained from the archive of the HelioClim website to determine the relationship between the two parameters. The study aimed at the relationship between rainfall and air temperature. The data of thirty-four (34) years spanning from ...
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This current study was conducted on rainfall and air temperature data obtained from the archive of the HelioClim website to determine the relationship between the two parameters. The study aimed at the relationship between rainfall and air temperature. The data of thirty-four (34) years spanning from 1985 to 2019 was analyzed using Mann-Kendal statistics on the trend of the rainfall series while the normality of rainfall series was determined using Kolmogorov- Smirnov test across six southwest stations of Nigeria. The results revealed the highest mean rainfall in Akure (198.9 mm) while the least rainfall in Ado-Ekiti (163.4 mm). The maximum rainfall was in Abeokuta (865.8 mm) with Iwo having the highest disparity in rainfall (SD=148.8 mm) compared with other stations. The skewness in Abeokuta (Skewness = 0.9 mm) was higher compared with Ado-Ekiti, Akure, Ibadan, Ikeja and Iwo with skewness values of 0.7 mm, 0.4 mm, 0.7 mm, 0.6 mm and 0.7 mm, respectively. The maximum air temperature was recorded in Iwo (301.7 K) and the minimum air temperature in Ado-Ekiti (293.3 K). The skewness obtained in Akure (-0.2) and Ikeja (-0.3) was less than zero indicating that air temperature decreased more than it increased in these areas while in other stations, Abeokuta (0.01), Ado-Ekiti (0.22), Ibadan (0.02) and Iwo (0.24), the skewness was greater than zero meaning that air temperature increased more than it decreased in these stations.
Energy
N. Amani; A. Sabamehr; L. M. Palmero Iglesias
Abstract
The building sectors are recognized as one of the essential contributors of global warming and climate change because of their high energy use. The building sector is responsible for 40% of all energy usage and 40% of the CO2 emissions in the developed countries. Researchers in the world are working ...
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The building sectors are recognized as one of the essential contributors of global warming and climate change because of their high energy use. The building sector is responsible for 40% of all energy usage and 40% of the CO2 emissions in the developed countries. Researchers in the world are working on energy management and conservation using simulation software to develop strategies that lead to an overall reduction of energy consumption in the buildings. This review is considered a modeling and simulation approach with a specific focus on residential building. Modeling and simulation methods reviewed are presented categorically as per the strategic approach adopted by the researchers. Simulation results available for residential building energy are also introduced. This research has reviewed the capabilities and performances on Ecotect simulation and modeling, including daylighting, solar radiation, thermal analysis, and shading for energy management and conservation of residential building. Different modeling and simulation approaches, from various building and climate, were reviewed and discussed. The analysis of present work greatly help the researchers' decision-making and selection of software to perform various simulations in energy management of residential buildings.
Energy
M. Pakdel; B. Alemi
Abstract
Silkworm cocoon is a natural biological and composite structure that has evolved over time and has high physical and mechanical properties against stress and acts as insulation against ambient temperature conditions. Understanding the relationships between the two-component structure of silkworm cocoons ...
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Silkworm cocoon is a natural biological and composite structure that has evolved over time and has high physical and mechanical properties against stress and acts as insulation against ambient temperature conditions. Understanding the relationships between the two-component structure of silkworm cocoons (sericin and fibroin) inspires the creation of composite structures, including lightweight, high-strength nonwoven biocomposites. In the present study, by analytical-descriptive method, we have tried to use cocoon sericin and introduce some famous and widely used natural fibers in materials science and study their characteristics - because for various reasons such as lightness, lack of pollution and low cost, etc. can be suitable alternative for a replacement of synthetic fibers - suggest the production of non-woven bio-composite materials. Natural fibers such as jute, hemp, flax, etc. with different volume percentages in combination with sericin as a binder, were proposed for this biocomposite and the thermal performance of each of them was compared using Maxwell's theoretical model. All compounds show low thermal conductivity and jute-sericin biocomposite with 70% by volume and 0.061 W/m2-K performance has better performance.
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.
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.
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.
Energy
S. A. Gandjalikhan Nassab
Abstract
This paper presents an original concept of using high flexible flapping vortex generator in a heat sink for airside heat transfer augmentation. The proposed thin winglet, made with an elastic sheet, is responsible for increasing the cooling rate and mixing quality performance in laminar convection airflow. ...
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This paper presents an original concept of using high flexible flapping vortex generator in a heat sink for airside heat transfer augmentation. The proposed thin winglet, made with an elastic sheet, is responsible for increasing the cooling rate and mixing quality performance in laminar convection airflow. This study focuses on the excessive bending of the flapping winglet and reducing its blockage effect and pressure drop. This novel concept is demonstrated using a numerical simulation of the flow field with a coupled Fluid-Solid-Interaction technique in transient conditions. The continuity, momentum, and energy equations for forced convection airflow are solved by the finite element method using the COMSOL Multi-physics. Numerical results reveal high amplitude for the flapping vortex generator while under a large deformation and bending. This behavior leads to flow mixing with a small blockage effect due to the deformed aerodynamic shape of the winglet. The present findings show that the high flexible winglet enhances the rejected heat by 100%, with a 33% decrease in pressure drop compared to the rigid vortex generator at the same air velocity.
Energy
S. Abdoli Naser; F. Haghparast; M. Singery; H. Sattari Sarbangholi
Abstract
Most of today's buildings, due to improper imitation of the architecture of buildings in other countries, are forced to use more energy to create conditions of thermal comfort. Building windows affect energy efficiency. So, the aim of this research is to be concerned with Tabriz climate; in selecting ...
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Most of today's buildings, due to improper imitation of the architecture of buildings in other countries, are forced to use more energy to create conditions of thermal comfort. Building windows affect energy efficiency. So, the aim of this research is to be concerned with Tabriz climate; in selecting the proportion and suitable glazing of the windows, in order to access the best design and execute a model to decrease energy consumption. The research approach is to utilize simulation and Design Builder software as a research tool. So, the annual gas consumed in the Building was received from the National Iranian Gas Company and a case study is modeled and after converting the unit from kWh to kg and kg to m3 and reliability of simulation results. Then, through parametric optimization, eight scenarios in designing windows and through the genetic algorithm, the glazing coating were evaluated. The simulations were performed again and the results index was examined. Eventually, based on the analysis of outputs, according to fixed area, it is more suitable to replace windows with the height of 1.5 to 1.74 meters instead of windows with the height of 1 or 1.2 meters. A window should be replaced with 2, 3, 4 or 5 windows with the same fixed area. I is desired to superseded triple-glazed glazing with low-emissivity filled with argon gas with clear double-glazed glazing filled with air to reduce energy consumption. The amount of heat losses for the window height of 1 to 1.5m, from one window to five windows and for the clear double-glazed glazing filled with air were 2.04%, 11.11%,. and 45.36%, respectively.
