Energy
M. Maghsoudizadeh; M. Ameri; E. Jahanshahi Javaran; A. MotamedSadr; A. A. Feili Monfared
Abstract
In recent years, the use of renewable energy sources and investigation on renewable energy have significantly grown. In this research, parabolic trough and linear Fresnel collectors, which are widely used in the field of solar energy, have been investigated from the point of view of exergy. First, the ...
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In recent years, the use of renewable energy sources and investigation on renewable energy have significantly grown. In this research, parabolic trough and linear Fresnel collectors, which are widely used in the field of solar energy, have been investigated from the point of view of exergy. First, the energy balance equations for different components of the collector were solved using numerical methods and the temperature distribution in each component of the collector was obtained. Then the values of exergy destruction in each component of the system were calculated. The comparison of the results obtained in the present work with the results of the previous research showed a good agreement. The results showed that the exergy efficiency in the parabolic trough collector is approximately 1.5 times that of the linear Fresnel reflector. Also, changes in exergy efficiency, exergy destruction of the whole collector, output exergy cost and CO2 emission with increasing solar radiation intensity and fluid mass flow rate for both collectors have been compared and investigated.
Energy
Z. Aouissi; F. Chabane; M. S. Teguia
Abstract
The study shows an experimental investigation for a solar air collector with a single pass by adding rectangular baffles for different positions inside the channel. The aim of this study is to improve the thermal efficiency for this collector, and that through testing four cases of baffles positions ...
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The study shows an experimental investigation for a solar air collector with a single pass by adding rectangular baffles for different positions inside the channel. The aim of this study is to improve the thermal efficiency for this collector, and that through testing four cases of baffles positions (mode 1, 2, 3, 4). The study was done under different operating conditions by changing the mass flow rates and positions of baffles. The results show the effectiveness of the baffles in improving the efficiency of the collector, The study also proved that the baffles positions affect thermal efficiency, where the greatest efficiency was recorded in the fourth mode and then in the positioning of obstacles at the middle of the channel for the mode 2 and the mode 4 with a percentage of 76.61 and 90.9, at mass flow rate m=0.0522 kg/s, while the pressure drop was very high in the mode 4, and after that the mode 2. Through the conditions of the study and taking into account all the results; we can say that the best case was mode 2.
Energy
H. Farzan; A. A. Abouee-Mehrizi; M. Khazali
Abstract
The current study introduces and analyzes a novel square cross-flow perforated solar air heater (SAH). Since the convection mechanism in SAHs is weak, numerous methods have been suggested to address this problem and improve thermal efficiency. Perforations and cross-flow configuration generate high turbulency ...
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The current study introduces and analyzes a novel square cross-flow perforated solar air heater (SAH). Since the convection mechanism in SAHs is weak, numerous methods have been suggested to address this problem and improve thermal efficiency. Perforations and cross-flow configuration generate high turbulency and, consequently, high convection rate resulted. Hence these methods have been applied to enhance thermal efficiency. To achieve this goal, an experimental setup was fabricated and tested at outdoor conditions for two air mass flow rates (mair) of 0.015 kg/s and 0.03 kg/s while several sensors monitored the collector’s heat dynamics and ambient conditions. The obtained results illustrate that outlet temperature reaches the peak values of 38 oC and 34 oC, which is only 6 oC and 7 oC lower than the maximum absorber temperature. This crucial issue proves a high heat exchange rate in the fabricated SAH that causes the absorber temperature to approach the outlet temperature due to high turbulency. The strong convection mechanism in the fabricated SAH improves daily thermal efficiency, in which its value reaches nearly 78.6% for the mass flow rate of 0.03 kg/s. In conclusion, the square cross-flow perforated SAH is an economy, applicable, compact collector, ensuring high thermal efficiency.
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
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
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
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.
