Showing 7 results for Mortezapour
Volume 14, Issue 4 (7-2012)
Abstract
In this paper, the performance evaluation of a two-way hybrid photovoltaic/thermal (PV/T) solar collector was analytically and experimentally carried out. Mathematical expressions for operating parameters in glass to glass and glass to tedlar PV/T solar collectors were developed and experimentally validated by a glass to tedlar PV/T solar collector system. Also the influence of air flow rate on the solar collector performance was investigated. The results showed that the glass to glass PV/T solar collector gave higher outlet air temperature, cell temperature and thermal efficiency than the glass to tedlar PV/T solar collector. However, back surface temperature and electrical efficiency were higher in case of glass to tedlar collector. Increasing the air flow rate led to a lower outlet air temperature and a higher electrical efficiency of the photovoltaic module. Maximum experimental electrical efficiency, thermal efficiency and overall thermal efficiency for the glass to tedlar PV module were found to be 10.35, 57.9 and 84.5%, respectively.
Volume 16, Issue 1 (1-2014)
Abstract
In the present study, saffron was dried using a heat pump-assisted hybrid photovoltaic-thermal solar dryer. The effect of different drying air temperatures at three levels (40, 50, and 60oC) and two different modes of the dryer (with and without heat pump system) were investigated on drying behaviour of saffron. After collecting the pertinent data, eleven drying models were used to describe drying characteristics of saffron. Quality characteristics of the dried products (including: colouring, aromatic strength and bitterness) were also evaluated. The results indicated that drying time decreased by 62% with increasing air temperature from 40 to 60oC. Moreover, applying heat pump with the dryer reduced RH of drying air and, consequently, enhanced drying rate and shortened drying period by 40%. A two-term drying model presented a relatively higher R2 and lower, MBE, and RMSE values at both modes of drying and, therefore, was selected to explain drying behaviour of saffron among the other models. The results of saffron quality evaluation showed that colouring characteristics of saffron improved with drying temperature and heat pump system. Meanwhile, aromatic strength of saffron increased with increasing air temperature. But, no significant change in bitterness was observed at different levels of temperature and heat pump system.
Volume 17, Issue 98 (April 2020)
Abstract
Sheep tail fat is a suitable frying oil due to its good flavor and oxidation stability. This oil with its useful fatty acids can to play beneficial effect on consumer health. The refining processes of sheep tail oil, including its deodorization have high importance in the enhancement of the oil quality. Deodorization is a separation process in which a certain amount of the volatile compounds separator gas passes through the hot oil under vacuum condition and removes the volatile and odorous compounds from the oil. In this study, the ultrasound-assisted deodorization of sheep tail fat was carried out and the effects of temperature, time, and ultrasonic power on odor intensity during the deodorization process were investigated using the response surface methodology. The intensity of the odor was assessed by electronic nose and sensorial evaluation. Also, the fatty acid composition was compared before and after the deodorization process. The results of fatty acids profile showed that about 46.72% of sheep tail oil fatty acids were saturated fatty acids (palmitic, stearic, margaric, and myristic) and the rest (53.28%) was unsaturated fatty acids, which the majority of them was oleic acid (39.67%). According to the results of analysis of variance, the composition and kind of the fatty acids before and after the deodorization were close together and the amount of fatty acids changed slightly during the deodorization. Finally, the optimized conditions at the temperature of 162 °C, the time of 110 min and the ultrasonic power of 165 W were determined using electronic nose and sensory evaluation for ultrasound-assisted deodorization of sheep tail oil.
Volume 17, Issue 102 (August 2020)
Abstract
In the present study, an infrared-assisted solar dryer was used to determine the drying kinetics, energy consumption and quality parameters evaluation of Echium amoenum. Experiments were conducted with two levels of drying air flow rate (0.0025 and 0.005 m3s-1) and three levels of IR lamp power (100, 150 and 213 W). Drying time, energy consumption and evaluation of quality properties in different air flow rates and lamp powers were compared to the conventional method (shade drying). Five empirical models were fitted on the experimental data and the goodness of regression models were evaluated using coefficient of determination (R2), root mean square error (RMSE), and Chi square (χ2). Results of drying time in the different experiments showed highly significant differences respect to the conventional method (p-value<0.01). Also results showed that increasing the air flow rate and IR power caused a reduction of 37% and 17% in drying time, respectively. Best empirical model to describe the drying behavior was the Page model. The lowest specific energy consumptions (SEC) was 4.63 MJ kg-1, which was occurred at the air flow rate and IR power of 0.005 m3s-1 and 150 W and the highest SEC was 5.26 MJ kg-1 and occurred at 0.0025 m3s-1 of air flow rate and 213 W of IR lamp, respectively. Finally, the air flow rate of 0.005 m3s-1 and the IR power of 150 W was recommended for Echium amoenum drying in the IR-ASD because of the fair energy consumption and the suitable product color.
Volume 18, Issue 5 (9-2018)
Abstract
To improve solar energy gain by the photovoltaic (PV) modules, a novel double-axis solar tracker was developed in the present study. The proposed system worked based on both active and passive methods of sun tracking using electromotor and gas actuator, respectively. The electromotor oriented the module in the east-west direction based on the principle of the chronology of the sun, and in the north-south direction, the change in the gas pressure, due to the temperature change, activated a pneumatic cylinder to rotate the module. The evaluation tests were carried out at the different modes of tracking (including east-west, north-south and double axis). The results showed that the available solar energy on the PV module increased by 5.03%, 33.75% and 38.78% using the tracker at the north-south, east-west and double axis modes, respectively. This, finally, improved electricity generation of the PV module by 4.82%, 31.43% and 36.25%, respectively. Moreover, employing the tracker system led to an increase in operating temperature of the PV module. Based on the operating temperature of the module with the tracking system, it was proposed for using in the photovoltaic-thermal collectors. The designed system could track the sun trajectory with the accuracies of 0.6% and 8% in the east-west and south-north directions, respectively.
Volume 18, Issue 117 (November 2021)
Abstract
Ultraviolet radiation was used in the present study to process lemon juice. The designed UV system had five UV-C lamps and irradiation was performed based on the distance of the lamps (10, 20, and 30 cm) from the fluid layer and the circulation time (10, 20, and 30 minutes) of lemon juice in the system. Non-irradiated sample was also considered as a control treatment. The control and irradiated samples were filled in dark polyethylene bottles and stored at ambient temperature for 90 days. Immediately after irradiation and during the storage period, parameters such as pH, titratable acidity, total soluble solids, ascorbic acid content, color indices (L*, a*, and b*), browning index, as well as sensory attributes were evaluated. The pH, acidity, and total soluble solids did not show a definite trend. The results showed that among the color indices, L* decreased significantly, but a* and b* increased significantly during the storage period. The rate of color changes in irradiated samples from a distance of 10 cm was higher than other treatments. Irradiation also significantly reduced the ascorbic acid content of irradiated samples from a distance of 10 cm compared to other samples and control. However, the browning of irradiated samples from 10 cm distance was significantly less than that of irradiated samples from 20 and 30 cm distance. The score of the panelists indicated that irradiation and storage time altered the quality characteristics of lemon juice. The panelistschr('39') scores showed more acceptance of irradiated samples from 20 and 30 cm distance compared to irradiated samples from 10 cm distance. In general, the designed system in this study is not recommended for lemon juice processing due to the destructive effect of UV-C radiation on the content of ascorbic acid.
Volume 19, Issue 6 (11-2017)
Abstract
In hot air dryers, only a small percentage of the provided thermal energy is used for the drying process, while a large fraction is lost via the exhaust air. To recycle waste heat from the exhaust air, the present study aimed to develop a solar dryer equipped with a novel heat recovery system. The designed dryer comprised of a solar air collector, a drying chamber, an internal closed-loop air circuit and an open-duct heat recovery system. The evaluation tests were conducted at different allowable relative humidities (RH) and mass flow rates of the recirculating air. The results indicated that the best solar fraction was at the highest RH and air flow rate. Increasing the RH from 7 to 17% caused a reduction of 51% in electricity consumption. Furthermore, electrical energy needed for drying increased by 24% with raising the air flow rate from 0.008 to 0.016 kg s-1. A minimum specific energy consumption of 7.54 MJ kg-1 was observed at the highest RH and the lowest air flow rate. At a constant RH, reduction of the air flow rate led to an increasing trend in lightness and decreasing trends in browning index of the products. Moreover, increasing the RH from 7 to 17% increased lightness and decreased browning index. In general, it can be stated that the best colour quality was achieved when the minimum air flow rate and the maximum RH were used for the solar drying.
