Food Engineering
Mohaddese Ahmadi; Hadi Samimi Akhijahani; Payman Salami
Abstract
IntroductionSolar energy is one of the sources of renewable energy that can be used in both buildings, industry and agriculture in the form of heat or electrical energy. According to previous researches, energy consumption in the world is doubling every 20 years. However, the use of renewable energy ...
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IntroductionSolar energy is one of the sources of renewable energy that can be used in both buildings, industry and agriculture in the form of heat or electrical energy. According to previous researches, energy consumption in the world is doubling every 20 years. However, the use of renewable energy is still less than fossil fuels, which has caused environmental problems in the world. In recent decades, the tendency to use renewable energy, especially solar energy, has increased. A significant portion of the world's energy (about 30%) is spent on agriculture, and about 3.62% is used to dry agricultural products (Iranmanesh et al, 2020). However, thermal and drying efficiency of the solar collectors are not in acceptable range. Applying different ways to improve the performance of solar dryers such as using thermal energy storage system, air recirculation mechanism and using dessican system. In this paper, phase change materials were placed vertically in consecutive rows at different distances inside the collector and the thermal performance of the collector was investigated. Also, the drying process of Oleaster were evaluated using PCM and air recirculation system. Materials and methodsThe indirect solar dryer used in this study includes the chassis, flat plate collector, electric fan, drying cabinet, pipes containing PCM and sensors. 25 copper tubes containing PCM are placed on the absorber plate with fixed intervals. The insulated cabinet of the dryer has three trays. A 220 volt 60 W electric fan is placed in the inlet of the collector and cuses to flow air inside the system. The process of drying Oleaster in a solar dryer was carried out for 9 consecutive days in August 1401. The drying process was performed at three positions of PCM pipes at 5, 10 and 15 cm intervals with air flow rate of 0.5, 1 and 2 m/s. The drying kinetics of Oleaster was investigated using seven mathematical models considering drying time and related constants. The selected model is selected based on the degree of fit (the highest R2 and the lowest RMSE) on the experimental data. Thermal efficiency was calculated according to ASHRAE standard 2003 (Eltawil et al., 2018). Moreover to determine the drying efficiency the amount of energy required to heat the dryer and the product and extract water from the Oleaster and the total energy (electrical and thermal) input to the dryer was considered. SCE is defined as the energy required to dry one kilogram of the product. Results and discussionThe drying time of the product by dryer is reduced from 2.09 to 4.16% on average by changing the position of PCM from 5 cm to 15 cm. On the other hand, with the increase of air velocity from 0.5 to 2 m/s, the drying time decreased from 8.32% to 16.64%. Henderson and Pabis model was the best model to describe and define the drying process of senjad with solar dryer. The curves of drying rate against the time in different conditions illustrated that in the initial stage of drying of samples. The amount of moisture evaporation is high due to the high water content in Oleaster, and a major part of the drying process took place in this period. The value of SEC for the dryer without PCM was 4.26 MJ/kg, while for the case with PCM, it was 2.04 MJ/kg with a distance of 15 cm. By increasing the distance between the tubes, the drying efficiency increases due to the reduction of drying time and energy consumption. In this case, the consumption of electrical energy by the fan (for fluid flow in the dryer and collector) and the thermal energy input to the dryer are reduced. However, with the increase of air speed from 1 m/s to m/s2, there is a significant reduction in drying efficiency. The highest drying efficiency was 36.72% and the lowest was 25.65% for distance 15 cm, air velocity of 1 m/s and distance 5 cm, air speed 2 m/s, respectively. Drying efficiency was improved by at least 12% using PCM.ConclusionIn this research, the analysis of the thermal process in the solar dryer system in three positions of the tubes containing PCM inside the flat plate collector for the distances of 5, 10 and 15 cm between the tubes at three air velocities of 0.5, 1 and 2 m/s was investigated. Using the return flow system and the phase changing material at the same time improved the thermal efficiency of the flat plate collector by 19.12%.
Food Engineering
Hadi Samimi Akhijahani
Abstract
Introduction: Drying of agricultural products is one of the main ways to prevent product spoilage. There are several methods to dry agricultural products, including direct sunlight, hot, sunny weather, microwave, vacuum, and freezer which use different energy sources. Due to constrain of fossil ...
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Introduction: Drying of agricultural products is one of the main ways to prevent product spoilage. There are several methods to dry agricultural products, including direct sunlight, hot, sunny weather, microwave, vacuum, and freezer which use different energy sources. Due to constrain of fossil fuels supply, the price of this type of energy is increasing thus the tendency to use renewable energies is increasing (Purohit and Kandapal, 2005; Purohit et al., 2006). In Iran the drying efficiency of solar dryers is low because less solar energy is converted into thermal energy. Therefore, many measures have been taken to increase the efficiency of solar collectors which causes to obtain the dried samples with better quality and lower cost. In this study a combination of tracking system and phase change materials (PCM) are used to increase the efficiency of solar dryer cabinet with three types of collectors including flat plat (FPC), parabolic trough (PTSC) and evacuated tube (ETSC) collectors. Materials and Methods: The dryers used in this study include a cabinet connected to a flat plat, parabolic trough and evacuated tube collectors. In all of the dryers, PCM have been used to maximize solar energy utilization. Moreover to get the maximum solar radiation the tracking system used in FPC and PTSC and a storage tank with fluid pump used in PTSC and ETSC. The air flow rate inside the system was about 0.018 kg.s-1 for all the experiments. The experiments were performed in three continues days from 16 to 18 June 2018, from 8:00 to 24:00. Tomato sample with a thickness of 9 mm was considered for drying process. To describe the drying process of the samples, the moisture ratio versus time was considered. Also, the drying efficiency was defined considering the ratio of energy (thermal and mechanical) consumed to heat the product and extract moisture from the product (Qm) to the total energy used for drying process, including fluid thermal energy (Qf) and mechanical energy (Emec) (Fudholi et al., 2014). In order to evaluate the quality of the dried product at different modes, three quality parameters including color difference, shrinkage and rehydration ratio were considered. Color difference between the fresh and dried samples was evaluated as one of the most important factors that the customer was considered for selection (Magdic et al., 2009). The change in the volume of the dried product compared to the fresh product is defined as shrinkage. Moreover, to evaluate the rehydration ratio the weight of water absorbed by the samples was considered. Results and Discussion: The effect of variations of the intensity of solar radiation on the amount of solar energy taken by the collectors was negligible. The time required to dry tomato slices by the dryer equipped with FPC was longer than the other systems. The results also showed that the highest drying efficiency is related to the dryer with ETSC and it was about 39.02%. The least value is related to the dryer with FPC and it was about 30.12%. Due to the long drying time the use of the fan and the pump increase and the amount of energy consumed to drying the product increases as well. Thus the efficiency of the dryer with FPC decreases. The values of specific energy for the dryer with FPC, PTSC and ETSC were obtained as 7.12, 7.92 and 8.34 MJ/kg, respectively. The results of qualitative evaluation of dried tomato slices showed that the product obtained from the dryer equipped with ETSC, due to the short drying time, the color changes and the shrinkage was suitable in comparison with the other reports. The amount of rehydration ration was the highest as well. Using PCM had no adverse effect on the quality of the dried samples. The results showed that the dryer with ETSC had higher efficiency (about 39.02%) and the quality of the samples was suitable compared to other systems. Using recycling system can improve the thermal efficiency of the solar dryer.
Food Engineering
Mojtaba Afsharipour; Hadi Samimi Akhijahani; Kazem Jafari Naeimi
Abstract
Introduction: The presence of various impurities leads to the problems in storage time, transmission, selling and consumption process of any product. Thus it is necessary to separate the impurities from the product for industrial processing. Descurainia Sophia is a tiny grain seed in light brown color ...
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Introduction: The presence of various impurities leads to the problems in storage time, transmission, selling and consumption process of any product. Thus it is necessary to separate the impurities from the product for industrial processing. Descurainia Sophia is a tiny grain seed in light brown color with elliptical shape and it grown up in humid climate. Electrostatic method is a proper way for separation and purification of materials which is based on the absorption and diffusion of charged particles in an electrical field with high voltage. An experimental research was carried out for recycling the plastic waste with tribo-electric system. The result of the research on plastic separation of waste materials showed that by increasing the voltage of the system the purification fold increases. The results of the effect of the applied voltage for recycling the plastic particles showed that by increasing the applied voltage in the electrodes the mass and purity of the polycarbonate (PC) increased and the mass and purity of polyamide (PA) decreased. There is a little information about separation and purification of fine grain seeds and this study is about separating of Descurainia Sophia seed and the effect of the parameters using regression analysis. Material and Methods: Descurainiaseed samples were collected from the farms located in Mahan city of Kerman province, Iran. Tribo-airo-electrostatic system contains of funnel and feeding container, the charger unit, the separating unit, air transmission channels and gathering unit. Charging unit consists of two aluminum electrode connected to a high voltage DC power supply adjustable between 0-100 kV. A blower was used to suspend material and increase the exposure time of particles in the electric field. The gathering is a box with different partitions divided by wooden sheets. Separated particles fall in the gaps based on the amounts of charges, weight and shape. The separating process takes place by considering physical properties. There are two important forces that acts on the falling of the object in electric field; the electric force acts in the horizontal direction, gravitational force acts in the vertical direction. Considering the purity of the separated seeds in the box, only four sections of the box were selected for size and frequency analysis. For obtaining gathered seed impurity, the digital pictures of the gathered samples imported in Matlab6.5 software and were analyzed using Image processing toolbar based on the differences between seed and impurity color. For regression analysis of the parameters voltage in the electrodes, the distance of the electrodes, the angle of the electrode and the mass of the boxes was considered. Laser diffraction method used for determination the size of separated particles and for this purpose FRITSCH Laser Particle Size Analyser -ANALYSETTE 22 NanoTec system was used. Results and discussion: The results illustrated that the Descurainiaseed takes negative charge and moves to the positive electrode and impure particles takes positive charge and moves to the negative electrode. The purity calculations of the experiments showed that the average percentage of box No.1 is more than 98%, box No.2 is between 65%-75%, box No.3 is between 30% to 50% and box No.4 is less than 50%. The values of correlation coefficient of the effective parameters for box No.1 was 90% and this means that 90% of the parameters of equation affected on the weight of the box No.1 for about 90%. By increasing the applied voltage and the angle of the electrodes of the separating unit and decreasing the distance of the electrodes, the purity of box increases. The size analysis of Descurainiaseed showed that the particles with larger dimensions take more negative charge and moves to negative electrode. The results of the study showed that tribo-airo-electrostatic system separated Descurainiaseed from waste particles properly. By considering the optimum value of separating parameters the purification increased by 98%. According to the results it can be stated that this system can be used for separation and purification of small grains such as alfalfa and clover.
Farhad Fatehi; Hadi Samimi Akhijahani
Abstract
Nowadays, in modern agriculture, the combination of image processing techniques and intelligent methods has been used to replace smart machine instead of humans. In this study, an artificial image processing and artificial neural network (ANN) method was used to classify strawberry fruit of Parus variety. ...
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Nowadays, in modern agriculture, the combination of image processing techniques and intelligent methods has been used to replace smart machine instead of humans. In this study, an artificial image processing and artificial neural network (ANN) method was used to classify strawberry fruit of Parus variety. In the first step, the fruit was divided into 6 classes (ANN outputs) by the expert, and 100 samples were randomly collected from each class. In the next step, the images of the samples were captured and three geometric properties with twelve color properties (as ANN inputs) were extracted. Optimum artificial neural network structures considering root mean squared error (RMSE) and correlation coefficient (R2) were investigated to classification process of the strawberry samples. Finally, the perceptron neural network with a structure of 6-18-15 was selected with an average accuracy of 83.83%.
Farhad Fatehi; Asghar Mahmoudi; Adel Hosseinpour; Hadi Samimi Akhijahani
Abstract
Introduction: Strawberry is one of the native and small fruits of moderate regions, which its cultivation has been increased in all over the world including Iran. Due to the abundance of vitamin C and mineral materials, it is very useful for some diseaseses. Lack of the knowledge in production ...
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Introduction: Strawberry is one of the native and small fruits of moderate regions, which its cultivation has been increased in all over the world including Iran. Due to the abundance of vitamin C and mineral materials, it is very useful for some diseaseses. Lack of the knowledge in production management, harvesting, cooling, transportion, storage, marketing and processing equipments and connection between these different parts are the main problems throgh industrial production of strawberry fruit (Salami et al., 2010). According to the various studies, the parameters such as color, shape, size and mass are not sufficient for the consumer to purchase the fruit (Abbot, 1991). They would like to have more information about the fruit which is supposed to be purchased (Voca et al., 2008). Several researchers have been investigated physical and chemical properties of different varieties of strawberry fruit (Wojdylo et al., 2009; Salamat, 2011; Nemzer et al., 2018). According to the litrature, any international standard classification for Parus strawberry (which is mostly cultivated in Iran) based on physical and chemical was not found. In this study, some physical, mechanical and chemical properties of strawberry fruit Parus variety, as well as the relationship between them, were investigated. The classification was performed based on the appearance features including color and size with the opinion of the expert in six classes. Materials and methods: In Kurdistan province strawberry fruit is often grown in open area and cultivated areas of Parus variety due to many reasons are increasing. To classify the strawberries, six classes were considered. Physical and mechanical properties such as dimensions, density, porosity, stiffness and biological yield point were measured at least at five replications. The porosity of the strawberries was also calculated through the division of the difference between actual and apparent density to actual density. Also, the stiffness and biological yield point were measured using Universal Instron Testing Machine (Zwick/Roll). Chemical properties of Parus strawberry including vitamin C, acidity, total soluble solids and flavor index were investigated at five replications. Results and discussions: The analysis of variance showed that all chemical properties including ascorbic acid, acidity, total soluble solids, and flavor index, were strongly influenced by the class. The LSD mean comparison showed that the highest levels of vitamin C were related to the ripe fruits which had a direct relationship with fruit size. The acidity values between the classes varied from 0.55 to 1.08, and the lowest value was related to the first, second and third classes, respectively. The total soluble solid material (TSS) was affected by some factors: sugar (as main part), organic acid and organic pectins and was increased by growing strawberries and increasing the amount of sugar. For the first, second and third classes, TSS was higher than those of the fourth, fifth and sixth clases. The flavor index value for the lower classes (first, second and third) is higher than the higher classes (almost 2 times). The analysis of variance for all physical and mechanical properties indicated that all parameters are affected by the classes. Due to its more soluble materials, the maximum value for actual density was related to the third and second classes, respectively. The apparent density of agricultural products depends on various factors such as geometric shape, size, surface properties, moisture content and measurement method. The apparent density for the first and fourth classes were 561.743 and 498.408 gr.mm-3, respectively. The maximum and minimum value of stiffness was related to first (about 5.2 N.mm-2) and fourth (about 28.2 N.mm-2), respectively. For biological yield the maximumvalue was related to the fourth class, as well. Conclusion: In this study, the classification of strawberry, variety of Parus was investigated based on physical, mechanical and chemical properties. All properties were affected by changing the classes. The results of this research can be used to design and construct post-harvest and sorting mechanisms of agricultural products which require comprehensive information about physical, mechanical, chemical properties.
