Design and Construction
A. Rezahosseini; K. Jafari Naeimi; H. Mortezapour
Abstract
Introduction Harvesting is one of the most difficult steps in cabbage production that is usually a costly intensive operation. Cabbage harvesting is often done by human labors in Iran. According to customs administration’s statistics, more than 54000 tons of cabbages have been exported from Iran ...
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Introduction Harvesting is one of the most difficult steps in cabbage production that is usually a costly intensive operation. Cabbage harvesting is often done by human labors in Iran. According to customs administration’s statistics, more than 54000 tons of cabbages have been exported from Iran in 2015. Development of cabbage harvesting industry is necessary, because of the large cultivation area and the short available harvesting time. So far, a few studies have been done on cabbage mechanized harvesting in Iran. The harvesting machines can reduce harvesting time to one-eighth in comparison with manual harvesting. Design and manufacturing of a harvester unit suitable for small cabbage farms in Iran were conducted in the present study. So the paper was aimed to investigate the performance of the harvester at the different forward velocities, attack angles and distances between the plants. Materials and Methods The proposed machine consists of two major units; the soil looser and the unit for pulling out, crops from the soil. In this machine, the blades loose the soil around the cabbage root after penetrating into the soil. Next, cabbage is pulled out from the soil by puller belts. The belts move contrary to forward speed direction and take crop to the backward of the machine. Mechanical and physical properties of the cabbages should be measured, because the harvester is directly in touch with the crop. These properties are firstly measured and then selection of the different components and machine manufacturing are done. Two narrow legs (tillage tools) equipped with one-side blade with attack angles of 20 and 25 degrees are used for losing the soil around the cabbage’s root. The force exerted on the blade was 5.47 kN. Finally, the harvesting force is estimated to be 164.8 N by using mechanical and physical properties of the cabbages. Experiments were conducted at the different forward velocity levels (2, 3.5 and 5 km h-1), attack angle of the blades at three levels (20, 25 and 30 degree) and the distance between the crops in two levels (40 and 60 cm) in a completely randomized design with three replications. Results and Discussion The analysis of variance of the effect of different parameters on the harvested crop numbers showed, that the effects of forward velocity and attack angle on the number of harvested crops were significant in 5 percent probability. But distance between crops did not have significant effect on the number of harvested crops. Also the effects of interaction between forward velocity and attack angle, forward velocity and distance between crops, attack angle and distance between crops on the number of harvested crops were significant in 5 percent probability. According to the results, the number of harvested crops and machine performance were decreased by increasing forward velocity. Moreover, designed machine had the best performance (80 percent) at an attack angle of 25 degrees and forward velocity of 2 km h-1. Conclusion The results showed, with increasing the forward speed from 2 to 5 km h-1 the harvest success decreased by 20 to 25 percent. Also, the harvesting quality did not change at the different distances between the plants. The highest machine capacity was more than 5300 plants per hour, which was observed at the forward velocity of 3.5 km h-1 and the attack angle of 25 degrees.
Design and Construction
M. A. Zamani Dehyaghoubi; K. Jafari Naeimi; M. Shamsi; H. Maghsoudi
Abstract
Introduction It is common to use rod weeders for onion harvesting according to their prevention of root blocking in front of the machine and separation of onion bulbs from soil by shaking. Chesson et al., (1977), used a rod weeder for manufacturing an onion harvester. This machine had a rectangular rotor ...
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Introduction It is common to use rod weeders for onion harvesting according to their prevention of root blocking in front of the machine and separation of onion bulbs from soil by shaking. Chesson et al., (1977), used a rod weeder for manufacturing an onion harvester. This machine had a rectangular rotor axis with 25mm×25mm cross section. The rotor power was provided by a hydro-motor. An investigation into onion losses during the harvesting operation showed that the majority of crop damages have been occurred due to the collision of rods with onion bulbs. Therefore, the objective of this study is to design and evaluate an onion harvester based on rod weeders with the capability of crop harvesting with minimum damage. Materials and Methods The main components of the examined onion harvester are chassis, furrower, and power transmission system and excrescence axes. Rectangular 100mm×100mm and 40mm×80mm profiles with 4mm profile thickness are used to fabricate the chassis. The furrowers were installed on each side of the chassis as the first parts of the harvester that comes into contact with the soil. Power transmission system provided rotation of two axes from both sides of the machine due to the lack of space for working of two chains on the one side. Therefore, a gearbox having one input shaft and two output shafts was selected for the machine. The gearbox output shafts turn the rotors with a reduction ratio of 1 to 3.5. The rotary motion of the excrescence axes cuts and moves the soil located under the onions bulbs upward and finally the onion bulbs are placed on the soil surface. Therefore, excrescence axes can be considered as the main part of the onion harvester. The excrescence shape of the axes were created by star wheels. Star wheels had a hole with a square section in center (30mm×30mm), for installing them on their shaft. Choosing this kind of the connection, dose not let star wheels to move freely. Also to limit the lateral movement of the star wheels on axis, metallic spacers were used between the adjacent pairs of them. To evaluate the machine performance three variable factors were defined: working depth (20 and 26 cm), forward speed (3, 4.5 and 6 km h-1) and rotational speed of the excrescence axes (150, 220 and 290 rpm). The conducted experiments were analyzed in a complete randomized design with three replications. Results and Discussion The analysis of variance showed that the working depth and forward velocity of axis had significant effect (in 5% level) on the success rate of onion harvester. Also the interaction between depth and forward velocity and the interaction between rotational speed of axes and forward speed were significant. The interaction between depth and rotational speed of axes and the interaction between depth, rotational speed of axes and forward speed were not significant. Evaluation of the interaction between depth and forward velocity showed that the most success rate of onion harvesting was in 20 cm depth and forward velocity equal to 3 and 4.5 km h-1. The least success was gained in 26 cm depth with 4.5 and 6 km h-1 forward speed. Evaluation of the interaction between rotational speed of axes and forward speed showed that the most success in the onion harvesting was occurred with a machine having 3 km h-1 forward velocity and 150 rpm rotational speed and also 4.5 km h-1 forward velocity and 220 rpm rotational speed. Conclusion The success rate of the onion harvesting decreased by increasing the working depth of the machine and axes distance to the onion bulbs. Also with excessive forward velocity the success rate of onion harvesting decreased because of difficulties in controlling the tractor guidance in straight line. The best performance of this onion harvesting machine was in 20 cm depth, 4.5 km h-1 forward velocity and 220 rpm axes rotational speed. Adjusting the machine working parameters according to these values, the ratio of the linear speed of the star wheel tips to the forward velocity of the machine (kinematic index) was equal to 0.82.
M. Jafari; H. Mortezapour; K. Jafari Naeimi; M. Maharlooei
Abstract
Introduction Greenhouses provide a suitable environment in which all the parameters required for growing the plants can be controlled throughout the year. Greenhouse heating is one of the most important issues in productivity of a greenhouse. In many countries, heating costs in the greenhouses are very ...
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Introduction Greenhouses provide a suitable environment in which all the parameters required for growing the plants can be controlled throughout the year. Greenhouse heating is one of the most important issues in productivity of a greenhouse. In many countries, heating costs in the greenhouses are very high, having almost 60-80% of the total production costs. In recent years, several studies have attempted to reduce the heating costs of the greenhouses by applying more energy efficient equipment and using the renewable energy sources as alternatives or supplementary to the fossil fuels. In the present study a novel solar greenhouse heating system equipped with a parabolic trough solar concentrator (PTC) and a flat-plate solar collector has been developed. Therefore, the aim of this paper is to investigate the performance of the proposed heating system at different working conditions. Materials and Methods The presented solar greenhouse heating system was comprised of a parabolic trough solar concentrator (PTC), a heat storage tank, a pump and a flat plate solar collector. The PTC was constructed from a polished stainless steel sheet (as the reflector) and a vacuum tube receiver. The PTC was connected to the tank by using insulated tubes and a water pump was utilized to circulate the working fluid trough the PTC and the heat exchanger installed between walls of the tank. The uncovered solar collector was located inside the greenhouse. During the sunshine time, a fraction of the total solar radiation received inside the greenhouse is absorbed by the solar collector. This rises the temperature of the working fluid inside the collector which led to density reduction and natural flow of the fluid. In other words, the collector works as a natural flow flat plate solar collector during the sunshine time. At night, when the greenhouse temperature is lower than tank temperature, the fluid flows in a reverse direction through the solar collector and the stored heat transferred from the collector surface to the greenhouse. The evaluation tests were conducted at three levels of fluid flow rate through the solar concentrator (0.44, 0.75 and 1.5 Lmin-1) and two different working modes of the heat exchanger. Results and Discussion The variation of thermal efficiency of the PTC at different flow rates has been illustrated in Fig 3. As shown, thermal efficiency increased with flow rate mainly because the fluid convection coefficient enhances with raising the velocity of the fluid inside the tubes. The heat storing process began from 9 am and the highest amounts of the stored heat during sunshine time occurred between 10 am and 2 pm. Fig 5 showed that the stored energy in the tank enhanced when the flat plate collector was employed beside the PTC. Also, increasing the fluid flow rate from 0.44 to 1.5 Lmin-1 improved the index of stored heat by 32.14%. Energy consumption during the night time was also significantly changed with flow rate and the mode of heating. Fig 7 indicated that the electrical energy consumption was lower with flat plate solar collector and it is possible to save the electrical energy by 26.67% using the flat plate collector. Bouadila et al., (2014) concluded that the electrical energy consumption reduced by 31% employing a natural convection flat plate solar collector system equipped with phase changed heat storage material for greenhouse heating. Since increasing the flow rate enhanced the thermal efficiency of the solar concentrator system and led to an improvement in stored thermal energy during the sunshine time, solar fraction increased with raising the flow rate from 0.44 to 1.5 Lmin-1. A maximum solar fraction of 66% was achieved at the highest flow rate when using the flat plate solar collector beside the PTC. Conclusion An experimental comparative study was conducted to investigate the performance of a novel solar greenhouse heating system at the different fluid flow rates and two modes of heating (with and without flat plat solar collector). The results can be summarized as follows: A maximum thermal efficiency of about 71% was achieved at the flow rate of 1.5 Lmin-1. Raising the flow rate from 0.44 to 1.5 Lmin-1 improved the index of stored heat and solar fraction by 32.14% and 21%, respectively. The highest value of solar fraction was found to be 66% at the highest flow rate when engaging the flat plate solar collector beside the PTC.
N. Gholamrezaei; K. Qaderi; K. Jafari Naeimi
Abstract
Introduction Energy consumption management is one of the most important issues in poultry halls management. Considering the situation of poultry as one of the largest and most developed industries, it is needed to control growing condition based on world standards. The neural networks as one of the intelligent ...
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Introduction Energy consumption management is one of the most important issues in poultry halls management. Considering the situation of poultry as one of the largest and most developed industries, it is needed to control growing condition based on world standards. The neural networks as one of the intelligent methods are applied in a lot of fields such as classification, pattern recognition, prediction and modeling of processes. To detect and classify several agricultural crops, a research was conducted based on texture and color feature. The highest classification accuracy for vegetables, grains and fruits with using artificial neural network were 80%, 86% and 70%. In this research, the ability to Multilayer Perceptron (MLP) Neural Network in predicting energy consumption, temperature and humidity in different coordinate placement of electronic control unit sensors in the poultry house environment was examined. Materials and Methods The experiments were conducted in a poultry unit (3000 pieces) that is located in Fars province, Marvdasht city, Ramjerd town, with dimensions of 32 meters long, 7 meters wide and 2.2 meters height. To determine the appropriate placement of the sensor, 60 different points in terms of length, width and height in poultry were selected. Initially, the data was divided into two datasets. 80 percent of total data as a training set and 20 percent of total data as a test set. From180 observations, 144 data were used to train network and 36 data were used to test the process. There are several criteria for evaluating predictive models that they are mainly based according to the difference between the predicted outputs and actual outputs. To evaluate the performance of the model, two statistical indexes, mean squared error (MSE) and the coefficient of determination (R²) were used. Results and Discussions In this study, to train artificial neural network for predicting the temperature, humidity and energy consumption, the trainlm algorithm (Levenberg-Marquardt) was used. To simulate temperature, humidity and energy consumption, networks were trained with two and three layers, respectively. Network with two layers with10 neurons in the hidden layer and one neuron in the output layer with (R²) equal to 0.96 and (MSE) equal to 0.00912, was given the best result for predicting temperature. For humidity electronic sensors, results showed that network with three layers with the 10 neurons in the first hidden layer, 20 neurons in the second hidden layer and one neuron in the output layer with (R²) equal to 0.8 and (MSE) equal to 0.00783 was the best for predicting humidity. Finally, network with two layers with 10 neurons in the first hidden layer, 10 neurons in the second hidden layer and one neuron in the output layer was selected as the optimal structure for predicting energy consumption. For this topology, (R²) and MSE were determined to 0.98 and 0.00114, respectively. Linear and multivariate regression for the parameters affecting temperature, humidity and energy consumption of electronic sensors was determined by the STATGR software. Correlation coefficients indicated that parameters such as length, height and width of the electronic control sensors placed in the poultry hall justified 82% of the temperature changes, 61% of the humidity changes and 92% of the energy consumption changes. Therefore, comparing with correlation coefficients obtained from the neural network models, the highest correlation coefficient was related to energy parameter and the lowest correlation was linked to humidity parameter. Conclusion The results of the study indicated the high performance for predicting temperature, humidity and energy consumption. The networks hadthree inputs including length, width and height of electronic sensor positions and an output for temperature, humidity and energy consumption. For training networks the multiple layer perceptron (MLP) with error back propagation learning algorithm (BP) was used. Functions activity for all networks in hidden layers were tangentsigmoid and in the output layer, linear (purelin). Comparing the results of artificial neural network and logistic regression model showed that artificial neural network model with correlation coefficients of 0.98 (energy), 0.96 (temperature) and 0.8 (humidity) provided closer data to the actual data compared with regression models with correlation coefficients of 0.92, 0.82 and 0.61 for the energy, temperature and humidity respectively.
M. Mohammadi Sarduei; H. Mortezapour; K. Jafari Naeimi
Abstract
Introduction Electrical performance of solar cells decreases with increasing cell temperature, basically because of growth of the internal charge carrier recombination rates, caused by increased carrier concentrations. Hybrid Photovoltaic/thermal (PVT) systems produce electrical and thermal energy simultaneously. ...
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Introduction Electrical performance of solar cells decreases with increasing cell temperature, basically because of growth of the internal charge carrier recombination rates, caused by increased carrier concentrations. Hybrid Photovoltaic/thermal (PVT) systems produce electrical and thermal energy simultaneously. PVT solar collectors convert the heat generated in the solar cells to low temperature useful heat energy and so they provide a lower working temperature for solar cells which subsequently leads to a higher electrical efficiency. Recently, in Iran, the reforming government policy in subsidy and increasing fossil fuels price led to growing an interest in use of renewable energies for residual and industrial applications. In spite of this, the PV power generator investment is not economically feasible, so far. Hybrid PVT devices are well known as an alternative method to improve energy performance and therefore economic feasibility of the conventional PV systems. The aim of this study is to investigate the performance of a PVT solar water heater in four different cities of Iran using TRNSYS program. Materials and Methods The designed PVT solar water system consists of two separate water flow circuits namely closed cycle and open circuit. The closed cycle circuit was comprised of a solar PVT collector (with nominal power of 880 W and area of 5.6 m2), a heat exchanger in the tank (with volume of 300 L), a pump and connecting pipes. The water stream in the collector absorbs the heat accumulated in the solar cells and delivers it to the water in the tank though the heat exchanger. An on/off controller system was used to activate the pump when the collector outlet temperature was higher than that of the tank in the closed cycle circuit. The water in the open circuit, comes from city water at low temperature, enters in the lower part of the storage tank where the heat transfer occurs between the two separate circuits. An auxiliary heater, connected to the tank outlet, rises the fluid temperature to the set point. The performance of the designed system has been investigated in different cities (including Tabriz, Tehran, Kerman and Bandar-Abbas) during 4 seasons of year using Transient System Simulation (TRNSYS) program. The performance parameters included electrical and thermal energy generation and solar fraction. Solar fraction, which expresses the share of energy supplied by solar radiation on the collector in total thermal energy consumption, was obtained from equation 1. Results and Discussion The results showed that the average daily electricity generation in the cities for summer and winter were 4.65 and 2.67 kWh day-1, respectively. The annual electricity generation of the designed system is almost constant in the various cities. In winter, in spite of lower solar intensity and sunny hours, lower average temperature of solar cells in Kerman leads to a slightly better electrical performance than Bandar-Abbas. The highest cell temperatures, in Bandar-Abbas between 12 noon and 1pm, were found to be 33, 37, 31 and 25 oC in spring, summer, autumn and winter, respectively. Thermal energy generation was significantly different at various cities and seasons. In winter, the designed system provides a little fraction (below 10 percent) of thermal demands in Tabriz and Tehran. This is mainly because of the low ambient temperature and solar intensity. The PVT system had a maximum average thermal energy of 16 kWh day-1 and solar fraction of 0.5 which were observed in Bandar-Abbas. Tabriz, because of the lowest ambient temperature, had the least thermal energy generation and solar fraction. The maximum average solar fraction obtained in summer was about 60% while its lowest value in winter was 24%. Conclusion In the present study, a hybrid PVT solar water heater with nominal power of 880 W was proposed for application in Iran. The system was comprised of a PVT solar water collector, an auxiliary heater, a pump and connecting tubes. Technical feasibility of applying the proposed system in different cities was investigated using TRNSYS program. The results are summarized as follows: The annual electricity generation of the designed system was almost constant in the various cities. The highest and lowest values of average electricity generation in summer and winter were determined to be 4.65 and 2.67 kWh day-1, respectively. The PVT system had the maximum average thermal energy of 16 kWh day-1 and solar fraction of 50%, which was observed in Bandar-Abbas.
M. Naghipour Zade Mahani; K. Jafari Naeimi; M. Shamsi; Gh. Mohamadi Nejad
Abstract
Due to the importance of weed control and the limitations of mechanical methods in some places, in this research the water jet cutting for weed control was investigated. The cutting tests were performed on camel thorn weed in Shahid Bahonar university of Kerman. The water jet pressure of 90 bars was ...
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Due to the importance of weed control and the limitations of mechanical methods in some places, in this research the water jet cutting for weed control was investigated. The cutting tests were performed on camel thorn weed in Shahid Bahonar university of Kerman. The water jet pressure of 90 bars was achieved with the aid of a suitable pump. The cutting time was studied in a completely randomized factorial design experiment (CRD) with five replications. Factors of experiments are: stem diameter in 2 levels (smaller and larger than 5 mm), distance of spraying jet from weeds in 3 levels (10, 20 and 30 cm) and two types of plant holders: blade and plate. The results showed that stem diameter and jet distance from the weed stem had significant effects on cutting time (at the 1%). The mean comparison of parameters showed that with increase of stem diameter the cutting time increased and any increase in jet distance from the weeds decreased the cutting time linearly with R2=0.96 and R2=0.99 for small and large diameter weeds, respectively. The minimum cutting time was measured at 30 cm of the jet from small diameter of stems. A multivariate linear regression model was also proposed for cutting weed parameters. It can be concluded that due to the flexibility of water jet cutting for restricted places, hydrodynamic control of weeds is proposed as a complementary method and sometimes a competing substitute method.
