Agricultural systems engineering (greenhouse, fish farming, mushroom production)
S. Noroozi; A. Maleki; Sh. Besharati
Abstract
IntroductionSolar energy is one of the most important sources of renewable energy, and it is used to address problems related to energy needs, including increasing fossil fuels, rising energy transportation costs, higher energy demand worldwide, and greenhouse gas emissions. Solar collectors harness ...
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IntroductionSolar energy is one of the most important sources of renewable energy, and it is used to address problems related to energy needs, including increasing fossil fuels, rising energy transportation costs, higher energy demand worldwide, and greenhouse gas emissions. Solar collectors harness the sun's thermal energy to convert it into useful and usable energy. Solar collectors are divided into several types, including parabolic trough collectors (PTCs), linear Fresnel reflectors (LFRs), solar plates, and central towers. Among these, the most common heat generation systems are linear adsorption technologies. In this study, we examine the use of LFR technology for greenhouse heating during the winter in Shahrekord.Materials and Methods Previous studies (Huang et al., 2014) were used for optical analysis. The Daneshyar model was utilized to calculate the amount of solar energy available at a particular location. Mathematical formulas were employed to calculate the instantaneous energy equilibrium, and a heat transfer resistance model was developed to calculate the heat loss of different parts of the collector. To create a model, the total amount of exergy must first be calculated, which can be done by using the Petlla formula given by Bellos et al. (2019).Results and DiscussionThe following results were obtained from this study:The proposed mathematical model for calculating solar energy was accurate in terms of daily and instantaneous performance. This model was valid for both clear and cloudy days, making it applicable in a variety of weather conditions.The maximum useful heat production of the current system for February was about 2.5 kW, resulting in an increased liquid temperature of 16 degrees Celsius in the heat tank.The maximum thermal efficiency of the Fresnel collector during the day was 64%, while the average daily efficiency was 56.4%.The most significant parameters that affected the production of useful energy were the position of the sun during the day and the number of cloudy days.The system was capable of heating stored water to 98 degrees per day, available for up to 14 hours.The system under consideration can be used to produce heat up to 1260 watts for 15 hours without heating the tank. The generated heat can be utilized in the food industry for steam production and industrial desalination of water.The decrease in exergy efficiency was due to the reduction in the thermal efficiency of the system and the increase in the thermal difference between the collector and ambient temperatures. Higher values can be achieved by reducing the heat losses, which is a reason to reduce the exergy efficiency of the system.Conclusion This paper investigated the daily performance of a linear Fresnel collector with an 18 square meter mirror field, a parabolic collector, and an insulated storage tank with a volume of 250 liters. The investigation included experimental analysis and theoretical formulation of thermal phenomena under the weather conditions of Shahrekord. The mathematical model developed for this system is based on the energy balance in the collector and storage tank. The results show that this is an efficient greenhouse heating system, with an average thermal efficiency of 56%, which is reasonable and competitive with other similar technologies. Additionally, the cost of construction and maintenance of this system is much lower than that of competitors.
Design and Construction
M. A. Ebrahimi-Nik; A. Rohani
Abstract
Introduction More than 40 percent of the world population is now dependent on biomass as their main source of energy for cooking. In Iran, the lack of access roads and inefficient transportation structure have made some societies to adopt biomass as the main energy source for cooking. In such societies, ...
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Introduction More than 40 percent of the world population is now dependent on biomass as their main source of energy for cooking. In Iran, the lack of access roads and inefficient transportation structure have made some societies to adopt biomass as the main energy source for cooking. In such societies, inefficient traditional three-wall cook stoves (TCS) are the sole method of cooking with biomass, which corresponds to the large fuel consumption and smoke emission. Biomass gasifier cook stoves have been on the focus of many studies as a solution for such regions. In these stoves, biomass is pyrolized with the supply of primary air. The pyrolysis vapors are then mixed with secondary air in a combustion chamber where a clean flame forms. In this study, a biomass cook stove was manufactured and its performance was evaluated feeding with three kind of biomass wastes (e.g. almond shell, wood chips, and corn cob). Materials and Methods A natural draft semi-gasifier stove was manufactured based on the stove proposed by (Anderson et al., 2007). It had two concentric metal cylinders with two sets of primary and secondary air inlet holes. It had 305 mm height and 200 mm diameter. The stove was fed by wood chips, almond shell, and corn cob. Thermal performance of the stove was evaluated based on the standard for water boiling test. It consisted of three phases of cold start, hot start, and simmering. Time to boil, burning rate, and fire power was measured in minute. A “K” type thermocouple was used to measure the water temperature. Emission of carbon monoxide from the stove was measured in three situations (e.g. open area, kitchen without hood, and kitchen under hood) using CO meter (CO110, Thaiwan). Results and Discussion Neither particulate matter nor smoke was visually observed during the stove operation except at the final seconds when the stove was going to run out of fuel. The flame color was yellow and partly blue. The average time to boil was 15 min; not significantly longer than that of the LPG stove (13 min). Time to boil in hot phase was almost the same for all fuels which is not in line with the studies reported by (Kshirsagar and Kalamkar, 2014; Ochieng et al., 2013; Parmigiani et al., 2014). This is probably due to the stove body material. In fact, the hot phase test, aims to show the effect of the stove body temperature on the performance. In contrast with the most of the stoves, the one was used in the present study was made of a thin (0.3 mm) iron sheet which has a high heat transfer and low heat capacity. This results in a rapid increase in the stove body temperature up to its highest possible. The longest flaming duration (51 min) was observed by 350 g almond shell. Thermal efficiency on the other hand, was different in using different biomass fuels. The average thermal efficiency of 40.8 was achieved by the stove which is almost three times of open fire. The results from emission test showed that the average of carbon monoxide surrounding the operator in the case of open area, kitchen without hood, kitchen under hood, and traditional open fire were 4.7, 7.5, 5.2, and 430 ppm, respectively. Conclusion The amount of carbon monoxide emitted to the room is in accordance with the US National ambient air quality standards (NAAQS) hence, compared with traditional methods of cooking in deprived regions, the stove burns cleaner with higher efficiency. In order to prohibit respiratory decreases in housekeeping women, this stove could be disseminated in some deprived regions of Iran.
B. Sabahi; M. J. Sheikhdavoodi; H. Bahrami; D. Baveli Bahmaei
Abstract
Introduction: Today, all kinds of vehicle engines work with fossil fuels. The limited fossil fuel resources and the negative effects of their consumption on the environment have led researchers to focus on clean, renewable and sustainable energy systems. In all of the fuels being considered as an alternativefor ...
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Introduction: Today, all kinds of vehicle engines work with fossil fuels. The limited fossil fuel resources and the negative effects of their consumption on the environment have led researchers to focus on clean, renewable and sustainable energy systems. In all of the fuels being considered as an alternativefor gasoline, methanol is one of the more promising ones and it has experienced major research and development. Methanol can be obtained from many sources, both fossil and renewable; these include coal, natural gas, food industry and municipal waste, wood and agricultural waste. In this study, the effect of using methanol–unleaded gasoline blends on engine performance characteristics has been experimentally investigated. The main objective of the study was to determine engine performance parameters using unleaded gasoline and methanol-unleaded gasoline blends at various engine speeds and loads, and finally achieving an optimal blend of unleaded gasoline and methanol.
Materials and Methods: The experimental apparatus consists of an engine test bed with a hydraulic dynamometer which is coupled with a four cylinder, four-stroke, spark ignition engine that is equipped with the carbureted fuel system. The engine has a cylinder bore of 81.5 mm, a stroke of 82.5 mm, and a compression ratio of 7.5:1 with maximum power output of 41.8 kW. The engine speed was monitored continuously by a tachometer, and the engine torque was measured with a hydraulic dynamometer. Fuel consumption was measured by using a calibrated burette (50cc) and a stopwatch with an accuracy of 0.01s. In all tests, the cooling water temperature was kept at 82±3˚C. The test room temperature was kept at 29±3˚C during performing the tests. The experiments were performed with three replications. The factors in the experiments were four methanol- unleaded gasoline blends (M0, M10, M20 and M30) and six engine speeds (2000, 2500. 3000, 3500, 4000 and 4500 rpm). Methanol with a purity of 99.9% was used in the blends. All experiments were performed at 50% open throttle. Engine performance characteristics for fuel blends were compared with unleaded gasoline.
Results and Discussion: The experimental results showed that adding methanol to unleaded gasoline increased brake torque and brake power in the M10 and decreased in the M30 compared to merely usingpure gasoline. Engine behavior when using M20 blend was similar to that of using pure gasoline (M0). The brake power and torque at engine speeds 2500, 3000, 3500 and 4000 rpm for M10 were increased by 5.42%, 7.76%, 14.89% and 16.78% compared to when these parameter relate to pure gasoline (M0), respectively, whereas the brake power and brake torque for M30 blend at engine speeds 2000, 2500, 3000, 3500, 4000 and 4500 rpm compared to when using pure gasoline was decreased by 6.91%, 8.1%, 6.23%, 5.29%, 4.59% and 14.27%, respectively.
The experimental results showed that brake specific fuel consumption for M30 blend was increased at all engine speeds. The increase in specific fuel consumption values for this blend from 2000 - 4500 rpm were 17.78%, 16.38%, 13.06%, 10.99%, 14% and 19.11%, respectively. Also, the specific fuel consumption for the M20 was similar to the specific fuel consumption of pure gasoline. Comparing the brake specific fuel consumption of M10 to M0 fuel at 2500, 3000, 3500, 4000 and 4500 rpm this parameter was decreased by 1.9%, 6.03%, 8.91%, 13.85% and 5.55%, respectively.
As the methanol content in the fuel blends increases, brake thermal efficiency also increases at all engine speeds and in all used fuels blends. The thermal efficiency at 2000, 2500, 3000, 3500, 4000 and 4500 rpm using M10 was increased by 3.73%, 8.12%, 12.43%, 15.57%, 22.34% and 12.01%, respectively in comparison to pure gasoline. These values for M20 were 4.14%, 7.82%, 10.12%, 13.37%, 18.94% and 13%, and for M30 were 2.69%, 3.89%, 6.35%, 8.01%, 5.12% and 0.78%.
Conclusions: From the results of the study, the following conclusions can be deduced:
1- Using methanol as a fuel additive to unleaded gasoline causes an improvement in engine performance.
2- The largest increment in engine torque and brake power compared with M0 showed about 16.78% with M10 at 4000 rpm.
3- Minimum brake specific fuel consumption was obtained at 4000rpm with M10 fuel.
4- Thermal efficiency increased compared to the pure gasoline usage at all engine speeds and in all used fuel blends. The largest increment in brake thermal efficiency compared with M0 showed 22.34% with M20 at 4000 rpm.
5- The 10 vol. % methanol in fuel blend gave the best results for all measured parameters at all engine speeds.
