جستجوی مقالات مرتبط با کلیدواژه "energy analysis" در نشریات گروه "محیط زیست"

In this research, the energy and exergy analysis of steam power-plant of the ninth refinery of South Pars Complex has been studied. Firstly, according to thermodynamic characteristics, pressure, temperature , flow rate and the type of fluid in terms of saturated water, dense liquid and super heat steam, enthalpy and entropy quantities were calculated and then using energy and exergy balance relationships, the losses and efficiency of various equipments have been calculated. The results of energy analysis showed that Boiler with 62.09 MW, Drum 107 with 17.75 MW and Deaerator with 14.17 MW have the highest energy losses and the efficiency of first law is 41%. Also, based on the results of exergy analysis, boiler with 94 MW, Heat exchanger with 5.297 MW and drum 107 with 5.233  have the highest amount of exergy destruction and the efficiency of second law is 33%. Also, the results showed that due to the use of the steam output from the turbine in other operating units in the studied refinery, the condensers have less exergy destruction and energy losses compared to other power-plants. In addition, by using the solution proposed in this research to heat input air of the combustion chamber through hot water coming out of the Continues Blow Down (CBD), it is possible significantly increase the exergy of the input air.

Using wind energy for hydrogen production in Iran can be important for reasons such as abundant wind resources in Iran, reducing dependence on fossil fuels, ensuring clean energy supply, the potential for hydrogen exports, technology development and job creation. Therefore, this study signifies the first exploration into the potential for generating electricity and producing hydrogen in ten wind-rich cities in Iran. HOMER V.2.81 software was used for simulations, and the wind data used are averaged over a 25-year period. The results show that in Iran, the price range for wind power is $0.515-$0.620 per kWh in the top 10 stations. Bandar Abbas, Parsabad, and Khalkhal had the best economic and environmental performance, respectively. The highest percentage of renewable electricity production is 71% in Bandar Abbas. Finally, the amount of hydrogen produced based on four common electrolyzer types in Iran was investigated. The total annual hydrogen production per ton for SOE, MCE, AE, and PEME electrolysis method at the examined stations is 131.29, 93.43, 40.99, and 30.69, respectively. According to the results, the highest hydrogen production with a value of 16.87 tons per year is related to the Bandar Abbas station and the SOE electrolysis method. The lowest hydrogen production, with a value of 2.36 tons per year, is related to Alvand station and the PEME electrolysis method.

In this paper, the performance of a hybrid humidification-dehumidification (HDH) desalination system is experimentally studied. The system operates as an Open-Air Closed-Water cycle and utilizes a solar air heater to heat the input air to the humidifier. An Ammonia absorption refrigeration cooling cycle is used to condense the humid air, producing fresh water. Parameters such as temperature and relative humidity were measured in different stages of the system by using humidity and temperature sensors, and the thermodynamic analysis was carried out using EES software. The effects of the mass flow rate and temperature of the inlet air flow on the rate of desalination, COP, GOR, and the efficiency of the humidifier and the dehumidifier were studied. The analysis proved that the highest rate of water production and GOR were 150 g/h and 1.2, respectively. It was also perceived that with an increase in the air mass flow rate, the rate of water production and COP increased, while GOR and the efficiency of the dehumidifier diminished. This is while the efficiency of the humidifier remains nearly constant. It was also concluded that an increase in the temperature of the input air, leads to a fall in the GOR, while the other parameters show an increasing trend. Following the economic analysis of the system, the CPL was found to be $0.16 /L.

Nowadays, the world is moving toward using renewable and sustainable energy sources, as much as possible. Photovoltaic (PV) technology is one of the most popular alternatives. PVs are widely used to supply electricity for pumping systems to irrigate the farmlands. It has been proved by many scholars that PV cell temperature is a crucial factor in cell’s efficiency. In this study, a novel arrangement of a PV/pumping system has been considered, in order to enhance the pumping performance. To make it feasible, a small part of the pumped water is directed to a box-type passage at the backside of the PV module, and then connect to the water pipe and drain to the farmland. Two various flow rates of 5 and 10 L/min were tested. The results showed two proposed cases have a bit difference in their outputs. Accordingly, the temperature of modified cases did not pass beyond 36°C while, the temperature of the conventional module reaches to 72°C. This temperature reduction leads to about 50% higher electrical efficiency. From the output power point of view, more than 45% increase was observed. Also, an environment evaluation is performed and it was found that the present improvement can reduce emission of 34.57 tons CO2, annually.

The turbofan engines are one of the constitutes significant components of the aero engines. In this study, the thermodynamic modeling of the TF30-P414 turbofan engine is developed and validated with reference values. The aims of this research are to determine the effect of the changes in the thrust, fuel mass flow rate, and thermal efficiency with changes of the flight-altitude (H) and the flight-Mach number (Ma). Then, the changing of the exergy efficiency and exergy destruction rate were investigated. The results show that between the different components of the engine in different flight circumstances, the highest exergy destruction occurred in the combustion chamber and the lowest exergy destruction occurred in the nozzle. Also, optimization with the objective function of finding optimum flight conditions to find the highest exergetic efficiency in the flight-Mach number of 1.2 to 2.2 and the flight altitude of 10,000 to 15,000 meters. The results of this optimization reported that the maximum exergetic efficiency happened to the conditions of H=11236 meters and Ma=1.944 with an amount of 32.64%.

Photovoltaic (PV) power plant is one of the most important renewable power generation methods, which is rapidly developing. One of the weak points of PV power plants is the negative effects of increasing the cells temperature on their power generation. In this study, a simple and low cost method is proposed to reduce the temperature of these panels. The use of fins has been proven in many industrial applications and here it is used as coolant of PV panel. This experiment was performed in maximum operating temperature of photovoltaic modules which is known as 85°C. By using numbers of aluminum fins on the back surface of photovoltaic panels under two different irradiation, the temperature reduction up to 7.4 °C was observed, and this reduction leads to 2.72 % increasing in efficiency. Finally, an economical assessment of the offered cases based on output power of PV panels carried out, which shows a suitable economic justifiability.