نشریه مهندسی مکانیک تبدیل انرژی
پیاپی 3 (زمستان 1389)

Many chemicals, such as Methanol synthesis reactor productions, are produced under high pressure and  temperature. The reactor operates at 80 (bar) pressure and 250 ( C) temperature. In a conventional process, high exergy in reactor outlet is not used. The high operating   pressure of the reactor outlet can be exploited to produce electricity by integration of a turbo expander. Moreover, increasing in production would be the other result of this method .In this research, simulation has been done by applying HYSYS (Ver. 2006) and the results are in consistent with the outcomes of modeling technique .Economic analysis shows that we can generate about 6.5 ( MW) electricity and return of investment is less than 2 years.

In this report the simulation of energy recovery from waste exhaust of a convention SI engine spark ignition (with a high compression ratio) in other to increase the volumetric efficiency and thermal efficiency is presented. Action to achieve the above goal a power turbine can be used to restrain waste exhaust gases power and transmitted this power to the compressor of car air conditioning system  by a planetary gear box and this combination of them named Turbo-cooler. Using the Turbo-cooler, volumetric efficiency of operation and finally the engine thermal efficiency will increase. In the simulation of combustion processes, combustion of the actual model is simulated by Woshni approximation model and through the successive approximation method. In this study all the thermodynamic properties of air, fuel type, duration and ignition spark timing, cylinder temperature and the heat transfer and etc, were considered. Also mechanical properties of lubrications, piston skirt  and rings friction take in to account  here.

In industrial processes, there are many processes that operate below ambient temperature. Usually when these processes demand refrigeration over a very wide temperature range, cascade refrigeration systems are employed. Unfortunately, the cascade refrigeration systems are capital intensive because of major use of installed equipment and large energy requirement in operations. Therefore, the continuing development of new methods to reduce net power and capital costs of refrigeration systems is important in the design of low temperature processes. A recent advancement has been the introduction of mixtures as refrigerants in place of pure refrigerants. In mixed refrigerant cycles, the composition of the mixture can be selected such that the liquid refrigerant evaporates over a temperature range similar to that of the process cooling demand to provide the desired refrigerant characteristics. Small temperature driving force leads to near-reversible operation, thus better thermodynamic efficiency and lower power requirement. Also, a mixed refrigerant cycles feature simpler machinery configuration and fewer maintenance problems. Due to the lack of comprehensive design method for mixed refrigerant cycle, conventional approaches are largely trial-and-error and therefore operations can be far away from optimal conditions. The difficulty in design mainly stems from two aspects: one is the expensive and highly nonlinear nature of computation and the other is the sensitivity of the cycles to the operating changes, especially the change in the composition of refrigerant mixtures and, the suction and discharge pressures of compressor. In this paper, a novel method for comprehensive design of mixed refrigerant cycles is proposed by combined mathematical programming and thermodynamics approach. This method combines the power of thermodynamics and mathematical programming. While the mathematical programming can satisfactorily give the optimal choice of pressures operating conditions and refrigerant compositions, thermodynamics at the same time gives the user insights and confidence in solution. The procedure is demonstrated using a case study of design of two mixed refrigerant cycles for cold section of olefin plant of Tabriz petrochemical complex.

Measurement difficulties and physical complexities for mathematical modeling’s caused to numerical simulation assumed as the most suitable way to  study flow field and heat transfer in electric arc furnace. Harmful gas from NOx family in electric arc furnace result to acidic rains and fog. Investigations show that NOx production mainly extracted from Zeldowich and thermal mechanisms which formed in the period of slag removal from the furnace. The main reasons for such a phenomena are high temperature and presence of Oxygen and nitrogen in air penetrated to the furnace when the furnace door is opened .The present study includes a 3D modeling of the flow field and heat transfer to simulate electric arc furnace when the door is opened and in period of slag removal.  The air flow is carefully studied In furnace and door type and Nox formation studied where door position and type are changed. Results show that door type is not so important in NOx formation but the best location to reduce NOx content is the place in opposite of outlet elbow for dedusting facility. 

Due to the limited energy resources and the need to save energy, use of solar energy as a strategic approach is extremely important. So in this article by using system to store solar Energy for heating buildings in Laboratory of Islamic Azad university -SemnanBranch. In this approach tried to optimized using of solar energy. In this system, the energy requirements of the building using software «Carrier» during the day and then the solar energy are calculated using mathematical equations. A code written in «MATLAB» for optimum Solar Energy consumption where calculates storage system level thermal load and thermal load of the auxiliary system (boiler) on the day. Utilizing the code, all needed magnitude of geometry as the collector area requirements according to the heat load are provided.

In this paper, the first level of a solid oxide fuel cell combined cycle and gas turbines, heat recovery, are considered as the basic cycle. Since heat recovery from exhaust gas turbine to produce injecting steam into the combustion chamber and also increase the cooling system evaporative inlet air to the inlet air compressor and water injection technology is a known to be efficient, to improve the basic cycle to work have been taken. The electrochemical fuel cell modeling and to identify loss voltages within the fuel cell voltage at different working conditions are achieved. The electrochemical analysis, the thermodynamic modeling however elements of the cycle are discussed. The results of modeling show that the benefits of improved cycle by injection of steam and water cycle of the base shows that has increased 18.95 percent compared to the basic cycle. Finally, cycle performance parameters compared to the three major factors: density, fuel cell, pressure, density and mass flow of fuel carried.

Catholic protection method is most applied in oil and gas industry, in order to prevent corrosion of oil and gas pipes buried into the earth. Catholic  protection based on impress Current consisted of development of a electrolysis system in which Anode and Cathode electrodes are created by direct electric generator, so that there is one or more Anode made of cast iron installed adjacent to a structure, also the structure and anode are be connected to negative and positive electrode of the generator, respectively. In this study, considering the actual data and information of a region soil, mechanical specifications of oil pipeline and its coverage in Ahvaz-city, as well as computational formulas and presented Handbooks regarding to various type of anodes and various types of solar cells and batteries available on the market, it was dealt with the design of solar Catholic  protection devoted to the region. According to the performed calculations, the best type of solar cell is AT50 and the number of panels, voltages, and productive currents are obtained 42, 52.2 V, and 40.04 A, respectively. The suggested batteries were Sealed Lead Acid which the number of them, its voltage and current are 4, 48 V, 250A,respectively

Designing synchronic recovery cycle was very complex due to existence two different recovery cycle power which was related to retrievers boiler. And any change in designing directly was eclipsed power, efficiency, and costs, and many other variables. Researchers always was tied to indicating a way for optimizing properties and different sections (parts) of synchronic recovery cycles, but complete reviewing cycle was less considered due to unique complexities. In this article, we are considered to complete modeling synchronic recovery cycle, indicating the results of energy and exergy analysis, defining appropriate fitness function and then optimizing the model which was indicated by powerful instruments, genetic and PSO algorithms. Also, the accuracy of calculated results was proved by comparing with practical cycle results of BILKENT University. It was necessary to say that in this research, for the first time, has been optimized complete cycle synchronic recovery by genetic algorithm.