Sharif Digital Repository

Application of Cogeneration systems based gas turbine for heat and power production is increasing. Because of finite natural energy resources and increasing energy demand the cost effective design of energy systems is essential. CGAM problem as a cogeneration system is considered here for analyzing. Two new approaches are considered, first in thermodynamic model of gas turbine and cogeneration system considering blade cooling of gas turbine and second using genetic algorithm for optimization. The problem has been optimized from thermodynamic and Thermoeconomic view point. Results show that Turbine Inlet Temperature (TIT) in thermodynamic optimum condition is higher than thermoeconomic one,... 

The aim of this work is to analyze methane-fed internal reforming solid oxide fuel cell-gas turbine (IRSOFC-GT) power generation system based on the first and second law of thermodynamics. Exergy analysis is used to indicate the thermodynamic losses in each unit and to assess the work potentials of the streams of matter and of heat interactions. The system consists of a prereformer, a SOFC stack, a combustor, a turbine, a fuel compressor and air compressor, recuperators and a heat recovery steam generator (HRSG). A parametric study is also performed to evaluate the effect of various parameters such as fuel flow rate, air flow rate, temperature and pressure on system performance. © 2007... 

Combined cycles, at present, have a prominent role in the power generation and advanced combined cycles efficiencies have now reached to 60 percent. Examination of thermodynamic behavior of these cycles is still carried out to determine optimum configuration and optimum design conditions for any cycle arrangement. Actually the performance parameters of these cycles are under the influence of various parameters and therefore the recognition of the optimum conditions is quiet complicated. In this research an extensive thermodynamic model was developed for analyzing major parameters variations on gas turbine performance and different configurations of advanced steam cycles: dual and triple... 

In this work, an exergy analysis is performed for the waste heat recovery section (WHRS) of the steam-natural gas reforming (SNGR) process as a major energy intensive process. Two alternate conditions are investigated to evaluate the required thermodynamic parameters: normal operating condition and increase of C2+ components in the process feed stream. At normal operating condition, the exergy efficiency of WHRS amounts to 0.58 while some 17.2 kJ energy is destructed for each mole of H2 produced. If heavier than methane components are increased in the feed up to 8.5 mole %, despite the increase of H2 production, the exergy efficiency decreases down to 0.54... 

The rising cost of energy and the global warming in recent years have highlighted the need of more advanced systems with higher efficiency and less gas emissions. Consequently, plenty of researches have done on waste heat recovery and renewable sources of energy recently. The target of the present research is feasibility study of heat recovery in automobiles' paint ovens and designing an efficient system to use the lost energy. Research has been carried out on the theory, evaluating the amount of lost and available energy through Thermodynamics and heat transfer principle and choosing applicable design and construction of heat exchanger, especially for their use in ovens for energy recovery,... 

The increment of using fossil fuels has caused many perilous environmental problems such as acid precipitation, global climate change and air pollution. More than 50% of the energy that is used in the world is wasted as heat. Recovering the wasted heat could increase the system efficiency and lead to lower fuel consumption and CO2 production. Organic Rankine cycle (ORC) which is a reliable technology to efficiently convert low and medium temperature heat sources into electricity, has been known as a promising solution to recover the waste heat. There are numerous studies about ORC technology in a wide range of application and condition. The main objective of this paper is to presents a... 

A transcritical carbon dioxide (T-CO2) cycle is analyzed for waste heat recovery from a gas turbine. The cycle is proposed to produce combined power and cooling using carbon dioxide as a single pure working fluid. Simple, cascade and split cycle configurations are compared for power generation using a recuperator while a low-temperature loop is added for the cascade and split cycles. In a previous report in the literature the power generation part alone was presented for the three configurations and it was concluded that the split cycle can produce the highest power among the three systems. Here, the same configurations are studied combined with a compression refrigeration cooling effect... 

In this paper, a conceptual study and quantification of using a thermophotovoltaic system (TPV) to convert incident radiation on furnace panels to electrical energy is presented. In typical electric arc furnaces (EAF), a considerable amount of energy is wasted during the melting process, that is, steel enthalpy, off-gas extraction, vessel cooling, slag enthalpy, and others. Although a remarkable share of the energy is wasted in circulating water, the contained exergy is simply too low to be considered for heat recovery (under 0.5% of input exergy) in comparison to energy content of the extracted gasses and slag. In the performed study, a TPV power output is calculated as a function of arc... 

This paper reports on the application of low-grade sensible waste heat (liquid phase) driven multi-effect distillation (MED) technology to exploit waste heat sources that are generally abundant in the petrochemical industries especially, those located close to the Persian Gulf's coastline. For this purpose, a techno-economic feasibility study by considering local capital and operating costs for a selected petrochemical plant has been conducted. In this study, a sensible waste heat stream (practically at 80 °C in the liquid phase), which is actively cooled by the cooling process of the plant, is considered as the heat source for the proposed desalination process. This process can recover... 

Recovering ventilated air heat in direct expansion (DX) HVAC systems has extensively been researched and many solutions have been introduced until now, such as air-to-air heat recovery ventilator (HRV) units. The ventilated air from building itself or an HRV unit, has heat recovery potentials yet to be exploited, owing to its lower temperature compared with the ambient. On the other hand, the thermal performance of the DX HVAC system's air-cooled condenser deteriorates in hot climates. Therefore, to improve the DX HVAC system and air cooled condenser thermal performance simultaneously, this study proposes and analyzes a novel integrated multistage heat recovery system that first recovers the... 

Wind turbine size has increased to megawatt capacity, and the related technologies and facilities have improved, including the cooling systems. Currently, all of the heat generated by wind turbine components is wasted to the environment. This study presents a conceptual design of a novel method for waste heat recovery of a wind turbine using an organic Rankine cycle (ORC). An organic Rankine cycle is implemented to the wind turbine as a part of the cooling system. The proposed system is thermodynamically modeled to evaluate the amount of recovered energy. Seven working fluids are chosen and investigated in the simulations to estimate the working fluid effect. The results revealed that the... 

The combination of concentrating photovoltaic (CPV) and organic Rankine cycle (ORC) systems not only leads to a reduction of photovoltaic (PV) operating temperature, but also leads to an additional electric power production. Increase in the temperature of the PV decreases its operating efficiency, while increases the ORC efficiency. Therefore, there is an optimum temperature in which the total electricity produced by the combined system will be maximum. In this study, a modified CPV/ORC system is simulated and the optimum operating temperature of the PV panel is determined for different PV efficiencies. The most striking result is that increase in the PV nominal efficiency will result in the... 

Three novel geothermal-based organic Rankine cycle (ORC) systems are proposed to enhance the efficiency and for waste heat recovery purpose. The proposed systems are modeled based on a basic ORC system (concept 1), an ORC system with an internal heat exchanger (concept 2), and a regenerative ORC system (concept 3). Accordingly, two thermoelectric generators (TEG) are introduced into the systems to exploit the waste heat of the system. The condenser is replaced with a TEG unit while the other TEG unit is used to recover the waste heat of the reinjected geothermal fluid. A comprehensive numerical investigation is conducted to compare the proposed systems from the thermodynamic and... 

Three novel geothermal-based organic Rankine cycle (ORC) systems are proposed to enhance the efficiency and for waste heat recovery purpose. The proposed systems are modeled based on a basic ORC system (concept 1), an ORC system with an internal heat exchanger (concept 2), and a regenerative ORC system (concept 3). Accordingly, two thermoelectric generators (TEG) are introduced into the systems to exploit the waste heat of the system. The condenser is replaced with a TEG unit while the other TEG unit is used to recover the waste heat of the reinjected geothermal fluid. A comprehensive numerical investigation is conducted to compare the proposed systems from the thermodynamic and... 

Global warming is currently one of the biggest concerns worldwide; hence, addressing this issue is a trending topic among the research community. Escalating global warming through the wasted energy (30% of its input chemical energy) from internal combustion engines (ICEs) by exhaust emission is a major issue that should be considered. One way to reduce the waste of energy from ICEs is to recover the heat using a thermodynamic cycle. Using this method, not only does the engine power increase but also the fuel consumption decreases. Toward this end, and in this study, the organic Rankine cycle (ORC) and high-temperature Kalina cycle (HTKC), which have been previously used for other purposes,... 

The combination of concentrating photovoltaic (CPV) and organic Rankine cycle (ORC) systems not only leads to a reduction of photovoltaic (PV) operating temperature, but also leads to an additional electric power production. Increase in the temperature of the PV decreases its operating efficiency, while increases the ORC efficiency. Therefore, there is an optimum temperature in which the total electricity produced by the combined system will be maximum. In this study, a modified CPV/ORC system is simulated and the optimum operating temperature of the PV panel is determined for different PV efficiencies. The most striking result is that increase in the PV nominal efficiency will result in the... 

Most of the vehicle pollutants during emission tests are raised from catalyst inefficiency during cold start. Catalysts usually convert harmful emissions only when their temperature reaches around 250 °C to 350 °C. In this research, the vortex tube is implemented to recover the waste heat energy of exhaust gas during the cold start to improve catalyst heating. The experiments are conducted on the turbocharged direct-injection gasoline engine to extract the boundary conditions of numerical simulations. Numerical simulations are performed to evaluate the effects of different hot exhaust mass fractions on the flow regime and waste heat recovery. The results reveal that the level of turbulence... 

This work deals with waste heat recovery from a proposed direct internal reforming molten carbonate fuel cell (DIR-MCFC), including an integrated pre-reformer. In this regard, some advantages are attainable over exhaust gas recycling. For instance, due to low temperature in the pre-reformer, carbon deposition and coke formation resulting from higher hydrocarbons can be eliminated. In this study, the cathode outlet provides the heat requirement for the pre-reforming process. After partial heat recovery from the cathode outlet, the stream still has a considerable energy and exergy (352.55 °C and 83.687 kW respectively). This study investigates waste heat recovery from the proposed DIR-MCFC,...