The Experts below are selected from a list of 1374 Experts worldwide ranked by ideXlab platform
Sergio Uson - One of the best experts on this subject based on the ideXlab platform.
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thermoeconomic assessment of a natural gas expansion system integrated with a co generation unit
Applied Energy, 2013Co-Authors: Wojciech Kostowski, Sergio UsonAbstract:The paper presents a thermoeconomic assessment of an expansion system applied in the natural gas transportation process. The system consists of two turboexpander stages reducing the natural gas pressure and providing mechanical energy to drive electric generators. Gas pre-heating, required to prevent hydrate formation, is performed upstream of each expansion stage using waste heat recovered from a gas engine, which contributes to the total system electricity production. The system constitutes a hybrid energy generation unit as the generated electricity derives partially from the Physical Exergy of pressurized natural gas, and partially from the primary energy of fuel. The presented thermoeconomic description of the system comprises definitions of system quality indicators, as well as an identification of irreversibility bound to the operation of the system’s components.
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Comparative evaluation of a natural gas expansion plant integrated with an IC engine and an organic Rankine cycle
Energy Conversion and Management, 2013Co-Authors: Wojciech Kostowski, Sergio UsonAbstract:Abstract The aim of the paper is to propose and evaluate an innovative Exergy recovery system for natural gas expansion, based on the integration of an internal combustion engine (ICE) and an organic Rankine cycle (ORC), and to compare it with other alternatives. Natural gas expansion plants are a substantial improvement to the conventional gas pressure reduction stations, based on the throttling process, since the available Physical Exergy of pressurized gas is converted into mechanical energy by means of an expansion machine (turbine or piston expander) instead of being lost in the throttling process. However, due to the hydrate formation problem the gas has to be pre-heated prior to the expansion, which diminishes the system performance. An efficient method for performing this pre-heating is by the proposed system that comprises an ICE and an ORC: Pre-heating of natural gas is carried out partially directly by the co-generation module, via the engine cooling cycle, and partially indirectly, by means of the engine exhaust gases, which supply heat for the ORC, while the ORC condenser is connected with the lowest stage of natural gas pre-heating. Other alternatives are the use of an ICE without ORC, the use of a boiler, and even expansion in a throttling valve. The paper evaluates the performance of the aforementioned four configurations by means of both energy and Exergy analysis. Several alternative performance indicators have been defined, calculated and discussed. Sources of irreversibilities have been identified by means of Exergy analysis methodology. The fuel-product approach was used to define the Exergy efficiency. Except for the reference system with a throttling valve, the analyzed systems achieve favourable values of Exergy efficiency (up to 52.6%), and outstanding performance ratios (0.69–0.77), relating the energy fluxes of generated work to the fuel locally combusted in the system.
Wojciech Kostowski - One of the best experts on this subject based on the ideXlab platform.
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thermoeconomic assessment of a natural gas expansion system integrated with a co generation unit
Applied Energy, 2013Co-Authors: Wojciech Kostowski, Sergio UsonAbstract:The paper presents a thermoeconomic assessment of an expansion system applied in the natural gas transportation process. The system consists of two turboexpander stages reducing the natural gas pressure and providing mechanical energy to drive electric generators. Gas pre-heating, required to prevent hydrate formation, is performed upstream of each expansion stage using waste heat recovered from a gas engine, which contributes to the total system electricity production. The system constitutes a hybrid energy generation unit as the generated electricity derives partially from the Physical Exergy of pressurized natural gas, and partially from the primary energy of fuel. The presented thermoeconomic description of the system comprises definitions of system quality indicators, as well as an identification of irreversibility bound to the operation of the system’s components.
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Comparative evaluation of a natural gas expansion plant integrated with an IC engine and an organic Rankine cycle
Energy Conversion and Management, 2013Co-Authors: Wojciech Kostowski, Sergio UsonAbstract:Abstract The aim of the paper is to propose and evaluate an innovative Exergy recovery system for natural gas expansion, based on the integration of an internal combustion engine (ICE) and an organic Rankine cycle (ORC), and to compare it with other alternatives. Natural gas expansion plants are a substantial improvement to the conventional gas pressure reduction stations, based on the throttling process, since the available Physical Exergy of pressurized gas is converted into mechanical energy by means of an expansion machine (turbine or piston expander) instead of being lost in the throttling process. However, due to the hydrate formation problem the gas has to be pre-heated prior to the expansion, which diminishes the system performance. An efficient method for performing this pre-heating is by the proposed system that comprises an ICE and an ORC: Pre-heating of natural gas is carried out partially directly by the co-generation module, via the engine cooling cycle, and partially indirectly, by means of the engine exhaust gases, which supply heat for the ORC, while the ORC condenser is connected with the lowest stage of natural gas pre-heating. Other alternatives are the use of an ICE without ORC, the use of a boiler, and even expansion in a throttling valve. The paper evaluates the performance of the aforementioned four configurations by means of both energy and Exergy analysis. Several alternative performance indicators have been defined, calculated and discussed. Sources of irreversibilities have been identified by means of Exergy analysis methodology. The fuel-product approach was used to define the Exergy efficiency. Except for the reference system with a throttling valve, the analyzed systems achieve favourable values of Exergy efficiency (up to 52.6%), and outstanding performance ratios (0.69–0.77), relating the energy fluxes of generated work to the fuel locally combusted in the system.
Ftwi Yohaness Hagos - One of the best experts on this subject based on the ideXlab platform.
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Thermal performance of gas turbine power plant based on Exergy analysis
Applied Thermal Engineering, 2017Co-Authors: Thamir K Ibrahim, Ahmed N. Abdullah, Rizlman Mamat, Omar I. Awad, Firdaus Basrawi, Gholamhassan Najafi, Ftwi Yohaness HagosAbstract:This study is about energy and Exergy analysis of gas turbine power plant. Energy analysis is more quantitatively while Exergy analysis is about the same but with the addition of qualitatively. The lack quality of the thermodynamic process in the system leads to waste of potential energy, also known as Exergy destruction which affects the efficiency of the power plant. By using the first and second law of thermodynamics, the model for the gas turbine power plant is built. Each component in the thermal system which is an air compressor, combustion chamber and gas turbine play roles in affecting the efficiency of the gas turbine power plant. The Exergy flow rate for the compressor (AC), the combustion chamber (CC) and the gas turbine (GT) inlet and outlet are calculated based on the Physical Exergy and chemical Exergy. The Exergy destruction calculation based on the difference between the Exergy flow in and Exergy flow out of the component. The combustion chamber has the highest Exergy destruction. The air compressor has 94.9% and 92% of Exergy and energy efficiency respectively. The combustion chamber has 67.5% and 61.8% of Exergy and energy efficiency respectively while gas turbine has 92% and 82% of Exergy and energy efficiency respectively. For the overall efficiency, the plant has 32.4% and 34.3% Exergy and energy efficiency respectively. To enhance the efficiency, the intake air temperature should be reduced, modify the combustion chamber to have the better air-fuel ratio and increase the capability of the gas turbine to receive high inlet temperature.
Thamir K Ibrahim - One of the best experts on this subject based on the ideXlab platform.
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Thermal performance of gas turbine power plant based on Exergy analysis
Applied Thermal Engineering, 2017Co-Authors: Thamir K Ibrahim, Ahmed N. Abdullah, Rizlman Mamat, Omar I. Awad, Firdaus Basrawi, Gholamhassan Najafi, Ftwi Yohaness HagosAbstract:This study is about energy and Exergy analysis of gas turbine power plant. Energy analysis is more quantitatively while Exergy analysis is about the same but with the addition of qualitatively. The lack quality of the thermodynamic process in the system leads to waste of potential energy, also known as Exergy destruction which affects the efficiency of the power plant. By using the first and second law of thermodynamics, the model for the gas turbine power plant is built. Each component in the thermal system which is an air compressor, combustion chamber and gas turbine play roles in affecting the efficiency of the gas turbine power plant. The Exergy flow rate for the compressor (AC), the combustion chamber (CC) and the gas turbine (GT) inlet and outlet are calculated based on the Physical Exergy and chemical Exergy. The Exergy destruction calculation based on the difference between the Exergy flow in and Exergy flow out of the component. The combustion chamber has the highest Exergy destruction. The air compressor has 94.9% and 92% of Exergy and energy efficiency respectively. The combustion chamber has 67.5% and 61.8% of Exergy and energy efficiency respectively while gas turbine has 92% and 82% of Exergy and energy efficiency respectively. For the overall efficiency, the plant has 32.4% and 34.3% Exergy and energy efficiency respectively. To enhance the efficiency, the intake air temperature should be reduced, modify the combustion chamber to have the better air-fuel ratio and increase the capability of the gas turbine to receive high inlet temperature.
Costante Mario Invernizzi - One of the best experts on this subject based on the ideXlab platform.
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the exploitation of the Physical Exergy of liquid natural gas by closed power thermodynamic cycles an overview
Energy, 2016Co-Authors: Costante Mario Invernizzi, Paolo IoraAbstract:Abstract The world trade in LNG (liquefied natural gas) has tripled in the last 15 years and the forecasts are for its further rapid expansion. Although the cryogenic Exergy of the LNG could be used in many industrial processes, it is recognized also as a source for power cycles. When using the low temperature capacity of LNG for power production, several thermodynamic cycles can be considered. This paper reports the state-of-the art of the most relevant solutions based on conventional and non-conventional thermodynamic closed cycles. Moreover, a novel metrics framework, suitable for a fairer comparison among the energy recovery performances of the different technologies is proposed. According to the defined indicators the compounds plants with gas turbine and closed Brayton cycles perform really better, with an almost full use of LNG available cold temperature and a fuel consumption with an efficiency better than that of the current combined cycles. The Rankine cycles with organic working fluids (pure fluids or non-azeotropic mixtures) using seawater or heat available at low temperature (for instance at 150 °C) also perform in a very satisfactory way. Real gas Brayton cycles and carbon dioxide condensation cycles work with very good thermal efficiency also at relatively low maximum temperatures (300 ÷ 600 °C) and could have peculiar applications.
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the role of real gas brayton cycles for the use of liquid natural gas Physical Exergy
Applied Thermal Engineering, 2011Co-Authors: G Angelino, Costante Mario InvernizziAbstract:Abstract When using the cooling capacity of LNG several thermodynamic schemes are proposable employing conventional and non conventional conversion cycles. All conventional systems make use of organic working fluids such as methane or propane in series of Rankine cycles used in a cascading mode. A simpler system is available, using a single cycle and a single fluid in a Brayton cycle. However ordinary Brayton cycles exhibit a modest efficiency. Resorting to Brayton cycles with strong real gas effects (which is possible selecting the base parameters of pressure and temperature in the vicinity of the critical point) improves considerable cycle performance. Since the level of cold in a LNG flow is thermodynamically predetermined, working fluids must be selected with a critical point which fit the LNG thermal capacity, i.e. some 5–15 C higher than the usual LNG temperature which is around −160 °C. Nitrogen was found as the best fluid to exploit real gas effects with efficiencies above 63% while perfect gas cycles give efficiencies around 56%. However, in real gas cycles the cooling capacity of LNG is only partially exploited: a better exploitation is obtained from perfect gas cycles or for more complex cascading Rankine cycle. Selecting working fluids with a higher critical temperature than nitrogen, as for example argon, the efficiency decreases to 58% respect to 63% for nitrogen, but the utilization of the cold of LNG improves from 0.30 MW/(kg/s) to 0.75 MW/(kg/s). Obviously as heat rejection temperature increases a larger fraction of cold in the LNG flow can be utilized. Combined cycles making use of a gas turbine offer also a good performance. The merits of real gas effect Brayton cycles also in this case remains evident. Finally, it is theoretically possible to use real gas effect Brayton cycles at low temperatures, which are typical of waste heat (say 100–150 °C: in this case cycle efficiency remain good, but power obtainable from a unit flow of LNG is modest.