The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Fengrui Sun - One of the best experts on this subject based on the ideXlab platform.
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performance of reciprocating brayton cycle with heat transfer friction and variable specific heats of Working Fluid
International journal of ambient energy, 2008Co-Authors: Lingen Chen, Fengrui SunAbstract:SYNOPSIS The performance of an irreversible air-standard reciprocating simple Brayton cycle with heat transfer loss, friction-like term loss and variable specific heats of Working Fluid is analysed by using finite-time thermodynamics. The relationships between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relationship between the power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of variable specific heats of the Working Fluid and the friction-like term loss on the irreversible cycle performance are analysed. The results show that the effects of variable specific heats of the Working Fluid and friction-like term loss on the irreversible cycle performance are obvious, and they should be considered in practical cycle analysis. The results obtained in this paper may provide guidelines for the design of practical reciprocating Brayton engines.
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performance of diesel cycle with heat transfer friction and variable specific heats of Working Fluid
Journal of The Energy Institute, 2007Co-Authors: Lingen Chen, Fengrui SunAbstract:AbstractThe performance of an air standard Diesel cycle with heat transfer loss, friction-like term loss and variable specific heats of Working Fluid is analysed by using finite time thermodynamics. The relationships between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relationship between the power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of temperature dependent specific heats of Working Fluid on the irreversible cycle performance are analysed. The results show that the effects of temperature dependent specific heats of Working Fluid on the irreversible cycle performance are obvious, and they should be considered in practice cycle analysis. The results obtained in the present paper may provide guidance for the design of practice Diesel engines.
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performance of an atkinson cycle with heat transfer friction and variable specific heats of the Working Fluid
Applied Energy, 2006Co-Authors: Lingen Chen, Fengrui SunAbstract:The performance of an air standard Atkinson cycle with heat-transfer loss, friction-like term loss and variable specific-heats of the Working Fluid is analyzed using finite-time thermodynamics. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between the power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of variable specific-heats of the Working Fluid and the friction-like term loss on the irreversible cycle performance are analyzed. The results show that the effects of variable specific-heats of Working Fluid and friction-like term loss on the irreversible cycle performance should be considered in cycle analysis. The results obtained in this paper provide guidance for the design of Atkinson engines.
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effects of heat transfer friction and variable specific heats of Working Fluid on performance of an irreversible dual cycle
Energy Conversion and Management, 2006Co-Authors: Lingen Chen, Fengrui Sun, Yanlin Ge, Chih WuAbstract:The thermodynamic performance of an air standard dual cycle with heat transfer loss, friction like term loss and variable specific heats of Working Fluid is analyzed. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between power output and the efficiency of the cycle, are derived by detailed numerical examples. Moreover, the effects of variable specific heats of the Working Fluid and the friction like term loss on the irreversible cycle performance are analyzed. The results show that the effects of variable specific heats of Working Fluid and friction like term loss on the cycle performance are obvious, and they should be considered in practical cycle analysis. The results obtained in this paper may provide guidance for the design of practical internal combustion engines.
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thermodynamic simulation of performance of an otto cycle with heat transfer and variable specific heats of Working Fluid
International Journal of Thermal Sciences, 2005Co-Authors: Yanlin Ge, Lingen Chen, Fengrui Sun, Chih WuAbstract:Abstract The performance of an air-standard Otto cycle with heat transfer loss and variable specific heats of Working Fluid is analyzed by using finite-time thermodynamics. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of heat transfer loss and variable specific heats of Working Fluid on the cycle performance are analyzed. The results show that the effects of heat transfer loss and variable specific heats of Working Fluid on the cycle performance are obvious, and they should be considered in practice cycle analysis. The results obtained in this paper may provide guidance for the design of practice internal combustion engines.
Christos N. Markides - One of the best experts on this subject based on the ideXlab platform.
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computer aided Working Fluid design thermodynamic optimisation and thermoeconomic assessment of orc systems for waste heat recovery
Energy, 2018Co-Authors: Oyeniyi A. Oyewunmi, Antonio M. Pantaleo, Martin T. White, Maria Anna Chatzopoulou, Andrew J Haslam, Christos N. MarkidesAbstract:The wider adoption of organic Rankine cycle (ORC) technology can be facilitated by improved thermodynamic performance and reduced costs. In this context the power system should be evaluated based on a thermeconomic assessment with the aim of improving economic viability. This paper couples the computer- aided molecular design (CAMD) of the Working-Fluid with thermodynamic modelling and optimisation, in addition to heat-exchanger sizing models, component cost correlations, and a thermoeconomic assessment. The proposed CAMD-ORC framework, based on the SAFT-γ Mie equation of state, allows the thermodynamic optimisation of the cycle and Working-Fluid in a single stage, thus removing subjective and pre-emptive screening criteria that would otherwise exist in conventional studies. Following validation, the framework is used to identify optimal Working-Fluids for three different heat sources (150, 250 and 350 °C), corresponding to small- to medium-scale applications. In each case, the optimal combination of Working-Fluid and ORC system is identified, and investment costs are evaluated. It is observed that Fluids with low specific-investment costs (SIC) are different to those that maximise power output. The Fluids with the lowest SIC are isoheptane, 2-pentene and 2-heptene, with SICs of 5,620, 2,760 and 2,070 £/kW respectively, and corresponding power outputs of 32.9, 136.6 and 213.9 kW.
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Working Fluid replacement in supersonic organic Rankine cycle turbines
Journal of Engineering for Gas Turbines and Power, 2018Co-Authors: Martin T. White, Christos N. Markides, Abdulnaser I. SaymaAbstract:In this paper the effect of Working-Fluid replacement within an organic Rankine cycle turbine is investigated by evaluating the performance of two supersonic stators operating with different Working Fluids. After designing the two stators, intended for operation with R245fa and Toluene with stator exit absolute Mach numbers of 1.4 and 1.7 respectively, the performance of each stator is evaluated using ANSYS CFX. Based on the principle that the design of a given stator is dependent on the amount of flow turning, it is hypothesised that a stator’s design point can be scaled to alternative Working Fluids by conserving the Prandtl-Meyer function and the polytropic index within the nozzle. A scaling method is developed and further CFD simulations for the scaled operating points verify that the Mach number distributions within the stator, and the non-dimensional velocity triangles at the stator exit, remain unchanged. This confirms that the method developed can predict stator performance following a change in the Working Fluid. Finally, a study investigating the effect of Working-Fluid replacement on the thermodynamic cycle is completed. The results show that the same turbine could be used in different systems with power outputs varying between 17 and 112 kW, suggesting the potential of matching the same turbine to multiple heat sources by tailoring the Working Fluid selected. This further implies that the same turbine design could be deployed in different applications, thus leading to economy-of-scale improvements.
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Performance of Working-Fluid mixtures in ORC-CHP systems for different heat-demand segments and heat-recovery temperature levels
Energy Conversion and Management, 2017Co-Authors: Oyeniyi A. Oyewunmi, Christoph J.w. Kirmse, Antonio M. Pantaleo, Christos N. MarkidesAbstract:Abstract In this paper, we investigate the adoption of Working-Fluid mixtures in ORC systems operating in combined heat and power (CHP) mode, with a power output provided by the expanding Working Fluid in the ORC turbine and a thermal energy output provided by the cooling water exiting (as a hot-water supply) the ORC condenser. We present a methodology for selecting optimal Working-Fluids in ORC systems with optimal CHP heat-to-electricity ratio and heat-supply temperature settings to match the seasonal variation in heat demand (temperature and intermittency of the load) of different end-users. A number of representative industrial waste-heat sources are considered by varying the ORC heat-source temperature over the range 150–330 °C. It is found that, a higher hot-water outlet temperature increases the exergy of the heat-sink stream but decreases the power output of the expander. Conversely, a low outlet temperature (~30 °C) allows for a high power-output, but a low cooling-stream exergy and hence a low potential to heat buildings or to cover other industrial thermal-energy demands. The results demonstrate that the optimal ORC shaft-power outputs vary considerably, from 9 MW up to 26 MW, while up to 10 MW of heating exergy is provided, with fuel savings in excess of 10%. It also emerges that single-component Working Fluids such as n-pentane appear to be optimal for fulfilling low-temperature heat demands, while Working-Fluid mixtures become optimal at higher heat-demand temperatures. In particular, the Working-Fluid mixture of 70% n-octane + 30% n-pentane results in an ORC-CHP system with the highest ORC exergy efficiency of 63% when utilizing 330 °C waste heat and delivering 90 °C hot water. The results of this research indicate that, when optimizing the global performance of ORC-CHP systems fed by industrial waste-heat sources, the temperature and load pattern of the cogenerated heat demand are crucial factors affecting the selection of the Working Fluid.
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thermo economic and heat transfer optimization of Working Fluid mixtures in a low temperature organic rankine cycle system
Energies, 2016Co-Authors: Oyeniyi A. Oyewunmi, Christos N. MarkidesAbstract:In the present paper, we consider the employment of Working-Fluid mixtures in organic Rankine cycle (ORC) systems with respect to thermodynamic and heat-transfer performance, component sizing and capital costs. The selected Working-Fluid mixtures promise reduced exergy losses due to their non-isothermal phase-change behaviour, and thus improved cycle efficiencies and power outputs over their respective pure-Fluid components. A multi-objective cost-power optimization of a specific low-temperature ORC system (operating with geothermal water at 98 °C) reveals that the use of Working-Fluid-mixtures does indeed show a thermodynamic improvement over the pure-Fluids. At the same time, heat transfer and cost analyses, however, suggest that it also requires larger evaporators, condensers and expanders; thus, the resulting ORC systems are also associated with higher costs. In particular, 50% n -pentane + 50% n -hexane and 60% R-245fa + 40% R-227ea mixtures lead to the thermodynamically optimal cycles, whereas pure n -pentane and pure R-245fa have lower plant costs, both estimated as having ∼14% lower costs per unit power output compared to the thermodynamically optimal mixtures. These conclusions highlight the importance of using system cost minimization as a design objective for ORC plants.
Lingen Chen - One of the best experts on this subject based on the ideXlab platform.
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performance of reciprocating brayton cycle with heat transfer friction and variable specific heats of Working Fluid
International journal of ambient energy, 2008Co-Authors: Lingen Chen, Fengrui SunAbstract:SYNOPSIS The performance of an irreversible air-standard reciprocating simple Brayton cycle with heat transfer loss, friction-like term loss and variable specific heats of Working Fluid is analysed by using finite-time thermodynamics. The relationships between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relationship between the power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of variable specific heats of the Working Fluid and the friction-like term loss on the irreversible cycle performance are analysed. The results show that the effects of variable specific heats of the Working Fluid and friction-like term loss on the irreversible cycle performance are obvious, and they should be considered in practical cycle analysis. The results obtained in this paper may provide guidelines for the design of practical reciprocating Brayton engines.
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performance of diesel cycle with heat transfer friction and variable specific heats of Working Fluid
Journal of The Energy Institute, 2007Co-Authors: Lingen Chen, Fengrui SunAbstract:AbstractThe performance of an air standard Diesel cycle with heat transfer loss, friction-like term loss and variable specific heats of Working Fluid is analysed by using finite time thermodynamics. The relationships between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relationship between the power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of temperature dependent specific heats of Working Fluid on the irreversible cycle performance are analysed. The results show that the effects of temperature dependent specific heats of Working Fluid on the irreversible cycle performance are obvious, and they should be considered in practice cycle analysis. The results obtained in the present paper may provide guidance for the design of practice Diesel engines.
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performance of an atkinson cycle with heat transfer friction and variable specific heats of the Working Fluid
Applied Energy, 2006Co-Authors: Lingen Chen, Fengrui SunAbstract:The performance of an air standard Atkinson cycle with heat-transfer loss, friction-like term loss and variable specific-heats of the Working Fluid is analyzed using finite-time thermodynamics. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between the power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of variable specific-heats of the Working Fluid and the friction-like term loss on the irreversible cycle performance are analyzed. The results show that the effects of variable specific-heats of Working Fluid and friction-like term loss on the irreversible cycle performance should be considered in cycle analysis. The results obtained in this paper provide guidance for the design of Atkinson engines.
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effects of heat transfer friction and variable specific heats of Working Fluid on performance of an irreversible dual cycle
Energy Conversion and Management, 2006Co-Authors: Lingen Chen, Fengrui Sun, Yanlin Ge, Chih WuAbstract:The thermodynamic performance of an air standard dual cycle with heat transfer loss, friction like term loss and variable specific heats of Working Fluid is analyzed. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between power output and the efficiency of the cycle, are derived by detailed numerical examples. Moreover, the effects of variable specific heats of the Working Fluid and the friction like term loss on the irreversible cycle performance are analyzed. The results show that the effects of variable specific heats of Working Fluid and friction like term loss on the cycle performance are obvious, and they should be considered in practical cycle analysis. The results obtained in this paper may provide guidance for the design of practical internal combustion engines.
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the effects of variable specific heats of Working Fluid on the performance of an irreversible otto cycle
International Journal of Exergy, 2005Co-Authors: Yanlin Ge, Lingen Chen, Chih WuAbstract:The performance of an air-standard Otto cycle with variable specific heats of Working Fluid and heat resistance and friction irreversible losses is analysed by using finite-time thermodynamics. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of variable specific heats of Working Fluid on the irreversible cycle performance are analysed. The results show that the effects of variable specific heats of Working Fluid on the cycle performance are obvious, and it should be considered in practice cycle analysis. The results obtained in this paper may provide guidance for the design of practice internal combustion engines.
Athanasios I. Papadopoulos - One of the best experts on this subject based on the ideXlab platform.
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Absorption refrigeration processes with organic Working Fluid mixtures- a review
Renewable and Sustainable Energy Reviews, 2019Co-Authors: Athanasios I. Papadopoulos, Panos Seferlis, Alexios-spyridon Kyriakides, Ibrahim HassanAbstract:Abstract The presented work includes a detailed review of organic Working Fluid mixtures and corresponding Absorption Refrigeration (ABR) cycles available in published literature. Such processes are important as they enable exploitation of cleaner and renewable energy sources for cooling generation. Research efforts may be benefited by a systematically organized account of previous works in organic Working Fluids, which have received considerably less attention than conventional inorganic options. The reviewed developments are separated into Working Fluids used in single effect cycles and alternative configurations such as double effect, half effect and so forth. Details are reported regarding the operating conditions tested, the criteria used for Working Fluid selection and the ones selected as desirable options either experimentally or in simulation studies. Research on thermodynamics of organic Working Fluids suitable for ABR processes is also reported with respect to measured properties, experimental conditions and types of thermodynamic models. The characteristics of different process flowsheets are also analyzed, while commercial scale ABR applications are reported to motivate research in industrial/commercial scale systems. It is observed that there are few types of chemical groups repeated in Working Fluid investigations, with halogenated refrigerants and ether- and amide-based absorbents prevailing compared to other substances. Most experimental works pertain to single effect systems, with model-based approaches mainly used due to introduction of increasingly complex process modifications. The latter have been assessed with considerably fewer different Fluid options compared to single effect systems. Thermodynamic investigations mainly combine experiments with parameter estimation for model development. Most works derive data and employ the NRTL activity coefficient model, often combined with cubic equations of state.
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selection of Working Fluid mixtures for flexible organic rankine cycles under operating variability through a systematic nonlinear sensitivity analysis approach
Applied Thermal Engineering, 2015Co-Authors: Paschalia Mavrou, Athanasios I. Papadopoulos, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:Abstract This work addresses the selection of Working Fluid mixtures in view of operating variability in solar Organic Ranking Cycles (ORC). A systematic sensitivity analysis procedure is proposed, which explicitly considers the impacts of Working Fluid and ORC design/operating decisions on the ability of the ORC to operate under conditions different from its nominal design settings. The method determines the effects of variability resulting from the simultaneous consideration of multiple system design and operating parameters on multiple ORC performance indicators. It further supports the identification of parameters with high influence in the overall ORC-Working Fluid performance and the quantification of the overall system sensitivity with respect to these parameters within a sensitivity index. The method is illustrated with several Working Fluid mixture candidates and supports identification of the mixtures with minimum sensitivity in operating variability and maximum overall ORC performance. The obtained results indicate that in order to avoid significant performance losses, variability should be systematically considered during the mixture selection. Mixture 70% 1,1,1-trifluoro-propane/1-Fluoromethoxy-propane exhibits the highest overall ORC performance and lowest sensitivity to variability.
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Novel and conventional Working Fluid mixtures for solar Rankine cycles: Performance assessment and multi-criteria selection
Applied Thermal Engineering, 2015Co-Authors: Paschalia Mavrou, Athanasios I. Papadopoulos, Mirko Stijepovic, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:Abstract This work investigates the performance of Working Fluid mixtures for use in solar ORC (Organic Rankine Cycle systems) with heat storage employing FPC (Flat Plate Collectors). Several mixtures are considered including conventional choices often utilized in ORC as well as novel mixtures previously designed using advanced computer aided molecular design methods (Papadopoulos et al., 2013). The impact of heat source variability on the ORC performance is assessed for different Working Fluid mixtures. Solar radiation is represented in detail through actual, hourly averaged data for an entire year. A multi-criteria mixture selection methodology unveils important trade-offs among several important system operating parameters and efficiently highlights optimum operating ranges. Such parameters include the ORC thermal efficiency, the net generated power, the volume ratio across the turbine, the mass flow rate of the ORC Working Fluid, the evaporator temperature glide, the temperature drop in the storage tank, the ORC total yearly operating duration, the required collector aperture area to generate 1 kW of power and the irreversibility. A mixture of neopentane – 2-fluoromethoxy-2-methylpropane at 70% neopentane is found to be the most efficient in all the considered criteria simultaneously.
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Assessment of Working Fluid Mixtures for Solar Organic
2014Co-Authors: Cal E, Paschalia Mavrou, Athanasios I. Papadopoulos, Mirko Stijepovic, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:This work investigates the performance of binary Working Fluid mixtures in a low temperature solar Organic Rankine Cycle (ORC) system including heat storage. Conventional mixtures widely considered in published literature are compared with optimum mixtures previously obtained using a computer-aided molecular design method in Papadopoulos et al. (2013). The system performance is investigated for a real solar radiation profile for an entire year of operation. Inclusive, steady-state mathematical models are used for the simulation of both the solar collectors and the ORC. The effects of different mixtures on several important system operating parameters are investigated. Results indicate that mixtures at different compositions and concentrations may have a significantly different performance in terms of parameters such as generated work, required collector aperture area and so forth. Neopentane- based mixtures appear as promising candidates of high overall performance for solar ORCs.
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on the role of Working Fluid properties in organic rankine cycle performance
Applied Thermal Engineering, 2012Co-Authors: Mirko Stijepovic, Athanasios I. Papadopoulos, Patrick Linke, Aleksanda GrujicAbstract:Abstract The performance of ORC systems strongly depends on Working Fluid properties. We explore the relationships between Working Fluid properties and ORC common economic and thermodynamic performance criteria from a theoretical and an analytical point of view. The mapping of individual properties and performance criteria presented in this paper will provide a basis for the development of efficient and systematic strategies and approaches for ORC Working Fluid selection in future.
Spyros Voutetakis - One of the best experts on this subject based on the ideXlab platform.
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selection of Working Fluid mixtures for flexible organic rankine cycles under operating variability through a systematic nonlinear sensitivity analysis approach
Applied Thermal Engineering, 2015Co-Authors: Paschalia Mavrou, Athanasios I. Papadopoulos, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:Abstract This work addresses the selection of Working Fluid mixtures in view of operating variability in solar Organic Ranking Cycles (ORC). A systematic sensitivity analysis procedure is proposed, which explicitly considers the impacts of Working Fluid and ORC design/operating decisions on the ability of the ORC to operate under conditions different from its nominal design settings. The method determines the effects of variability resulting from the simultaneous consideration of multiple system design and operating parameters on multiple ORC performance indicators. It further supports the identification of parameters with high influence in the overall ORC-Working Fluid performance and the quantification of the overall system sensitivity with respect to these parameters within a sensitivity index. The method is illustrated with several Working Fluid mixture candidates and supports identification of the mixtures with minimum sensitivity in operating variability and maximum overall ORC performance. The obtained results indicate that in order to avoid significant performance losses, variability should be systematically considered during the mixture selection. Mixture 70% 1,1,1-trifluoro-propane/1-Fluoromethoxy-propane exhibits the highest overall ORC performance and lowest sensitivity to variability.
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Novel and conventional Working Fluid mixtures for solar Rankine cycles: Performance assessment and multi-criteria selection
Applied Thermal Engineering, 2015Co-Authors: Paschalia Mavrou, Athanasios I. Papadopoulos, Mirko Stijepovic, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:Abstract This work investigates the performance of Working Fluid mixtures for use in solar ORC (Organic Rankine Cycle systems) with heat storage employing FPC (Flat Plate Collectors). Several mixtures are considered including conventional choices often utilized in ORC as well as novel mixtures previously designed using advanced computer aided molecular design methods (Papadopoulos et al., 2013). The impact of heat source variability on the ORC performance is assessed for different Working Fluid mixtures. Solar radiation is represented in detail through actual, hourly averaged data for an entire year. A multi-criteria mixture selection methodology unveils important trade-offs among several important system operating parameters and efficiently highlights optimum operating ranges. Such parameters include the ORC thermal efficiency, the net generated power, the volume ratio across the turbine, the mass flow rate of the ORC Working Fluid, the evaporator temperature glide, the temperature drop in the storage tank, the ORC total yearly operating duration, the required collector aperture area to generate 1 kW of power and the irreversibility. A mixture of neopentane – 2-fluoromethoxy-2-methylpropane at 70% neopentane is found to be the most efficient in all the considered criteria simultaneously.
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Assessment of Working Fluid Mixtures for Solar Organic
2014Co-Authors: Cal E, Paschalia Mavrou, Athanasios I. Papadopoulos, Mirko Stijepovic, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:This work investigates the performance of binary Working Fluid mixtures in a low temperature solar Organic Rankine Cycle (ORC) system including heat storage. Conventional mixtures widely considered in published literature are compared with optimum mixtures previously obtained using a computer-aided molecular design method in Papadopoulos et al. (2013). The system performance is investigated for a real solar radiation profile for an entire year of operation. Inclusive, steady-state mathematical models are used for the simulation of both the solar collectors and the ORC. The effects of different mixtures on several important system operating parameters are investigated. Results indicate that mixtures at different compositions and concentrations may have a significantly different performance in terms of parameters such as generated work, required collector aperture area and so forth. Neopentane- based mixtures appear as promising candidates of high overall performance for solar ORCs.
