The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Hoseyn Sayyaadi - One of the best experts on this subject based on the ideXlab platform.
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a novel second order thermal model of Stirling Engines with consideration of losses due to the speed of the crack system
Energy Conversion and Management, 2018Co-Authors: Hoseyn Sayyaadi, Hossein GhasemiAbstract:Abstract Very accurate second-order thermal models have been developed for the thermal simulation of Stirling Engines in recent years. One of the last ones is the comprehensive polytropic model of Stirling engine called the CPMS model. The accuracy of the CPMS model was found to be sufficient for the nominal operation of a prototype Stirling engine known as the GPU-3 engine. Nevertheless, the accuracy of the CPMS model was drastically reduced at high rotational speeds of the engine. In this paper, power loss and pressure change due to the inertial force of the crank system were integrated into the CPMS thermal model in order to compensate inaccuracy of the CPMS model at high rotational speeds. Moreover, the effect of rotational speed on the gas temperature in heater and cooler was also incorporated. A precise model for evaluating the mechanical friction loss was also employed and compared with the simple frictional model of the simple frictional model used in the CPMS. The model was examined on the GPU-3 engine, and it was found that it has superior accuracy compared to the previous thermal model over the entire working regime of the GPU-3 engine.
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analytical closed form model for predicting the power and efficiency of Stirling Engines based on a comprehensive numerical model and the genetic programming
Energy, 2016Co-Authors: M Babaelahi, Hoseyn SayyaadiAbstract:Abstract High accuracy and simplicity in use are two important required features of thermal models of Stirling Engines. A new numerical second-order thermal model was presented through the improvement of our previous modified-PSVL model in order to have an elevated accuracy. The modified-PSVL model was modified by considering a non-isothermal model for heater and cooler. Then, the model called as CPMS-Comprehensive Polytropic Model of Stirling engine, was used to simulate the GPU-3 Stirling engine, and the obtained results were compared with those of the previous thermal models as well as the experimental data. For the sack of the simplicity, the combination of the CPMS model and genetic programming was employed to generate analytical closed-form correlation. In this regards, a comprehensive data bank of results of the CPMS was constructed and exported to the GP tool and analytical expressions of the power, efficiency, and polytropic indexes were obtained. It was shown that the analytical correlations not only had the same accuracy as the CPMS model, but also, it can be simply used without difficulties of numerical models. The CPMS and its out coming analytical expressions, predicted the power and efficiency of the GPU-3 Stirling with +1.13% and +0.45 (as difference), respectively.
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modified psvl a second order model for thermal simulation of Stirling Engines based on convective polytropic heat transfer of working spaces
Applied Thermal Engineering, 2015Co-Authors: M Babaelahi, Hoseyn SayyaadiAbstract:Abstract The new numerical second order thermal model for the simulation of Stirling Engines was presented. In the new model, the previously developed model of the present authors called PSVL model (polytropic analysis of Stirling engine with various losses) was modified based on coupling the convective heat transfer mechanism to polytropic expansion/compression processes. Furthermore, an exponential temperature distribution of the gas along the regenerator length was assumed in the new model. Similar to the original PSVL model, effects of heat and mass leakages were implemented in basic differential equations and the ordinary differential equations (ODE) system was numerically solved by fourth order Runge-Kutta methods. Results of the numerical model were corrected to include various non-idealities. Finally, the new polytropic–convective model called modified PSVL was implemented to simulate he GPU-3 Stirling engine and the obtained results were compared with those of the previous thermal models as well as experimental data. It was found that the correction of PSVL led to better accuracy compared with the original PSVL as well as other models. Further, coupling the heat transfer to model caused a slightly greater amount of polytropic indexes than the original PSVL model.
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A new thermal model based on polytropic numerical simulation of Stirling Engines
Applied Energy, 2015Co-Authors: M Babaelahi, Hoseyn SayyaadiAbstract:The new numerical thermal model based on polytropic expansion/compression processes was developed for predicting thermal performance of Stirling Engines. In this regard, differential governing equations of early adiabatic model of Stirling Engines were modified to consider polytropic heat transfers of the working fluid to the surrounding through expansion/compression cylinder walls. Therefore, adiabatic expansion/compression processes of the early adiabatic model were substituted with polytropic expansion/compression processes in the new thermal model. In order to increase accuracy of the thermal model, various loss mechanisms including effect of mass leakage from working to buffer spaces and heat leakage from expansion to compression spaces, due to thermal conductivity (shuttle heat transfer effect) of the displacer, were implemented in basic differential equations of polytropic analysis. In addition, in a similar manner to the early simple analysis, effect of non-ideal heat recovery of the regenerator and hydraulic pressure drop were considered in heater, cooler and regenerator. Also, magnitude of the piston back pressure was corrected in terms of piston velocity using the principle of finite speed thermodynamics (FST) and mechanical friction between piston and cylinder was taken into account in the new thermal model. On the other hand, longitudinal heat conduction between the heater and cooler through the regenerator wall was modeled as an additional loss mechanism. Finally, the new model called polytropic analysis of Stirling engine with various losses (PSVL) mechanisms was applied to a prototype Stirling engine, namely GPU-3 Stirling engine, and the obtained results were evaluated through comparison with previous thermal models and experimental results. Based on the new PSVL model, the output power and thermal efficiency of the GPU-3 engine were predicted with +14.34% and +3.14% (as a difference), respectively.
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a new closed form analytical thermal model for simulating Stirling Engines based on polytropic finite speed thermodynamics
Energy Conversion and Management, 2015Co-Authors: Hadi Hosseinzade, Hoseyn Sayyaadi, M BabaelahiAbstract:Thermal models for the simulation of Stirling Engines need to have greater accuracy along with simple and low-cost calculation. In this regard, a new closed-form thermal model was presented for the thermal simulation of Stirling Engines. The new model called PFST (polytropic-finite speed thermodynamics) was developed based on the combination of polytropic analysis of expansion/compression processes and the concept of finite speed thermodynamics (FST). Therefore, compression/expansion works of compression/expansion processes and transferred heat into the heater of Stirling Engines were determined based on polytropic analysis, instead of isothermal processes of the ideal Stirling cycle. The calculated work of polytropic processes was corrected to include the effects of internal irreversibilities including pressure throttling in heat exchangers, mechanical friction, and finite motion of the pistons. Output power and thermal efficiency of Stirling Engines were calculated as functions of various engine parameters. The developed PFST model was implemented on a prototype Stirling engine, called GPU-3 engine, and the obtained results were compared with those of other closed-form and numerical models as well as experimental data. It was found that the new closed-form model, in addition to its simple and low-cost calculation, had the same order of accuracy as recently developed numerical models.
M Babaelahi - One of the best experts on this subject based on the ideXlab platform.
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analytical closed form model for predicting the power and efficiency of Stirling Engines based on a comprehensive numerical model and the genetic programming
Energy, 2016Co-Authors: M Babaelahi, Hoseyn SayyaadiAbstract:Abstract High accuracy and simplicity in use are two important required features of thermal models of Stirling Engines. A new numerical second-order thermal model was presented through the improvement of our previous modified-PSVL model in order to have an elevated accuracy. The modified-PSVL model was modified by considering a non-isothermal model for heater and cooler. Then, the model called as CPMS-Comprehensive Polytropic Model of Stirling engine, was used to simulate the GPU-3 Stirling engine, and the obtained results were compared with those of the previous thermal models as well as the experimental data. For the sack of the simplicity, the combination of the CPMS model and genetic programming was employed to generate analytical closed-form correlation. In this regards, a comprehensive data bank of results of the CPMS was constructed and exported to the GP tool and analytical expressions of the power, efficiency, and polytropic indexes were obtained. It was shown that the analytical correlations not only had the same accuracy as the CPMS model, but also, it can be simply used without difficulties of numerical models. The CPMS and its out coming analytical expressions, predicted the power and efficiency of the GPU-3 Stirling with +1.13% and +0.45 (as difference), respectively.
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modified psvl a second order model for thermal simulation of Stirling Engines based on convective polytropic heat transfer of working spaces
Applied Thermal Engineering, 2015Co-Authors: M Babaelahi, Hoseyn SayyaadiAbstract:Abstract The new numerical second order thermal model for the simulation of Stirling Engines was presented. In the new model, the previously developed model of the present authors called PSVL model (polytropic analysis of Stirling engine with various losses) was modified based on coupling the convective heat transfer mechanism to polytropic expansion/compression processes. Furthermore, an exponential temperature distribution of the gas along the regenerator length was assumed in the new model. Similar to the original PSVL model, effects of heat and mass leakages were implemented in basic differential equations and the ordinary differential equations (ODE) system was numerically solved by fourth order Runge-Kutta methods. Results of the numerical model were corrected to include various non-idealities. Finally, the new polytropic–convective model called modified PSVL was implemented to simulate he GPU-3 Stirling engine and the obtained results were compared with those of the previous thermal models as well as experimental data. It was found that the correction of PSVL led to better accuracy compared with the original PSVL as well as other models. Further, coupling the heat transfer to model caused a slightly greater amount of polytropic indexes than the original PSVL model.
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A new thermal model based on polytropic numerical simulation of Stirling Engines
Applied Energy, 2015Co-Authors: M Babaelahi, Hoseyn SayyaadiAbstract:The new numerical thermal model based on polytropic expansion/compression processes was developed for predicting thermal performance of Stirling Engines. In this regard, differential governing equations of early adiabatic model of Stirling Engines were modified to consider polytropic heat transfers of the working fluid to the surrounding through expansion/compression cylinder walls. Therefore, adiabatic expansion/compression processes of the early adiabatic model were substituted with polytropic expansion/compression processes in the new thermal model. In order to increase accuracy of the thermal model, various loss mechanisms including effect of mass leakage from working to buffer spaces and heat leakage from expansion to compression spaces, due to thermal conductivity (shuttle heat transfer effect) of the displacer, were implemented in basic differential equations of polytropic analysis. In addition, in a similar manner to the early simple analysis, effect of non-ideal heat recovery of the regenerator and hydraulic pressure drop were considered in heater, cooler and regenerator. Also, magnitude of the piston back pressure was corrected in terms of piston velocity using the principle of finite speed thermodynamics (FST) and mechanical friction between piston and cylinder was taken into account in the new thermal model. On the other hand, longitudinal heat conduction between the heater and cooler through the regenerator wall was modeled as an additional loss mechanism. Finally, the new model called polytropic analysis of Stirling engine with various losses (PSVL) mechanisms was applied to a prototype Stirling engine, namely GPU-3 Stirling engine, and the obtained results were evaluated through comparison with previous thermal models and experimental results. Based on the new PSVL model, the output power and thermal efficiency of the GPU-3 engine were predicted with +14.34% and +3.14% (as a difference), respectively.
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a new closed form analytical thermal model for simulating Stirling Engines based on polytropic finite speed thermodynamics
Energy Conversion and Management, 2015Co-Authors: Hadi Hosseinzade, Hoseyn Sayyaadi, M BabaelahiAbstract:Thermal models for the simulation of Stirling Engines need to have greater accuracy along with simple and low-cost calculation. In this regard, a new closed-form thermal model was presented for the thermal simulation of Stirling Engines. The new model called PFST (polytropic-finite speed thermodynamics) was developed based on the combination of polytropic analysis of expansion/compression processes and the concept of finite speed thermodynamics (FST). Therefore, compression/expansion works of compression/expansion processes and transferred heat into the heater of Stirling Engines were determined based on polytropic analysis, instead of isothermal processes of the ideal Stirling cycle. The calculated work of polytropic processes was corrected to include the effects of internal irreversibilities including pressure throttling in heat exchangers, mechanical friction, and finite motion of the pistons. Output power and thermal efficiency of Stirling Engines were calculated as functions of various engine parameters. The developed PFST model was implemented on a prototype Stirling engine, called GPU-3 engine, and the obtained results were compared with those of other closed-form and numerical models as well as experimental data. It was found that the new closed-form model, in addition to its simple and low-cost calculation, had the same order of accuracy as recently developed numerical models.
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Simple-II: A new numerical thermal model for predicting thermal performance of Stirling Engines
Energy, 2014Co-Authors: M Babaelahi, Hoseyn SayyaadiAbstract:A new thermal model called Simple-II was presented based on modification of the original Simple analysis. First, the engine was modeled considering adiabatic expansion and compression spaces, in which effect of gas leakage from cylinder to buffer space and shuttle effect of displacer were implemented in the basic differential equations. Moreover, non-ideal thermal operation of the regenerator and the longitudinal heat conduction between heater and cooler through the regenerator wall were considered. Based on the magnitudes of pressure drops in heat exchangers, values of pressure in the expansion and compression spaces were corrected. Furthermore, based on the theory of finite speed thermodynamics (FST), the corresponding power loss due to the piston motion and also the mechanical friction were considered. Simple-II was employed for thermal simulation of a prototype Stirling engine. Finally, result of the new model was evaluated by comprehensive comparison of experimental results with those of the previous models. The output power and thermal efficiency were predicted with +20.7% and +7.1% errors, respectively. Also, the regenerator was demonstrated to be the main source of power and heat losses; nevertheless, other loss mechanisms have reasonable effects on output power and/or thermal efficiency of Stirling Engines.
Somchai Wongwises - One of the best experts on this subject based on the ideXlab platform.
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a review of solar powered Stirling Engines and low temperature differential Stirling Engines
Renewable & Sustainable Energy Reviews, 2003Co-Authors: Bancha Kongtragool, Somchai WongwisesAbstract:This article provides a literature review on solar-powered Stirling Engines and low temperature differential Stirling Engines technology. A number of research works on the development of Stirling Engines, solar-powered Stirling Engines, and low temperature differential Stirling Engines is discussed. The aim of this review is to find a feasible solution which may lead to a preliminary conceptual design of a workable solar-powered low temperature differential Stirling engine. Results from the study indicate that Stirling Engines working with relatively low temperature air are potentially attractive Engines of the future, especially solar-powered low temperature differential Stirling Engines with vertical, double-acting, gamma-configuration.
Bancha Kongtragool - One of the best experts on this subject based on the ideXlab platform.
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a review of solar powered Stirling Engines and low temperature differential Stirling Engines
Renewable & Sustainable Energy Reviews, 2003Co-Authors: Bancha Kongtragool, Somchai WongwisesAbstract:This article provides a literature review on solar-powered Stirling Engines and low temperature differential Stirling Engines technology. A number of research works on the development of Stirling Engines, solar-powered Stirling Engines, and low temperature differential Stirling Engines is discussed. The aim of this review is to find a feasible solution which may lead to a preliminary conceptual design of a workable solar-powered low temperature differential Stirling engine. Results from the study indicate that Stirling Engines working with relatively low temperature air are potentially attractive Engines of the future, especially solar-powered low temperature differential Stirling Engines with vertical, double-acting, gamma-configuration.
Valeriy Kirillov - One of the best experts on this subject based on the ideXlab platform.
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single piston alternative to Stirling Engines
Applied Energy, 2012Co-Authors: Maxim Glushenkov, Martin Sprenkeler, Alexander Kronberg, Valeriy KirillovAbstract:Thermodynamic analysis of an unconventional heat engine was performed. The engine studied has a number of advantages compared to state-of-the-art Stirling Engines. The main advantage of the engine proposed is its simplicity. A power piston is integral with a displacer and a heat regenerator. It allows solving the problem of the high-temperature sealing of the piston and the displacer typical of all types of Stirling Engines. In addition the design proposed provides ideal use of the displacer volume eliminating heat losses from outside gas circuit. Both strokes of the piston are working ones in contrary to any other types of piston Engines. The engine can be considered as maintenance-free as it has no piston rings or any other rubbing components requiring lubrication. The only seal is contactless and wear free. It is located in the cold part of the cylinder. As a result the leakage rate in operation can be one-two orders of magnitude as small as that in Stirling Engines. Balancing of the engine is much easy compared to Stirling Engines with two reciprocating masses because of the only moving part inside the engine cylinder. The engine suits ideally to be fuelled with “difficult” fuels such as bio oil and can be used as a prime mover for micro-CHP systems.
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single piston alternative to Stirling Engines
Applied Energy, 2012Co-Authors: Maxim Glushenkov, Martin Sprenkeler, Alexander Kronberg, Valeriy KirillovAbstract:Abstract Thermodynamic analysis of an unconventional heat engine was performed. The engine studied has a number of advantages compared to state-of-the-art Stirling Engines. The main advantage of the engine proposed is its simplicity. A power piston is integral with a displacer and a heat regenerator. It allows solving the problem of the high-temperature sealing of the piston and the displacer typical of all types of Stirling Engines. In addition the design proposed provides ideal use of the displacer volume eliminating heat losses from outside gas circuit. Both strokes of the piston are working ones in contrary to any other types of piston Engines. The engine can be considered as maintenance-free as it has no piston rings or any other rubbing components requiring lubrication. The only seal is contactless and wear free. It is located in the cold part of the cylinder. As a result the leakage rate in operation can be one-two orders of magnitude as small as that in Stirling Engines. Balancing of the engine is much easy compared to Stirling Engines with two reciprocating masses because of the only moving part inside the engine cylinder. The engine suits ideally to be fuelled with “difficult” fuels such as bio oil and can be used as a prime mover for micro-CHP systems. The thermodynamic model developed incorporates non-ideal features of the cycle, such as specific regenerator efficiency, dead volumes and other geometrical parameters of the engine. The model shows that the energy efficiency is highly sensitive to regenerator performance. For realistic geometric and operating parameters and the regenerator efficiency of about 95% the ultimate energy conversion efficiency of the engine proposed can be as high as 40–50%. A prototype of the engine was built and the feasibility of the engine concept was demonstrated.