The Experts below are selected from a list of 3027 Experts worldwide ranked by ideXlab platform

Mohammad H. Ahmadi - One of the best experts on this subject based on the ideXlab platform.

Michel Feidt - One of the best experts on this subject based on the ideXlab platform.

  • Designing a powered combined Otto and Stirling Cycle power plant through multi-objective optimization approach
    Renewable and Sustainable Energy Reviews, 2016
    Co-Authors: Mohammad H. Ahmadi, Hadi Hosseinzade, Emin Acikkalp, Fathollah Pourfayaz, Iskander Tlili, Mohammad Ali Ahmadi, Michel Feidt
    Abstract:

    Throughout the recent years, several efforts have been conducted in studying Stirling engine which have yielded various models for analysis of Stirling engine thermal efficiency and output power. In the present study, the applicability of a combined Stirling and Otto Cycle power plant where a Stirling Cycle engine would serve as a bottoming Cycle for a stationary Otto Cycle engine is investigated. Output power of Stirling engine and Stirling engine thermal efficiency are optimized and total pressure losses of Stirling engine is optimized executing NSGA approach and finite speed thermodynamic analysis. The outcomes gained are satisfactory verified versus actual recorded data of Stirling engine. Decision making was performed via three well-known methods. Finally, error analysis was performed on the outputs obtained from this optimization.

  • validation of a simulation model for a combined otto and Stirling Cycle power plant
    ASME 2010 4th International Conference on Energy Sustainability Volume 2, 2010
    Co-Authors: Jim Mcgovern, Michel Feidt, Barry Cullen, Stoian Petrescu
    Abstract:

    A project has been underway at the Dublin Institute of Technology (DIT) to investigate the feasibility of a combined Otto and Stirling Cycle power plant in which a Stirling Cycle engine would serve as a bottoming Cycle for a stationary Otto Cycle engine. This type of combined Cycle plant is considered to have good potential for industrial use. This paper describes work by DIT and collaborators to validate a computer simulation model of the combined Cycle plant. In investigating the feasibility of the type of combined Cycle that is proposed there are a range of practical realities to be faced and addressed. Reliable performance data for the component engines are required over a wide range of operating conditions, but there are practical difficulties in accessing such data. A simulation model is required that is sufficiently detailed to represent all important performance aspects and that is capable of being validated. Thermodynamicists currently employ a diverse range of modeling, analysis and optimization techniques for the component engines and the combined Cycle. These techniques include traditional component and process simulation, exergy analysis, entropy generation minimization, exergoeconomics, finite time thermodynamics and finite dimensional optimization thermodynamics methodology (FDOT). In the context outlined, the purpose of the present paper is to come up with a practical validation of a practical computer simulation model of the proposed combined Otto and Stirling Cycle Power Plant.Copyright © 2010 by ASME

Hans-detlev Kuehl - One of the best experts on this subject based on the ideXlab platform.

  • numerical model for Stirling Cycle machines including a differential simulation of the appendix gap
    Applied Thermal Engineering, 2017
    Co-Authors: Jan Sauer, Hans-detlev Kuehl
    Abstract:

    Abstract One-dimensional differential models are an important tool for the design optimization of Stirling engines and other regenerative machines, since they require far less computing time than multi-dimensional CFD-models and are yet capable of describing the various loss mechanisms including their mutual interdependencies. So far, the so-called appendix gap losses – thermal losses caused by the annular gap around the insulating dome, which is typically attached to pistons or displacers exposed to elevated or cryogenic temperatures – have usually not been directly included in differential models, because available estimates based on simplified analytical models only predicted a moderate magnitude of these. Instead, these estimates were therefore simply superimposed on the numerical results. However, recent findings indicate that these losses have thus been underestimated, since the analytical models are based on partially questionable assumptions. To investigate their actual magnitude, an existing one-dimensional differential simulation code, which is capable of modelling various regenerative Cycles by selection of the required components from a library, was extended by another cylinder component that includes a differential model of the appendix gap. This contribution presents and discusses the results obtained by this extended simulation code in comparison to the predictions by a simplified and a more enhanced analytical model. It turns out that the numerical results are highly dependent on the modelling of both axial convection and the radial heat exchange between the gas and the walls, and that the unsteady flow and temperature profiles in the gap presumably need to be considered here by enhanced approaches – possibly based on complex numbers. Furthermore, an introductory overview of the simulation code is given, particularly focusing on the model structure, the basic assumptions and limitations of applicability, the discretization technique as well as the formulation and the solution of the differential equation system.

  • New Analytical Model for Appendix Gap Losses in Stirling Cycle Machines
    Journal of Thermophysics and Heat Transfer, 2016
    Co-Authors: Jens Pfeiffer, Hans-detlev Kuehl
    Abstract:

    This contribution presents a new enhanced modeling approach for appendix gap losses for Stirling Cycle machines. According to recent findings, previously available models are based on too gross simplifications and require further refinement. It was demonstrated that the flow in the gap is laminar but unsteady, and that existing modeling approaches can be improved by analytical solutions for the flow pattern and the temperature profile in the gap. Assuming locally constant values for the fluid density and the axial temperature gradient, such analytical solutions have been derived as complex functions, accounting for both inertia effects and the correct pressure-driven flow component as imposed by the displacer seal and the mass balance, whereas previous models are impaired by the assumption of plain drag flow. Thus, a refined evaluation of the appendix gap losses was possible. Furthermore, the sum of these losses was found to depend on the axial gap position in case of a constant axial temperature gradient...

  • review of models for appendix gap losses in Stirling Cycle machines
    Journal of Propulsion and Power, 2014
    Co-Authors: Jens Pfeiffer, Hans-detlev Kuehl
    Abstract:

    A thorough understanding of appendix gap losses may help to improve the efficiency of Stirling Cycle machines by optimizing related design parameters, particularly the gap width. Reported deviations between theoretical predictions and experimental results suggest the need for further refinement of the available models, which can be classified into two groups. First, there are analytical closed-form approaches, the underlying assumptions of which will be discussed regarding their impact on accuracy. Second, there are some numerical, differential approaches. The general applicability of these appears to be limited due to a lack of sufficiently detailed experimental data and due to uncertainties concerning the modeling of the heat transfer. The existing modeling approaches may generally be improved by analytical solutions for the flow pattern and the temperature profile in the gap, which can be obtained, because the flow is found to be essentially laminar. However, inertia effects are not negligible, which r...

Ö Ercan Ataer - One of the best experts on this subject based on the ideXlab platform.

  • performance of v type Stirling Cycle refrigerator for different working fluids
    International Journal of Refrigeration-revue Internationale Du Froid, 2010
    Co-Authors: Yusuf Tekin, Ö Ercan Ataer
    Abstract:

    The thermodynamic analysis of a V-type Stirling-Cycle Refrigerator (VSR) is performed for air, hydrogen and helium as the working fluid and the performance of the VSR is investigated. The V-type Stirling-Cycle refrigerator consists of expansion and compression spaces, cooler, heater and regenerator, and it is assumed that the control volumes are subjected to a periodic mass flow. The basic equations of the VSR are derived for per unit crank angle, so time does not appear in the equations. A computer program is prepared in FORTRAN, and the basic equations are solved iteratively. The mass, temperature and density of working fluid in each control volume are calculated for different charge pressures, engine speeds, and for fixed heater and cooler surface temperatures. The work, instantaneous pressure and the COP of the VSR are calculated. The results are obtained for different working fluids, and given by diagrams.

  • Thermodynamic analysis of the V-type Stirling-Cycle refrigerator
    International Journal of Refrigeration-revue Internationale Du Froid, 2005
    Co-Authors: Ö Ercan Ataer, Halit Karabulut
    Abstract:

    The thermodynamic analysis of a V-type Stirling-Cycle refrigerator is performed. The Stirling-Cycle refrigerator consists of expansion and compression spaces, cooler, heater and regenerator, and divided into 14 fixed control volumes subjected to a periodic mass flow. The conservation of mass and energy equation are written for each control volume. A computer program is prepared in FORTRAN, and the basic equations are solved iteratively. The mass, temperature and density of working fluid in each control volume are calculated for a given charge pressure, engine speed, and fixed heater and cooler surface temperatures, and the results are obtained from a PC. The heat transfer coefficients are assumed constant. The work, instantaneous pressure and COP of the Stirling-Cycle refrigerator are also calculated. The steady cyclic conditions are obtained for temperature after few Cycles and the results are given by diagrams.

Saeed Dehghani - One of the best experts on this subject based on the ideXlab platform.