Stoian Petrescu

Solar Thermal Engineering

Department of Renewable Energies, Faculty of New Sciences & Technologies, University of Tehran, Tehran, Iran Department of Physics and Mechanics, Faculty of Sciences and Technology, University Henri Poincaré, Nancy, France Department of Engineering Thermodynamics, Engines, Thermal and Refrigeration Equipments, University Politehnica of Bucharest, Bucharest, Romania Renewable Energy Laboratory, Jijel University, 1800 Jijel, Algeria

Nonlinear Thermodynamic Analysis and Optimization of a Carnot Engine Cycle

As part of the efforts to unify the various branches of Irreversible Thermodynamics, the proposed work reconsiders the approach of the Carnot engine taking into account the finite physical dimensions (heat transfer conductances) and the finite speed of the piston. The models introduce the irreversibility of the engine by two methods involving different constraints. The first method introduces the irreversibility by a so-called irreversibility ratio in the entropy balance applied to the cycle, while in the second method it is emphasized by the entropy generation rate. Various forms of heat transfer laws are analyzed, but most of the results are given for the case of the linear law. Also, individual cases are studied and reported in order to provide a simple analytical form of the results. The engine model developed allowed a formal optimization using the calculus of variations.

Validation of a Simulation Model for a Combined Otto and Stirling Cycle Power Plant

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

Concepts and fundamental equations in Thermodynamics with Finite Speed

This paper presents the basic concepts and fundamental equations of the Thermodynamics with Finite Speed (TFS) resulted by the systematically study of the thermal reciprocating machine in relation with the piston finite speed and thermal molecular speed measured in the considered thermodynamic system. These concepts are based on the idea that any propagation of the interaction in the thermodynamic systems of finite dimensions is achieved by finite speeds: (1) - piston speed, (2) - average speed of the gas molecules inside the cylinder. A specific approach (scheme of calculation) for non-equilibrium (irreversible) thermodynamic processes is developed within TFS in order to find the fundamental equations appropriate for Optimizing Efficiency or COP and Power of thermal reciprocating machines. Analytical equations for all 5 irreversible thermodynamic processes in gases (isometric, isothermal, isobaric, adiabatic, polytropic) are deduced by integration of the combined First and Second Laws equation for processes with Finite Speed. This paper is limited to Irreversible Processes with Finite Speed, without taking into account the Friction and Throttling effects. It also notes the main moments in the development of TFS that led to these concepts and fundamental equations.