The Direct Method from Finite Speed Thermodynamics is used in order to Determine in a complete analytical format of the COP and consumed Power of a Reversed Cvasi-Carnot Cycle (Refrigeration Machine with vapor) taking into account internal irreversibility generate by: Finite Speed, Friction, Throttling and Internal Heat Loses.

The paper presents an analysis of a recuperative gas turbine system used for micro-cogeneration based on energetic and exergetic principles. The system is composed of two compressors (one for the fuel, the other for air), a combustion chamber, a gas turbine, a recuperator used to preheat the air before entering the combustion chamber and a heat exchanger for heating water. The analysis compares three different configurations obtained by placing the recuperator upstream of, downstream of, or in parallel with the water heater. It is subject to the following assumptions: the fuel is injected steadily and ideally (without irreversibility), the air is a perfect gas, the heat exchangers are adiabatically isolated from the surroundings and the compressors and the turbine are adiabatic. A detailed analysis of the thermal and mechanical irreversibilities of the cycle is also presented. The optimization goal is to minimize the entropy generation or to maximize the useful exergy output of the system. With this approach the best configuration for a specified operating regime of micro-cogeneration can be determined.

The aim of this paper is to propose a set of thermal models for the regenerator by taking into account the time dependent heat transfer processes, and to combine them with the thermodynamic lumped description of the solar Stirling engine, accordingly to recent description. By using analytical and numerical methods, the optimum power of the engine is sought when various constrains (or not) are considered, particularly fixed heat transfer rate available at the source. A sensitivity analysis of the optimum power of the engine and the corresponding set of thermodynamics state variable with respect to the main model parameters of the machine is performed. The main conclusion of this work will reconsider the transient behavior of the regenerator heat exchanger for maximum power output and corresponding optimum design of a solar Stirling engine.

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