A new realistic characteristics of real energy conversion processes: A contribution of finite size thermodynamics

Overview & Synopsis

The perfection of energy conversion process is currently gauged through out different kind of quality indicator that compare the real performance of the process to that of the ideal reversible Carnot process. The criteria resulting from this commonly used approach give a false idea of the real quality of the energy conversion process. Indeed, the real energy conversion process that generates true energetic power levels is compared to ideal associated Carnot process that generates zero-output power level. The real conversion process implementing finite heat exchanger areas is then compared to the ideal process that needs infinite heat exchanger area to fulfill the same power requirements. This paper presents a new thermo-economic approach, based on Finite Size Thermodynamics, more suitable for qualifying real energy conversion processes. This approach takes into account the external thermodynamic irreversibilities relative to the heat transfer rate through a finite size heat exchanger surface between the external heat sources or sinks and an ideal process without internal thermodynamic irreversibilities. This new approach enables to evaluate more realistically ideal performances of real energy conversion processes. It makes possible the definition of new criteria that characterize more reasonably the quality of a real thermal process compared with the corresponding endoreversible process either for the same power duty (performance criterion) or either for the same involved total heat exchanger surface (technical criterion).