2017/10/02 by Ilki Kim, Hui Wan, Kim, Ilki +3
Engineering · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #FOS: Physical sciences #General Physics (physics.gen-ph) #Heat Transfer and Optimization #Thermodynamic and Exergetic Analyses of Power and Cooling Systems
paper · pdf · doi:10.48550/arxiv.1710.03570
openalex publication_date 2017/10/02 · openalex created_date 2017/10/20 · openalex updated_date 2026/07/28
We consider two specific thermodynamic cycles of engine operating in a finite time coupled to two thermal reservoirs with a finite heat capacity: The Carnot-type cycle and the Lorenz-type cycle. By means of the endo-reversible thermodynamics, we then discuss the power output of engine and its optimization. In doing so, we treat the temporal duration of a single cycle rigorously, i.e., without neglecting the duration of its adiabatic parts. Then we find that the maximally obtainable power output Pm and the engine efficiency ηm at the point of Pm explicitly depend on the heat conductance and the compression ratio. From this, it is immediate to observe that the well-known results available in many references, in particular the (compression-ratio-independent) Curzon-Ahlborn-Novikov expressions such as ηm --> ηCAN = 1 - (TL/TH)^(1/2) with the temperatures (TH, TL) of hot and cold reservoirs only, can be recovered, but, significantly enough, in the limit of a vanishingly small heat conductance and an infinitely large compression ratio only. Our result implies that the endo-reversible model of a thermal machine operating in a finite time and so producing a finite power output with the Curzon-Ahlborn-Novikov results should be limited in its own validity regime.