Approaching an Efficient and Feasible Carnot Engine by Carnot Cycle Analysis

Abstract

Based on the knowledge exhibited in the literature on the Carnot cycle, a preliminary study is carried out on Carnot machines capable of implementing the Carnot cycle at high thermal efficiency. Therefore, two engine structures are proposed: (i) reciprocating single and double-acting cylinder-based thermal engines implemented under a closed processes-based Carnot thermal cycle characterised by a mechanical structure internally coupled, and (ii) similar engines characterised by a mechanical structure internally decoupled. In order to perform the cycle analysis, however, observational (experimental) evidence confirms on a daily basis the fact that there are two performance criteria: conventional (output net work/input heat) thermal efficiency and output/input energetic-based first law efficiency. Based on such premises, this study investigates both coupled and decoupled Carnot engine structures. The results confirm that an important fraction of heat can be converted into useful work by configuring a decoupled structure of the Carnot engine. Indicative results support the use of internally decoupled thermal machines, especially when the heat source has a low or medium temperature. Even at high temperatures, such machines are advantageous in terms of energy efficiency. Furthermore, avoiding internal coupling allows for power regulation without disturbing interactions due to variations in load, thus enabling robust control.