Influence of Heat Loss on the Second-Law Efficiency of an Otto Cycle

The second-law efficiency is one of the most important criteria for measuring the performance of a thermodynamic system that is described as the ratio of the actual thermal efficiency (first-law efficiency) to the maximum possible (reversible) thermal efficiency under the same conditions. In this article, the second-law efficiency of an air-standard Otto cycle with consideration of heat losses is analyzed, using finite-time thermodynamics (FTT). Moreover, influence of various design parameters such as the initial temperature of the working fluid and the constants related to combustion and heat transfer through the cylinder wall, on variation curve of the second-law efficiency versus first-law efficiency are indicated. The obtained results of this article also can be a useful guide for the analysis and comparison of real engines.