Teaching Reitlinger Cycles To Improve Students' Knowledge And Comprehension Of Thermodynamics

Abstract

The second law of thermodynamics puts a limit on the thermal efficiency of heat engines. This limit value is the efficiency of the ideal reversible engine represented by the Carnot cycle. During the lectures on physics, the emphasis on this cycle is generally so strong that students could be induced to consider the Carnot cycle as the only cycle having the best thermal efficiency. In fact, an entire class of cycles exists possessing the same maximum efficiency: this class is that of the regenerative Reitlinger cycles. Here we propose to teach also these cycles to the engineering students of physics classes, to improve their knowledge and comprehension of thermodynamics. Introduction: Generally, the Carnot cycle is the only thermodynamic cycle that, during the lectures on physics, is discussed as having the maximum possible thermal efficiency. This happens because Carnot cycle is directly connected to the second law of thermodynamics, which puts a limit on the thermal efficiency of heat engines. This limit value is the efficiency of the ideal reversible engine cycle represented by the Carnot cycle. Sometimes, an approach considering only Carnot engines with emphasis on their efficiency, could yield the following result: it is unknown that an entire class of cycles exists, having a thermal efficiency which is the same of that of Carnot cycle. This is the class of the regenerative Reitlinger cycles. Of course, since a large part of engineering students will be required as engineers to deal with relatively simple thermodynamic problems, a discussion of Reitlinger cycles could appear as unnecessary. However, it is unquestionable that a proper knowledge of the fundamentals of thermodynamics is necessary for engineers as well as for scientists in general. For this reason, in the following discussion, we will propose some notes suitable for teaching these cycles to students of physics classes, to improve their knowledge and comprehension of thermodynamics.