CYCLES WITH ONLY ONE WORK EXCHANGER, AND THERMODYNAMIC ANALYSIS OF HEAT ENGINE WITH A KNUDSEN-EFFECT PRESSURE GENERATOR

摘要

The analysis on the basis of the two laws of thermodynamics entails that, in order to obtain work, two heat exchangers and one work exchanger are necessary (even if in general they are not sufficient). In general two work exchangers (turbine and pump or compressor) are present. Nevertheless, since the presence of two work exchangers is not a consequence of the two laws of thermodynamics, one must not be surprised that, in some cases, it is possible to obtain work in a continuous process with only one work exchanger. Examples of similar systems have been already considered in literature. We quote a magnetocaloric converter of thermal energy into mechanical energy and a steam engine cycle with a steam-water injector instead of water pump. A new pressure generator for a heat engine, which has been recently proposed, is a similar case. The device works on the basis of the thermal transport of gas according to the "Knudsen effect". The aim of this paper is a particular thermodynamic analysis of this last case after a general consideration of the cycles with only one work exchanger.