Abstract: The present invention refers to a procedure and a machine which make it possible to produce a quasi-isothermal compression or expansion process in any thermodynamic cycle consisting of such transformations. The procedure is possible owing to the fact that heat exchangers (A, B) independent of each other are used, in each of these heat exchangers (A, B) the working agent circulating intermittently in only one direction owing to the fact that the exchangers (A and B) are successively and cyclically connected to and disconnected from the volume of the working space (a).