The present work describe tests of performance of a positive displacement rotary compressor which is part of a new type of refrigerating machine under development. The working fluid is air and the machine operates at the Brayton Cycle. The mass flow rate, eventual mass leakages, the power delivered to the compressor shaft and the actual power developed are obtained based upon experimental procedures. The theorectical mass flow rate and the isentropic power was calculed through a theorectical simulation, and, from these results, the isentropic mechanical and volumetric efficiencies have been evaluated allowing the determination of the favorable and critical conditions of operation. An uncertainty analysis is developed in order to control the experimental procedures and acuracy of the experiments conducted. Using experimental results as an input, a classical avaiability thermodynamics analysis of the process was developed in order to explain the nature of the associated irreversibilities and to indicate the optimum conditions of operation of the compressor. Based upon the described approach, this new type of refrigerating machine has been carefully analysed. Aiming better performance, design modifications are suggested as an attempt to better qualify this type of compressor for operation in systems which operate in the Brayton Cycle. Finalle, an improved design of an expander is discussed.