ULTRA HIGH PRESSURE TRIBOMETER FOR TESTING CO_2 REFRIGERANT AT REALISTIC COMPRESSOR CONDITIONS AND THE ROLE OF CO_2 IN THE TRIBOLOGICAL BEHAVIOR OF COMPRESSOR SURFACES

摘要

In recent years, the environmental necessity to replace HFC refrigerants with natural refrigerants like carbon dioxide (CO_2) in refrigeration and air-conditioning applications has led to the development of an Ultra High Pressure Tribometer (UHPT) specifically customized for testing in CO_2 environment at pressures comparable to those found in compressors up to 13.8 MPa (2000 psi). It was found that at three different pressures of CO_2 refrigerant under unlubricated conditions the experimental results were similar. However, under boundary-lubricated conditions, the highest pressure had a slightly more positive effect on friction than in the case of the lower pressures. Furthermore, the role of oxygen and in particular CO_2 in the tribological performance of compressor surfaces was examined. It was found that the presence of oxygen is beneficial and that the use of CO_2 promotes a different wear mechanism than in the case of pure O_2 while it is superior to other environments.