Ultra High Pressure Tribometer for Testing CO2Refrigerant at Chamber Pressures up to 2000 psi to Simulate Compressor Conditions

Abstract

The growing interest for using the natural refrigerant carbon dioxide (CO₂) in refrigeration and air-conditioning applications instead of HFC refrigerants, due to environmental concerns, has led to the development of an ultra high pressure tribometer (UHPT) specifically tailored for testing in CO₂ environment. The existing research on tribology related to CO₂ environment has focused on investigations at relatively low chamber pressures due to equipment restrictions. The UHPT is a unique tribometer that has been custom designed and manufactured to allow testing under CO₂ refrigerant at environmental pressures comparable to those found in compressors. A special housing, which surrounds the tribological surfaces subject to testing, is capable of withstanding chamber pressures up to 13.8 MPa (2000 psi) and can be temperature controlled from 0°C to 100°C via a thermal control system. A multi-axis strain gauge force transducer measures the applied load, frictional forces, and moments during friction testing, and computer control permits different loading profiles. Using this machine, experiments were performed at a range of pressures between 1.4 MPa (200 psi) and 6.9 MPa (1000 psi) of CO₂ refrigerant. The results suggest a slightly better tribological performance at higher pressures compared to lower pressures.