An investigation of possibilities for CO2 compression in a hermetic compressor

A small single cylinder hermetic reciprocating compressor is built to compress the refrigerant carbon dioxide (CO2). The design suction pressure is 30 bar, i.e. an evaporating temperature of -5.6 degree Celsius and the design discharge pressure is 100 bar, i.e. a supercritical pressure. The compressor was designed to work with a maximum pressure difference of 100 bar. A performance test has been conducted in a compressor test rig which was built to test small CO2 compressors. The compressor test rig system is described together with a brief explanation of how the operation of the test is conducted. Maximum test rig pressure is 140 bar. Some aspects regarding the choice of appropriate mineral oil lubricant for the CO2 compressor are also investigated. Experimental results have been displayed in a pressure ratio range which is typical for CO2 compressors in most applications. Measurements of cylinder pressure, discharge chamber pressure and suction chamber pressure are displayed as a function of crank angle.