Mitsubishi Heavy Industries Thermal Systems, Ltd. has developed a large-capacity two-stage refrigeration compressor which uses low-GWP CO2 as the refrigerant. To increase capacity to 40 horsepower from the conventional 10, the compressor's basic structure was reviewed and a mechanism for intercooler, etc. were added. The rated compressor speed was decreased to reduce mechanical loss, achieving high efficiency. The lubricant oil viscosity was measured under actual operating conditions. Based on the results, oil passage inside the compressor and bearing clearance were optimized to ensure reliability. Consequently, the CO2 compressor has large capacity, high efficiency and high reliability, and contributes to the reduction of global environmental load.
