Development of the CO2 hermetic compressor

Natural refrigerant has been studied as alternatives for HFC under the regulations of global warming gases. Especially, carbon dioxide is nontoxic, inflammable, and cheap refrigerant, therefore worldwide research is done in various refrigerating and air-conditioning applications. But working pressure of carbon dioxide is very high. (High pressure is about 9-10MPa, and low pressure is about 3-4MPa.) Therefore development of the compressor which can operate with high efficiency under such condition, has been expected. We developed a prototype C02 hermetic compressor, which is able to use in carbon dioxide refrigerating systems for practical use. The compressor has small dimensions such as 117.2mm outer diameter, 244.3mm tall, and 2.633cc displacement. The compressor has two rolling pistons, and it leads to low-vibration, low-noise. In addition, two-stage compression with two cylinders is adopted, because pressure deference is too large to compress in one stage. In first stage, the suction gas is raised up to about 5-6MPa (what we call intermediate pressure). And inner pressure of the shell case is intermediate pressure to minimize gas leakage between compressing rooms and inner space of shell case. As a result, the compressor achieved high efficiency and high-reliability by these technology. After this, we plan to study heat pump water heater and various refrigerating and air-conditioning applications with C02.