The vapor injection refrigeration cycle using the scroll compressor driven by inverter was investigated to improve the performance of room air conditioner with R 410A. One injection hole was bored on a fixed scroll plate, and through this hole the vapor refrigeration is injected into two compression rooms of a scroll compressor at different time. Then the pressure change of the compression room and the performance of vapor injection refrigeration cycle are calculated. And the performance of the room air conditioner using vapor injection refrigeration cycle was measured. As the result, the cooling/heating compressor input was decreased to 7.4/3.2 % at capacity 4.0/5.9 kW, and the heating capacity at outdoor temperature -15 °C was increased to 11.9 %.
