抄録
Performance test of CO_2 heat pump was carried out experimentally. Effects of refrigeration oil on the performance were especially investigated. The experiments were conducted under the different oil circulation ratio from 0 to 1.5 mass%. Flow configurations of the oil were observed. Flow of oil droplets and oil film on the wall started to be observed from the oil circulation ratio of 0.1mass%. The oil film was formed on the entire wall and its thickness increased with the increase of mass flux. The COP was decreased with increase of the oil circulation ratio and the decrease is saturated from the oil circulation ratio of 0.5mass%.
