抄録
From ozone depletion and global warming, it is urgent need to convert from HFCs to natural refrigerants. Among several candidate of natural refrigerants, CO_2 which has an excellent thermal property has advantage for practical application. However study of heat transfer cofficient and pressure drop hasn't been sufficiently explored and there isn't any available correlation. Furthermore, research on oil mixing effect is very limited. Under these circumstance, the purpose of this research is to grasp the feature of oil mixing effect on thermal and fluid dynamic behaviors
