Oil separator and refrigerant compressor having the same

An oil separator for a CO2 refrigerant cycle, comprising:

• a separation part including a separation cylinder, an inner cylinder and an inlet pipe, the inner cylinder having an outer diameter smaller than an inner diameter of the separation cylinder and disposed in the separation cylinder, the inlet pipe connecting to the separation cylinder tangential to an inner surface of the separation cylinder, such that refrigerant introduced in the separation cylinder from the inlet pipe turns or whirls in a cylindrical inner space along the inner surface of the separation cylinder, the separation part defining an inlet opening in the inner surface of the separation cylinder to allow CO2 refrigerant containing oil from the inlet pipe to enter the separation cylinder, the separation part separating the oil from the CO2 refrigerant by centrifugal force while turning the CO2 refrigerant containing the oil along the inner surface of the separation cylinder;
• and
• an oil storage part disposed in communication with the separation cylinder, the oil storage part storing separated oil therein, wherein
• the separation part provides a ratio G/A of a flow rate G (kg/h) of the CO2 refrigerant flowing into the separation cylinder from the inlet pipe under a rated condition to a cross-sectional area A (mm2) of the inlet opening is at least 4, and at most 20 such that an oil separation efficiency is improved by increasing the centrifugal force in response to an increase in velocity of the refrigerant flowing in the separation part while reducing energy loss.