In order to improve the separation efficiency and decrease the pressure loss

the cyclone oil separators used in air conditioner system were designed with optimization. Based on the fluid simulation

the influences of different parameters on the separation efficiency and pressure loss of oil separator were researched

from which the optimum size ratios were obtained. The performances of the oil separator designed according to the optimum size ratio were tested in an air conditioning system. The experimental results show that in oil-return condition (lowest refrigerant velocity) the separation efficiency of new oil separator is increased from 95.5% to 99.0%

while in rated cooling capacity condition

the separation efficiency is increased from 97.3% to 99.6%

and the pressure loss is decreased from 55.2 kPa to 23.1 kPa. The distribution function of oil-particle is also obtained from experiment results.