The purpose of this study is to evaluate the heat transfer performance of the evaporator. The evaporator is a shell-and-tube type heat exchanger with high-flux tubes. The experimental apparatus is a 23 USRT chiller system with working refrigerant, R-404A. By monitoring temperature and pressures, the superheat and stages of compressors were kept stable through PLC(Programmable Logic Control) with PID(Proportional Integral Derivative) control. The mass flow rate of refrigerant was adjusted ranging from 0.3 to 0.7 ㎏/s according to each flow rate of chilled water ranging from 12 to 18 ㎥/hr. In the experiment, it was verified that the heat transfer coefficient of the refrigerant could be increased by roughly 35 % when volume flow rate of the water is also increased from 12 to 18 ㎥/hr.