The main objective of this paper is to estimate the system performance of an evaporative cooling assisted outdoor air system for air conditioning a data center. To evaluate the computer room air conditioning (CRAC) system used evaporative cooling technology, a mock-up for evaporative cooling assisted outdoor air system was designed. The feasibility of the evaporative cooling assisted outdoor air system is analysed by experimental test for a modular data center in Anseong, Korea. A mock-up system is designed by 43,000 m3/h of design fan flow, 160kW of the cooling capacity for air conditioning a data center. A design condition for the indirect evaporative cooler was set in 50% of sensible heat exchange efficiency and 65% of indirect evaporative cooling efficiency, respectively. A server rack simulator was installed to adjust the 160kW of sensible heat emission of modular data center. The experiment results show that the 59% of a sensible heat exchange efficiency and 78% of indirect evaporative cooling efficiency under experimental conditions
