Optimization of Outside Air Cooling in Data Centers

Airside economizers in data centers introducing outside air directly in cold aisles or at CRAC level have been considered recently to reduce overall energy to cool IT equipment. However, such designs limit the operational envelope of free cooling based on the required supply air temperature to the IT equipment. More studies are required to optimize airside economizer layouts to increase the operation time and hence, increase the energy savings. This paper presents a case study of different outside air delivery configurations including outside air introduced in cold aisles, in plenum close to CRAC units’ supply side, at return side of CRAC units and in hot aisles. The temperature and flow fields are studied numerically and are compared to each other. Mixing of the cooler outside air with the hot air is studied to determine optimal local distribution of the outside air in a non-homogeneous data center to maximize natural cooling. The paper also quantifies the annual average performance of the outside air infrastructure to include the effects of the seasonal variations in the ambient temperature.