A review on airflow management in data centers

Highlights: • The airflow management technologies in data centers are classified as long and short distance in the present review. • Hot-air recirculation, cold-air bypass, leakages, and airflow distributions are the most critical factors. • Strategies on improving airflow uniformity and preventing bypass and hot-air recirculation are reviewed. • Computational fluid dynamics plays essential role but requires prior calibration before further implementation. -- Abstract: This study provides a review upon airflow management in data centers. Based on the available airflow path, cooling systems in data centers are categorized as long-distance cooling or short-distance cooling systems. Investigations on airflow management include tests in real data center or in simulated data center. Besides, the computational fluid dynamics (CFD) had been widely employed upon the thermal and airflow management of the data centers. For the long-distance cooling system, the airflow management normally adopts raised-floor configuration and hot/cold aisle arrangement. The major problems in airflow management include hot-air recirculation, cold-air bypass, leakages, over-provisioned and under-provisioned air supply, and airflow/temperature non-uniformity. The aforementioned effects often interact with the geometry layout of the data center. Related literatures regarding the effect of plenum depth, perforated tiles, enhanced facility such as induced bypass fans, infrastructure layout, aisle containment and leakage are discussed and compared. In addition, studies on the overhead air supply method are also examined and compared with the raised-floor ones. For the short-distance cooling system, the effect of server layout and heat exchanger layout concerning the airflow uniformity are investigated. It is found that the appropriate management of the original design into centralized server layout can ease the mal-distribution of airflow into the severs by 30%. This review aims to emphasize the criteria of implementing airflow management to data centers that serve as a reference guide for energy saving in data center as far as airflow arrangement is concerned. Moreover, some recommended future research efforts are also addressed.