Raised-floor air supply (RFAS) system is widely used in data centers (DCs) for its superior thermal environment and air distribution. However, the occurrence of leakage and bypass airflow (LBA) results in a poor thermal environment and ineffective air cooling in a computer room. Most existing DCs either failed to consider the above airflow effects incurring hot spots, or considered these effects using over-cooling which resulted in high energy consumption. In this paper, we propose a determination method of supply airflow rate for computer room air conditioning (CRAC). With the two-dimensional network diagram of airflow and heat transfer in a DC, the relationship of airflow rates between server demand and CRAC supply is deduced based on the conservation of energy. Then a CFD model was built according to a practical DC and its accuracy was verified by field tests, and the room thermal environment is simulated under three different supply airflow rates obtained by traditional method, proposed method and empirical method. The thermal environment performance is evaluated and compared using SHI. Besides, the energy consumption of these three cases is also investigated. Compared with traditional method, the proportion of racks with SHI>0.2 is reduced from 39.5% to 24.2% and 17.2% for proposed method and empirical method, respectively. The corresponding incremental energy consumption of the empirical method is 4.8 times higher than that of the proposed method. The comparison results show that the proposed determination method of supply airflow rate is a proper option that can reduce hot spots with an energy saving of 406.24 kW of the cooling system.
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