A Numerical Steady State and Dynamic Study in a Data Center Using Calibrated Fan Curves for CRACs and Servers

This study presents the results of a detailed parametric study for a data center that is air cooled using a set of four CRAC units in a cold/hot aisle raised floor configuration. The fans of the CRAC units and the servers are calibrated using their practical characteristics fan curves. A commercial CFD code is utilized for this purpose in which the buoyancy forces are taken into account. The k-epsilon model and the Boussinesq approximation are used to model the turbulent airflow and the buoyancy effect, respectively. A dynamic model is developed to take into account the changes in flow rates and power dissipation in the data center environment. The current dynamic model does not take into account the thermal mass of the CRAC units or the servers. The effect of the CRAC fan speed, instantaneous change in power dissipation, tiles perforation ratio, and servers fan speeds on the total flow rate in the room and the inlet temperatures of the racks are investigated. In the transient model, we investigate the effect of different CRAC failure scenarios on the time history of the temperatures and the flow pattern in the data center. Time constants and safe time are estimated from this study. A fundamental understanding of the effect of different data center entities on the flow and the temperatures is developed. Interesting flow patterns are observed in the case of different CRAC failures that could be used to recommend general design guidelines.