Experimental methods to characterize the impact of cross flow orientation on jets of air after a perforated tile

Abstract

In most air cooled data centers the required air for cooling of IT equipment is supplied from a raised floor to server racks through perforated tiles; therefore, an understanding of tile impact on flow features is an essential step for designing an efficient air delivery scheme. In recent years, different approaches have been implemented to increase the efficiency of air delivery through tiles such as the use of directional tiles or adding understructure scoops. In such tiles, the approaching angle of the cross flow to the tile, the angle of approach, becomes very important, since it may result in different velocity stratification patterns. Although many studies have focused on the use of computational fluid dynamics (CFD) for predicting tile airflow delivery to the racks, very few controlled experimental results are available. An important factor that has been often ignored in perforated tile modeling is the direction of the flow approaching the tile. In this study, an experimental setup has been designed and built to examine the effects of the direction of the approaching airflow to the tile on the airflow rate and resulting jet of coolant for different types of perforated tiles. In the designed setup, rotating the tile on a horizontal surface changes the angle of approaching airflow. The effect of angle of approach (AoA) on the direction of the jet is visualized by creating a laser sheet and performing airflow smoke visualization tests for four different types of tiles. Visualizations showed that the airflow direction changes significantly with AoA. Furthermore, the velocity distribution of air after the tiles at various AoA are measured, presented, and compared using a vane anemometer and a velocity sensor grid. Finally, the airflow rates for each case is calculated from the measured velocities by a grid of velocity sensors and a vane anemometer, which are then compared with flow rates measured by a commercial flow hood.