Airflow distribution through perforated tiles in raised-floor data centers

Raised-floor data centers are the most commonly used facilities for housing computer and telecommunication equipment. To adequately cool this equipment, the cooling air through perforated tiles must be distributed properly. The airflow distribution depends on the pressure distribution or the flow field in the space under the raised floor (plenum); it is a complex function of a large number of variables, including the size of the plenum, the open area of the perforated tiles, the locations and flow rates of the computer room air conditioner (CRAC) units, and the size and location of the under-floor obstructions like cables and pipes. In this article, the effect of these parameters on the airflow distribution is studied using an idealized one-dimensional computational model. Within the one-dimensional framework, the airflow distribution is governed by two dimensionless parameters: one related to the pressure variation in the plenum and the other to the frictional resistance. Results, in terms of distributions of pressure in the plenum and flow rates through the perforated tiles, are presented over a range of values of these two parameters. These results provide an understanding of the fundamental fluid mechanical processes controlling the airflow distribution through the perforated tiles. The one-dimensional model is used to calculate flow rates for two possible arrangements of the CRAC units, and these results are compared with those given by a three-dimensional model.