Experimental-Numerical Comparison for a High-Density Data Center: Hot Spot Heat Fluxes in Excess of 500 W/FT2

Abstract

The current trend of using denser server environments is continuously increasing to satisfy the growing needs of e-commerce and other emerging technologies. The resulting high room-level heat fluxes present significant challenges with respect to maintaining acceptable computer rack inlet temperatures and minimizing total data center energy consumption. Numerical methods are widely used to model existing and new facilities. Validation of existing numerical techniques is an important step in facilitating good thermal design of data centers. This paper uses previously published experimental data to present a comparison between test results and numerical simulations. The example considered is a large 7400 ft <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> data canter that houses over 130 heat-producing racks (1.2 MW) and 12 air conditioning units. Localized hot spot heat fluxes were measured to be as high as 512 W/ft <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (5.5 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) for a 400 ft (37 m) region. A numerical model based on computational fluid dynamics (CFD) was constructed using inputs from the measurements. The rack inlet air temperature was considered to be the basis for experimental vs. numerical comparison. The overall mean rack inlet temperature predicted numerically at a height of 1.75 m is within 4degC of the test data with a rack-by-rack standard deviation of 3.3 degC