A comparative study of raised-floor and hard-floor configurations in an air-cooled data centre

The thermal performance of an air-cooled data centre with raised-floor and hard-floor configurations are compared with respect to the room and ceiling return strategies. The supply heat index, rack cooling index and number of racks that exceed the maximum recommended and allowable rack inlet air temperature according to ASHRAE´s thermal guidelines, are used to evaluate the thermal performance. Numerical simulations are conducted to obtain thermal and velocity fields. Results show that using a ceiling return strategy for the return of hot exhaust air to the CRACs gives a better thermal performance of the data centre, for both raised and hard-floor strategy as against the room return. The paper also addresses an important limitation of the supply heat index performance metric.