Data Centers – How to Avoid the Negative Effect of Thermal Plumes on Energy Performance

Aimee Smith, M. Eng., P.Eng., RWDI

Data centers are unique facilities that have significant cooling and back-up power requirements. The amount of equipment necessary to support these facilities can often result in a significant design challenge with regard to placement of the cooling towers and back-up generators. The concern is that thermal plumes exhausted from this equipment can enter the cooling tower intakes and the cooling intakes for the generators, affecting the operation of the equipment. The potential impact from the thermal plumes can reduce the thermal efficiency of the cooling towers and overheat the generators, resulting in possible failure of the back-up power systems.

In an ideal setting, the threat from these thermal plumes can be addressed through space planning and equipment location. However, in many cases, there is not enough space to provide adequate separation of the equipment and the question of how the thermal plumes may affect the performance of the cooling and back-up power systems must be answered as part of the design process. This question can be answered through the use of exhaust dispersion modeling.

Predicting the behavior of the thermal plumes can be accomplished using either numerical or physical (i.e., wind tunnel) dispersion modeling techniques. For most scenarios, the influence that the large intakes of concern will have on the overall flow field must also be simulated. The need to consider this detail as part of the simulation makes physical modeling or computational fluid dynamics (CFD) much more applicable than traditional numerical dispersion models. The application of CFD can also be beneficial for scenarios where the buoyancy of the thermal plume is expected to be an important factor in the dispersion levels. Ultimately, the selection of the most appropriate model will depend on the site, the building and roof geometry and the equipment specifications.

This presentation will use specific case studies to illustrate how CFD and wind tunnel modeling can be used effectively to evaluate the risk from cooling tower and generator thermal exhaust plumes, and how the results of this modeling are applied to optimize the location and design of this critical data center equipment.

Biography:

Aimée Smith has a Bachelor of Science in Environmental Engineering from the University of Guelph and a Masters Degree in Civil Engineering from Carleton University and is a registered Professional Engineer in the province of Ontario. Aimée is a Principal of Rowan Williams Davies & Irwin Inc. (RWDI) in Guelph, Ontario, Canada and a Project Director in RWDI's Building Science division. Aimée provides design ideas to clients, and focuses on different aspects of building performance as it is influenced by the local microclimate. In particular, Aimée specializes in exhaust re-entrainment studies for the design of building exhaust and air intake systems for laboratory, health care and other related facilities.

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