Date of Award

8-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical and Aerospace Engineering

Advisor(s)

H. Ezzat Khalifa

Second Advisor

Can Isik

Keywords

air cooled data centers, computational fluid dynamics, hybrid lumped capacitance model, room level transient experiments, server thermal characterization, transient thermal response

Subject Categories

Mechanical Engineering

Abstract

This work investigates the transient response of the thermal environment in air cooled data centers through experiments, analytical and computational tools. The key thermal characteristics of the various data center components were extracted from a set of experiments. This includes the development of practical experimental procedures for the thermal characterization of servers solely based on air temperature measurements and the transient response of the computer room air handlers. The knowledge of thermal characteristics paves the way for the physics-based lumped-capacitance models. A CFD-based transient simulation of the air temperature field, in which the transient thermal response of the servers was included via user-defined functions failed to predict the time-dependent server inlet temperature with acceptable accuracy and highlighted the need for including the thermal capacitance and heat transfer characteristics of the entire room, not just the servers. Hence, a practical faster-executing hybrid lumped capacitance-CFD/Experimental model was developed to investigate the thermal response of data centers under certain scenarios of cooling interruption, server shutdown and cooling air flow changes. Beyond the servers, the model takes into account the effect of the air volume, the building materials of the room and plenum and the CRAH units. The model is capable of predicting server inlet temperatures to within the experimental uncertainty (±1°C) with inputs that are relatively easy to obtain in a production data center.

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Open Access

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