Investigation of exergy destruction in CFD modeling for a legacy air-cooled data center

To keep up with the growing energy demand, legacy aircooled data centers have begun to implement simple but effective energy efficiency strategies or best practices. Improving “air management”, optimizing the delivery of cool air and the collection of waste heat, are among these efficiency strategies. One of the most powerful tools for identifying energy wasteful practices is the application of the second law of thermodynamics to estimate the exergy destruction in a system. Exergy is defined as the “available energy” in a system, hence wasteful practices are said to “destroy exergy.” Systematic analysis of data centers using this approach will identify the major contributors to wasteful energy practices including premature mixing of hot and cold air streams. In this study, a numerical model was developed for estimation of the data center airspace exergy destruction following the three-dimensional CFD simulation of room airspace. A second exergy destruction model available in the literature was implemented as well. Both models were tested on one simplified case with available analytical solution. They were then utilized to estimate the airspace exergy destruction in an existing research data center. Both approaches proved to be adequate, although the one proposed in this work presented significant sensitivity to numerical inaccuracies compared to the second model, even leading to zones of artificial negative exergy destruction.