Evaluation metrics of thermal management in data centers based on exergy analysis

Cooling system has caused huge energy consumption in high-density data centers (DCs). Efficient thermal management makes a significant impact on energy saving of air conditioning system and safe operation of IT equipment. Air mixing in air flow space is an irreversible process leading to exergy loss from the view of Second-Law of Thermodynamics. In this paper, new exergetic evaluation metrics are proposed at room level and rack level respectively to reflect the causes and locations of inefficiency of cooling system in DCs. The effectiveness of new metrics is identified in a typical DC. Towards this, experimental measurement and numerical simulation are carried out to obtain the air distribution of thermal environment in a practical DC. Subsequently, the comparison with existing metrics demonstrates the applicability and advantage of new exergetic metrics. Exergy Loss Index below 50% is considered as good performance and it is suggested to be controlled below 80%. Finally, the contributions as well as the limitations of new proposed metrics are discussed when used in design and operation stages. It shows that introducing new exergetic metrics to the existing evaluation system is a more comprehensive way to evaluate the thermal management in typical DCs.