Simulation of a temperature adaptive control strategy for an IWSE economizer in a data center

Nowadays, with the constant evolution of Information Technology (IT) equipments, the energy consumption of data center over the world becomes a major concern. In 2011 the ASHRAE Technical committee 9.9 (TC9.9) issued important guidelines concerning server temperature and hygrometric environment to help engineer in the design of cooling solutions. While raising the temperature may be a source of heat pump energy savings, it induces an increase in the Computer Room Air Handling (CRAH) unit energy requirement, lowering the benefits. Hence optimal temperature cooling set point must be found to maximise the efficiency of the cooling plant. To test various chiller control strategy a “full scale” model is proposed. A 32kW data center is considered, cooled by a centrifugal heat pump linked to a wet cooling tower. An Integrated Water Side Economizer (IWSE) is added to minimize the energy consumption the regulation and the chilled air production is simulated with the software TRNSYS. The temperature field in the server room is calculated with the CFD code Thetis. To create a link between the 2 simulation environments, a Reduced Order Model (ROM) using Proper Orthogonal Decomposition (POD) is program with MATLAB. Finally this numerical model is used to investigate the effect of server room temperature increase on the cooling plant energy consumption. A new Temperature Adaptive Control Strategy (TACS) that minimizes the energy need is proposed and tested.