Performance Evaluation of an Indirect Evaporative Cooler

Nowadays, buildings are responsible for 40% of energy consumption in the European Union, according to the International Energy Agency (IEA). To reach the European objective aiming for CO2 neutrality of buildings, the IEA has developed the Energy in Buildings and Communities program (EBC), from which Annex 85 on Indirect Evaporative Cooling (IEC) is part of. This work contributes to assess the energy performance of indirect evaporative coolers in mixed-humid climates. A reference cooling system has been chosen as a base case to evaluate the performance of the IEC. The reference cooling system is composed of terminal units, a chiller, and a cooling tower as primary cooling system. In the upgraded cooling system, the cooling tower has been replaced by an indirect evaporative cooler. The latter is a modified version of the cooling tower that comprises an additional heat exchanger for air-pre-cooling. The energy consumption of both systems over a one-year period are then compared, including auxiliaries consumption. The possibility to perform free chilling has also been investigated. The models used to describe each system component are overviewed as well as their limitations. The annual energy consumption of the systems has been computed using three control methods: temperature control, flow rate control and optimized operation. While free chilling has a significant impact on the energy consumption (30% reduction), the IEC has a more moderate effect (up to 5% reduction). It is also shown that the advantage of the IEC over the cooling tower is directly dependent on the temperature difference between the dry bulb temperature and the dew point temperature.