Performance evaluation of multi-stage indirect evaporative cooling systems

This study analysed the performance of multi-stage indirect evaporative cooling systems under two operational modes. A series of indirect evaporative coolers (IECs) were operated in a tandem arrangement. A mathematical model was established to investigate the theoretical performance of the multi-stage IEC. The model was validated by comparing the predicted air treatment conditions with experimental data acquired from literature. The calculated results show that the multi-stage arrangement is capable of improving the cooling performance and reducing the outlet air temperature. In addition, the Mode-2 IEC generally provided the product air with a lower outlet temperature compared with the Mode-1 IEC. On the other hand, the multi-stage IEC displayed a higher pressure drop resulting in a larger consumption of fan power. The cooling effectiveness, the pressure drop, and the cooling capacity are determined for the IEC with different stages. The calculation of Performance Evaluation Criteria (PEC) showed that the improvement of cooling effectiveness was achieved by sacrificing the cooling capacity for the multi-stage arrangement. It is inferred from the simulation results that the appropriate maximum stage was three-stage and two-stage for mode-1 and mode-2 IEC respectively.