Performance characterization and optimization of counter-flow dew point indirect evaporative cooler through response surface methodology

The optimal performance of dew point indirect evaporative cooler with respect to the operational environment is a challenging task as the same is affected by many parameters. This paper reports the regression modeling and optimization of a counter flow indirect evaporative cooler using the response surface methodology. Experimentation is conducted using the central composite design and regression models are statistically evaluated for adequacy and found within 7% maximum error limit as compared with literature. Results show that supply temperature and cooling capacity increase with increasing inlet air velocity and inlet air temperature. Moreover, dew point and wet bulb effectiveness have a direct relationship with inlet air temperature and an inverse relationship with inlet air velocity. After validation, the regression models are subjected to single-objective and multi-objective optimization based upon the desirability function technique. The multi-objective formulation reveals that optimal performance of the system is achieved at 41.31 degrees C inlet air temperature, 3.61 m/sec inlet air velocity, 12 g/kg inlet air humidity, and 24.48 degrees C water temperature. Finally, an operational envelope is proposed to evolve a zone for the best-suited operation of such a device which ensures a reasonable cooling capacity within 1.5 - 2.5 kW while enabling thermal comfort for the conditioned space.