This book describes dedicated research aiming to improve the performance of existing indirect evaporative coolers. A new dew point indirect evaporative cooler with counter-current heat and mass exchanger was developed in this book by optimal design, material selection, numerical simulation, experimental investigations and economic, environmental, regional acceptance analysis. The research found that the dew point cooler can achieve higher performance than typical indirect evaporative coolers without adding too much cost. The cooler's effectiveness and energy efficiency were found to be largely dependent upon channel geometries, intake air velocity, temperature, humidity, and working-to-intake air ratio but less on input water temperature.