Technology proposal and experimental study on an indirect evaporative cooling technology based on ultrasonic atomization

To improve the ventilation and air-conditioning energy efficiency of buildings in hot and dry climates, this paper proposed and experimentally investigated an indirect flash evaporative cooling (IFEC) technology combining plate heat exchanger with ultrasonic atomizer. Compared with traditional indirect evaporative cooling (IEC) technology, working air is humidified to be over-saturated by ultrasonic atomizer in the IFEC technology which enhances water evaporation efficiency and reduces thermal resistance between working air/water and product air. The prototype and experimental setup units of the IFEC were developed to investigate its wet-bulb effectiveness, dry-bulb effectiveness, cooling capacity and thermal resistance under hot/dry and warm/dry climates. Results show the IFEC prototype could supply product air with temperatures of 3–7 °C lower than indoor air, which indicated the IFEC could not only fulfill the incoming outdoor air cooling load, but also provide additional cooling capacity for indoor environment. The wet-bulb effectiveness and dry-bulb effectiveness were measured to be 0.80–0.92, 117%–254% respectively. The wet-bulb effectiveness is higher than existing single stage IEC technology. Sensitivity analysis show the outlet product air temperature is dominantly affected by working air humidity ratio, and the cooling capacity is affected by both working air humidity ratio and airflow rates.