Based on a self-built indirect evaporative cooler experimental prototype

high-precision temperature and humidity sensors were placed inside a narrow airflow channel for dynamic data acquisition. An enthalpy difference chamber was used to create a stable external environment and hence inlet parameters for the channel. The influence of different inlet air velocities

primary to secondary air ratios

and environmental heat and humidity parameters on the heat and humidity exchange process of the airflow inside the channel was studied. The results showed that the relative humidity of the secondary air changed rapidly. When the relative humidity exceeds 95%

the evaporation process is saturated. A wet-channel length of 40 cm satisfies the design requirements of most evaporative coolers. At low air velocity and primary to secondary air ratios

the saturation evaporation length of the evaporative cooler was shorter

while the cooling capacity was higher. For the standard initial conditions of dry bulb temperature 37.8 °C and wet bulb temperature 21.1 °C

the channel air velocity was constant at 0.5 m/s

and the relative humidity rose to 95.7% after an evaporation distance of 10 cm. The relative humidity of the ambient air had a significant impact on the cooling performance. Under the same dry bulb temperature of 33.5 °C

the average temperature of the secondary air in Urumqi with a wet bulb temperature of 18.2 °C is 7 °C lower than that in Beijing with a wet bulb temperature of 26.4 °C.