Experimental study on the flow resistance of inner tube and characteristics of drifting water in a tubular indirect evaporative cooler

Insufficient research has been conducted on the pressure losses resulting from secondary air flow through tubular channels in indirect evaporative coolers, as well as the phenomenon of water drift. This study aims to methodically examine the impact of distinct heat exchanger tube structures (such as tube shape, tube material, and tube diameter) and various operating conditions (such as tube length, wind speed, and spray water flow rate) on the airflow resistance and water drifting phenomenon in the secondary air channel of a tubular indirect evaporative cooler. The experimental results indicate that the resistance increases quadratically with wind speed and is directly proportional to the tube length and spray water volume. Furthermore, it is found that flat oval tubes demonstrate greater resistance when compared to round tubes, the maximum increase is 288.97 %, whereas PVC tubes exhibit lower resistance when compared to aluminum tubes, the reduction is 13.51–29.46 % for a 25 mm tube diameter, and the reduction is 0.33–6.54 % for a 20 mm tube diameter. Additionally, the study reveals that water drifting increased as the wind speed and spray water flow rate increased. A multivariate fitting model of resistance was established to optimize the performance of the indirect evaporative cooler through a comprehensive analysis of each factor. This study provides valuable guidance on reducing the airflow resistance of the indirect evaporative cooling system, minimizing water drift, and enhancing overall efficiency.