Experimental study on the external resistance of vertical tube indirect evaporative coolers

Abstract

To address the calculating difficulty of external resistance of vertical tube in the widely used indirect evaporative coolers, this paper experimentally investigates the influencing factors of the tube external resistance and develops calculation formula for tube external resistance. An experimental setup was constructed to test the external resistance of different numbers of tube rows at wind speeds of 1 m/s, 1.5 m/s, 2 m/s, 2.5 m/s, and 3 m/s. A specific vertical tube indirect evaporative cooler with a tube diameter of 25 mm, tube-to-tube center distance of 35 mm, and row-to-row center distance of 30 mm was studied. It was found that the tube external resistance of the studied cases is mainly affected by the face wind speed and the number of tube rows. Based on the response surface method (RSM), a formula for calculating the tube external resistance was fitted using the measured data, which provides guidance for engineering applications of vertical tube type indirect evaporative coolers.

Keywords

• Vertical tube
• Indirect evaporative cooler
• External resistance
• Interaction