AN EXPERIMENTAL INVESTIGATION ON AIR-SIDE PERFORMANCES OF FINNED TUBE HEAT EXCHANGERS FOR INDIRECT AIR-COOLING TOWER

A tremendous quantity of water can be saved if the air cooling system is used, comparing with the ordinary water-cooling technology. In this study, two kinds of finned tube heat exchangers in an indirect air-cooling tower are experimentally studied, which are a plain finned oval-tube heat exchanger and a wavy-finned flat-tube heat exchanger in a cross flow of air. Four different air inlet angles (90 degrees, 60 degrees, 45 degrees, and 30 degrees) are tested separately to obtain the heat transfer and resistance performance. Then the air-side experimental correlations of the Nusselt number and friction factor are acquired. The comprehensive heat transfer performances for two finned tube heat exchangers under four air inlet angles are compared. For the plain finned oval-tube heat exchanger, the vertical angle (90 degrees) has the worst performance while 45 degrees and 30 degrees has the best performance at small Repo and at large Re-Dc, respectively. For the wavy-finned flat-tube heat exchanger, the worst performance occurred at 60 degrees, while the best performance occurred at 45 degrees and 90 degrees at small Re-Dc, and at large Re-Dc respectively. From the comparative results, it can be found that the air inlet angle has completely different effects on the comprehensive heat transfer performance for the heat exchangers with different structures.