Experimental study of the condensing heat transfer characteristics in a circular tube bank fin air cooler and the comparison to a flat tube bank fin air cooler

Abstract

The direct air-cooling technology employed in power plants offers significant potential for conserving water resource. The condensing heat transfer characteristics in the tubes of air cooler are crucial, and such condensation is enforced by air flow. Now most air-cooling islands of power plant use finned flat tube instead of finned circular tube or circular tube bank fin air cooler (CTBFAC) to decrease the air flow pressure drop. This paper performs an experimental study of the condensing heat transfer characteristics in a CTBFAC. The condensing heat transfer characteristics of the CTBFAC are compared to that of the flat tube bank fin air cooler (FTBFAC). The main experimental results demonstrate that: air flow rate plays a vital role in condensation heat transfer, there are strong coupling correlations between the tube side liquid/steam Reynolds number (Re_LS/Re_s), Nusselt number (Nu_s) and the air side Reynolds number (Re_a): Re_LS = 0.748Re_a^0.759 (1−β/180)^−0.169, Re_s = 12.704Re_a^0.760 (1−β/180)^−0.162, Nu_s = 1.510Re_a^0.455 (1−β/180)^−0.216, within the range of Re_a from 295 to 1100 and the range of inclination angle (β) from 30° to 90°. At the same Re_LS/Re_s, Nu_s of the CTBFAC is significantly higher than that of the FTBFAC.