Experimental study on heat transfer performance improvement of wavy finned flat tube

Abstract

Three types of enhanced fin structures, including that of discontinuous fin, staggered fin and fin with vortex-generator, are proposed to enhance air side heat transfer of air-cooled condenser of power generating unit. Wind tunnel experiments with a visualized window for temperature distribution measurement of fin surface are taken to investigate heat transfer characteristics of the enhanced wavy fins, and compare with that of the original continuous wavy fin. Infrared thermography technique is employed to obtain the temperature distributions of fin surfaces, based on which, accurate fin efficiency can be acquired. While the air flow Reynolds number ranges from 1340 to 13,476, the experimental correlations of flow and heat transfer for all four types of wavy fins are obtained. The Nusselt numbers of discontinuous type, staggered type and vortex-generator type are increased by 11.29%, 28.61% and 56.46% on average, and the friction factors are increased by 3.23%, 66.26% and 48.58% on average, respectively. The PECs of three enhance wavy fin structures are higher than 1.0 in most operating conditions, implying their positive effect on heat exchange process. However, fin efficiencies obtained of all types of wavy fin are quite low, indicating that the present fin types should be shorter for higher heat transfer effectiveness.