Heat transfer enhancement in a circular tube inserted with wavy twisted tape and alternate axes

Abstract

This paper reports the experimental study on the heat transfer (Nusselt number, Nu), friction factor (f) and thermal enhancement factor (TEF) of a heat exchanger tube equipped with six types of tube inserts including 1) smooth surface twisted tape (STT), 2) wavy twisted tape (WTT), 3) smooth surface twisted tape and alternate axes (STTA), 4) wavy twisted tape and alternate axes (WTTA), 5) wavy/smooth/wavy twisted tape with alternate axes (WSW-TTA) and 6) smooth/wavy/smooth twisted tape with alternate axes, (SWS-TTA). The investigations were conducted using the twisted tapes with a constant twist ratio (y/W) = 3.0 for Reynolds number ranging from 4,000 to 8,000 under uniform heat flux condition. The experimental results demonstrated that the WTTA has a heat transfer performance of about 10 percent higher than that of the STT. At constant pumping power, the maximum thermal enhancement factor obtained is 1.12 by the use of WTTA inserts.