Influence of Broken Twisted Tape on Heat Transfer Performance in Novel Axial Corrugated Tubes: Experimental and Numerical Study

Abstract

The insertion of a broken twisted tape (BTT) in tube is a novel passive heat transfer augmentation method, which constitutes the subject of the present investigation. Effect of BTT on heat transfer performance in novel triangular axial corrugated tubes is investigated experimentally and numerically. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The analyses are conducted for Reynolds number extending from 10,000 to 80,000 within the turbulent regime. The shear stress transport model is applied as the turbulence model. Air is used as the working fluid. The typical full-length twisted tapes with two different twist ratios and the broken twisted tape with two different twist ratios, and three gap ratios are used for the comparative analysis. The angular pitch between the two neighboring corrugations and the angle of the corrugation are kept constant through the experiments at 120° and 60°, respectively, while three different corrugations heights are analyzed. Eventually, correlations for predicting friction factor and Nusselt number are developed. The thermohydraulic performance is also calculated. The results show a good correspondence with the measurements and the published correlations of other researchers. For all examined cases, the performance factors are always larger than unity.