Heat Transfer Augmentation in Tube Fitted with Rotating Twisted Tape Insert

Experimental investigation is carried out to study the forced convection heat transfer in a uniformly heated tube inserted with stationary and rotating twisted tape as a turbulator. The study covered two twisted tape ratios (Y=6 and 7.2), three Reynolds numbers (8000, 10000, and 13000), and three rotating velocities (0, 200, and 400) RPM. It is found that the twisted ratio (Y) and the rotating velocity of twisted tape have a significant effect on the thermal performance. The results illustrated that the usage of rotating twisted tape inserted in tube produces a higher heat transfer rate than that produced by the stationary twisted tape. Empirical correlations of Nusselt number, friction factor, and enhancement efficiency as a function of Reynolds number were deduced. The results show that the heat transfer rate and friction factor increase with rotational velocity of twisted tape increase and twisted tape ratio decrease. It is concluded from experimental study that the maximum increasing in Nusselt number at Y=6, RPM=400, and Re=8000 was 65.55% higher than that in a plain tube, while the maximum increasing in the fraction factor at Y=6, RPM=400, and Re=13000 was 78.83% higher than that in a plain tube. The maximum performance factor was 1.455 at Y=6, Re=8000, and RPM=400.