Abstract
The effect of perforated twisted tapes with alternate axis (PATT), perforated twisted tapes (PTT) and regular twisted tapes (TT) with twist ratios (TR) of 3 are compared by an experimental investigation in a circular tube with Silicon carbide (SiC)-water nanofluid flowing in it under constant heat flux condition. Using 0.1 wt. % concentration of the SiC nanofluid containing SiC nanoparticles obtained after 5 h of ball milling as the testing fluid, experiments are conducted within the Reynolds number range of 3000 – 16000. The heat transfer rates in the tube fitted with TT, PTT and PATT at TR = 3 are respectively improved up to 9.59 %, 18 % and 19.51 % of that in the plain tube. Similarly, the increase in friction factor for TT, PTT and PATT at a TR = 3 is 22.5 %, 24 % and 28.9 % respectively, compared to that of the plain tube. As PATT is giving maximum heat transfer enhancement, the empirical correlations were established for its Nusselt number and friction factor at different twist ratios and the obtained correlations are fitted with the experimental data. Hence, the passive elements when employed along with the nanofluid gives better energy efficiency along with lower operating cost and is therefore suggested for commercial heat transfer applications.
