Experimental Study for the Effect of the Modified Twisted Tape Insert on Heat Transfer Through Circular Tube

This work presents an experimental study on the mean Nusselt number, friction factor and enhancement efficiency characteristics in a circular tube. This was investigated for four twist ratios (Y= 2.3, 2.9, 3.5, and 4.1) The obtained results show that the mean Nusselt number and the mean friction factor in the tube with Plain, Perforated, perforated with notch type twisted tapes inserts increase with decreasing twist ratios (Y). Subsequently, an empirical correlation also was formulated to match with experimental results with ±4.22% variation for the Nusselt number and 5.59% for the friction factor. Also, the experimental results show higher values of heat transfer for perforated with notch type insert for higher values of Re. And shows lower values of friction factor for higher values of Re. Maximum F is observed for the insert with perforation with notch having Y=2.3. The average F increases 5 to 7 times than that of the plain tube and the heat transfer enhancement ranges from 2.9 to 3.3 times that of the plain tube over the range of Re 10000 to 16000 with air as working fluid.