**8.1 About the inserts**

Mild steel twisted tapes were utilized as inserts in the experiment **Table 2**. The purpose of this study is to determine the friction factor and heat transfer coefficient for twisted tape with a twist ratio of (Y1 = 4.3, Y2 = 7.7) and compare them to those of a smooth tube.

Twist ratio 1 = 4.3. Twist ratio 2 = 7.7. Twisted tape thickness = 0.002 m. Twisted tape length = 0.90 m. Twist width = 0.012 m.
