Author : Aditi Uday Desai, R. D. Shelke and H. N. Deshpande

One of the key ways to enhance the heat transfer is use of twisted tape inserts. But along with the heat transfer it also
increases pressure drop which results in increase in pumping power.So optimized tape design is required to achieve
optimum cost. To get improved heat transfer coefficient with reasonable pressure drop two twisted tapes with center
clearance is proposed. Effect of addition of two twisted tapes inside a tube at constant heat flux condition is reported
in this paper. Results obtained for single twisted tape insert and two twisted tape inserts are compared analytically as well as numerically. Air is used as a test fluid. Study is carried out in turbulent region. Results are compared at
Reynolds’s number 45,000 for no twisted tape, one twisted tape & two tapes. Results for two twisted tapes with twist
ratios 3, 4, 5 are compared at Reynolds’s number 45,000. Heat transfer coefficient is improved as compared to plain
tube& single tape by 2.2% to 10.1%.Optimum results are obtained at twist ratio 5.

Keywords: Centrally Cleared Twisted Tape, Heat transfer coefficient, Twist Ratio.