Effect of square wings in multiple square perforated twisted tapes on fluid flow and heat transfer of heat exchanger tube

This work presents, an experimental study on Nusselt number (Nu(rs)) and friction factor (f(rs)) of heat exchanger circular tube fitted with multiple square perforated with square wing twisted tape inserts. The experimental determination encompassed the geometrical parameters namely, wing depth ratio (W-d/W-T) of 0.042-0.167, perforation width ratio (a/W-T) of 0.250, twist ratio (T-L/W-T) of 2.5, and number of twisted tapes (N-T) of 4.0. The effect of multiple square perforated twisted tape with square wing has been investigated for the range of Reynolds number (Re-n) varied from 5000 to 27,000. The maximum enhancement in Nu(rs) and f(rs) is observed to be 6.96 and 8.34 times of that of the plain circular tube, respectively. Correlations of Nu(rs), f(rs) and eta(p) are established in term of Re-n and geometrical parameters of wings twisted tape which can be used to predict the values of Nu(rs), f(rs) and eta(p) with considerably good accuracy.