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To enhance overall thermal performance factor of tubular heat exchanger, use of twisted tape has been very effective. Twisted tape creates turbulence in the flow which enhances rate of heat transfer and friction factor. Present experimental study aims to limit this penalty of increase in friction factor and achieve high thermal performance factor. For this, present article analyzes the effect of different design modifications in twisted tape on thermo-hydraulic performance of heat exchanger tube. Different inserts, i.e. Simple Twisted tape (STT), Double V-Cut Twisted Tape (DVCTT) and Perforated Double V-Cut Twisted Tape (PDVCTT), of varying twist ratio (TR) 3, 4 and 5 are considered for the investigation. Further design modification such as V-cut with width of cut (wc) 5 mm, depth of cut (dc) 4 mm, and perforation of 5 mm diameter is produced in twisted tape. Water is used as the working fluid for the study. Data pertaining to Nusselt number and friction factor is collected for the analysis in turbulent region where Reynolds number varied from 4000 to 16,000. Maximum enhancement in Nusselt number and friction factor is recorded 2.44 times and 3.71 times of plain tube respectively at Re = 4000 in case of TR = 3. Further PDVCTT leads to maximum decrement in Nusselt number and friction factor 3.83% and 27.35% when compared with DVCTT. Maximum thermal performance obtained is 1.71 in case of PDVCTT with TR of 3 at Re = 4000.
Kumar et al. (Thu,) studied this question.