Hydrothermal performance of twisted elliptical tube equipped with twisted tape insert

Twisted elliptical tube heat exchangers are promising in terms of improving the heat transfer efficiency on the tube side, decreasing the pressure drop on the shell side, and reducing the size of the equipment. Although offering immense potential, the examination of heat transfer enhancement techniques inside a heat exchanging twisted elliptical tube is less understood in the literature. In this study, the thermo-hydraulic performance of a twisted elliptical tube equipped with twisted tape insert is investigated. A three-dimensional steady-state laminar flow of the above-mentioned computational domain is developed in ANSYS Fluent. The effect of key design parameters including geometrical configurations, Reynolds number, and different pitches of twisted elliptical tube and twisted tape insert is analysed over the Nusselt number, the friction factor, and the PEC (performance evaluation criterion) number. The simultaneous implementation of twisted elliptical tube and twisted tape inserts at the pitch number equivalent to one-third of the tube length (L/3) and Reynolds number of 1000 increases the Nusselt number and friction factor by 123.9% and 131.9% compared to the smooth elliptical tube case. The PEC number is above unity in most of the considered cases, verifying the effectiveness of the proposed technique. The highest PEC of 1.6 is achieved at the optimum P = L/3 for both twisted elliptical tube and twisted tape insert and Reynolds number of 1000.

Automated summary

The study investigates the thermo-hydraulic performance of a twisted elliptical tube equipped with twisted tape inserts, showing significant improvement in Nusselt number and friction factor under specific conditions compared to smooth elliptical tube case. The proposed technique achieves a PEC number above unity, with the highest PEC of 1.6 at the optimum pitch of L/3 for both twisted elliptical tube and twisted tape insert under Reynolds number of 1000.