Comparative study on turbulent flow characteristics and heat transfer mechanism of a twisted oval tube with different twisted tapes

In this paper, new enhanced tubes have been proposed. The overall thermal-hydraulic performance of twisted tube installed with seven different twisted tapes which including classic, triple-channel, four-channel, five-channel, perforated, center cleared and ribbed twisted tape are numerically studied in turbulent flow at Re = 5000–53,000. Comparing the result of experiment and simulation of plain tube with classic twisted tape, standard k–ω model is employed. The results show that the Nusselt number of twisted tube with twisted tapes increased by 23.44%–35.58% compared with twisted tube without twisted tapes. For friction factor, the level of increased is 149.46%–432.56%. It is found that the best case is twisted tube with center cleared twisted tape which has the maximum performance evaluation criterion (PEC). And the PEC decreases with an increase in the number of the channel of twisted tape and the contact area of the tape and the fluid. The results are reported in figures of streamline, local Nusselt number distribution, turbulence kinetic energy distribution, temperature distribution, averaged Nusselt number, friction factor and performance evaluation criterion.