Numerical analysis of flow and heat transfer in an elliptical duct fitted with two rotating twisted tapes

This study investigates the effects of using the rotating twisted tapes on fluid flow, heat transfer, and thermal performance of a duct flow. The section of the channel is oval and with two rotating twisted tapes. The twisted tapes are analyzed in fixed and rotating cases with three different rotational speeds. The flow regime is laminar with Re = 50 to 1000 and heat flux of 5000 Wm(-2) was applied to the outer surface of the wall. The height of twisted tapes is equivalent to 90% of the channel height which creates the secondary flow. The simulation results suggest that increasing the Re number increases both the Nu number and the pumping power, and increasing the Re number increases the Nu number in all cases. At each Re number, the lowest and the highest increments resulted by using the tapes are for cases of stationary and rotating tapes with maximum speed, respectively. Using the twisted tapes increases the average Nu number by 24 to 179% and pumping power requirement by 50 to 250% for the same Re numbers. The value of FOM is less than 1 in the case of using fixed tapes while it is above 1 for the rotating tape. The highest value of FOM is 1.55 which is for the highest rotating speed at the lowest inlet velocity.

Automated summary

This study investigates the effects of using rotating twisted tapes on fluid flow, heat transfer, and thermal performance in a duct flow. The results suggest that increasing the Reynolds number increases heat transfer and pumping power, and using twisted tapes can significantly improve average heat transfer and pumping power requirements.