No abstract

The heat transfer performance of a novel tube configuration that combines the swirling velocity induced by oval-twisting and secondary flow generated by a helical geometrical flow path is presented. The Nusselt number (𝑁𝑢) and friction factor (𝑓) are compared for the laminar flow regime (𝑅𝑒 = 250-2000) under isothermal wall conditions. Under the same flow and boundary conditions, the oval-twisted helical tube increased the 𝑁𝑢 and slightly increased the 𝑓 over the circular helical tube. The best performance with the highest 𝑁𝑢 and lowest 𝑓 occurs at the coil curvature ratio (𝑑 ! /𝐷) of 0.17. The quantified enhancement performance factor (h) shows a 46 -56% increase for the oval-twisted helical tube over the circular helical tube with 𝑑 ! /𝐷 = 0.17. Correlations for the 𝑁𝑢 and 𝑓 are developed and agreed with the numerical results: ± 6% and ± 5% for the 𝑁𝑢 and 𝑓, respectively.

No abstract

No abstract