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Frontiers in Heat and Mass Transfer (FHMT) Available at www.ThermalFluidsCentral.org |
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LAMINAR FLOW HEAT TRANSFER IN HELICAL OVAL-TWISTED TUBE FOR HEAT EXCHANGER APPLICATIONS

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- 2500) 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 coil curvature ration (𝑑ℎ/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 𝑑ℎ/𝐷 = 0.17. Correlations for the 𝑁𝑢 and 𝑓 are developed and showed good agreement with the numerical results: ± 6% and ± 5% for the 𝑁𝑢 and 𝑓, respectively.
Full Text: PDF
DOI: http://dx.doi.org/10.5098/hmt.18.35
ISSN: 2151-8629