Abstract
In this paper, numerical investigations on heat transfer and flow resistance characteristics of a variable-direction twisted-oval tube (VDTOT) were performed. The effects of different geometric parameters (transverse and longitudinal tube pitches, ratio of major to minor axis, twist angle and pitch) on the heat transfer coefficient, pressure drop and heat transfer capacity per pump work were investigated. Contribution ratios of different factors were also analyzed. The results show that the transverse tube pitch and twist angle have a great impact on the overall performance of the tube bundle. VDTOT realizes the synergistic enhancement of flow and heat transfer performance. Compared to the circular tubes, the heat transfer capacity of VDTOT bundles is increased by 13.6%–20.6 % under the same pump power consumption. The average deviations of Nu and Eu correlations fitted by the multiple regression method are 0.99 % and 1.64 %, which is helpful for the rapid design and optimization of VDTOTs.
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