A Review and Correlations for Convection Heat Transfer and Pressure Losses in Toroidal and Helically Coiled Tubes |
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| Authors: | Mohamed S. El-Genk Timothy M. Schriener |
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| Affiliation: | 1. Institute for Space and Nuclear Power Studies, University of New Mexico, Albuquerque, New Mexico, USA;2. Nuclear Engineering Department, University of New Mexico, Albuquerque, New Mexico, USA;3. Mechanical Engineering Department, University of New Mexico, Albuquerque, New Mexico, USA;4. Chemical and Biological Engineering Department, University of New Mexico, Albuquerque, New Mexico, USA |
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| Abstract: | The conducted review of the experiments for pressure losses and convection heat transfer in toroidal and coiled tubes yielded 2,410 pressure losses data for water, air, and ethylene glycol flows in 62 different coiled tubes. These data are used to develop a friction factor correlation, in terms of a modified Dean number. The compiled Nusselt number database of 176 data points for flows of water, air, and water–10% and 43.5% glycerol mixtures and additional 17 data points for flows of ethylene glycol, n-amyl alcohol, n-butanol, and n-amyl acetate, with higher Prandtl numbers of 15–175, is correlated in terms of the modified Reynolds number. The friction factor and Nusselt number correlations span the entire range of the data, and agree with the data to within ±20%. In addition, the experimental data of the critical Reynolds number are correlated to within ±10%. The developed correlations are compared to those reported previously. The comparison of the calculated results for a coiled tube and a straight tube, of the same diameter and total length, quantifies the relative heat transfer enhancement and increase in pressure losses. A review of the thermal development in toroidal and coiled tubes indicates that the value and the oscillatory behavior of the local Nusselt number depend on the angular location. |
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