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Author: search.filters.author.Nanan, K.Subject: search.filters.subject.Turbulator

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    Characterization of heat transfer and artificial neural networks prediction on overall performance index of a channel installed with arc-shaped baffle turbulators
    (2021-08-01)
    Promvonge, P.
    ;
    Eiamsa-Ard, S.
    ;
    Wongcharee, K.
    ;
    Chuwattanakul, V.
    ;
    Samruaisin, P.
    Influences of baffle pitch ratio (p/w) and attached angle of arc-shaped baffles (AB) on the overall performance index (OPI) of a channel installed with AB have been carefully studied. In addition, an artificial neural network (ANN) model for predicting the OPI of the channel was reported. The arc-shaped baffle (AB) showed a significant effect on the augmented heat transfer and friction loss penalty as compared to a smooth channel. As the attached arc shaped angle (θ) increased, both Nusselt number and friction factor intensified. The Nusselt number values at θ = 90° were higher than those at θ = 20°, 40°, 60°, and 80° by up to 5.8%, 3.9%, 2.3% and 2.5%, respectively. The Nusselt number increased when the p/w was raised from 4.0 to 8.0 while the opposite trend was observed when the p/w was raised from 8.0 to 12.0. The maximum OPI of 1.43 was achieved by using the baffles with θ = 90° and pitch ratio of 8.0 at Re = 4000. For the development of ANN models for predicting the OPI, it was found that the best predictive performance was (R2) of 0.99843407 for ANN model of 3-50-50-1 with Tanh-Tanh activation function at epoch of 1200.
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    Flow and thermal mechanisms in a heat exchanger tube inserted with twisted cross-baffle turbulators
    (2017-03-05)
    Nanan, K.
    ;
    Thianpong, C.
    ;
    Pimsarn, M.
    ;
    Chuwattanakul, V.
    ;
    Eiamsa-ard, S.
    The turbulent forced convective heat transfer behaviors in a tube inserted with baffle turbulators (typical straight baffles, straight cross-baffles, straight alternate-baffles, twisted-baffles, alternate twisted-baffles, and twisted cross-baffles) have been experimentally and numerically investigated. The influence of pitch ratio (P/D) from 1.0 to 2.0 and Reynolds numbers (Re) from 6000 to 20,000 are also reported. Among the studied turbulators, the twisted cross-baffles gave the highest heat transfer enhancement and thermal enhancement factor while the straight cross-baffles gave the lowest heat transfer rate and thermal enhancement factor. The twisted-baffles, alternate twisted-baffles, and twisted cross-baffles created high longitudinal vortex/swirl around the tube core. The strongest longitudinal vortex/swirl was achieved by the use of twisted cross-baffles. The recirculation flows were found in the tube fitted with straight baffles (a recirculation flow), straight alternate-baffles (double recirculation flows) and straight cross-baffles (quadruple recirculation flows). The heat transfer rate, friction factor and thermal enhancement factor increased with decreasing pitch ratio (P/D) and increasing Reynolds number (Re). At the optimum condition of the smallest pitch ratio (P/D = 1.0) and the lowest Reynolds number (Re = 6000), the twisted cross-baffles offered the highest thermal enhancement factor of 1.7.
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    Heat transfer augmentation through the use of wire-rod bundles under constant wall heat flux condition
    (2013-11-01)
    Nanan, K.
    ;
    Pimsarn, M.
    ;
    Jedsadaratanachai, W.
    ;
    Eiamsa-ard, S.
    This article reports an experimental investigation on heat transfer, friction factor and thermal performance characteristics of turbulent flow (6000. ≤. Re≤. 20,000) in heat exchanger tubes with wire-rod bundles as flow turbulators. The experiments were carried out at three different pitch ratios (P/D) of 1.0, 1.5 and 2.0 and three wire-rod number per bundle (N) of 4, 6 and 8. The experimental results show that Nusselt number increases with increasing Reynolds number and wire-rod number per bundle, and decreasing pitch ratio (P/D) of the turbulators. As compared to the results of the tube without wire-rod (the plain tube), heat transfer rate and friction factor are respectively increased in ranges of 3.5 to 68.8% and 156 to 353%, depending on the operating conditions. At the same pumping power, the use of wire-rod turbulators results in thermal performance factor up to 1.02 times of those of the plain tube. In addition, the correlations that developed from the present experimental data for Nusselt number, friction factor and thermal performance factor are also presented. © 2013 Elsevier Ltd.