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Influence of Delta Winglets on Improving heat transfer and friction factor characteristics in tubular heat exchanger
(2025-05-19)
Ruengpayungsak, K.
;
Samruaisin, P.
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Kaewkosum, P.
;
Pingta, S.
;
Wongcharee, K.
Heat transfer rate and pressure drop characteristics are two critical constraints that substantially influence the advancement of solar air heaters. The thermal efficacy of these systems is significantly improved by factors such as flow configurations, thermal mechanisms, and geometric modifications. The integration of insertion in turbulators is a common method to improve heat transfer efficiency in solar air heaters. This article presents heat transfer and thermal efficiency in a tubular heat exchanger incorporating Delta winglet (DW). The thermal transfer and pressure drop of air as a working fluid in a tube with a constant heat flux were quantified for Reynolds numbers (Re) between 6000 and 20,000. The DW elements were positioned on two tape sides in a configuration with attack angles (θ) of 30°, 45°, and 60°. Delta winglet height ratios (h/D=0.10) and pitch ratios (p/D=0.1) were examined. Data from the current smooth or plain tubes were also analyzed for comparative purposes. According to the experimental results, the tube with this inserted has a much higher Nusselt number (Nu) and friction factor (f) than a plain tube. Both Nu and f increase as θ decrease. The DW enhances Nu and f by approximately 2.51-3.04 times and 5.21-7.16 times, respectively. The maximum TEF of 1.34 is achieved at an attack angle of 30° and a Reynolds number of 6000. The statistical correlations for Nu f and TEF were analysed and demonstrated a strong fit to the observed data, with discrepancies of ±4%, ±5% and ±3%, respectively. This design improves the conservation of energy in heat exchanger tube applications.
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Heat transfer enhancement in tube by inserting uniform/non-uniform twisted-tapes with alternate axes: Effect of rotated-axis length
(2013-03-25)
Eiamsa-Ard, S.
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Somkleang, P.
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Nuntadusit, C.
;
Thianpong, C.
Heat transfer enhancement in a tube using twisted tapes with alternate axes at different alternate lengths (in term of alternate length to twist length ratio, l/y = 0.5, 1.0, 1.5 and 2.0) has been investigated in the present work. The twisted tapes with both uniform and non-uniform alternate lengths (TAs and N-TAs) as well as a typical twisted tape (TT) were comparatively tested for Reynolds number between 5000 and 21,500. The experimental results revealed that all the TAs and N-TAs yielded higher Nusselt number and friction factor than the TT and the Nusselt number and friction factor obtained were considerably increased with decreasing the alternate length (l). Heat transfer and friction factor by the N-TAs were found to be directly dependent of alternate length rather than the variation of the length. In the present study, the optimum tradeoff between the enhanced heat transfer and increased friction was found by using the TA at l/y = 0.5, giving the highest heat transfer rate as well as the maximum thermal performance factor. In addition, empirical correlations for Nusselt number, friction factor and performance evaluation criteria to assess the real benefits in using the TAs/N-TAs of the enhanced tube were also determined. © 2013 Elsevier Ltd. All rights reserved.
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Thermohydraulic characteristics of co/counter swirl flow through a round tube fitted with helical screw tape and twisted tape
(2013-03-01)
Eiamsa-Ard, S.
;
Yongsiri, K.
;
Nanan, K.
;
Thianpong, C.
Influence of co/counter swirl flow on the characteristics of friction, heat transfer and thermal performance factor in heat exchanger tubes has been experimentally investigated. Each twisted tape is inserted into a helical screw tape and then these combined tapes are subsequently equipped in a heat exchanger tube for generating the swirl flow. The combined tapes are arranged in two different forms, namely (i) co-swirl arrangement in which their twist are in the same direction and (ii) counter-swirl arrangement in which their twists directions are in the opposite directions. The experiments using helical tapes alone are also performed for assessment. The helical screw tapes are used at three different tape-twist ratios (PR = p/D = 1.0, 1.5 and 2.0), each with three different tape-width ratios (WR = w/D = 0.15, 0.2 and 0.25), while twisted tapes are used at three different twist ratios (YR = y/W = 3, 4 and 5). The results show the maximum thermal performance factor of 1.49 for helical tape alone with PR=2.0 and WR=0.2. At similar conditions, the heat transfer rate associated with the combined tapes in counter-swirl arrangement is 3.4% and 10% higher than those in co-swirl arrangement and helical tape alone.
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Effect of perforated twisted-tapes with parallel wings on heat transfer enhancement in a heat exchanger tube
(2012-01-01)
Thianpong, C.
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Eiamsa-Ard, P.
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Promvonge, P.
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Eiamsa-Ard, S.
This article reports an experimental investigation on heat transfer and pressure drop characteristics of turbulent flow in a heating tube equipped with perforated twisted tapes with parallel wings (PTT) for Reynolds number between 5500 and 20500. The design of PTT involves the following concepts: (1) wings induce an extra turbulence near tube wall and thus efficiently disrupt a thermal boundary layer (2) holes existing along a core tube, diminish pressure loss within the tube. The parameters investigated were the hole diameter ratio (d/W = 0.11, 0.33 and 0.55) and wing depth ratio (w/W = 0.11, 0.22 and 0.33). A typical twisted tape was also tested for an assessment. Compared to the plain tube, the tubes with PTT and TT yielded heat transfer enhancement up to 208% and 190%, respectively. The evaluation of overall performance under the same pumping power reveal that the PTT with d/W = 0.11 and w/W = 0.33, gave the maximum thermal performance factor of 1.32, at Reynolds number of 5500. Empirical correlations of the heat transfer, friction factor and thermal performance for tubes with PTTs were also developed. In addition, the swirling/axial flow patterns of tube with PTT were visualized using dye injection technique. © 2011 Published by Elsevier Ltd.
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Heat transfer enhancement in a rectangular channel with twisted tape inserts
(2009-01-01)
Nuthong, W.
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Eiamsa-Ard, S.
;
Nanan, K.
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Eiamsa-Ard, P.
;
Thianpong, C.
Experimental investigation of heat transfer and friction factor behaviors in a rectangular channel with multiple twisted tapes (MTTs) is carried out. In each run, five MTTs are simultaneously used as the swirl flow generators in a test section. The lower wall of the channel is subjected to uniform heat flux conditions while the upper wall is insulated. Parametric runs are made for Reynolds numbers ranging from 2700 to 9000, the tapes with twist-length to twist-width ratios (y/w) of 3, 4 and 5 while the aspect ratio of AR = W/H = 10 is fixed throughout. Experiments using smooth channel are also performed for comparison. The experimental results reveal that heat transfer in the channels with MTTs at twist ratios (y/w) of 3, 4 and 5 are respectively increased around 55%, 37% and 22% over those in the smooth channel. In addition, the empirical correlations of the Nusselt number and friction factor in the developed flow region for the channels fitted with MTTs are also derived.

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