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Thermal performance evaluation of a channel with twisted baffles installed: Effect of twisted baffle arrangement
(2026-03-01)
Eiamsa-ard, S.
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Pingta, S.
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Phila, A.
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Woncharee, K.
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Chamoli, S.
This research aims to introduce newly designed twisted baffle for enhancing heat transfer in solar air heater. This study examined the thermo-hydraulic performance of converging twisted baffles (C-TBs) and diverging twisted baffles (D-TBs) with different numbers of loops (n = 2, 4, 6, and 8) over a Reynolds number range (Re) of 6000–24,000. The results demonstrated that both converging twisted baffles and diverging twisted baffles significantly enhanced heat transfer compared to a smooth channel. The Nusselt number, friction factor, and thermal performance factor (TPF) increased as the number of loops decreased, attributed to stronger flow reattachment. Specifically, twisted baffles with 2, 4, 6, and 8 loops enhanced Nu by approximately 2.29–3.43, 2.02–3.05, 1.77–2.74, and 1.61–2.48 times, respectively, while the friction factor increased by 5.19–5.71, 4.61–5.01, 4.06–4.43, and 3.73–4.06 times, respectively. For a given number of loops, diverging twisted baffles consistently provided higher heat transfer enhancement than converging twisted baffles, albeit with slightly increased friction losses. Across the investigated range, the 2-loop diverging twisted baffles exhibited the best overall performance, achieving the highest Nusselt number ratio (Nu/Nu<inf>SC</inf> where Nu<inf>SC</inf> is the Nusselt number of the smooth channel) of 3.43 and a maximum thermal performance factor of 1.92 at Reynolds number of 6000, establishing it as the optimal configuration among those tested. This research contributes valuable design guidelines for selecting optimal baffle configurations, thereby supporting the development of more energy-efficient solar thermal systems.
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Experimental investigation and ANN prediction of heat transfer enhancement in a heat exchanger tube utilizing twin corrugated twisted tapes
(2025-12-01)
Du, Y.
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Wongcharee, K.
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Thianpong, C.
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Chuwattanakul, V.
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Chamoli, S.
This report introduces a novel twin-corrugated twisted tape (TC-TT) insert designed to enhance heat transfer in exchanger tubes. The key innovation lies in the twin-corrugated structure, which generates a twin-swirl flow effect. The corrugated surface synergistically increases flow disturbance and expands the effective heat transfer area. The studied parameters were twist ratios (y/w = 3.0, 3.5, and 4.0) and corrugation angles (θ = 45°, 60°, 75°, and 90°) at 6,000 ≤ Re ≤ 20,000. The results show that using twin-corrugated twisted tapes increases the average Nusselt number by roughly 60–135% compared to a plain tube and by 16–35% compared to a conventional single-twisted tape, confirming the effectiveness of this structural modification. This enhancement is primarily due to the combination of double swirling-flows and enhanced effective heat transfer generated by the corrugated surface. Reducing the corrugation angle (θ) and twist ratio (y/w) led to increases in the Nusselt number (Nu), friction factor (f), and thermal performance factor (TPF). Within the studied range, the Nusselt number, friction factor, and thermal performance factor reached maximum values of 5.18, 0.153, and 1.44, respectively, at a twist ratio of 3.0, a corrugation angle of 45°, and Re = 6,000. Regression analysis was utilized to develop correlations for the Nu and f, considering the Re, Pr, y/w, and θ as influencing variables. The proposed correlations for predicting the friction factor and Nusselt number have errors within ±3% and ±2%, respectively. In addition, an artificial neural network (ANN) was developed for predicting the thermal performance values occurring below the experimental study range. The optimal state ANN model shows remarkable prediction accuracy with R<sup>2</sup> of 0.965.
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Multi objective optimization of TiO2/water nanofluid flow within a heat exchanger enhanced with loose-fit delta-wing twisted tape inserts
(2022-02-01)
Thianpong, C.
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Wongcharee, K.
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Safikhani, H.
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Chokphoemphun, S.
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Saysroy, A.
A hybrid technique by using TiO<inf>2</inf>/water nanofluid together with loose-fit delta-wing twisted tape (LTT-W) was employed for heat transfer enhancement. Experiments encompassed the TiO<inf>2</inf>-water nanofluids having concentration (φ) of 0.05%–0.15 vol% and the loose-fit delta-wing twisted tapes having two different wing arrangements (co- and counter arrangement) and three loose-fit ratios (c/D) of 0.0, 0.15, and 0.2. Experimental revealed that the system with combined enhancement technique gave considerably higher heat transfer than the one without enhancement technique. This can be attributed to the combined influences of swirling flow and higher thermal conductivity of the working fluid. Heat transfer rate and thermohydraulic performance rose with the decrease of loose-fit ratio and the rise of nanofluid concentration. The maximum thermohydraulic performance (TPF) of 1.36 was obtained at c/D = 0.0 and φ = 0.15%. The Multi-Objective Optimization (MOO) was also performed to study the optimal thermohydraulic performance by using GMDH models and NSGA II algorithms. The Pareto front, which contains very useful information, were extracted for both co and counter arrangements. The Pareto fronts have recognized very accurately, the best boundary of the experimental data with respect to the lowest friction factor and highest Nusselt number.
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Thermal Performance Evaluation of a Channel Installed with Inclined-Baffle Turbulators
(2020-02-01)
Phila, A.
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Eiamsa-ard, S.
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Thianpong, C.
This study shed light on how heat transfer in a rectangular channel can be significantly enhanced by integrating it with inclined baffles. Experiments were performed to investigate the effect of the inclined baffles at different attack angles (θ) of 0° up to 165° in 15° incremental steps. The pitch length (between the consecutive baffles) to baffle height ratio (P/e) and the baffle height to channel height ratio (e/H) remained constant at 10 and 0.15, respectively. Experiments on a channel without baffles and one with typical transverse baffles (θ = 90°) were also conducted for comparison. Temperatures measured by the thermochromic liquid crystal image processing technique were employed for plotting the temperature contours on the heated surface. The Reynolds number associated with turbulent flow varied from 9000 to 24,000 under a constant wall heat flux scenario. The heat transfer and pressure drop were characterized by the Nusselt number (Nu) and friction factor (f), respectively. The results showed a promising ability of the inclined baffles to improve the heat transfer rate in the channel, however, this came at the price of an increased pressure drop in the system. The impact of the attack angle on heat transfer and thermal efficiency showed that a 60° attack angle was superior to other attack angles. The results were comparable to those for a 120° attack angle. Additionally, this attack angle enabled the system to accomplish a zenith thermal enhancement factor (η) of 1.11 at a Reynolds number of 9000.
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Heat transfer enhancement by tapered twisted tape inserts
(2015-10-01)
Piriyarungrod, N.
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Eiamsa-ard, S.
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Thianpong, C.
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Pimsarn, M.
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Nanan, K.
The effects of inserted tapered twisted tapes, their taper angle and twist ratio on heat transfer rate, pressure drop and thermal performance factor characteristics have been reported. The experiments were carried out by using the tapered twisted tapes with 4 different taper angles which θ= 0.0° (typical twisted tape), 0.3°, 0.6° and 0.9°. At each taper angle, the tapered twisted tapes were twisted at three different twist ratios (y/W) of 3.5, 4.0 and 4.5. All tapes were tested under turbulent flow regime for Reynolds numbers between 6000 and 20,000. A twist ratio is defined as the ratio of twist length (y) to twisted tape width at the large end (W). The plain tube was also tested for comparison. Heat transfer enhancement and friction loss increased with decreasing taper angle and twist ratio. Thermal performance factor tended to increase with increasing taper angle and decreasing tape twist ratio. For the present range, the tube with the tape with taper angle (θ) of 0.9° and twist ratio (y/W) of 3.5 yielded the maximum thermal performance factor of 1.05 at Reynolds number (Re) of 6000.
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Heat transfer augmentation by helically twisted tapes as swirl and turbulence promoters
(2012-10-01)
Eiamsa-ard, S.
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Yongsiri, K.
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Nanan, K.
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Thianpong, C.
This paper describes heat transfer enhancement attributed to helically twisted tapes (HTTs). Each helically twisted tape was fabricated by twisting a straight tape to form a typical twisted tape then bending the twisted tape into a helical shape. The experiments were performed using HTTs with three twist ratios (y/. W) of 2, 2.5 and 3, three helical pitch ratios (p/. D) of 1, 1.5 and 2 for Reynolds number between 6000 and 20,000. The conventional helical tape (CHT) was also tested for comparison. The obtained results reveal that at similar conditions (y/. W and . p/. D), HTTs give lower Nusselt number and friction but higher thermal performance factor than CHTs. Heat transfer rate and friction factor increase as the tape twist ratio and helical pitch ratio decrease, while the thermal performance shows opposite trend. In the present range, the highest thermal performance factor of 1.29 is achieved by utilizing the tape with the largest twist ratio (y/. W=3) and helical pitch ratio (p/. D=2) at Reynolds number of 6000. © 2012 Elsevier B.V.
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Thermal performance evaluation of heat exchangers fitted with twisted-ring turbulators
(2012-07-01)
Thianpong, C.
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Yongsiri, K.
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Nanan, K.
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Eiamsa-ard, S.
Heat transfer, friction factor and thermal performance characteristics in a tube equipped with twisted-rings (TRs) are experimentally investigated. The experiments were conducted using TRs with three different width ratios (W/D. =. 0.05, 0.1 and 0.15) and three pitch ratios of (p/D. =. 1, 1.5 and 2) for Reynolds numbers ranging from 6000 to 20,000 using air as a test fluid. The typical circular rings (CRs) were also tested for an assessment. The experimental results reveal that most TRs yield lower Nusselt numbers and friction factor than CRs, except at the largest width ratio (W/D. =. 0.15) and the smallest pitch ratio (p/D. =. 1.0). In addition, Nusselt number and friction factor increase as width ratio increases and pitch ratio decreases. However, a maximum thermal performance factor is associated by TRs with the smallest width ratio and pitch ratio. The empirical correlations of the heat transfer (Nu) and friction factor (f) are also included in this paper. © 2012 Elsevier Ltd.
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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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