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Characterization of Heat Transfer Enhancement and Flow Topology in a Three-Start Spirally Corrugated Tube
(2025-12-01)
Du, Yuexiang
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Phila, Arnut
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Promthaisong, Pitak
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Chuwattanakul, Varesa
;
Eiamsa-ard, Smith
The article provides a numerical analysis of the heat transfer characteristics and laminar periodic flow in a three-dimensional 3-start spirally corrugated tube. The working fluid is air, with a flow rate in terms of Reynolds numbers (Re) that ranges from 200 to 2,000. The investigation is conducted at six different pitch ratios (PR = 0.75, 1.0, 1.25, 1.5, 2.0, and 2.5) and five different depth ratios (DR = 0.02, 0.04, 0.06, 0.08, and 0.10). The results indicated that the spiral flow along the tube length was generated by the 3-start spirally corrugated tube. The swirl flow is divided into two components: the primary swirl flow, which is visible at the core, and the secondary swirl flow, which is visible at the near wall. These components contribute to the enhancement of fluid mixing, boundary layer disruption, and heat transfer on the tube wall. The Nusselt number (Nu) and friction factor (f) were increased as a result of the decrease in PR and the increase in Re and DR. The range of the Nu/Nu₀, f/f₀, and thermal performance factor (TPF) in a range analysis is 1.02 - 15.90, 0.97 - 5.52, and 0.73 - 2.33, respectively. At Re = 2,000, the corrugated tube with DR = 0.10 exhibited the greatest TPF of 2.33. Additionally, the results indicate that the 3-start spirally corrugated tube significantly improves heat transfer compared to the corresponding straight tube. The findings suggest that the structural characteristics of the flow path within the tube can be changed by a suitable PR and DR to optimize the overall heat transfer rate and thermal performance factor.
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Evaluation of aerothermal performance of a round tube with regularly-spaced multi-channel twisted tape elements installed
(2024-06-01)
Phila, Arnut
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Chuwattanakul, Varesa
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Thianpong, Chinaruk
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Bhattacharyya, Suvanjan
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Naphon, Paisarn
This article presents a study of aerothermal performance of tubes with regularly-spaced multi-channel twisted tape elements (RS-MTT) installed. This research aimed to find the proper design RS-MTTs that induce swirl flow which potentially improves fluid mixing between the core fluid and the fluid near the tube wall, thereby accelerating the heat transfer rate. Additionally, the effects of Reynolds numbers and free-spacing ratios (s/y) on heat transfer, friction loss, and thermal performance behaviors were examined. The RS-MTTs having different free-spacing ratios (s/y) of 0.0, 0.25, 0.5, 0.75, and 1.0 were tested. Air was utilized as the testing fluid in experiments with Reynolds numbers (Re) spanning from 6000 to 20,000. The utilization of RS-MTTs with s/y = 0.0, 0.25, 0.5, 0.75, and 1.0 augmented heat transfer rates up to 1.74, 1.80, 1.85, 1.90, and 2.15 times given by the plain tube alone while the friction factors increased by 4.22, 4.61, 3.87, and 4.05 times, respectively. At the lowest Reynolds number of 6000, the thermal enhancement factors of the tube containing the RS-MTTs with s/y = 0.0, 0.25, 0.5, 0.75, and 1.0 reached the maximum values of 1.42, 1.35, 1.31, 1.27, and 1.23, respectively. Among the RS-MTTs tested, the RS-MTT with s/y = 0.0 showed the best thermal enhancement factor of 4.56%, corresponding to the heat transfer augmented of 11.52% with a friction penalty of 8.71%.
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Enhanced heat transfer performance in channel with delta-wing perforated V-type baffles
(2023-10-01)
Eiamsa-ard, Smith
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Phila, Arnut
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Thianpong, Chinaruk
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Chuwattanakul, Varesa
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Maruyama, Naoki
The article examines the influence of delta-wing V-type baffles (DW-PVBs) on the average Nusselt number, local Nusselt number distribution, pressure losses, and thermal performance behaviors in a channel. Delta-wing perforated V-type baffles (DW-PVBs) mounted in a regular manner on the bottom of a channel produced two pairs of longitudinal counter-rotating vortices to enhance chaotic fluid mixing and destabilize the boundary layer, hence boosting the heat transfer. The geometric characteristics of the delta-wing V-type baffle (DW-PVBs) located on the bottom of the channel were examined at relative baffle blockage and pitch ratios (BR = h/H = 0.3 and p/H = 1.5), and five delta-wing attack angles, θ = 0<sup>o</sup> (solid V-shaped baffle), 22.5°, 45°, 67.5°, and 90°. The present DW-PVBs mounted on the channel were designed to mitigate pressure loss due to flow blockage. The experiment was done by permitting air to flow through a channel at Reynolds numbers (Re) ranging from 6000 to 24,000. The present results show that the friction factor using the DW-PVBs decreased considerably with increasing θ values. The experimental results revealed that small θ values yielded greater heat transfer and resistance than large θ values. The DW-PVBs with θ = 22.5° performed better than inserts with other θ values in terms of heat transfer rate. It was also observed that the DW-PVBs with θ = 45° gave the maximum thermal performance factor (TPF), while presenting a 13.64–17.26% lower friction factor than the solid V-shaped baffle. Furthermore, it was also found that the DW-PVBs with θ = 0°, 22.5°, 45°, 67.5°, and 90° gave peak TPF values of up to 1.87, 1.89, 1.91, 1.87, and 1.84 at the lowest Reynolds number, 6000.
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Influence of sawtooth twisted tape on thermal enhancement of heat exchanger tube
(2023-03-01)
Samutpraphut, Boonsong
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Eiamsa-ard, Smith
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Chuwattanakul, Varesa
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Thianpong, Chinaruk
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Maruyama, Naoki
This article employs sawtooth twisted tapes to generate swirling flow and interrupted flowing disturbance in order to increase the level of heat transfer rate. The influences of the sawtooth twisted tape (S-TT) on enhanced heat transfer rate, friction factor and aerothermal performance index (API) behaviors are analyzed. The sawtooth twisted tapes (S-TTs) possessing constant pitch/twist ratio (y//W) of 3.0 and six sawtooth angles (α) of 20°, 30°, 40°, 50°, 60°, and 70° are assessed. Considering turbulent flow using air as the testing fluid, experiments were investigated at 6,000 < Re < 20,000 under boundary conditions of constant heat flux. According to the experimental findings, sawtooth twisted tape (S-TT) improves heat transfer rate and raises pressure loss with varying rates based on sawtooth angles (α). With the sawtooth twisted tape (S-TT) and 70° sawtooth angles, the optimum API of 1.33 is attained, while Nusselt number and friction factor are 32 and 0.135 at Re = 6,000. The recommended sawtooth twisted tape (S-TT) yields a highest Nusselt number of 78, which is 1.6 times greater than the typical twisted tape (TT) and 1.1 times greater than the plain tube. The combination of the TT and sawtooth patterns can be beneficial in terms of boosting heat transfer rate and API relating coupling of swirling flow and interrupted flowing disruption effects since the sawtooth twisted tape (S-TT) offers superior performance than the TT. Additionally, the heat exchanger tubes fitted with sawtooth twisted tape (S-TT) at sawtooth angles (α) of 20°, 30°, 40°, 50°, 60°, and 70° gain greater Nusselt number than the plain tube up to 158.3%, 162.2%, 166.1%, 171.7%, 179.7% and 186.2%, respectively.
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Effect of arc-shaped twisted-baffles on augmented heat transfer in a rectangular duct
(2023-02-01)
Promvonge, Pongjet
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Phila, Arnut
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Chuwattanakul, Varesa
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Chokphoemphun, Suriya
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Eiamsa-Ard, Smith
In this current work, the effect of utilizing arc-shaped twisted-baffles (T-ABs) in a rectangular air channel on thermal performance factor (TPF) has been experimentally studied. In these experiments, the influence of the changes in parameters such as dimensions of pitch ratio (p/w), attached arc-shape angle (α), and Reynolds number (Re) are explored. The comparisons demonstrate that a channel mounted with arc-shaped twisted-baffles yielded considerably greater Nusselt numbers than a smooth channel, possibly attributable to multiple-impinging jets near the channel surface. Heat transfer enhancements of twisted arc-shaped baffles (T-AB) having larger attack angles were superior to those having smaller attack angles. The one with α = 90o offered greater heat transfer rates than the ones with α = 20o, 40o, 60o, and 80o by approximately 8%, 7%, 4%, and 2%, respectively. The superior heat transfer was attributed to the better contact between the working fluid and heat transfer surfaces. In addition, utilizing arc-shaped twisted-baffles with the lowest p/w of 4.0, in a channel produced stronger vortices and multiple impinging jets, which caused better fluid mixing than other p/w. The optimum condition is achieved using T-ABs at an attached arc-shape angle of α = 90o, p/w = 4.0 and Re = 4000, where the heat transfer rate (Nu), friction factor (f) and TPF are found to be, respectively, 3.31, 4.68 and 1.98 times greater than those of a plain channel.
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Heat transfer visualization of swirling impinging jets using nozzle with centrally hollow helical-tape
(2020-05-01)
Eiamsa-Ard, Smith
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Kunnarak, Kengkla
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Wongcharee, Khwanchit
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Chuwattanakul, Varesa
The present research was conducted to determine the heat transfer visualization of swirling impinging jets (SIJs) induced by nozzle with centrally hollow helical-tape using a thermochromic liquid crystal (TLC) sheet. The effects of jet-to-plate spacing ratios (L/D= 2.0, 4.0, 6.0 and 8.0) and Reynolds numbers (10,000 Re 20,000) on the radial uniformity and intensity of convective heat transfer were investigated. The experimental results of SIJs were compared with those of conventional impinging jets (CIJs). The formation of swirl flow of swirling impinging jet (SIJs) helped in improving the uniformity of local heat transfer or Nusselt number (Nu) and also average Nusselt number, as compared to those of conventional impinging jets (CIJs). Furthermore, the average Nusselt number (Nu) increased as jet-to-plate spacing ratio (L/D) decreased while Reynolds number (Re) increased for both conventional impinging jets (CIJs) and swirling impinging jets (SIJs). The highest Nusselt number (Nu) of swirling impinging jet (SIJ) was obtained at the jet-to-plate spacing ratio (L/D) of 4.0 and Reynolds number (Re) of 20,000. The maximum Nusselt number (Nu) of swirling impinging jet (SIJ) was higher than that of conventional impinging jets (CIJs) at similar conditions by around 5.3%.
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Thermal and swirl flow topologies in a twisted square duct with a multi-twisted tape installed
(2020-01-01)
Promthaisong, Pitak
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Chuwattanakul, Varesa
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Eiamsa-Ard, Smith
This paper presents 3D numerical investigation of the turbulent flow and heat transfer characteristics of a twisted square duct installed with multi-twisted tapes. Air was used as the working fluid with flow rates in terms of Reynolds numbers ranging from 3000 to 20,000. The effects of (1) multi-twisted tape width ratios (w/H) of 0.2 to 1.0 and (2) the number of channels (N = 2 and 4) on heat transfer and flow mechanisms were studied at constant twist ratio of y/D = 3.5. The numerical results showed that twisted square duct combined with twisted tape caused swirl flows which effectively promoted fluid mixing and provided heat transfer over those of both a straight smooth square duct and twisted square duct. Increasing w/H led to increases in both heat transfer and the friction factor. At a given multi-twisted tape width ratio (w/H), the heat transfer and friction factor with N = 4 were higher than those with N = 2, while thermal enhancement factor showed the opposite trend. A maximum thermal enhancement factor of 1.93 was obtained at tape width ratio of w/H = 1.0, channel number of N = 2 and Re = 3000.
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Impingement cooling by round jet with longitudinal swirling strip
(2018-03-01)
Kunnarak, Kengkla
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Somravysin, Prachya
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Eiamsa-Ard, Smith
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Chuwattanakul, Varesa
The objective of this research is to study the effect of swirling impinging jet on the heat transfer in the impinged plated by using thermochromic liquid crystal (TLC) sheet. In the experiments, the nozzle having a diameter of 20 mm (D) was installed with four-channel twisted tape as a longitudinal swirling strip. The jet impingement was performed at jet-to-plate distances (L/D) of 2, 3, 4, 5, 6 and 7, and constant Reynolds number (Re) of 5000. The experimental results showed that the swirling jet induced by the four-channel twisted tape gave higher heat transfer rates than the conventional jet at the same operating conditions. The highest average heat transfer rate was obtained at the jet-to-plate distance (L/D) of 2.
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Heat transfer in turbulent tube flow inserted with loose-fit multi-channel twisted tapes as swirl generators
(2017-11-01)
Kunlabud, Suttisak
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Chuwattanakul, Varesa
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Kongkaitpaiboon, Vichan
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Promthaisong, Pitak
;
Eiamsa-ard, Smith
Heat transfer and flow behaviors in three-dimensional circular tubes with loose-fit multiple channel twisted tapes were numerically studied. The investigation was examined for Reynolds numbers (Re) ranging from 5000 to 15,000, by using air as testing fluid. Effects of the multiple channel number (N=2,3, and 4), clearance ratio (CR=0.0, 0.025, 0.05, and 0.075) on heat transfer enhancement and flow friction were examined. The numerical results indicate that the tubes with loose-fit multiple channel twisted tapes perform higher heat transfer rates than the plain tube. The enhanced heat transfer rate is escorted with larger pressure drop. Both heat transfer and pressure drop increase with increasing multiple channel number (N) and decreasing clearance ratio (CR). Heat transfer augmented by the loose-fit multiple channel twisted tape with N=4 is higher than those enhanced by the ones with N=2 and 3 by around 9.5–17.8% and 5.8–7.8%, respectively. In addition, the loose-fit multiple channel twisted tapes with clearance ratio of 0.025, 0.05, and 0.075 give lower heat transfer rates than the one with CR=0.0 by around 8.4%, 17.5%, and 28.8%, respectively.
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Influence of delta-winged dual twisted tapes insertion on heat transfer and pressure drop characteristics
(2015-01-01)
Samruaisin, Prachya
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Changcharoen, Wayo
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Chuwattanakul, Varesa
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Eiamsa-Ard, Smith
The article presents the heat transfer and friction factor characteristics of turbulent flow in a uniform wall heat flux tube inserted with delta-winged dual twisted tapes. The typical dual twisted tapes (DTs) with constant twist ratio of y/W = 3.0 and delta-winged dual twisted tapes with delta-winged attack angle of α = 30° and β = 30° were carried out. Influences of the delta-winged arrangements in (1) the parallel direction (DT-PW) and (2) the counter direction (DT-CW) on the thermal performance characteristics were also described. The experimental results found that the use of the dual twisted tapes with parallel wing arrangements (DT-PW) provide the heat transfer higher than those the typical dual twisted tapes (DTs) and dual twisted tapes with counter wing arrangements (DT-CW) around 6.6-7.3% and 5.5-8%, respectively, due to stronger of dual-swirling/turbulent flow leading to better fluid mixing between the core and near tube walls while the friction factor is increasing up to 10.9 times above the plain tube. The typical dual twisted tapes (DTs), dual twisted tapes with parallel wing arrangements (DT-PW) and dual twisted tapes with counter wing arrangements (DT-CW) performs the highest thermal performance factor up to 1.2, 0.9 and 0.85 at Reynolds number of 6000.

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