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Author: search.filters.author.Chuwattanakul, VaresaSubject: search.filters.subject.Swirl flow

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    Characterization of Heat Transfer Enhancement and Flow Topology in a Three-Start Spirally Corrugated Tube
    (2025-12-01)
    Du, Yuexiang
    ;
    Phila, Arnut
    ;
    Promthaisong, Pitak
    ;
    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
    ;
    Chuwattanakul, Varesa
    ;
    Thianpong, Chinaruk
    ;
    Bhattacharyya, Suvanjan
    ;
    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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    Influence of sawtooth twisted tape on thermal enhancement of heat exchanger tube
    (2023-03-01)
    Samutpraphut, Boonsong
    ;
    Eiamsa-ard, Smith
    ;
    Chuwattanakul, Varesa
    ;
    Thianpong, Chinaruk
    ;
    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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    Heat transfer visualization of swirling impinging jets using nozzle with centrally hollow helical-tape
    (2020-05-01)
    Eiamsa-Ard, Smith
    ;
    Kunnarak, Kengkla
    ;
    Wongcharee, Khwanchit
    ;
    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%.