Chuwattanakul, Varesa

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Preferred name
Chuwattanakul, Varesa
Alternative Name
Chuwattanakul, V.
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Email
varesa.ch@kmitl.ac.th

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    Effect of arc-shaped twisted-baffles on augmented heat transfer in a rectangular duct
    (2023-02-01)
    Promvonge, Pongjet
    ;
    Phila, Arnut
    ;
    Chuwattanakul, Varesa
    ;
    Chokphoemphun, Suriya
    ;
    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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    Impingement cooling by round jet with longitudinal swirling strip
    (2018-03-01)
    Kunnarak, Kengkla
    ;
    Somravysin, Prachya
    ;
    Eiamsa-Ard, Smith
    ;
    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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    Influence of delta-winged dual twisted tapes insertion on heat transfer and pressure drop characteristics
    (2015-01-01)
    Samruaisin, Prachya
    ;
    Changcharoen, Wayo
    ;
    Chuwattanakul, Varesa
    ;
    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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    Thermal and swirl flow topologies in a twisted square duct with a multi-twisted tape installed
    (2020-01-01)
    Promthaisong, Pitak
    ;
    Chuwattanakul, Varesa
    ;
    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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    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%.