Chuwattanakul, Varesa

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

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    Item type:Publication,
    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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    Item type:Publication,
    Heat transfer enhancement of turbulent flow through dimpled tubes fitted with twisted tapes
    (2015-01-01)
    Eiamsa-Ard, Smith
    ;
    Wongcharee, Khwanchit
    ;
    Eiamsa-Ard, Petpices
    ;
    Chuwattanakul, Varesa
    Heat transfer, pressure drop and thermal performance characteristics in ellipsoidal dimpled tubes fitted with twisted-tape swirl generators have been studied experimentally. Ellipsoidal dimpled surfaces function as the turbulence promoter near the tube wall while twisted-tapes act as the swirling flow generators. The experiments were performed by using twisted tapes with different twist ratios (y/W = 3.0, 4.0 and 5.0) and water as the working fluid for Reynolds numbers between 5000 and 15,000. The experimental results of the dimpled tubes equipped with twisted-tape were compared with those of the dimpled and plain tubes without twisted tape. Evidently, the dimpled tubes fitted with twisted-tapes consistently yield higher Nusselt numbers and friction factors than the dimpled and plain tubes without twisted tape. It is also found that the average Nusselt numbers of the dimpled tubes equipped with twisted-tapes at y/W = 3.0, 4.0 and 5.0 are higher than those of the dimpled tube alone up to 40.7%, 32% and 26.7%, respectively which correspond to the higher thermal performance factors up to 10.8%, 6.7% and 3.6%, respectively. Depending upon Reynolds number, the dimpled tube with twisted-tape at the smallest twist ratio, y/W = 3.0, give higher thermal performance factors than those at y/W = 4.0 and 5.0 by around 3.9% and 6.7%.