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Author: search.filters.author.Eiamsa-Ard, SmithSubject: search.filters.subject.Twisted tape

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    Thermal performance evaluation of micro-fin tube with twisted tape inserts
    (2015-01-01)
    Eiamsa-Ard, Smith
    ;
    Kunlabud, Suttisak
    ;
    Wongcharee, Khwanchit
    ;
    Pimsarn, Monsak
    ;
    Eiamsa-Ard, Petpices
    The heat transfer coefficient and pressure drop characteristics of turbulent flow through micro-fin tubes fitted with twisted tape in co/counter-arrangement have been studied. In the experiments, water as the tested fluid is passed in a Reynolds number range of 7800 to 17,650. The results reveal that, the Nusselt numbers in the system with a micro-fin tube and twisted tape are considerably higher than those in the system without tape. Evidently, the tape with the smaller twist ratio gives higher heat transfer rate, friction factor as well as thermal performance factor than the one with larger twist ratio as a result of a larger contact surface area, and stronger turbulence intensity and thus better fluid mixing which leads to a thinner thermal boundary layer. The result reveals that for using the micro-fin tube with twisted tape, the increases in the mean Nusselt number and friction factor are, respectively, up to 181% and 3.86 times of the plain tube and the maximum thermal performance factor is 1.52. It is also obvious that the heat transfer and friction factor obtained from the micro-fin tube with twisted tape in counter-arrangement is higher than that from the micro-fin tube with twisted tape in co-arrangement.
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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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    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%.
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    Turbulent heat transfer in a microfin tube with twisted tape insert
    (2012-12-01)
    Eiamsa-Ard, Smith
    ;
    Kongkaitpaiboon, Vichan
    ;
    Eiamsa-Ard, Petpices
    ;
    Pimsarn, Monsak
    The purpose of the present study is to investigate experimentally the heat transfer, turbulent flow friction and thermal performance factor characteristics in a microfin tube with a twisted tape insert. In the experiment, heat transfer augmentation is expected from both the turbulence of flow near the tube wall produced by fin surface and the swirling flow generated by the twisted tape. Effect of the twisted tape at different twist ratios of y/W = 3, 4 and 5 on the heat transfer enhancement characteristics is also reported. In the experimental set-up, cold water was passed through the uniform heat flux tube in a range of Reynolds number between 5000 and 17000. The experimental results obtained are compared with those from plain tubes. The results show that the thermal performance from using the microfin tube fitted with twisted tape is considerably higher than that from the microfin tube alone. The Nusselt numbers and friction factors are found to be, respectively, 3.0, 4.0 and 5.0 times over the microfin tube alone for the microfin tube combined with twisted tape. In addition, the results demonstrate that as the twist ratio (y/W) decreases, the twisted tape will give better heat transfer enhancement. The microfin tube combined with twisted tape provides higher thermal performance factor than those the microfin tube alone around 172%, 142% and 124%, respectively, for y/W = 3, 4 and 5. The results were correlated in the form of Nusselt number as a function of Reynolds number, Prandtl number and twist ratio.