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Author: search.filters.author.Thianpong, ChinarukSubject: search.filters.subject.Winglet

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    Heat transfer augmentation in a circular tube with winglet vortex generators
    (2015-04-01)
    Chokphoemphun, Suriya
    ;
    Pimsarn, Monsak
    ;
    Thianpong, Chinaruk
    ;
    Promvonge, Pongjet
    The article presents the influence of winglet vortex generators (WVGs) placed in the core flow area on thermal performance enhancement of a tube heat exchanger. The experiment was carried out in a uniform wall heat-fluxed tube by varying turbulent airflow for Reynolds number ranging from 5300 to 24000. In the present work, the WVGs with an attack angle of 30° were inserted into the test tube at four different winglet pitch ratios (R<inf>P</inf> = P/D) and three winglet-width or blockage ratios (R<inf>B</inf> = e/D). The experimental results at various R<inf>P</inf> and R<inf>B</inf> values were evaluated and compared with those for smooth tube and tubes with twisted tape or wire coil. The measurement reveals that the WVGs enhance considerably the heat transfer and friction loss above the plain tube, wire coil and twisted tape. The Nusselt number and friction factor increase with the increment of R<inf>B</inf> and Re but with the decreasing R<inf>P</inf>. The average Nusselt numbers for the WVGs with various R<inf>B</inf> are in the range of 2.03-2.34 times above the plain tube. The thermal performance for the WVGs is found to be much higher than that for the wire coil and twisted tape and is in a range of 1.35-1.59. Also, a numerical investigation is conducted to study the flow structure and heat transfer enhancement mechanisms in the winglet-inserted tube.
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    Experimental study on heat transfer in square duct with combined twisted-tape and winglet vortex generators
    (2014-12-01)
    Promvonge, Pongjet
    ;
    Suwannapan, Supattarachai
    ;
    Pimsarn, Monsak
    ;
    Thianpong, Chinaruk
    The article presents an experimental investigation on thermal performance enhancement in a constant heat-fluxed square duct fitted with combined twisted-tape and winglet vortex generators. The experiments are carried out for the airflow rate through the tested square duct fitted with both the vortex generators for Reynolds number from 4000 to 30,000. The effect of the combined twisted tape and rectangular winglet inserts on heat transfer and pressure drop presented in terms of respective Nusselt number and friction factor is experimentally investigated. The characteristics of the combined twisted-tape and winglet include two twist ratios (Y=4 and 5), three winglet- to duct-height ratios, (R<inf>B</inf>=0.1, 0.15 and 0.2), four winglet-pitch to tape-width ratios, (R<inf>P</inf>=2, 2.5, 4 and 5) and a single attack angle of winglet, α=30°. The experimental results reveal that the Nusselt number and friction factor for the combined twisted-tape and V-winglet increase with increasing R<inf>B</inf> but decreasing R<inf>P</inf>. The inserted duct at R<inf>B</inf>=0.2, R<inf>P</inf>=2 and Y=4 provides the highest heat transfer rate and friction factor but the one at R<inf>B</inf>=0.1, R<inf>P</inf>=2 and Y=4 yields the highest thermal performance. The application of combined vortex-flow devices gives thermal performance around 17% higher than the twisted tape alone.
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    Enhanced heat transfer in a triangular ribbed channel with longitudinal vortex generators
    (2010-06-01)
    Promvonge, Pongjet
    ;
    Chompookham, Teerapat
    ;
    Kwankaomeng, Sutapat
    ;
    Thianpong, Chinaruk
    Effects of combined ribs and winglet type vortex generators (WVGs) on forced convection heat transfer and friction loss behaviors for turbulent airflow through a constant heat flux channel are experimentally investigated in the present work. The cross-section of the ribs placed inside the opposite channel walls to create a reverse flow is an isosceles triangle shape. Two rib arrangements, namely, in-line and staggered arrays, are introduced. Also, two pairs of the WVGs with various attack angles (α) of 60°, 45° and 30° are mounted on the test duct entrance to create a longitudinal vortex flow through the test channel. Measurements are carried out for a rectangular duct of aspect ratio, AR = 10 and height, H = 30 mm with a single rib height, e/H = 0.13 and rib pitch, P/H = 1.33. The flow rate is in terms of Reynolds numbers based on the inlet hydraulic diameter of the channel ranging from 5000 to 22,000. The experimental results show a significant effect of the presence of the rib turbulator and the WVGs on the heat transfer rate and friction loss over the smooth wall channel. The values of Nusselt number and friction factor for utilizing both the rib and the WVGs are found to be considerably higher than those for using the rib or the WVGs alone. The larger the attack angle value leads to higher heat transfer and friction loss than the lower one. The in-line rib together with the WVGs provides higher heat transfer and friction loss than the staggered one for similar operating conditions. In common with the WVGs, the in-line rib yields the highest increase in both the Nusselt number and the friction factor but the rib with staggered array shows better thermal performance than the others. © 2010 Elsevier Ltd. All rights reserved.
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    Heat transfer augmentation in a wedge-ribbed channel using winglet vortex generators
    (2010-02-01)
    Chompookham, Teerapat
    ;
    Thianpong, Chinaruk
    ;
    Kwankaomeng, Sutapat
    ;
    Promvonge, Pongjet
    Experimental investigations have been carried out to study the effect of combined wedge ribs and winglet type vortex generators (WVGs) on heat transfer and friction loss behaviors for turbulent airflow through a constant heat flux channel. To create a reverse flow in the channel, two types of wedge (right-triangle) ribs are introduced: wedge ribs pointing downstream and pointing upstream. The arrangements of both rib types placed inside the opposite channel walls are in-line and staggered arrays. To generate longitudinal vortex flows through the tested section, two pairs of the WVGs with the attack angle of 60° are mounted on the test channel entrance. The test channel has an aspect ratio, AR = 10 and height, H = 30 mm with a rib height, e/H = 0.2 and rib pitch, P/H = 1.33. The flow rate in terms of Reynolds numbers is based on the inlet hydraulic diameter of the channel ranging from 5000 to 22,000. The presence of the combined ribs and the WVGs shows the significant increase in heat transfer rate and friction loss over the smooth channel. The Nusselt number and friction factor values obtained from combined the ribs and the WVGs are found to be much higher than those from the ribs/WVGs alone. In conjunction with the WVGs, the in-line wedge pointing downstream provides the highest increase in both the heat transfer rate and the friction factor while the staggered wedge pointing upstream yields the best thermal performance. © 2009 Elsevier Ltd. All rights reserved.