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Author: search.filters.author.Suwannapan, SupattarachaiSubject: search.filters.subject.Square duct

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    Enhanced heat transfer in a heat exchanger square-duct with discrete V-finned tape inserts
    (2015-03-01)
    Noothong, Watcharin
    ;
    Suwannapan, Supattarachai
    ;
    Thianpong, Chinaruk
    ;
    Promvonge, Pongjet
    The article presents an experimental and numerical study on thermal performance enhancement in a constant heat-fluxed square-duct inserted diagonally with 45° discrete V-finned tapes (DFT). The experiments were carried out by varying the airflow rate through the tested square duct with DFT inserts for Reynolds number from 4000 to 25000. The effect of the DFT with V-tip pointing upstream at various relative fin heights and pitches on heat transfer and pressure drop characteristics was experimentally investigated. Both the heat transfer and pressure drop were presented in terms of Nusselt number and friction factor respectively. Several V-finned tape characteristics were introduced such as fin- to duct-height ratio or blockage ratio (R<inf>B</inf> = e/H = 0.075, 0.1, 0.15 and 0.2), fin pitch to duct height ratio (R<inf>P</inf> = P/H = 0.5, 1.0, 1.5 and 2.0) and fin attack angle, α = 45°. The experimental results reveal that the heat transfer and friction factor values with DFT inserts increase with the increment of R<inf>B</inf> but the decrease of R<inf>P</inf>. The inserted square-duct at R<inf>B</inf> = 0.2 and R<inf>P</inf> = 0.5 provides the highest heat transfer and friction factor while the one with R<inf>B</inf> = 0.1 and R<inf>P</inf> = 1.5 yields the highest thermal performance. Also, a numerical simulation was conducted to investigate the flow structure and heat transfer mechanism inside the tested duct with DFT inserts.
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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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    Heat transfer improvement in a square duct with diagonal inclined ribs
    (2014-01-01)
    Suwannapan, Supattarachai
    ;
    Poomsalood, Ratsak
    ;
    Promvonge, Pongjet
    ;
    Jedsadaratanachai, Withada
    ;
    Limkul, Thitipat
    This research presents a numerical study of turbulent periodic flow and heat transfer in three-dimensional isothermal-fluxed square duct with diagonal inclined rib inserted. The fluid flow and heat transfer characteristics are presented for Reynolds numbers in the range of 4000 to 20,000. The computations based on the finite volume method, and the SIMPLE algorithm has been implemented. Effects of rib pitch ratios (0.5 to 2) at a single blockage ratio of 0.2 and attack angle of 60° on heat transfer and friction factor in the duct are examined and their results of the inclined rib are also compared with those of the smooth duct. It is found that the inclined rib provides higher heat transfer rate and friction factor than the smooth duct for all cases. In addition, the decreasing of the pitch ratio leads to the rise in the Nusselt number and friction factor. © (2014) Trans Tech Publications, Switzerland.