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Author: search.filters.author.Suwannapan, SupattarachaiSubject: search.filters.subject.Heat transfer

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    Experimental study on flow friction and heat transfer in a square-duct heat exchanger with winglet turbulators
    (2014-01-01)
    Suwannapan, Supattarachai
    ;
    Hoonpong, Panuwat
    ;
    Promvonge, Pongjet
    ;
    Juengjaroennirachon, Sirisawat
    ;
    Pimsarn, Monsak
    The paper presents an experimental study on airflow friction and heat transfer behaviors in a heat exchanger square-duct fitted with winglet turbulators. The experiments are carried out by varying the airflow rate in terms of Reynolds number from 4000 to 25,000. The winglets were mounted in tandem with three attack angles (α=30°, 45° and 60°), two winglet-pitch to duct-height ratios, (called pitch ratio, PR=P/H=1.0 and 1.5) and a single winglet-to duct-height ratio, (called blockage ratio, BR=e/H=0.2). Effects of the winglet parameters on heat transfer and pressure loss in terms of Nusselt number and friction factor are investigated. The experimental result reveals that the application of the winglets provides considerably higher heat transfer and pressure loss values than the smooth duct alone. The winglet at α=60o and PR=1 gives the maximum heat transfer and pressure loss but the one at α = 30o and PR=1.5 yields the highest thermal enhancement factor of about 1.49 at the lowest Reynolds number. © (2014) Trans Tech Publications, Switzerland.
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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.
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    Numerical study of laminar heat transfer in baffled square channel with various pitches
    (2011-01-01)
    Jedsadaratanachai, Withada
    ;
    Suwannapan, Supattarachai
    ;
    Promvonge, Pongjet
    The article presents a numerical analysis of laminar periodic flow and heat transfer characteristics in a constant temperature-surfaced square channel mounted with 30° angled baffles of various pitches. The computations were based on a finite volume method and the SIMPLE algorithm implemented. The fluid flow and heat transfer characteristics are presented for Reynolds number based on the channel hydraulic diameter ranging from 100 to 2000. The angled baffles were placed repeatedly on the lower and upper channel walls with in-line arrangement to generate a pair of streamwise counter - rotating vortex flows. Effects of different pitch ratios (PR=P/H) with a single baffle height ratio of 0.2 on heat transfer and pressure loss in the channel were examined. The baffled channel flow showed a fully developed periodic flow profile at about x/D≈7. The computation revealed that the pair of vortex flows created by the baffles exists and induces impingement/attachment flows on a side and the upper and lower walls leading to substantial increase in heat transfer rate over the test channel. The decrease in the PR led to the rise of friction factor only. The result showed that the optimum thermal performance enhancement factor of about 3.78 is found at PR=2.5. © 2011 Published by Elsevier Ltd.