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Author: search.filters.author.Wongcharee, K.Subject: search.filters.subject.Friction factor

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    Silver–water nanofluid flow and convective heat transfer in a microfin tube equipped with loose-fit twisted tapes
    (2020-06-01)
    Samruaisin, P.
    ;
    Wongcharee, K.
    ;
    Chuwattanakul, V.
    ;
    Eiamsa-ard, S.
    Heat transfer enhancement and performance of compact heat exchangers have been extensively studied in the past century for the purpose of promoting energy efficiency. Microfin tubes in single/two/multiple-phase flow heat exchangers into which twisted tape swirl generators are installed can promote heat transfer with a moderate pressure loss penalty. This article reports on the enhanced heat transfer of silver–water nanofluids in a microfin tube into which loose-fit twisted tapes are installed in a counter-flow arrangement. The experiments were carried out using nanofluids with various silver concentrations (0.007–0.03 vol%), loose-fit twisted tapes with clearance ratios (c/D) of 0.0 (tight-fit), 0.05, 0.075 and 0.1, for a twist ratio, y/W, of 2.0. The results indicate that the heat transfer rate (Nu) and pressure drop (f) increase with a decrease in clearance ratio (c/D) and increase in silver (Ag) nanoparticle concentration. Additionally, the thermal performance factor tends to increase with the decrease in Reynolds numbers.
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    Heat transfer enhancement by helically twisted tapes inducing co- and counter-swirl flows
    (2013-08-01)
    Nanan, K.
    ;
    Yongsiri, K.
    ;
    Wongcharee, K.
    ;
    Thianpong, C.
    ;
    Eiamsa-ard, S.
    An experimental investigation has been conducted for determining heat transfer enhancement by inserting helically twisted tapes, to induce co- and counter-swirl flows, (the tapes are symbolized as co-HTT and C-HTT, respectively). Tape pitch ratio (p/ D) was varied between 1.0 and 2.0, while tape width ratio (w/D) and twist ratio (y/w) were fixed at 0.2 and 3.0, respectively. The experiments were performed for fully developed turbulent flow with Reynolds number range (Re) between 6000 and 20,000, under uniform wall heat flux condition. At similar conditions, the use of Co-HTT results in lower Nusselt number and friction factor but higher thermal performance factor than that of C-HTT. Nusselt number and friction factor increase with decreasing pitch ratio, while thermal performance factor possesses opposite trend. In addition, the empirical correlations for Nusselt number, friction factor and thermal performance factor as functions of the Reynolds number (Re), Prandtl number (Pr) and tape pitch (p/D), were developed through a multi-variant linear normal regression. © 2013 Elsevier Ltd.
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    Heat transfer enhancement in a tube using delta-winglet twisted tape inserts
    (2010-03-01)
    Eiamsa-ard, S.
    ;
    Wongcharee, K.
    ;
    Eiamsa-ard, P.
    ;
    Thianpong, C.
    Heat transfer, flow friction and thermal performance factor characteristics in a tube fitted with delta-winglet twisted tape, using water as working fluid are investigated experimentally. Influences of the oblique delta-winglet twisted tape (O-DWT) and straight delta-winglet twisted tape (S-DWT) arrangements are also described. The experiments are conducted using the tapes with three twist ratios (y/w = 3, 4 and 5) and three depth of wing cut ratios (DR = d/w = 0.11, 0.21 and 0.32) over a Reynolds number range of 3000-27,000 in a uniform wall heat flux tube. The obtained results show that mean Nusselt number and mean friction factor in the tube with the delta-winglet twisted tape increase with decreasing twisted ratio (y/w) and increasing depth of wing cut ratio (DR). It is also observed that the O-DWT is more effective turbulator giving higher heat transfer coefficient than the S-DWT. Over the range considered, Nusselt number, friction factor and thermal performance factor in a tube with the O-DWT are, respectively, 1.04-1.64, 1.09-1.95, and 1.05-1.13 times of those in the tube with typical twisted tape (TT). Empirical correlations for predicting Nusselt number and friction factor have been employed. The predicted data are within ±10% for Nusselt number and ±10% for friction factor. © 2009 Elsevier Ltd. All rights reserved.