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Author: search.filters.author.Jedsadaratanachai, WithadaSubject: search.filters.subject.Nusselt number

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    HEAT TRANSFER AND FLOW PROFILES IN ROUND TUBE HEAT EXCHANGER EQUIPPED WITH VARIOUS V-RINGS
    (2022-01-01)
    Boonloi, Amnart
    ;
    Jedsadaratanachai, Withada
    This study numerically investigates pressure loss, heat transfer and thermal efficiency in round tube heat exchangers attached with various types of V-rings. A typical type A V-ring is compared with two types of modified V-rings (type B and C). The impacts of blockage ratios, b/D = 0.05, 0.10, 0.15 and 0.20 for all V-ring types in the turbulent region are discussed (Re = 3000 – 20,000). Flow directions in the round pipe attached with the V-rings are varied. The V-apex setting downstream is referred to as “V-Downstream, while the V-apex setting upstream is referred to as “V-Upstream”. The flow and heat transfer profiles in the tested section are analyzed using the finite volume method (a commercial code with the SIMPLE algorithm). The thermal performance of the tested tube is measured in terms of dimensionless variables: thermal enhancement factor (TEF), Nusselt number (Nu) and friction factor (f). Numerical results reveal that type B and C V-rings can reduce pressure drop compared with type A V-ring. Additionally, the V-Upstream of type C V-ring yields the maximum TEF of 3.10 at b/D = 0.05.
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    Flow and heat transfer characteristics of air in square channel heat exchanger with c-shaped baffle: A numerical study
    (2019-01-01)
    Boonloi, Amnart
    ;
    Jedsadaratanachai, Withada
    The purpose of the present work is to study flow configuration and heat transfer behavior in a square channel heat exchanger equipped with C-shaped baffle. The influences of flow attack angle and baffle size on flow and heat transfer characteristics are considered for the laminar flow regime with the Reynolds number around 100 – 2000. The numerical study with finite volume method is selected for the present investigation. The SIMPLE algorithms is opted to solve the numerical problem. The numerical results are concluded in terms of flow and heat transfer mechanisms in the tested section. The thermal performance analysis; Nusselt number ratio (Nu/Nu0), friction factor (f/f0) and thermal enhancement factor (TEF), are also summarized. The numerical model of the smooth square channel is validated with the correlations on both Nusselt number and friction factor. The numbers of grid cell for the computational domain are also compared. The numerical results reveal that the C-shaped baffle in the tested section leads to the appearance of the thermal boundary layer disturbance on the channel walls that the important cause for heat transfer rate and thermal efficiency enhancements. The maximum TEF of the square duct with C-shaped baffle is around 3.89. In addition, the optimum gap spacing value for the square channel inserted with C-shaped baffle is around 5%.
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    Influence of ring size and location on flow topology, heat transfer structure and thermal efficiency in heat exchanger square channel placed with 30-degree inclined square ring
    (2019-01-01)
    Boonloi, Amnart
    ;
    Jedsadaratanachai, Withada
    This paper presents the numerical investigations (finite volume method with SIMPLE algorithm) on flow structure, heat transfer behavior and performance assessment in heat exchanger square channel placed with 30<sup>o</sup> inclined square ring (ISR). The influences of ring size and placement on flow and heat transfer characteristics are considered for laminar flow region with the Reynolds number in the range around 100 – 2000. The purpose for the insertion of the ISR in the square channel is to induce the vortex flow and also increase the turbulent mixing. The numerical result reveals that the ring size and location have effects for the changes of the flow and heat transfer behaviors in the tested section. The present of the ISR in the tested section gives the maximum heat transfer rate around 8.13 times above the smooth square channel. In addition, the optimum thermal performance at similar pumping power or TEF is around 3.10.
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    Heat transfer augmentation in a round tube with 60° winglet pair inserts
    (2014-01-01)
    Chokphoemphun, Suriya
    ;
    Tongyote, Pattarapan
    ;
    Promvonge, Pongjet
    ;
    Jedsadaratanachai, Withada
    ;
    Chompookham, Teerapat
    The experimental study on heat transfer enhancement in a tubular heat exchanger fitted with 60o winglet pairs is carried out by varying airflow velocity in turbulent region in the test section having a constant wall heat-flux. Effects of three blockage ratios (BR=e/D= 0.1, 0.15 and 0.2) and three pitch ratios (PR=P/D= 1, 1.5 and 2) of the winglet pairs on heat transfer rates in the terms of Nusselt number (Nu) and pressure loss in the form of friction factor (f) are examined. The experimental results illustrated that the tube with winglet pair insert provides the heat transfer rate higher than the smooth tube around 1.7 to 2.6 times, depending upon operating conditions. The thermal enhancement factor for using the winglet-pair turbulator is in a range of 1.03 - 1.31. © (2014) Trans Tech Publications, Switzerland.