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Author: search.filters.author.Phila, ArnutSubject: search.filters.subject.Heat transfer enhancement

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    Enhanced heat transfer performance in channel with delta-wing perforated V-type baffles
    (2023-10-01)
    Eiamsa-ard, Smith
    ;
    Phila, Arnut
    ;
    Thianpong, Chinaruk
    ;
    Chuwattanakul, Varesa
    ;
    Maruyama, Naoki
    The article examines the influence of delta-wing V-type baffles (DW-PVBs) on the average Nusselt number, local Nusselt number distribution, pressure losses, and thermal performance behaviors in a channel. Delta-wing perforated V-type baffles (DW-PVBs) mounted in a regular manner on the bottom of a channel produced two pairs of longitudinal counter-rotating vortices to enhance chaotic fluid mixing and destabilize the boundary layer, hence boosting the heat transfer. The geometric characteristics of the delta-wing V-type baffle (DW-PVBs) located on the bottom of the channel were examined at relative baffle blockage and pitch ratios (BR = h/H = 0.3 and p/H = 1.5), and five delta-wing attack angles, θ = 0<sup>o</sup> (solid V-shaped baffle), 22.5°, 45°, 67.5°, and 90°. The present DW-PVBs mounted on the channel were designed to mitigate pressure loss due to flow blockage. The experiment was done by permitting air to flow through a channel at Reynolds numbers (Re) ranging from 6000 to 24,000. The present results show that the friction factor using the DW-PVBs decreased considerably with increasing θ values. The experimental results revealed that small θ values yielded greater heat transfer and resistance than large θ values. The DW-PVBs with θ = 22.5° performed better than inserts with other θ values in terms of heat transfer rate. It was also observed that the DW-PVBs with θ = 45° gave the maximum thermal performance factor (TPF), while presenting a 13.64–17.26% lower friction factor than the solid V-shaped baffle. Furthermore, it was also found that the DW-PVBs with θ = 0°, 22.5°, 45°, 67.5°, and 90° gave peak TPF values of up to 1.87, 1.89, 1.91, 1.87, and 1.84 at the lowest Reynolds number, 6000.
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    Influence of notched baffles on aerothermal performance behaviors in a channel
    (2023-07-01)
    Phila, Arnut
    ;
    Keaitnukul, Warin
    ;
    Eiamsa-ard, Smith
    ;
    Naphon, Paisarn
    ;
    Maruyama, Naoki
    The proper designs of modified heat transfer surfaces or turbulence enhancement inserts for heat transfer augmentation are extremely important for improving overall aerothermal performances relating to the energy-saving capabilities of thermal systems. A major challenge is to control friction loss as little as possible while maintaining reasonable heat transfer enhancement. Transverse baffles with rectangular notches or notched baffles (NBs) were applied for improving aerothermal performance in a channel with a constant aspect ratio of 3.75 while notch height-to-baffle height ratio (a/e) ranged from 0.125 to 0.5. Reynolds number ranged from 6000 to 24,000, in experiments. Heat transfer enhancement, pressure loss, and aerothermal performance in a rectangular channel with notched baffles were examined. Compared to the solid transverse baffle (SB, a/e = 0), the NBs with a/e = 0.125 increased the heat transfer rate while lessening the pressure loss, as shown by the experimental findings. Obviously, Nusselt number, friction factor and aerothermal performance increased as the a/e ratio decreased. The NBs with the smallest notch height-to-baffle height ratio (a/e = 0.125) exhibited the highest aerothermal performance of 1.17, which can be attributed to the efficient heat transfer enhancement by the strong multi-jet impingements and the moderate friction loss penalty resulting from the presence of notches (spaces) on the baffles.
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    Heat transfer mechanism and thermal performance of a channel with square-wing perforated transverse baffles installed: effect of square-wing location
    (2023-05-01)
    Eiamsa-Ard, Smith
    ;
    Phila, Arnut
    ;
    Pimsarn, Monsak
    ;
    Maruyama, Naoki
    ;
    Hirota, Masafumi
    The aim of this study is to report the influence of wing position (h/e) of perforated transverse baffles with square-wings (SW-PBs) on heat transfer rate and pressure drop characteristics in a channel. The channel has a cross-sectional dimension of 15 cm × 4 cm and a length of 60 cm. Two types of baffles: Solid transverse baffles and square-wing perforated transverse baffles, are comparatively tested. The baffle pitch ratio (p/e) is set to 5.0 and remains constant throughout all experiments which encompass Reynolds numbers (Re) of 6000, 9000, 12,000, 15,000, 18,000, 21,000, and 24,000. Square-wings are introduced at four different locations, h/e = 0.92 (highest wing location), 0.83, 0.75, and 0.67 (lowest wing location). The maximum heat transfer rates achieved in channels with SW-PBs at h/e = 0.92, 0.83, 0.75, and 0.67 are 148%, 157%, 166%, and 180% above that of a plain channel, while pressure losses increase by 9.51–10.69, 9.56–10.79, 9.59–10.86, and 9.64–10.99 times, respectively. Experimental results show that square-wings create multiple impinging jet flows and Nusselt number peaks appear adjacent to the rear of the perforated transverse baffles. When compared to solid transverse baffles, SW-PBs cause lower pressure losses and yield higher thermal performance.