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    Heat Transfer Analysis in a Channel Mounted with In-Line Downward-Facing and Staggered Downward-Facing Notched Baffles
    (2025-09-01)
    Phila, A.
    ;
    Keaitnukul, W.
    ;
    Kumar, M.
    ;
    Pimsarn, M.
    ;
    Chokphoemphun, S.
    This study presents a comprehensive analysis of heat transfer enhancement, flow resistance, and thermal performance in rectangular channels equipped with three baffle configurations: conventional transverse baffles (TBs), in-line downward-facing notched baffles (IDF-NBs), and staggered downward-facing notched baffles (SDF-NBs). The influence of the pitch-to-baffle height ratio (P/e), ranging from 2.0 to 10, was examined across Reynolds numbers from 6000 to 24,000. Results indicate that a P/e ratio of 6.0 consistently yielded the highest Nusselt numbers across all configurations. While the TB configuration produced significant heat transfer at P/e= 6.0, it experienced a substantial friction penalty, with its best thermal enhancement factor (TEF = 1.168) observed at P/e = 8.0. The IDF-NB configuration achieved optimal performance at P/e = 6.0 with a TEF of 1.257, offering a better balance between heat transfer and flow resistance. The SDF-NB arrangement outperformed all other cases, delivering the highest Nusselt number (Nu = 116.9), TEF (1.362), and improved flow reattachment, primarily due to enhanced mixing from the staggered layout. These findings demonstrate that the staggered notched baffle configuration at P/e = 6.0 offers the most effective thermal performance enhancement among the configurations studied.
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    Numerical Methodology for Enhancing Heat Transfer in a Channel with Arc-Vane Baffles
    (2025-03-01)
    Thapmanee, Piphatpong
    ;
    Phila, Arnut
    ;
    Wongcharee, Khwanchit
    ;
    Maruyama, Naoki
    ;
    Hirota, Masafumi
    This study numerically investigates flow and heat transfer in a channel with arc-vane baffles at various radius-to-channel high ratios (r/H = 0.125, 0.25, 0.375, and 0.5) for Reynolds numbers between 6000 and 24,000, focusing on solar air-heater applications. The calculations utilize the finite volume method, and the SIMPLE algorithm is executed with the QUICK scheme. For the analysis of turbulent flow, the finite volume method with the Renormalization Group (RNG) k-ε turbulence model was used. The results show that arc-vane baffles create double vortices along the axial direction, promoting flow reattachment on the heated surface and enhancing heat transfer. Baffles with smaller r/H ratios strengthen flow reattachment, reduce dead zones, and improve fluid contact with the heat transfer surface. The baffles with the smallest r/H ratio achieve a Nusselt number ratio (Nu/Nu<inf>s</inf>) of 4.91 at Re = 6000. As r/H increases, the friction factor (f) and friction factor ratio (f/f<inf>s</inf>) rise due to increased baffle curvature and surface area. The highest thermal performance factor (TPF) of 2.28 occurs at r/H = 0.125 and Re = 6000, reflecting an optimal balance of heat transfer and friction losses. Arc-vane baffles with a r/H ratio of 0.125 yield a TPF exceeding unity, indicating potential energy savings. These findings provide valuable insights for optimizing baffle designs to enhance thermal performance in practical applications.
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    Thermal Visualization and Performance Analysis in a Channel Installing Transverse Baffles with Square Wings
    (2022-11-01)
    Eiamsa-Ard, Smith
    ;
    Phila, Arnut
    ;
    Wongcharee, Khwanchit
    ;
    Chuwattanakul, Varesa
    ;
    Pimsarn, Monsak
    The experimental examination of local heat transfer, thermal intensification, friction factors, and thermal performance factors (TPF) in a rectangular channel with square-winged transverse baffles (SW-TB) are presented in this paper. The purpose of this study is to modify the typical transverse baffles (TB) into square-winged transverse baffles (SW-TB) in order to improve the thermal performance and heat transfer rate of the channel. The effects of SW-TBs with various wing attack angles and Reynolds numbers on the heat transfer performance characteristics were examined using a thermochromic liquid crystal sheet. In the experiments, the SW-TBs were attached to the bottom wall of the channel, which had an aspect ratio (W:H) of 3.75:1. The SW-TBs had a width (w) of 150 mm, a square perforated cross-sectional area (a × b) of 8 × 8 mm<sup>2</sup>, and attack angles (θ) of 0° (solid transverse-baffle), 22.5°, 45°, 67.5°, and 90°. The bottom wall of the channel was evenly heated, while the other walls were insulated. The temperature contours on the heated surface were plotted using temperatures obtained through using the thermochromic liquid crystal (TLC) image-processing method. Experimental results revealed that the SW-TBs created multiple impinging jets, apart from the recirculation. At the proper attack angles (θ = 22.5° and 45°), the SW-TBs offered greater heat transfer rates and caused lower friction losses, resulting in higher TPFs than the solid transverse baffles. In the current work, channels where the SW-TBs display a θ = 45° presented the greatest TPF, as high as 1.26. The multiple impinging jets issuing by the SW-TBs suppressed the size of the recirculation flow and allowed better contact between the fluid flow and channel wall.
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    Turbulent heat transfer and pressure loss in a square channel with discrete broken V-rib turbulators
    (2016-04-01)
    Pitak, Promthaisong
    ;
    Petpices, Eiamsa Ard
    ;
    Withada, Jedsadaratanachai
    ;
    Smith, Eiamsa Ard
    Turbulent periodic flow, heat transfer, friction loss and thermal enhancement characteristics in a three-dimensional horizo- ntal square channel with broken V-ribs (B-VR) are numerically investigated. The computations are based on the finite volume method, and the SIMPLE algorithm with QUICK scheme is implemented. The B-VR were installed on both sides of a plate which was diagonally placed in a square channel to produce longitudinal vortex flows through the tested section. Effects of different open corner ratios (d/H 0, 0.01, 0.02, 0.03, 0.04 and 0.05) on heat transfer and pressure loss in the channel and the results of the B-VR are studied. The pitch ratio (PR = p/H) and blockage ratio (BR = p/H) of B-VRs were fixed at 1.0 and 0.15, respectively. As compared with the channel without V-rib, the one with B-VRs possessed considerably higher heat transfer and friction loss. It is observed that apart from the rise of Reynolds number, the reduction of the open corner ratios leads to an increase in the Nusselt number and friction factor due to the weaker turbulence and lower resistance to the flow. According to the computational results for B-VRs, the optimum thermal enhancement is found at d/H = 0.