Promvonge, Pongjet

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Promvonge, Pongjet
Alternative Name
Promvonge, P.
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Email
pongjet.pr@kmitl.ac.th

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    Effect of arc-shaped twisted-baffles on augmented heat transfer in a rectangular duct
    (2023-02-01)
    Promvonge, Pongjet
    ;
    Phila, Arnut
    ;
    Chuwattanakul, Varesa
    ;
    Chokphoemphun, Suriya
    ;
    Eiamsa-Ard, Smith
    In this current work, the effect of utilizing arc-shaped twisted-baffles (T-ABs) in a rectangular air channel on thermal performance factor (TPF) has been experimentally studied. In these experiments, the influence of the changes in parameters such as dimensions of pitch ratio (p/w), attached arc-shape angle (α), and Reynolds number (Re) are explored. The comparisons demonstrate that a channel mounted with arc-shaped twisted-baffles yielded considerably greater Nusselt numbers than a smooth channel, possibly attributable to multiple-impinging jets near the channel surface. Heat transfer enhancements of twisted arc-shaped baffles (T-AB) having larger attack angles were superior to those having smaller attack angles. The one with α = 90o offered greater heat transfer rates than the ones with α = 20o, 40o, 60o, and 80o by approximately 8%, 7%, 4%, and 2%, respectively. The superior heat transfer was attributed to the better contact between the working fluid and heat transfer surfaces. In addition, utilizing arc-shaped twisted-baffles with the lowest p/w of 4.0, in a channel produced stronger vortices and multiple impinging jets, which caused better fluid mixing than other p/w. The optimum condition is achieved using T-ABs at an attached arc-shape angle of α = 90o, p/w = 4.0 and Re = 4000, where the heat transfer rate (Nu), friction factor (f) and TPF are found to be, respectively, 3.31, 4.68 and 1.98 times greater than those of a plain channel.
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    Heat transfer distribution and flow characteristics in a channel with perforated-baffles
    (2022-11-01)
    Eiamsa-ard, Smith
    ;
    Sripattanapipat, Somchai
    ;
    Saysroy, Anucha
    ;
    Promvonge, Pongjet
    ;
    Maruyama, Naoki
    The current paper reports the prediction of heat transfer performance of a channel with a modified perforated-baffle in a square wings (SW-PB) form. Numerical results include flow/temperature field, local heat transfer distribution, and thermal performance of a channel installed with the transverse solid baffle (TB), perforated-baffle (PB), and perforated-baffle with square wings (SW-PB). The simulation results demonstrated that TB brought a large recirculation flow, PB induced small recirculation and SW-PB produced several impinging jets as well as recirculation flows. Heat transfer rates given by PB were lower than those provided by TB and SW-PB by around 6.8% and 7.3%, respectively which were accompanied by lower friction losses by about 11.8% and 3.6%, respectively. Although, SW-PB gave higher heat transfer, the assessment of thermal performance factor (TPF) showed that the benefit from lower friction losses was more important. Under the same pumping power, TPFs assisted by SW-PB were higher than that assisted by PB and TB by 6.0% and 3.3%, respectively. The highest TPF of 1.2 was captured by SW-PB at Re = 9,000.
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    Thermal performance augmentation in a solar air heater with twisted multiple V–baffles
    (2024-11-01)
    Chompookham, Teerapat
    ;
    Eiamsa-ard, Smith
    ;
    Buanak, Kalong
    ;
    Promvonge, Pongjet
    ;
    Maruyama, Naoki
    A 3D numerical investigation of thermal performance augmentation of a twisted multiple V–baffles in a solar air heater is presented. Two important functions of the twisted multiple V–baffles are to generate multiple impinging flows upon the wall to improve the convective heat transfer (compared with a smooth channel) and reduce the pressure drop (compared with a typical multiple V–baffles). These outcomes enhance thermal performance. The results of heat transfer (in terms of a Nusselt number ratio), pressure drop (in terms of a friction factor ratio) and thermal performance (in terms of a thermal enhancement factor) of a twisted multiple V–baffles were compared with both a smooth channel and a typical multiple V–baffles. Eighty–one cases including those with a pitch ratio of PR = 0.4–2.0; blockage ratio, BR = 0.10–0.20; angle of attack, α = 30<sup>o</sup> – 60<sup>o</sup> and a fixed number of twisted loops, n = 2, were investigated in turbulent flow. The results revealed that the twisted multiple V–baffles created multiple impinging jets at the heated wall and help accelerate heat transfer between the wall and the fluid. Compared to a typical multiple V–baffles, the friction factor showed a large decrease while the Nusselt number was slightly lower leading to better thermal performance. Over the study range, PR = 0.4, BR = 0.20, and α = 60<sup>o</sup> appeared to yield the highest thermal enhancement factor, 2.81 at Re = 3000.
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    Thermal performance and exergy analysis in a round tube with louvered trapezoidal winglets
    (2023-09-15)
    Promvonge, Pongjet
    ;
    Eiamsa-ard, Smith
    ;
    Skullong, Sompol
    ;
    Maruyama, Naoki
    ;
    Hirota, Masafumi
    An experiment was performed to investigate the influence of inserting a louver-punched trapezoidal-winglet (LPTW) into a uniform heat-fluxed tube in order to create a longitudinal vortex generator. This research aims to maximize both the thermal performance to increase energy savings, and the relative Nusselt number (Nu<inf>R</inf>) at the optimal performance to reduce heat exchanger sizes. Therefore, the experimental result was emphasized on the thermal and pressure loss characteristics including entropy, and exergy analysis of the turbulent tube flow for Reynolds numbers (Re) that extended from 4760 to 29,280. The LPTWs were arranged by letting V-tip direct downstream with three attack angles (α = 30°, 45° and 60°) and five louver angles (θ<inf>1</inf> = 0°, 25°, 30°, 45° and 90°), all at a single relative winglet pitch (P<inf>R</inf> = 1.0) and height (B<inf>R</inf> = 0.25). According to the findings, it revealed that the friction factor (f) and Nusselt number (Nu) of the LPTW at α= 60° and θ<inf>1</inf> = 0° are, respectively, up to 29.1 and 5.5 times above those of the plain tube. With decreasing Re and θ<inf>1</inf>, the entropy generation (S˙<sup>′</sup><inf>gen</inf>) was reduced to a lower value and the maximum exergy efficiency (η<inf>Ex</inf>) was obtained for the LPTW at α = 60° and θ<inf>1</inf> = 0° The peak thermal performance around 2.5 together with Nu<inf>R</inf> = 4.68 was found at a= 60°, θ<inf>1</inf> = 45° and the lowest Re. However, the optimal condition at α= 60°, θ<inf>1</inf> = 30° was preferable because it provides the greatest Nu<inf>R</inf> = 5.04 at TEF = 2.47. Additionally, correlations for f and Nu were derived and presented for the range of parameters that were taken into consideration.