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    Item type:Publication,
    Augmented thermal effectiveness in solar air receiver with flapped curved winglets: Experimental and numerical analysis
    (2025-12-01)
    Sripattanapipat, Somchai
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    ; ;
    Promthaisong, Pitak
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    Nakhchi, Mahdi Erfanian
    Thermal effectiveness was examined on a solar air receiver equipped with a new lengthwise vortex generator, namely a flapped curved winglet (FCW) mounted on the absorber, utilizing experimental and numerical approaches. Two arrays were employed to assemble two FCWs on the absorber at an angle of attack (α = 59.5°). The FCWs' V-tips were orientated upstream (VU-FCW) and downstream (VD-FCW). Air served as the working fluid, entering a constantly heat-fluxed channel at Reynolds numbers (Re) varying from 5280 to 22,510. Three relative winglet pitches (P<inf>R</inf> = P/H = 1.0–2.0), five winglet-mounted flap angles (β = 0° - 90°), and one winglet blockage ratio (b/H=B<inf>R</inf> = 0.6) were among the major factors. According to the findings, lowering P<inf>R</inf> and β greatly enhances the f (friction factor) and Nu (Nusselt number) of the two FCW arrays. The FCW with P<inf>R</inf> = 1.0 and β = 0° has the largest Nu and f values, approximately 8.3 and 77.39 times bigger than the smooth flat channel, as per the test data. The maximal thermal effectiveness factors (TEF) of the VD-FCW and VU-FCW were approximately 2.83 and 2.61, respectively, at comparable β = 45° and P<inf>R</inf> = 1.5. The f and Nu correlations in employing FCW were also provided. A 3D computational analysis employing the realizable k-ε turbulence model was conducted to examine heat transmission and flow patterns, with the corresponding measured data validating the expected results. The numerical and measured data sets yielded consistent results, and the FCW's heat transmission mechanism was also described.
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    Item type:Publication,
    Enhanced thermal effectiveness of square duct with V-type double-baffles: Numerical study
    (2024-09-01) ;
    Sripattanapipat, Somchai
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    Skullong, Sompol
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    Promthaisong, Pitak
    The article puts forward three-dimensional computational research on heat transmission augmentation within a square channel containing 45<sup>o</sup> V-type double-baffles positioned on the lower and top parts at regular intervals in the turbulence zone for Reynolds numbers (Re) that vary from 3000 to 20,000. The primary goal of this research is to increase the thermal effectiveness and relative Nusselt number (Nu/Nu<inf>0</inf>), in order to conserve energy and reduce the size of the heating or cooling system. The simulations utilize a finite volume approach in common with the SIMPLE algorithm, whereas the turbulent model used is the realizable k–ε. The baffles are designed to be separated vertically for reducing pressure loss. Both single V-baffles and double V-baffles have four relative pitches (PR = 0.4, 0.5, 0.6, and 1.0) and height/blockage ratios (BR = 0.05, 0.1, 0.15, and 0.2), with a fixed attack angle (α) of 45<sup>o</sup>. The computational findings show that both V-baffles are capable of producing the primary vortices, but only the double V-baffles have the ability to provide the impinging streams onto the wall, cooling the region behind the baffles. This suggests that the double V-baffles not only boost heat transmission but also reduce frictional loss. When compared to a single V-baffle, the double ones enhance heat transfer by an average of 1.04–9.94% while decreasing frictional loss by an average of 9.88–31.73%. The thermal effectiveness factor (TEF) of the double V-baffles ranges from 1.03 to 3.21, and its peak value of around 3.21 is for PR = 0.4, BR = 0.05, at lower Re.
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    Item type:Publication,
    Effect of louver-perforated V-type baffles on thermal effectiveness and entropy in round tube
    (2025-08-01) ;
    Sripattanapipat, Somchai
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    ;
    Nakhchi, Mahdi Erfanian
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    Skullong, Sompol
    An experimental investigation was conducted to assess the influence of insertion of a louver-perforated V-type baffle (LVB) vortex generator into a consistent heat-fluxed tube on thermal performance. This study aimed to optimize thermal effectiveness to boost energy savings and reduce the heat exchanger size. The experiments focused on investigating the thermal features, as well as estimating the entropy of turbulent flow at Reynolds numbers (Re) varying between 4750 and 29,290. The LVBs were positioned in two different arrays on a supporting tape during the present experiment: “V-down” and “V-up,” with the V-apex oriented upstream and downstream, respectively, at a fixed attack angle (α = 52°). At one relative baffle height (B<inf>R</inf> = 0.3) and pitch (P<inf>R</inf> = 1.0), the LVBs dealt with six louver flapped angles (θ = 0°, 10°, 20°, 30°, 45°, and 90°) in addition to three louver-hole sizes and locations (θ<inf>1</inf>, θ<inf>2</inf> and θ<inf>12</inf>). Comparative analysis was also conducted on data obtained from the current smooth tube. According to the findings, the louver angle θ<inf>1</inf> = 20°, located on the baffle's trailing end, had the greatest relative Nusselt number (Nu<inf>R</inf>), which was 5.9 times for V-down and 6.38 times for V-up. Furthermore, compared to the V-down and V-up solid baffles (θ = 0°), their friction losses were lessened. The V-up LVB reached its minimum value at θ<inf>1</inf> = 20°, corresponding to the lowest Re. At θ<inf>1</inf> = 20°, the V-up LVB attained its minimum entropy generation (S˙<inf>gen</inf><sup>′</sup>) and maximum reduced entropy factor (S<inf>R</inf>) around 20.3. At a comparable θ<inf>1</inf> = 20°, the maximal thermal effectiveness factor (TEF) of V-down and V-up were approximately 2.39 and 2.59, respectively. The estimation and documentation of correlations were also performed for the parameters under consideration, namely Nu, f, and TEF.
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    Item type:Publication,
    Thermal effectiveness and entropy-exergy estimation in a tube with punched double V-winglets
    (2026-06-01) ;
    Sripattanapipat, Somchai
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    ;
    Erfanian Nakhchi, Mahdi
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    Skullong, Sompol
    Vortex generators are effective devices for enhancing heat transfer rates in heating or cooling systems with minimal frictional losses via the production of streamwise vortices. This research effort presents the perforated double V-winglet (P-DVW) and looks at how it affects heat transmission and friction when mounted inside a heat exchange tube that is consistently heated for producing multiple vortices whereas its flow is turbulent. Optimizing thermal performance for increased energy savings and maximizing the Nusselt number ( Nu ) to minimize heat exchanger size are the major goals. Thermal characteristics, including generated entropy and exergy efficiency, are explored in depth. A Reynolds number (Re) that varies from 4760 to 29,270 is employed to explore the friction and thermal features of the tube. The P-DVW parameters encompass attack angles of α<inf>2</inf> = 15° and α<inf>1</inf> = 30°, four porosity ratios ( A <inf>h</inf>/ A <inf>w</inf> = 0, 0.0188, 0.0523, and 0.1026), and three pitch ratios, P<inf>R</inf>, (0.75, 1, and 1.25), while maintaining a constant winglet height. At P<inf>R</inf> = 0.75 and A <inf>h</inf>/ A <inf>w</inf> = 0, the P-DVW exhibits peak f and Nu values around 23.83 and 5.31 times bigger than those of the plain tube, accordingly. Further, under the specified conditions, it yields minimal entropy production, while the optimal exergy efficiency is roughly 0.9829. The thermal effectiveness of P-DVW is anticipated to reach its maximum at 2.55 with Nu<inf>R</inf> = 4.54 at A <inf>h</inf>/ A <inf>w</inf> = 0.0523 and P<inf>R</inf> = 0.75 to reveal its actual benefits. Furthermore, the correlations of f , Nu , and TEF were determined for the examined range of values.
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    Item type:Publication,
    Numerical Heat Transfer Investigation in a Heat Exchanger Tube with Hexagonal Conical-ring Inserts
    (2016-11-01)
    Sripattanapipat, Somchai
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    Tamna, Sombat
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    The hexagonal conical rings (HCR) modified from the typical conical ring (CR) are used as a turbulence promoter for producing the vortex flows to enhance the heat transfer rate in a heat exchanger tube. To reduce the pressure loss, the V-shaped HCR (V-HCR) obtained by cutting both symmetric plane of the cone-tip of HCR at 30°, 45°and 60°is offered in the present work. The tube fitted with V-HCR elements having a fixed inlet and outlet diameter is numerically investigated. The computation is carried out for Reynolds number in a range of 3000 to 20,000 in a uniform heat-fluxed test tube. The numerical results show that the V-HCR insert leads to much higher heat transfer than the typical CR/HCR insert or the smooth tube alone and also provides lower friction factor. The 30°V-shaped HCR gives the highest heat transfer and thermal performance due to the lowest friction loss, indicating the promising device of the V-HCR.
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    Item type:Publication,
    Enhanced thermal performance in solar receiver duct with louver-punched V-type winglets: Numerical and experimental study
    (2025-03-01) ;
    Sripattanapipat, Somchai
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    Promthaisong, Pitak
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    Skullong, Sompol
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    An experimental and computational research was performed to explore the augmentation of turbulent convection in a solar receiver channel by utilizing louver-punched V-type winglets (LPVWs) that were fixed to the absorber plate. The simulation utilized the realizable k-ε turbulent model, and the predicated outputs were verified by the relevant measured data. At a fixed attack angle (α) of 45°, the LPVW components were mounted on the absorber with the V-tip facing downstream. Using the LPVW, the newly developed absorber is intended to boost thermal performance by generating multiple flows of longitudinal vortices that induce impinging air streams onto the absorber, thereby enhancing heat transmission. The louvered hole on the winglet serves to reduce pressure loss while preserving the primary vortices. In the current investigation, the winglet parameters consisted of a single relative winglet height (B<inf>R</inf> = 0.4), four louver size ratios (R<inf>L</inf> = e<inf>1</inf>/b = 0.9, 0.7, 0.5, and 0.3), and five louver-flapped angles (β = 90°, 60°, 45°, 30°, and 0°). The LPVW with β > 0° substantially reduced the solid-winglet (β = 0°) friction loss, whereas the heat transmission was slightly declined, as indicated by the results. The solid winglet (β = 0°) exhibited the largest frictional loss and heat transmission, with values approximately 6.3 and 48.2 times the smooth flat duct, respectively. The optimal performance of the LPVW was roughly 2.58, at R<inf>L</inf> = 0.9 and β = 45° Furthermore, empirical correlations for heat transmission and frictional loss were established for this solar receiver duct system. To investigate the heat transmission and flow patterns, a 3-dimensional numerical simulation was implemented, and the predictions were verified against the measured data. The findings were in good accord between the numerical and measured data. For greater thermal performance, the LPVW is reconfigured by altering the locations of the louver holes. The revised LPVW exhibits a peak TEF of 2.7 at β = 35°, l<inf>2</inf>/l<inf>1</inf> = 0.15, l<inf>3</inf>/l<inf>1</inf> = -0.15 and R<inf>L</inf> = 0.9, about 4.65 % superior than the initial analysis.
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    Item type:Publication,
    Experimental and numerical evaluations of thermal performance in heat exchange channel with punched V-type delta-winglets
    (2026-09-01)
    Promthaisong, Pitak
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    Sripattanapipat, Somchai
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    Nakhchi, Mahdi Erfanian
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    An experimental examination on the heat transmission improvement of a heat exchange channel (HXC) with punched V-shaped delta-winglets (PVDWs) positioned at regular intervals along the heated wall is presented in the article. This channel has a consistent heat flux for the fluid flow with a Reynolds number (Re) between 5295 and 22,700. By producing vortex flows, the PVDWs help to mix the airflow more rapidly, decrease friction loss via the winglets' louver flap, and direct air jets onto the hot-plate wall. PVDWs with three relative pitches (P<inf>R</inf> = 1, 1.5, and 2) and five louver flap angles (θ = 90°, 60°, 45°, 30°, and 0°) were spaced regularly on the heated surface. The relative winglet height (B<inf>R</inf>) was maintained at 0.5 and the attack angle was fixed at 45°. Two types of winglet patterns were in use: inline PVDW and staggered PVDW. Thermal effectiveness factor (TEF), Nusselt number (Nu), and friction factor (f) were all influenced by the PVDW parameters. Varieties of θ and P<inf>R</inf> are examined parametrically. The smallest Reynolds number results in the greatest rise in frictional factor (f<inf>R</inf> = 75.07), while the largest Reynolds number gives the greatest improvement in heat transfer rate (Nu<inf>R</inf> = 7.63) for I-PVDW at θ = 0° and P<inf>R</inf> = 1.0. Both the S-PVDW and the I-PVDW reached their maximum TEFs at θ = 45° and P<inf>R</inf> = 1, with the former reaching 2.67 and the latter 2.63. Nu and f correlations can also be estimated using their measured data. The best thermal effectiveness and lower friction in the test channel are achieved by using S-PVDWs. The predicted findings were validated by the matching measured data after a 3D numerical study was performed to analyze heat transfer and flow patterns using the realizable k-ε turbulence model. Both the experimental and computational results were in good agreement, and the heat transfer mechanism of the PVDW was elucidated. A reconfiguration of the S-PVDW is performed by reversing the flap angle to increase thermal effectiveness. At θ = −45° and P<inf>R</inf> = 1, the updated S-PVDW shows a highest TEF of 2.78, which is approximately 4% better than the previous analysis.
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    Item type:Publication,
    Thermal effectiveness augmentation in heated tube with louver-punched delta winglets
    (2025-09-01) ;
    Sripattanapipat, Somchai
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    Promthaisong, Pitak
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    ;
    Nakhchi, Mahdi Erfanian
    Louver-punched delta winglet (LPDW) vortex generators were presented as a way to increase convective heat transmission in a tubular exchanger. LPDW arrays were categorized as inline or staggered louver-punched delta winglets (I-LPDW and S-LPDW, respectively). Experimental and numerical research was carried out for Reynolds numbers varying from 4760 to 29,290 to analyze the thermal patterns and flow characteristics within a constant heat flux tube with LPDWs. The turbulence model adopted for the present research was the realizable k-ε model. For both I-LPDW and S-LPDW winglet arrangements, a single ratio of blockage (B<inf>R</inf> = e/D = 0.25), pitch ratio (P<inf>R</inf> = P/D = 1), and attack angle (α = 60°) was utilized as well as three ratios of louver length (L<inf>R</inf> = d/e = 0.24–0.56) and five flap angles (θ = 0°–90°). The research showed that when the θ and L<inf>R</inf> values fall, the LPDW's friction factor (f) and Nusselt number (Nu) grow since streamwise vortices that possess greater kinetic energy of turbulence promote fluid mixing. The winglet with θ = 45°, L<inf>R</inf> = 0.24 exhibited a peak TEF of 2.56 for I-LPDW and 2.63 for S-LPDW whereas the winglet with θ or L<inf>R</inf> = 0° had the largest Nu and f values, at 5.41 and 24.38 times, respectively. The numerical results illustrated that both LPDWs produce many longitudinal vortices throughout the tube. These flow patterns improved fluid mixing in the tube by raising the fluid's kinetic energy of turbulence. Additionally, the findings of the verification between the computational and experimental data were satisfactory. The Nu and f correlations for the I-LPDW and S-LPDW were also established using measured data.
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    Item type:Publication,
    Numerical Heat Transfer Study of Turbulent Tube Flow through Winglet-pairs
    (2016-11-01)
    Tamna, Sombat
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    Sripattanapipat, Somchai
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    A numerical investigation on heat transfer behaviors in a constant heat-fluxed round tube inserted with winglet vortex generators is conducted. Air as the working medium flows through the tube for Reynolds numbers (Re) between 4000 and 20,000. The effect of using the rectangular-winglet tape (RWT) on heat transfer characteristics in the tube is numerically examined. For comparison purpose, the trapezoidal-winglet tape (TWT) and delta-winglet tape (DWT) are also offered. The RWT parameters in this work include four relative winglet-to-tube heights or blockage ratios (B<inf>R</inf>=b/D= 0.1, 0.15, 0.2, and 0.25) while the TWT and DWT are only at B<inf>R</inf>= 0.2. All the winglet pairs are at a single attack angle (α= 45°) and pitch ratio (p/D=P<inf>R</inf>=4). The numerical results show that the Nusselt number (Nu) and friction factor (f) of the tube inserts are enhanced with increasing B<inf>R</inf> values. The Nu for the inserted tube is about 1.8-2.7 times above that for the smooth tube while the f is around 4.5-11 times higher. For the studied B<inf>R</inf> ranges, the highest thermal performance is 1.48 for the RWT with B<inf>R</inf>= 0.1 at lower Reynolds number.
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    Augmentation of solar air heater effectiveness with flapped triangular-wings
    (2025-12-01) ;
    Sripattanapipat, Somchai
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    ;
    Nakhchi, Mahdi Erfanian
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    Skullong, Sompol
    An experiment was conducted to identify the optimal method for enhancing the thermal effectiveness of a solar air heater duct utilizing flapped triangular-wing (FTW) vortex generators affixed to the absorber. The wings are structured in two configurations: backward FTW (B-FTW) and forward FTW (F-FTW), each incorporating a louver-flapped opening for lowering frictional loss. This study seeks to improve the Nusselt number ratio (Nu<inf>R</inf>) while lowering friction loss to optimize thermal effectiveness, hence minimizing the overall dimensions of thermal energy systems. The research findings focus on heat transmission (Nu) and frictional loss (f), encompassing thermal effectiveness across the entire range of Reynolds numbers (Re) from 5280 to 22,510. The FTW elements are configured in B-FTW and F-FTW forms, employing three relative pitches (P<inf>R</inf> = 0.75, 1.25, and 1.75) and five flap angles (θ = 0°, 35°, 45°, 65°, and 90°), while maintaining a constant attack angle (α = 45°) and a wing height ratio (B<inf>R</inf> = 1). The research findings demonstrate that the FTWs produce a significant increase in Nu contrasted to the smooth duct, which varies from 4.72 to 8.05 times, while the increase in f is approximately 13 to 68.1 times. For P<inf>R</inf> = 1.25, θ = 45°, and lower Re, the greatest thermal effectiveness factor (TEF) is roughly 2.87 for the F-FTW and 2.64 for the B-FTW, while Nu<inf>R</inf> is approximately 6.98 for the F-FTW and 6.29 for the B-FTW. This implies that the largest TEF is exclusively associated with the F-FTW, and therefore, the B-FTW should be averted in practice. Additionally, correlations are established and documented for the key quantities (Nu, f, and TEF).