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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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Suchatawat, Maturose
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Nakhchi, Mahdi Erfanian
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Promvonge, Pongjet
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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Thermal effectiveness augmentation in heated tube with louver-punched delta winglets
(2025-09-01)
Promvonge, Pongjet
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Sripattanapipat, Somchai
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Promthaisong, Pitak
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Suchatawat, Maturose
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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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Thermal effectiveness analysis of heat exchange tube with staggered louver-punched V-baffles
(2024-12-01)
Promvonge, Pongjet
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Jayranaiwachira, Nuthvipa
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Promthaisong, Pitak
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Nakhchi, Mahdi Erfanian
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Skullong, Sompol
An experiment has been conducted to ascertain the optimal approach for enhancing the convective transmission of heat in a heat exchanger tube by periodically positioning staggered louver-punched V-baffle (SLVB) vortex generators on a perforated tape. The louver-punched V-baffles were staggered and set up with two patterns: V-apex directing upstream (VU) and downstream (VD), and each featured a louver-punched aperture to minimize friction loss. The aim of this work was to rise the thermal effectiveness as well as the Nusselt number ratio (Nu<inf>R</inf>) at optimal effectiveness in order to cut down on overall dimension of heat exchangers. Consequently, the research findings focused on behaviors of heat transmission and frictional loss, incorporating generated entropy, through a variety of Reynolds numbers (Re) spanning 29,270 to 4762. The SLVB elements were designed and placed in VU and VD forms using three relative pitches (P<inf>R</inf> = 0.5, 1.0, and 1.5) as well as six louver-flapped angles (θ = 0°, 10°, 20°, 30°, 45°, and 90°), all at the same attack angle (α = 52°), a baffle height ratio (B<inf>R</inf> = 0.3) and a louver size ratio (L<inf>R</inf> = 0.73). As demonstrated by the experiment, the θ = 20° generated the best heat transfer of all P<inf>R</inf> values, up to 6.55 times greater than the smooth tube, despite having a lower friction loss than the θ = 0° (solid baffle). At P<inf>R</inf> = 0.5, θ = 20° and smaller Re, the optimum thermal effectiveness factor (TEF) and Nu<inf>R</inf> values were, respectively, about 2.65 and 6.55 for the VU SLVB and 2.52 and 6.04 for the VD one. It implied that the TEF strategies can be utilized to anticipate the best effectiveness under identical scenarios. Also, correlations for the critical parameters, namely, Nu, f, and TEF, were estimated and documented.
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Thermo-Hydraulic Performance of a Heat Exchanger Tube with Inserted Curved-Wing Tape Vortex Generators
(2024-10-24)
Koolnapadol, Narin
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Promvonge, Pongjet
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Promthaisong, Pitak
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Hoonpong, Panuwat
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Khanoknaiyakarn, Chitakorn
In the current study, thermal patterns and flow resistance in a heat exchange tube equipped with a curved-wing tape (CWT) vortex generator were experimentally analyzed to boost performance. A range of Reynolds numbers (Re) from 4130 to 25,370 was utilized in the experiment. The curved wings were arranged in forward array patterns for pitch length ratios (P/D = PR = 2.5, 2, and 1.5) and three wing attack angles (α = 10°, 20°, and 30°). The friction factor, f, and the Nusselt number, Nu, were utilized to quantify the pressure loss and heat transmission caused by the CWT insertion. The measured data reveal that utilizing the CWT resulted in a roughly 2.55-4.37 times greater increase in Nu than the smooth tube, whereas the rise in f is approximately 7.36-46.9 times. Raising the α value causes the Nu and f to trend upward, but increasing PR causes them to trend downward. The CWT's maximal thermal performance is approximately 1.58 at α = 10o and PR = 1.5. Correlations for f and Nu in the functional form of the CWT parameters have also been established.
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Enhanced thermal effectiveness of square duct with V-type double-baffles: Numerical study
(2024-09-01)
Promvonge, Pongjet
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Sripattanapipat, Somchai
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Thianpong, Chinaruk
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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 45o 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 45o. 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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Analysis of exergy and heat transfer in a tube fitted with flapped V-baffles
(2024-07-01)
Jayranaiwachira, Nuthvipa
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Promvonge, Pongjet
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Tongyote, Paritkavin
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Skullong, Sompol
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Nakhchi, Mahdi Erfanian
Vortex generator is a device that shows promise in generating streamwise vortices that can be utilized for boosting the rate of heat transmission inside a cooling/heating system with a relatively smaller penalty in terms of friction loss. The primary goal of the current research is to maximize the comparative Nusselt number ratio (Nu/Nu<inf>0</inf>) to be as large as possible to lower the size of the system while keeping thermal performance as high as feasible to save more energy. Thus, in the current study, the impacts of inserting the flapped V-baffle vortex generator (FBVG) on the thermal effectiveness improvement of a round tube were experimentally investigated. At a fixed attack angle (α = 60°) and baffle blockage ratio (B<inf>R</inf> = b/D = 0.3), the geometrical behaviors of FBVGs placed periodically along two edges of a straight tape were six different flap angles (θ = 0°, 25°, 35°, 45°, 65° and 90°) and three ratios of baffle pitches (P/D = P<inf>R</inf> = 2.0, 1.5, and 1.0). The current V-baffles, which were positioned on both tape edges, were designed to reduce friction loss caused by interrupting the central core flow when placed on both tape sides. The measurement results focused on the friction loss and thermal behaviors, including exergy and entropy analyses for Reynolds number from 4750 to 29,270. In the findings, the Nusselt number and friction factor of FBVG at θ = 0° and P<inf>R</inf> = 1 are, respectively, up to 5.6 and 35.24 times larger than those of the smooth tube. The entropy generation (S˙<inf>gen</inf>′) seems to decline as θ and P<inf>R</inf> increase, with the smallest S˙<inf>gen</inf>′ found at θ = 0° and P<inf>R</inf> = 1 for lower Re. The FBVG has the greatest exergy efficiency (η<inf>Ex</inf>) at θ = 0° and P<inf>R</inf> = 1. To find the true benefits of FBVG, its thermal performance is estimated and seen to reach a maximum at about 2.44 with Nu<inf>R</inf> = 4.65 at θ = 45° and P<inf>R</inf> = 1. The optimal scenario at θ = 25° and P<inf>R</inf> = 1 was preferred, however, since it yielded the largest Nu<inf>R</inf> = 5.42 at TEF = 2.39.
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Thermal effectiveness enhancement in heat exchange tube using louver-punched V-baffles
(2024-06-15)
Promvonge, Pongjet
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Promthaisong, Pitak
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Skullong, Sompol
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Nakhchi, Mahdi Erfanian
An efficient technique for reducing frictional loss by punching holes on the surface of vortex generators has been extensively researched, particularly in the form of louver-punched holes. This article describes an experimental and numerical examination of thermal effectiveness in a heat exchange tube with louvered baffle vortex generators (LBVG). As air was directed to the LBVG-inserted tube with a consistent heat flux, the flow was measured in a turbulent regime. The LBVGs were set at 30° attack angle (α) and mounted at regular intervals on a two-sided flat tape with one relative baffle height (b/D = R<inf>B</inf> = 0.25) and pitch (P/D= R<inf>P</inf> = 1) at the first step. The baffles had five different louver angles (θ = 0 ˗ 90°) and three different relative louver sizes (L<inf>R</inf>= e/b = 0.4, 0.56, and 0.72). The Nusselt number ratio (Nu<inf>R</inf>), friction factor ratio (f<inf>R</inf>), and thermal effectiveness factor (TEF) were utilized to quantify the performance of LBVGs. The findings showed that LBVGs had much lower f<inf>R</inf> values than solid baffles (without holes), whereas Nu<inf>R</inf> values decreased slightly. When θ and L<inf>R</inf> were reduced, the f<inf>R</inf> and Nu<inf>R</inf> for LBVGs increased until they resembled those for solid baffles. Through numerical simulations using the realizable k-ε turbulent model based on the finite volume method, the flow and temperature fields of various cases were generated; their results were verified via analysis of the fluid flow patterns. The computational findings revealed that the jet flow from the louver hole could boost heat transfer, and TEF of LBVGs varied depending on the placement of the hole. According to the computations, the optimal TEF at R<inf>P</inf> = 0.75, L<inf>R</inf> = 0.4, and θ<inf>1</inf> = 20° is roughly 2.64, and the hole should be placed toward the baffle ends rather than in the middle.
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Heat transfer analysis in a tube contained with louver-punched triangular baffles
(2024-06-01)
Jayranaiwachira, Nuthvipa
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Promvonge, Pongjet
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Promthaisong, Pitak
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Nakhchi, Mahdi Erfanian
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Skullong, Sompol
The present research assesses the thermal effectiveness of a heat exchange tube incorporating louver-punched triangular baffle (LPTB) vortex generators under turbulent conditions. For Reynolds numbers between 4760 and 29,270, the heat transfer and flow behaviors in the consistent heat-fluxed tube equipped with LPTBs were studied numerically and experimentally. A single baffle height/blockage ratio (b/D = B<inf>R</inf> = 0.25) and relative baffle pitch (P/D = P<inf>R</inf> = 1) were used for both baffle attack angles, (α) 30° and 45°, along with three louver size ratios (e/b = L<inf>R</inf> = 0.24–0.56) as well as five louver angles (θ = 0°, 20°, 30°, 45°, 60°, and 90°). The results show that as the L<inf>R</inf> and θ values decrease, the Nusselt number (Nu) and friction factor (f) of the LPTB rise owing to the improved fluid mixing process generated by streamwise vortices with stronger turbulence kinetic energy. The LPTB with L<inf>R</inf> = 0 and θ = 0° provides the greatest f and Nu of about 22.18 and 5.1 times, respectively, although the one with L<inf>R</inf> = 0.24 and θ = 45° has the largest TEF of about 2.39 and 2.5 for the α = 30° and 45° LPTBs, respectively. Furthermore, an examination into the thermal and flow patterns was conducted through a three-dimensional computation; the validation of the numerical and experimental data yielded satisfactory results. Using measured data, the f and Nu correlations of the α = 30° and 45° LPTBs were additionally established.
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Thermal performance and exergy analysis in a round tube with louvered trapezoidal winglets
(2023-09-15)
Promvonge, Pongjet
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Eiamsa-ard, Smith
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Skullong, Sompol
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Maruyama, Naoki
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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˙′<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.
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Entropy generation and thermal performance of tubular heat exchanger fitted with louvered corner-curved V-baffles
(2023-02-01)
Jayranaiwachira, Nuthvipa
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Promvonge, Pongjet
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Thianpong, Chinaruk
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Skullong, Sompol
The current article deals with an experimental study on entropy generation analysis and thermohydraulic performance of a uniform heat-flux tube equipped with louvered corner-curved baffle tape (LCBT). Air was drawn into the inserted tube for the Reynolds number (Re) between 4760 and 29,300. The V-shaped LCBT arranged by V-tip in downstream direction was introduced with three baffle pitch ratios (P<inf>R</inf> = 1–2) and six louver angles (θ = 0–90°) for a fixed attack angle (α) of 30° and baffle height ratio (B<inf>R</inf> = 0.25). The impacts of investigated parameters on the thermal enhancement factor (TEF), Nusselt number (Nu), friction factor (f), and total entropy generation (S˙<inf>gen</inf>′) were examined. The measurements showed that the LCBT with the smallest values of P<inf>R</inf> = 1, θ = 0° give the largest Nu and f at about 4.4 and 19.2 times above the plain tube values, respectively. However, the greatest TEF around 2.23 was seen for employing the LCBT at P<inf>R</inf> = 1, θ = 45°. The entropy analysis also showed that the S˙<inf>gen</inf>′ is found to decline with the increment of P<inf>R</inf> and θ, whereas the minimal S˙<inf>gen</inf>′is at P<inf>R</inf> = 1, θ = 0° for lower Re but at P<inf>R</inf> = 1, θ = 45° for higher Re. Furthermore, the Nu and f empirical correlations for employing LCBTs were also proposed.

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