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Influence of divergence tapered V-baffles on heat transfer behaviors in a rectangular channel
(2026-05-15)
Keaitnukul, Warin
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Pingta, Supapat
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Phila, Arnut
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Wongcharee, Khwanchit
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Maruyama, Naoki
This study examines the effects of Divergence Tapered V-Baffle (henceforth DT-VB) regarding the heat transfer and friction loss behavior within the rectangle-shaped duct. The baffle attack angles (α) were set at 45°, 60°, 75°, and 90°. The experimental results indicated that as Reynolds numbers increased, the Nusselt numbers exhibited an upward trend, while the friction values showed a corresponding decrease. The Nusselt number improved consistently as the attack angle decreased, with baffles at a 60° attack angle producing the highest friction loss, followed by those at 45°, 75°, and 90°. Among the configurations tested, the 45° attack angle demonstrated the best thermal performance due to its relatively low friction loss and enhanced heat transfer. The highest thermal performance factor (TPF) of 2.13 was attained at a 45° attack angle and a Reynolds number of 6,000.
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Path Optimization Using an Improved APF-RRT* Algorithm
(2026-01-01)
Zheng, Yongyang
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Pimsarn, Monsak
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Chuwattanakul, Varesa
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Chokphoemphun, Suriya
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Eiamsa-Ard, Smith
Path planning remains a critical research area in mobile robotics, yet current approaches often suffer from suboptimal path quality, limited sampling efficiency, and inadequate adaptability across diverse operational scenarios. To address these issues, this paper proposes an improved algorithm combining Artificial Potential Field (APF) and Restricted Path Time (RRT*) approaches. This algorithm employs an optimization model that combines dynamic sampling with potential field guidance, constructing a two-stage dynamic sampling mechanism. During sampling, candidate nodes with Gaussian noise are generated along the resultant force direction. Finally, path cost comparison and parent node reselection are performed within the dynamic optimization radius to ensure asymptotic optimality of the path. Experimental results show that in complex maps, path length is reduced by 33.41% and 26.64%, respectively, and planning time is reduced by 21.36% and 86.32%, respectively; in narrow passages, path length is reduced by 49.6% and 49.8%, respectively. The results confirm the effectiveness of the two-stage dynamic sampling mechanism, which not only preserves the probabilistic completeness of the RRT* algorithm but also adaptively adjusts the sampling strategy, improving both planning length and time.
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Recent Advances in Welding Processes for High-Entropy Alloys: A Comprehensive Review
(2026-01-01)
Li, Min
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Pimsarn, Monsak
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Chuwattanakul, Varesa
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Eiamsa-Ard, Smith
High-Entropy Alloys (HEAs) have gained attention for their exceptional mechanical properties, corrosion resistance, and unique microstructure. However, welding HEAs remains challenging, attributed to intricate microstructures, inadequate thermal conductivity, and elevated melting points. This review systematically summarizes recent advances in metal welding of HEAs with both similar and dissimilar alloys, including stainless steel, titanium alloys, aluminum alloys, and nickel-based alloys. Welding techniques, including Gas Metal Arc Welding (GMAW), Laser Welding (LW), Electron Beam Welding (EBW), and Gas Tungsten Arc Welding (GTAW) are critically compared in terms of joint microstructure, mechanical performance, and corrosion behavior. The influence of filler composition, heat treatment, and process parameters on weld quality are discussed. Key challenges, including microstructure evolution under complex service conditions and controlling brittle intermetallic phases, are identified. Finally, potential research directions and application prospects of HEA welding in advanced manufacturing are outlined.
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Evaluation of heat transfer performance of a channel mounted with square-wing perforated V-type baffles
(2025-01-01)
Eiamsa-Ard, Smith
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Phila, Arnut
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Thianpong, Chinaruk
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Chuwattanakul, Varesa
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Maruyama, Naoki
The current study examines the aerothermal performance behaviors of a rectangular-channel with square-wing perforated V-type baffles (SW-PVBs). The SW-PVBs were attached to lower channel walls at five attack angles, θ = 0° (solid V-type baffle), 22.5°, 45°, 67.5° and 90°. The heat transfer and pressure drop results of a channel without SW-PVBs were performed to normalize the results of the SW-PVBs and evaluate thermal performance factors (TPFs). It can be observed that as the attack angles decreased, the heat transfer and pressure loss rose. Among the SW-PVBs that were tested, those characterized by θ = 22.5° exhibited the most significant improvement in heat transfer, whereas SW-PVBs with θ = 45° gave the highest thermal performance factors. Additionally, the SW-PVBs with θ = 45° offered the highest TPF, as high as 1.93.
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COMPUTATIONAL ANALYSIS OF FLOW CHARACTERISTICS AROUND A TWIN-SPLINED CYLINDER WITHIN A 2-D CHANNEL
(2024-01-01)
Chamoli, Sunil
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Sahi, Samarth
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Jaiswal, Shivam
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Negi, Anant
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Pant, Pawan Kumar
In the present research work, external flow-induced stresses on a circular cylinder with double-splined surfaces are investigated at a Reynolds number Re of 100. Opposite sides of the cylinder have splined surfaces. The splines are positioned between 0° and 90° from the cylinder's front and rear stagnation points. It is demonstrated that the spline on the cylinder's leading edge modifies the vortex dynamics and causes considerable changes in flow-induced forces. At Re = 100, when a spline is placed on a cylinder's surface, noticeable reduction is observed in the coefficients of lift and drag compared to a smooth cylinder. When the inclination angle is increased to a maximum of 60°, the stagnation point moves to the windward side. Additionally, the spline in the front and back side of the cylinder significantly strengthens the vortex flow. At inclinations of 90° and 0°, maximal and minimal vorticities are obtained. Furthermore, the present work's double-spline cylinder demonstrates the advantage of reduced drag over many previously reported bluff bodies.
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Effect of a TiO2/Water Nanofluid on the Thermal Cooling of a Central Processing Unit
(2024-01-01)
Nanan, Kwanchai
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Chuwattanakul, Varesa
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Pramuanjaroenkij, Anchasa
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Eiamsa-Ard, Smith
An investigation was conducted to evaluate the impact of TiO2/water nanofluids on the cooling system of a central processing unit (CPU). Tests were carried out using nanofluids with TiO2 concentrations of 0.02%, 0.05%, 0.1%, and 0.15% by volume at a Reynolds number of 20,000. Pure water (as the base fluid) was also tested for comparative analysis. The experimental findings emphasized the significant influence of nanofluid application on CPU cooling. Under identical operating conditions, the heat transfer rate of TiO2/water nanofluids proved more effective compared to pure water. Moreover, the results indicated that the nanofluid with a 0.05% volume concentration reduced CPU temperature by 1%, 0.7%, and 1.5% compared to TiO2 concentrations of 0.02%, 0.1%, and 0.15% by volume, respectively. At the optimal condition, the TiO2/water nanofluid with a volume concentration of 0.05% exhibited the highest Nusselt number, leading to a 2.4% decrease in CPU temperature compared to the base fluid.
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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
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Phila, Arnut
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Pimsarn, Monsak
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Maruyama, Naoki
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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.
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Effect of arc-shaped twisted-baffles on augmented heat transfer in a rectangular duct
(2023-02-01)
Promvonge, Pongjet
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Phila, Arnut
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Chuwattanakul, Varesa
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Chokphoemphun, Suriya
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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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Investigation of Combustion Characteristics in a Vortexing Fluidized-bed Combustor with a Contraction Chamber
(2023-01-01)
Manop, Chalermchat
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Chokphoemphun, Suriya
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Chuwattanakul, Varesa
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Promvonge, Pongjet
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Eiamsa-Ard, Smith
This investigation was undertaken to obtain information on the effects of a contraction chamber and secondary air ratio (λ) on combustion temperature distribution, gas emissions of rice husk combustion and flow behaviours in a vortexing fluidized-bed combustor with a contracted chamber (VFBCC).The combustor chamber was modified by reducing the diameter chamber size (contraction) near the top part of the chamber to create a large central recirculation zone. In the experiment, the effects of secondary air ratio (λ) of 0.0, 0.25 and 0.4, and the equivalent ratio, (ϕ) of 0.2, 0.25, 0.3 on combustion characteristics and temperature distribution were examined. The results indicated that the temperature profile inside the combustor between a typical vortexing fluidized-bed combustor (VFBC) and VFBCC was slightly different.The emission of VFBCC was lower than in the original VFBC. At the equivalent ratio of 0.3 and secondary air ratio of 0.4, the average concentrations of O2, CO2, CO and NOx of the flue gases from the original VFBC were 10.5%, 6.7%, 717 ppm and 287 ppm, respectively while those from the modified VFBCC were 9.7%, 6.3%, 357 ppm, and 250 ppm, respectively. In addition, flow visualization results showed the presence of a contracted part led to the recirculation formation in the top chamber.
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Influences of Spray Drying Conditions on the Physiochemical Properties of Karanda Fruit
(2023-01-01)
Chuwattanakul, Varesa
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Yavirach, Koravit
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Eiamsa-Ard, Smith
Karanda fruits are widely cultivated in Thailand. The fruit has several vitamins and minerals. One of the most fascinating possibilities is to transform it into a powdered drink. This study aimed to determine the optimal conditions for preparing karanda juice powder considering its physicochemical properties. Three levels of inlet air temperature were evaluated, 160 oC, 180 oC and 200 oC. Subsequently, three levels of maltodextrin (dextrose equivalent 10, DE10) were evaluated, 30%, 40%, and 50% by weight. Finally, three levels of whey protein (WPI) were evaluated, 5%, 10%, and 15% by weight. The moisture content dropped by 48.51% when the input air drying temperature rose from 160-200 °C. Yield increased by 15.08% and solubility by 5.06%. The maltodextrin content was increased from 30% to 50%, resulting in a 23.17% increase in product yield, while the WPI content was increased from 5% to 15%, leading in an 82.88% increase in anthocyanin content. SEM investigation indicated that the particle morphology was spherical with smooth surfaces, but an increase in inlet air temperature led to greater deformation and particle surface roughness. Additionally, the optimal parameters for spray drying karanda fruit were an inlet air temperature of 174 °C, maltodextrin (MD) content of 32%, and WPI content of 15% of soluble solids, with a product yield of 55.93±0.25%, solubility of 85.51±0.54%, and anthocyanin concentration of 12.58±0.36 mg/l.

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