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Evaluation of Heat Transfer Augmentation in a Tube Fitted with Grooved Twisted Tapes: A Comparative Thermal-Hydraulic Performance Study
(2026-06-01)
Du, Yuexiang
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Liengsirikul, Sathaporn
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Phila, Arnut
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Wongcharee, Khwanchit
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Pimsarn, Monsak
A computational fluid dynamics (CFD) analysis is conducted to systematically investigate heat transfer enhancement in tubes fitted with grooved twisted tapes and to identify the groove geometry that provides the best thermo-hydraulic performance. Three grooved twisted tape configurations—circular-grooved twisted tapes (CGTT), rectangular-grooved twisted tapes (RGTT), and triangular-grooved twisted tapes (TGTT)—are evaluated and compared with a smooth tube and a conventional twisted tape over a Reynolds number range of 5000–20,000 under isothermal wall conditions. The grooved twisted tapes enhance heat transfer through the combined effects of swirl-induced secondary flows and groove-generated flow disturbances, which intensify turbulent mixing and reduce the thickness of the thermal boundary layer. Compared with the plain tube, the grooved configurations increase the Nusselt number by 1.472–1.98 times while increasing the friction factor by 3.21–3.58 times. Relative to the conventional twisted tape, the grooved designs provide an additional 8.0–12.1% enhancement in heat transfer with only a marginal increase of 0.2–1.5% in friction factor. The thermodynamic analysis indicates that the CGTT configuration exhibits the lowest entropy generation rate and exergy loss throughout the investigated Reynolds number range. In particular, the CGTT achieves a Bejan number of 0.999841 at Re = 5000, demonstrating an excellent balance between heat transfer enhancement and frictional losses. Furthermore, the CGTT attains the highest thermal performance factor (TPF) of 1.294 at Re = 5000 and maintains TPF > 1.0 over the entire Reynolds number range. The overall performance ranking is consistently established as CGTT > TGTT > RGTT based on comprehensive analyses of velocity fields, streamline patterns, turbulent kinetic energy distributions, temperature contours, and thermodynamic characteristics. Although the present study identifies the circular-groove configuration as the optimal design for a twist ratio (y/W) of 3.0, further parametric investigations involving variations in twist ratio, groove dimensions, and groove pitch are required to develop generalized design guidelines.
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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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Influence of perforated twisted tapes with vortex generator wings on heat transfer performance and entropy in a heat exchanger tube
(2026-01-01)
Mehta, Rajesh
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Gupta, Anirudh
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Kumar, Nitin
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Eiamsa-ard, Smith
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Pimsarn, Monsak
This study conducts an investigative exploration of thermal and hydraulic performance regarding hybrid inserts which combine perforated twisted tapes with vortex generator wings mounted inside circular tubes. The insert design makes use of both swirl flow and secondary vortex generation which breaks up the thermal boundary layer and boosts convective heat transfer rates. During this investigation, researchers utilized water as the working fluid at Reynolds number (Re) from 3000 to 21,000 to study the effect of three perforation diameter ratio (d/D) 0.143, 0.19, and 0.238 and respective Vortex generator (VG) edge cut ratio (a/D) 0.143, 0.19, and 0.238. Nusselt number (Nu) reach 182.3 % and thermal enhancement factor (TEF) achieve 1.68 at Re = 15,000 when using the enhanced tube compared to a smooth tube. The industrial application of larger VG openings at standard spacing produced a beneficial relationship between thermal performance and flow resistance when the pressure rise reached 345 %. The analysis of entropy generation showed heat transfer irreversibility gave way to frictional irreversibility when both perforation dimension and Re became larger. System design optimization prerequisites involved trade-offs which met Bejan number (Be) analysis trends. The Random Forest machine learning model combined with ANN and Linear Regression models contributed to thermal parameter prediction (Nu, f, TEF) by delivering a predictive accuracy level with less than 6.6 % deviation. The research leads to vital knowledge needed for developing compact heat exchangers integrating passive enhancement methods.
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A comprehensive review on femtosecond laser polishing of silicon nitride: fundamentals, current progress, and industrial outlook
(2026-01-01)
Jian, Huang
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Pimsarn, Monsak
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Chuwattanakul, Varesa
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Eiamsa-ard, Smith
Silicon nitride ((Formula presented.)) ceramics are indispensable in aerospace bearings and semiconductor substrates due to their exceptional mechanical and thermal properties. However, achieving damage-free, atomic-level surface finishes remains problematic. Traditional mechanical polishing induces subsurface microcracks, while chemical mechanical polishing (CMP) is plagued by low material removal rates and environmental toxicity. This review critically evaluates femtosecond laser polishing as a transformative, “green” non-contact alternative. We first elucidate the laser-matter interaction mechanisms specific to wide-bandgap (Formula presented.) ((Formula presented.) eV), clarifying how multiphoton absorption enables “cold ablation” by suppressing the heat-affected zone (HAZ) via the two-temperature model (TTM) dynamics. A distinct material removal mechanism driven by rapid thermal decomposition ((Formula presented.)) and phase explosion is highlighted. Synthesizing recent experimental data, we establish a quantitative process window. Operating slightly above the ablation threshold ((Formula presented.)) with high spot overlap (70%–90%) is critical to balance surface leveling against the incubation effect, which otherwise triggers porosity. Furthermore, we address the unique challenges of inducing periodic structures (LIPSS) on dielectric surfaces and propose a hybrid manufacturing strategy—integrating high-speed laser roughing with CMP finishing—to resolve efficiency constraints. Finally, an industrial roadmap involving high-throughput polygon scanners and AI-driven closed-loop control is outlined, providing a comprehensive reference for advancing femtosecond laser polishing toward scalable, high-precision manufacturing.
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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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Numerical analysis of the influence of press-fitting on the fatigue life of railway axle
(2024-05-17)
Nwe, Theingi
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Pimsarn, Monsak
This study investigated the influence of press-fitting on the stress concentration and fatigue life of axles. Models of finite element analysis (FEA) with and without the press-fitting effect were developed using Abaqus software. These models were used to analyze the axle strength and profile the stress histories under various loads and running conditions, such as bending load, wheel-rail contact force, lateral force, and press-fitting force. Their combined loads were responsible for the axle fracture. Also, the prediction of fatigue life was extended to a three-dimensional stress state under fully reversed cyclic loading and variable overload spectra using commercial Fe-safe software with a strain-based Brown-Miller Morrow fatigue algorithm. With the press-fitting effect, the maximum von Mises stress at the groove notch transition zone of the axle was 6% higher than without the press-fitting effect. Press-fitting reduced the fatigue life of an axle by 37% compared to the ones without press-fitting, and the most damage happened at the same node as the maximum von Mises stress.
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Effectiveness of various finite element analysis method for the dynamic cornering fatigue test of an automotive wheel
(2024-05-17)
Poungkom, Vana
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Pimsarn, Monsak
The automotive wheel is an indispensable part of a motor vehicle as it is the first part that receives loads in various forms from applications such as falls, heavy cargo and cornering, etc. This paper presents the effectiveness of the analysis process using a finite element method to simulate the dynamic cornering fatigue test by comparing the experimental results with the finite element analysis (FEA) results obtained from three methods: full transient, modal transient and static structural methods. The static structural method was found to have the highest accuracy, with less than 2% error, and also the least computational time. It takes 97% less computational time than the full transient method. Therefore, this paper demonstrates that the static structural method is most effective in using the fatigue life analysis to improve design prior to actual testing to help reduce the cost and time of launching new products in the alloy manufacturing industry.
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Thermal evaluation of flow channels with perforated-baffles
(2023-05-01)
Eiamsa-ard, Smith
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Phila, Arnut
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Wongcharee, Khwanchit
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Pimsarn, Monsak
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Maruyama, Naoki
The influences of perforated-baffles on the local Nusselt number (Nu) and thermo-hydraulic behaviors were comprehensively studied using thermochromic liquid crystal sheet. The perforated-baffles were designed in two forms: perforated-baffle (PB) and perforated-baffle with square wings (SW-PBs). Transverse solid baffles (TBs) were also tested for an assessment. All baffles had an identical height of 12 mm (e/H = 0.3). Experimental results showed that SW-PBs offered better Nu than PBs. It is also seen that PBs and SW-PBs caused lower pressure loss than TBs by around 20.49% and 13.98%, respectively. The reduction of friction loss was primarily due to the baffle perforation. In addition, the PBs yielded the thermal performance factors (TPF) up to 1.01 at the lowest Reynolds number of 6000.
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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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