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Integrated CFD–drying model for design optimisation of multi-layer rack drying systems for mackerel processing
(2026-08-01)
Nabudda, Kriengkrai
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Thasnas, Natakorn
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Poungthong, Pongthep
This study presents an integrated Computational Fluid Dynamics (CFD)–Page model framework for analysing and optimising the drying performance of a six-layer mackerel drying system. Experimental drying data were fitted using the Page model (k = 0.185, n = 1.32), achieving high predictive accuracy (RMSE = 0.018). The coupled CFD–drying model was applied to evaluate moisture removal behaviour and the effect of rack spacing on airflow distribution, temperature uniformity, and heat transfer. Results revealed distinct layer-dependent drying characteristics, with the uppermost layer exhibiting the fastest moisture removal due to greater exposure to hot, low-humidity airflow. CFD simulations for rack spacings of 8–12 mm showed that spacing significantly influences airflow penetration and thermal distribution. A mesh-independent model with 261,785 elements ensured numerical reliability. The optimal rack spacing was identified as 10 mm, providing the most uniform airflow and temperature distribution. Surrogate model optimisation further predicted an optimal spacing of 10.21 mm, improving drying uniformity, energy efficiency, and overall system performance.
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Experimental optimization of defrosting duration for enhanced energy efficiency in large-scale ammonia-based tube ice-making systems
(2026-08-01)
Ohnjaikla, Natcha
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Poungthong, Pongthep
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Kasayapanand, Nat
This study experimentally investigates the impact of defrosting duration on the operational performance and energy efficiency of an industrial-scale 80-ton-per-day ammonia (NH<inf>3</inf>)-based tube ice-making system with a tube diameter of 38 mm. Experiments were performed under controlled ambient conditions (28 °C dry bulb temperature and 80% relative humidity) with defrosting times of 5, 6, and 7 min. Key performance indicators, including suction and discharge pressures, temperatures, power consumption, cooling capacity, freezing time, ice weight per cycle, and the coefficient of performance (COP), were systematically monitored. Each experiment was repeated three times (n = 3), and the results are reported as mean ± standard deviation. Results indicate that extending defrosting time beyond 5 min increases discharge pressure by up to 9% and discharge temperature by up to 12 °C, leading to a 3.14–9.52% rise in compressor energy consumption. At the same time, cooling capacity decreased by 2.8% (6 min) and 7.1% (7 min), lengthening freezing cycles and reducing daily ice production by 4–10% compared with the 5-minute baseline. Although slightly more ice mass per cycle was achieved with longer defrosts, this advantage was offset by higher energy demand and lower cooling efficiency. The findings underscore the importance of optimizing defrosting duration to achieve an effective balance between energy consumption and production efficiency in industrial ice-making systems. Furthermore, thermo-hydraulic evaluation using SEC confirms that a 5-minute defrost duration optimally balances energy efficiency and production capacity, providing a validated experimental benchmark for defrost optimization in large-scale ammonia-based tube ice systems.
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Physics-Guided CFD–ML Framework for Sustainable Classical Wire Coating with Power-Law Fluids
(2026-07-01)
Nabudda, Kriengkrai
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Poungthong, Pongthep
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Ritthong, Wirote
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Elumalai, P. V.
This study presents an integrated Computational Fluid Dynamics (CFD) and machine learning framework for analyzing and optimizing classical wire coating processes involving non-Newtonian power-law fluids. A two-dimensional axisymmetric CFD model was developed in ANSYS Fluent 2024R1 to investigate the effects of the power-law index (n = 0.3–1.0) on flow, pressure, temperature, and density fields under non-isothermal conditions. A Latin Hypercube Sampling-based Design of Experiments was coupled with surrogate modelling and Sobol sensitivity analysis to evaluate process performance and identify optimal operating conditions. The results showed that velocity distributions were highly dependent on fluid rheology, with shear-thinning fluids producing broader plug-like flow regions and more uniform velocity profiles. In contrast, pressure, temperature, and density fields exhibited limited sensitivity to variations in the power-law index. Optimization indicated that low power-law indices, moderate pressure gradients, and low-to-moderate wire speeds maximize coating thickness while minimizing material loss. Ridge Polynomial Regression achieved excellent predictive accuracy for all response variables (R<sup>2</sup> > 0.995). Sensitivity analysis revealed that the initial die gap is the dominant factor governing coating thickness, whereas material loss is influenced by combined effects of die geometry, fluid rheology, and wire speed. The proposed framework provides an efficient tool for process optimization and material conservation in industrial wire coating applications.
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Innovative educational technology for visually impaired learners using a 3D-Printed foot reflexology robot
(2026-06-01)
Nabudda, Kriengkrai
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Nabudda, Kanokpit
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Kitprathaung, Nustha
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Phumpho, Suwilai
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Poungthong, Pongthep
This study presents the design, development, and validation of a foot reflexology teaching robot that integrates multidisciplinary design, rapid prototyping, and user-centred assistive educational strategies to support tactile learning for visually impaired individuals. A digital foot model, derived from anthropometric data of an average Thai female, was refined to achieve a balance between anatomical accuracy and manufacturability. The structural design featured modular internal compartments, precision openings, and detachable covers to support maintenance without compromising anatomical realism. Fabrication using PLA-based fused deposition modelling (FDM) produced a lightweight, durable, and cost-effective prototype incorporating interactive tactile sensing and modular electrical components. A Raspberry Pi platform programmed in Python enabled audio-based instructional feedback triggered by tactile interaction, creating a multisensory educational device for experiential reflexology training. Structured evaluation sessions with 29 visually impaired learners confirmed its effectiveness in facilitating hands-on engagement, multisensory learning, and usability, with high satisfaction across safety and practicality. Overall, this work establishes a replicable framework for developing accessible and inclusive assistive educational technologies.• Integrated multidisciplinary design and user-centred development approach.• Applied rapid prototyping to translate digital anatomical models into functional physical components.• Conducted user-based evaluation to assess educational effectiveness and accessibility.
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Viscosity functions of shear flows for fractional maxwell fluids
(2026-06-01)
Promjariyakoon, Rattanaporn
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Poungthong, Pongthep
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Kolitawong, Chanyut
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Giacomin, Alan J.
Fractional calculus is applied increasingly to fluid dynamics. We derive exact analytical solutions for shear stress growth rheological responses of the fractional Maxwell fluid (FMF) in extra-stress tensor form. We do so by using the Laplace transform and its inverse. By shear stress growth, we mean the sudden inception of steady shear flow. We first determine the shear stress growth viscosity, then extend this to the steady shear viscosity using empirical Gleissle mirror relations. We choose to explore the FMF because of its four-parameter versatility and because it describes fluid elasticity measurements accurately. We compare with the ordinary non-fractional Maxwell fluid (OMF) in shear stress growth. Our FMF exact solution agrees well with available measurements on aqueous xanthan gum solutions, so long as the initial residual stresses in the sample are accounted for. We discover that, in practice, positive initial residual shear stress shifts the viscosity in shear stress growth downward. Finally, we construct concentration master curves for our xanthan gum solution shear stress growth rheological functions. We do so to generalize predictions of viscosity under varying conditions. Our worked examples illustrate how to use this dimensionless master curve.
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Viscosity functions of shear flows for fractional Jeffreys fluids
(2026-04-01)
Promjariyakoon, Rattanaporn
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Poungthong, Pongthep
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Kolitawong, Chanyut
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Giacomin, Alan J.
In our previous work (Promjariyakoon 2025; Promjariyakoon et al. 2026), we derive exact analytical solutions for (1) steady shear viscosity, and (2) shear stress growth rheological responses of the fractional Maxwell fluid (FMF) generalized to tensor form. By shear stress growth, we mean the sudden inception of steady shear flow. We found good agreement with experimental observation, though this left some room for improvement. In this work, following our previous method, we improve upon the FMF by adding one more fractional derivative for retardation to get the fractional Jeffreys model (FJM), a fractional Kelvin-Voigt model arranged in series with a spring-pot. We determine (1) complex viscosity, (2) the shear stress growth viscosity function, (3) then extend these to the steady shear viscosity between the stress and the local properties of theusing Gleissle mirror relations, and (4) shear stress relaxation following cessation of steady shear flow. Our FJM exact solution improves significantly upon the FMF, agreeing well with available measurements on aqueous xanthan gum solutions, so long as the initial residual stresses in the sample are accounted for. We show that its material functions are experimentally measurable and physically interpretable quantities. Finally, we construct temperature master curves for a low-density polyethylene melt. We do so to generalize predictions of viscosity under varying temperatures. Our worked example illustrates how to use our main results.
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Energy-Efficient Paddy Rice Dehumidification using a Thermosyphon System
(2025-07-01)
Poungthong, Pongthep
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Promprasansuk, Sookjai
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Tanaratchat, Vikorn
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Promchai, Anuruk
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Ritthong, Wirote
Efficient post-harvest drying is vital to maintain paddy rice quality, prevent spoilage, and extend storage life. This study presents a thermosyphon-based dehumidification system, tested with hot air and hot water heating at 60, 70, and 80 °C. The system includes a cylindrical drying chamber with automated controls for higher efficiency. Performance was evaluated using drying time, energy efficiency, and specific energy consumption (SEC). Results showed the system reduced paddy rice moisture from 26.65% to the target 14% (d.b.). Drying times with hot air were 128, 76, and 50 hours, while hot water required 104, 62, and 42 hours at 60, 70, and 80 °C, respectively. Hot water at 80°C achieved the fastest drying, completing the process in 42 hours. Energy performance analysis revealed the lowest SEC of 89.05 kWh/kg water for hot water at 80 °C, whereas hot air at 60 °C recorded the highest SEC of 1,204 kWh/kgwate. Overall, the thermosyphon system demonstrated strong potential for balancing drying speed and energy use. The study supports thermosyphon-based drying as a scalable, energy-efficient solution for post-harvest rice management, with hot water offering both rapid drying and efficiency
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Optimization of Degradable Polylactic Acid-Based Coating Materials for Sustainable Wire Manufacturing Injection Process Using Computational Fluid Dynamics Analysis
(2025-06-01)
Nabudda, Kriengkrai
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Promjariyakoon, Rattanaporn
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Kitprathaung, Nustha
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Ritthong, Wirote
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Intasonti, Sontinan
This study investigates the impact of injection angle on polylactic acid (PLA) wire coating performance, focusing on flow dynamics, heat transfer, mass density, and pressure distribution. Three angles: 30°, 45°, and 60° were assessed for their effects on coating characteristics. At 30°, the flow is smooth with minimal turbulence, ensuring consistent deposition. The 60° angle increases velocity and material penetration but risks turbulence and uneven coating. The 45° angle optimally balances material mixing and flow stability. In terms of heat transfer, the 30° angle concentrates heat near the injection point, creating a steep thermal gradient, while the 60° angle disperses heat more broadly but with lower intensity. The 45° angle ensures uniform heat distribution, improving energy efficiency. Regarding mass density, the 30° angle favours localized deposition, ideal for concentrated applications, while the 60° angle promotes broader distribution with reduced concentration. The 45° angle optimises density uniformity and maintains structural integrity. Pressure distribution follows similar trends, with 30° and 60° angles causing uneven deposition, whereas the 45° angle ensures balanced pressure distribution. In conclusion, the 45° angle offers superior performance across all parameters, providing an optimal balance of efficiency, uniformity, and structural integrity, thus enhancing PLA wire coating quality for sustainable engineering applications.
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Optimal Design of Cooling Rooms for Mackerel Using Computational Fluid Dynamics
(2025-06-01)
Nabudda, Kriengkrai
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Suntivarakorn, Ratchaphon
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Artnaseaw, Apichart
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Ritthong, Wirote
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Poungthong, Pongthep
This study utilises computational fluid dynamics (CFD) simulations to investigate airflow and temperature distributions in cold storage environments equipped with various fan and duct configurations. It assesses the effectiveness of single and dual evaporator fans (mounted at both front and rear) and front-and rear-positioned air ducts in enhancing air circulation and thermal uniformity. Results indicate that single rear-mounted fans promote localised airflow but lead to thermal stratification and stagnant zones, while front-mounted fans struggle to circulate air effectively towards the rear. Rear-positioned ducts improve air distribution but require further optimisation to address residual stratification. Dual rear-mounted evaporator fans deliver the most consistent cooling, minimising temperature variation and reducing compressor load, thus improving energy efficiency. Although dual front-mounted fans enhance circulation, they still exhibit thermal inconsistencies. The study also underscores the importance of measuring fan outlet velocity to ensure stable environmental conditions. Overall, the findings emphasise the necessity of optimised airflow strategies, appropriate fan placement, and ongoing system monitoring to achieve uniform cooling and preserve the quality of temperature-sensitive products in cold storage applications.

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