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Effect of hydrocyclone size on microplastics separation: a computational fluid dynamics investigation
(2026-01-01)
Thiemsakul, Dulyapat
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Kuang, Shibo
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Sukmas, Wiwittawin
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Bumrungthaichaichan, Eakarach
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Korkerd, Krittin
Microplastics pose a significant environmental threat, particularly to aquatic ecosystems. Removing microplastics from water is a critical challenge due to their small size and widespread presence. In this study, the separation of polystyrene (PS) and polyethylene terephthalate (PET) microplastics in hydrocyclones was investigated using Computational Fluid Dynamics (CFD) simulations. A three-dimensional Eulerian-Eulerian multiphase model was employed to simulate the separation process, with water, air, and microplastics. The model demonstrated good agreement results, confirming the reliability of the simulation results. Two factors affecting hydrocyclone performance were investigated. The base hydrocyclone model was scaled down using factors ranging from 1.0 to 0.2 to investigate how size reduction influenced separation efficiency. The results showed that smaller hydrocyclones enhanced recovery (PS: 5.88 to 7.64%; PET: 7.79 to 14.86%) due to stronger centrifugal forces, while higher inlet velocities improved recovery but increased the pressure drop from 49 to 59 kPa, indicating a clear trade-off between separation efficiency and energy consumption. This increase was attributed to the higher centrifugal forces generated in smaller hydrocyclones, which more effectively pushed particles toward the walls, enhancing separation based on density. In addition, higher inlet velocities improved microplastic recovery by amplifying the centrifugal forces within the hydrocyclone, but this came at the cost of increased pressure drop and energy losses due to intensified turbulence and friction.
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How Can an Appropriate CFD Model be Developed for Turbulent Flow in Rough Pipes?: Evidence from Friction Factor Prediction
(2026-01-01)
Boonsamer, Kraiwit
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Temsiriphan, Barami
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Thongnoi, Piyawut
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Areerat, Surat
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Bumrungthaichaichan, Eakarach
This paper answers the question: “How can an appropriate turbulent rough pipe flow computational fluid dynamics (CFD) model be developed?” The Reynolds-averaged Navier-Stokes equations with the standard k-epsilon turbulence model and scalable wall functions were solved to obtain Fanning friction factors and mean velocity profiles in inflectional and monotonic rough pipes. CFD models with near-wall grid sizes from four dimensionless wall distances and two roughness treatment approaches were simulated. Eight roughness Reynolds numbers, covering the lower end of the transitionally rough regime through the fully rough regime, were studied for each roughness type. Appropriate roughness and turbulence model constants for turbulent rough pipe flows in the transitionally rough regime were determined. For model validation, the predicted mean axial velocity profiles for Reynolds numbers of 5 × 104 and 5 × 105 exhibited good agreement with the reference experimental data. A total of 208 CFD simulations (32 from our previous works and 176 from the present study) were analyzed. Finally, based on comparisons between predicted Fanning friction factors and established correlations, appropriate CFD models for turbulent flows in inflectional and monotonic rough pipes were identified. Suitable CFD models for accurately predicting mean velocity profiles at roughness Reynolds numbers below 11.225 were also obtained, although with the caution that improved mean velocity prediction may reduce Fanning friction factor accuracy. Furthermore, the present CFD work provides essential guidance for extending simulations to other rough surface types and rough-wall flow situations.
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Novel method for predicting the cracks of oxide scales during high temperature oxidation of metals and alloys by using machine learning
(2025-12-01)
Chawuthai, Rathachai
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Promchan, Teeratat
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Rojsanga, Jularak
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Chandra-ambhorn, Somrerk
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Nilsonthi, Thanasak
Material degradation is one of the main problems in various high-temperature processes, directly resulting in the failure of the material. Crack and protective oxide film spallation caused either by mechanical stress development in the oxidation process or thermal stress due to a mismatch of the thermal expansions of the formed oxide and alloy are common forms of failure in high-temperature processes. Typically, the Pilling-Bedworth ratio (PBR) is employed to predict crack and spallation of the oxide by determining the volume changes of oxide and alloy because of its simplicity. However, this approach provides poor crack and spallation predictions. Hence, machine learning was adopted in the present work to predict oxide formation and spallation in the temperature range of 600-1,200 °C. The inputs for the present developed model were alloy compositions, oxide formed during oxidation, and oxidation conditions and periods. Furthermore, the predicted results of the present developed machine learning model were compared to those obtained by the PBR method. The present results revealed that the accuracy of the oxide spallation prediction of the present model was better than that of the PBR method. The random forest with 15 estimators was the best machine learning model. Finally, it can be concluded that the machine learning model is essential for accurate material failure prediction.
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Corrigendum to “How can the appropriate near-wall grid size for gas cyclone CFD simulation be estimated?” [Powder Technology 396 (2022) 327–344, (S0032591021009128), (10.1016/j.powtec.2021.10.031)]
(2024-02-15)
Bumrungthaichaichan, Eakarach
The author regrets errors that occurred in the original article [1], which are now amended as follows: The near-wall grid size [mm] for cyclone A1 cone of “0.8764” in Table 3 of the original article [1] is corrected to be “0.6550”. The near-wall grid size [mm] for cyclone A1 vortex finder of “0.6550” in Table 3 of the original article [1] is corrected to be “0.8764”. Although the author has already described in section 3.4. Grid independent solutions and grid convergence index of the original article [1] that the experimental data of Hoekstra [2] displayed by circle symbols in Fig. 6 of the original article [1] was employed to compare with the simulated results performed in the original article [1] as “Further, the numerical uncertainties were approximated by GCI as illustrated by error bars on the normalized velocity profiles, which were compared with experimental data of Hoekstra [9], as represented in Fig. 6.” (Number “9” displayed in the brackets refers to the reference order for the Hoekstra's work [2] in the original article [1].), this information should also be added to the Fig. 6 caption of the original article [1] to prevent the confusion of readers. Therefore, the Fig. 6 caption of the original article [1] is now changed to the more appropriate Fig. 6 caption as “Radial profiles of mean tangential and mean axial velocities for cyclone B2 at z/D<inf>b</inf> = 0.75 predicted by (a) three different grid resolutions and (b) fine grid level with discretization error bars (EXP [9])”. Note that number “9” displayed in the brackets refers to the reference order for the Hoekstra's work [2] in the original article [1]. Furthermore, the same set of Hoekstra's experimental data [2] was also used in the graphical abstract of the original article [1] published on online pages as displayed by circle symbols. The name “ter Linder” in section 4.2. Mean static pressure and pressure drop of the original article [1] is corrected as “ter Linden”. An explanation of the Greek symbol “ν” in the inline equation of Stokes number represented in section 4.4. Collection efficiency of the original article [1] was not given in any section of the original article [1]. Hence, this Greek symbol is now described in this erratum as “ν is the kinematic viscosity of fluid [m2 s−1]”. The author would like to apologise for any inconvenience caused.
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A note of caution on numerical scheme selection: Evidence from cyclone separator CFD simulations with appropriate near-wall grid sizes
(2023-09-01)
Bumrungthaichaichan, Eakarach
In this paper two things are done. (i) The appropriate numerical scheme set for computational fluid dynamics (CFD) simulations of cyclone separators with various vortex-finder-to-cone-tip diameter ratios (D⁎) has been achieved by comparing the mean flow patterns and performances simulated by two previously proposed numerical scheme sets. The predicted results revealed that the CFD simulations of different cyclone separator designs require the third-order accuracy scheme and proper near-wall grid sizes to preserve flow similarity, especially for cyclone separators with D⁎ < 1. Therefore, the present research alerts caution concerning the lower-order numerical scheme for cyclone separator CFD simulation. (ii) The present CFD work confirms that the near-wall grid size estimation method originally developed for gas cyclones is a possible method for estimating near-wall grid sizes for hydrocyclone with air core diameter (D<inf>a</inf>) ≤ 0.4D<inf>v</inf>. In addition, the capabilities of pressure-strain sub-models for cyclone separator CFD simulations were preliminarily discussed.
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Simple Empirical Relation for an Evacuated-Tube Solar Collector Performance Prediction from Solar Intensity
(2023-09-01)
Pongboriboon, Nattapat
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Wu, Wei
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Chandra-ambhorn, Walairat
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Wongpromrat, Patthranit
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Bumrungthaichaichan, Eakarach
In this paper, the effect of solar intensity on the heat pipe tip temperature in a heat pipe type—evacuated-tube solar collector (HP-ETSC) was investigated. A simple relation was proposed, relating the solar intensity to the heat pipe tip temperature generated from the experimental data. This simple empirical relation was applied in a set of heat transfer equations derived to predict the heating medium temperature at the manifold outlet of the evacuated-tube solar collector. The calculated results corresponding to two types of heating medium, i.e., palm oil and water, were compared with experimental results from the literature. The results show that the average error was 6.41% for the case of palm oil and 4.66% for the case of water. Based on the case of water as a heating medium fluid, it was found that the flow rate of the heating medium fluid affected the accuracy of prediction, as the percentage error increased with the heating medium flow rate. The maximum percentage error increased from only 1.83% for a water inlet flowing at a Reynolds number of about 2.4 × 103 to 15.23% for a water flow rate at a Reynolds number of about 2.6 × 104. The correction factor was added into the correlation to predict the heat transfer coefficients of heating medium fluids. With this correction factor, the maximum error could be reduced from 11.78% to 7.29% for the palm oil case and from 15.23% to 5.57% for the water case. The average errors corresponding to palm oil and water cases could be reduced to 0.74% and 1.26%, respectively.
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On the Semi-Analytical Solution of Displacement Thickness in a Laminar Streamwise Corner Flow Assisted by Computational Fluid Dynamics Simulation
(2023-01-01)
Bumrungthaichaichan, Eakarach
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Unaprom, Prajaree
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Sathianchok, Pakapong
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Wattananusorn, Santi
In this paper, the new semi-analytical correlation for displacement thickness of laminar fluid flow along an arbitrary-angle corner formed by the intersection of two plates has been proposed because of the discrepancy in displacement thickness for strong interference corner between the present computational fluid dynamics simulation and previous analytical correlation.
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Possibility of metallic cobalt formation in the oxide scale during high-temperature oxidation of Co-27Cr-6Mo alloy in air
(2023-01-01)
Wongpromrat, Patthranit
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Tunthawiroon, Phacharaphon
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Bumrungthaichaichan, Eakarach
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Ponpo, Phisan
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Nilsonthi, Thanasak
Co-based alloys are known to be high oxidation-resistant material and used in several high temperature applications. During high temperature oxidation, duplex oxides containing Co and Cr were formed. It was thermodynamically elucidated that when the growing scale was thick enough, the partial pressure of O<inf>2</inf> in the scale dropped. Then, the reduction of CoO occurred for promoting O<inf>2</inf> which was responsible for Cr<inf>2</inf>O<inf>3</inf> production. This work experimentally proved this point by in situ char-acterising Co-27Cr-6Mo at high temperatures in air by X-ray diffractometer in a grazing incident mode and metallic Co was confirmed to be formed by the reduction of CoO consistent with the image taken and analysed by field emission scanning electron microscope, energy-dispersive X-ray, and electron backscatter diffraction. Furthermore, the change in lattice parameter and the phase transition were observed when the temperature was altered.
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Corrosion Resistance Enhancement of Reinforced Concrete in Marine Environment by Partial Replacement of Black Rice Husk Ash
(2023-01-01)
Chandra-Ambhorn, Walairat
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Bumrungthaichaichan, Eakarach
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Rotchan, Chayanit
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Haema, Narunat
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Wongpromrat, Patthranit
In this work, the black rice husk ash (BRHA), a pozzolanic material, was used as a partial replacement in concrete with the weight percentages of 0%, 10%, 20%, 30%, 40% and 50% for enhancing the corrosion resistivity in the marine environment. The compressive strength, corrosion by accelerated corrosion test by impressed voltage (ACTIV), and chloride (Cl− ) penetration of concrete specimens were investigated after 28 days of curing. For corrosion and chloride penetration analyses, the 20% of BRHA replacement specimen was the most effective concrete specimen because the deformation was not observed within 19 days of the test. The cement specimens with lower BRHA percentages were cracked due to the development of stress by the rust formation. For higher BRHA percentages, the protective Fe2O3 was dissolved due to the acidic environment caused by higher chloride accumulation in the cement specimens. The steel rebar was then aggressively attacked by the chloride and it was finally broken. Therefore, the optimization of the BRHA percentage is needed to minimize corrosion. However, the longer curing time of 20% BRHA replacement specimen is required for increasing the compressive strength because its compressive strength is slightly lower than the standard.
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Performance investigation for CRMC and CPM ejectors applied in refrigeration under equivalent ejector geometry by CFD simulation
(2022-11-01)
Bumrungthaichaichan, Eakarach
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Ruangtrakoon, Natthawut
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Thongtip, Tongchana
In this paper, one of the remaining questions for ejector design, “Does the constant rate of momentum change (CRMC) ejector provide better performance than the constant pressure mixing (CPM) ejector under identical ejector area ratio, ejector length, and operating conditions?”, has been answered. Two steam ejector designs operating with the various boiler and evaporator temperatures were simulated by the SST k-omega turbulence model. The present computational fluid dynamics (CFD) model produced a reasonable agreement with our previous published experimental data. The upstream operating conditions were simultaneously considered to assess the better performance ejector design with the help of the primary expansion coefficient. The predicted results revealed that the CRMC ejector showed an advantage in entrainment ratio and a disadvantage in critical condenser pressure. However, the ejector efficiency comparison confirmed that the CRMC ejector design provided better performance than the CPM ejector design for a primary expansion coefficient greater than unity. The maximum percentage improvement of ejector efficiency was 32.418%.

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