Chuwattanakul, Varesa

Preferred name

Alternative Name

Chuwattanakul, V.

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School of Engineering

varesa.ch@kmitl.ac.th

Now showing 1 - 10 of 45

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Influences of Spray Drying Conditions on the Physiochemical Properties of Karanda Fruit
(2023-01-01)
Chuwattanakul, Varesa
;
Yavirach, Koravit
;
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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Intensification of Thermal Performance of a Heat Exchanger Tube with Knitted Wire Coil Turbulators Installed
(2025-12-01)
Wongcharee, K.
;
Shoon Wai, T.
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Maruyama, N.
;
Hirota, M.
;
Chuwattanakul, V.
This study reports on heat transfer augmentation by knitted wire coil turbulators in a fully developed turbulent regime. Four knitted wire coil turbulators with different wire loop number densities (N = 6, 8, 10, and 12 loops per pitch, with 1.0 pitch = 6.8 mm) were tested. Each was made by winding a 0.7 mm copper wire around a 1.0 mm core rod. Experiments were conducted under a constant 600 W/m2 wall heat flux. The flow behaviors observed through a dye injection technique revealed that the wire coil induced secondary flows and developed shear layers, contributing to enhanced heat transfer. Heat transfer improved with increasing wire loop number density. Application of knitted wire coil turbulators increased the Nusselt number (Nu) by 86, 95.4, 103.2, and 109.3% for N = 6, 8, 10, and 12, respectively. This corresponded to increased friction factors (f) by 1.77, 1.97, 2.15, and 2.31 times, respectively. The tube with coils having N = 12 yielded the highest thermal performance index (TPI), 1.4, at a Reynolds number of 5000. The empirical correlations for Nu, f, and TPI showed deviations within ±2.1, ±0.68, and ±2.28%, respectively.
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Investigation of turbulent thermal-hydraulic behaviors of a heat exchanger tube with U-cut twisted-tape
(2025-03-01)
Wongcharee, K.
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Chuwattanakul, V.
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Chamoli, S.
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Maruyama, N.
;
Hirota, M.
This study examines the influences of U-cut twisted tapes (U-TTs) on thermal-hydraulic behaviors in a circular tube with uniform heat flux. The geometric parameters studied include six U-cut ratios (s/t = 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0) and two twist ratios (y/w = 3.5 and 4.0). Experimental results revealed that their U-cut ratios highly influenced heat transfer enhancement. U-TTs with U-cut ratios (s/t) of 0.5, 1.0, 1.5, and 2.0 achieved higher Nusselt numbers than conventional twisted tapes (TTs). In contrast, U-TTs with larger U-cut ratios (s/t = 2.5 and 3.0) showed reduced Nusselt numbers. However, friction losses with all U-TTs were consistently higher than those with TTs. Due to their excellent heat transfer enhancement, U-TTs with s/t ratios of 0.5 and 1.0 exhibited significantly higher thermal performance factors (TPF) than conventional TTs. The highest TPF, 1.28, was achieved by U-TTs with an s/t ratio of 0.5 and a y/w of 3.5 at a Reynolds number of 6000.
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Analysis of fluid flow across a 2D bluff body in a tandem arrangement with varying aspect ratios near a moving wall
(2026-01-01)
Kumar Pant, Pawan
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Chamoli, Sunil
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Pant, Naval
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Joshi, Hitesh
;
Rana, Saurav
This study numerically investigates the flow characteristics around single and tandem cylinders positioned in close proximity to a moving wall at a Reynolds number of Re = 100. Using the finite volume method, simulations were performed for aspect ratios (AR) ranging from 1 to 5, while maintaining a fixed gap ratio (G/A = 0.5) and spacing ratio (S/A = 0.5). The results demonstrate that the moving wall significantly influences flow dynamics and stabilizes the wake. For an aspect ratio of 1, the merging of shear layers leads to the formation of elongated, steady vortices. As the aspect ratio increases from 2 to 5, the wake becomes increasingly smooth and the magnitude of positive vortices decreases, resulting in steady wake formation without significant oscillations. Force analysis reveals that the upstream cylinder exhibits chaotic drag (C<inf>d</inf>) and lift (C<inf>L</inf>) coefficients, whereas the downstream cylinder shows a consistent trend. Notably, the upstream cylinder maintains a higher drag coefficient than the downstream cylinder, with both being lower than that of a single isolated cylinder. The observed suppression of vortex shedding is primarily attributed to the interaction and coupling of shear layers between the moving wall and the cylinders, identifying shear alignment rather than viscous damping as the core mechanism of wake control.
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Aerothermal performance evaluation of a tube mounted with broken V-ribbed twisted tape: Effect of forward/backward arrangement
(2023-01-01)
Chuwattanakul, V.
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Wongcharee, K.
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Ketain, P.
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Chamoli, S.
;
Thianpong, C.
An experimental investigation on the aerothermal performance of a heat exchanger tube equipped with newly designed broken V-ribbed twisted tapes (B-VRT), was carried out. In the present work, the heat transfer intensification by a B-VRT can be attributed to greater mixing caused by two flow characteristics: 1) longitudinal vortices from the ribs and 2) swirling flow from the twisted tape. The B-VRT with rib attack angles (α) of 45°, 60°, 75°, and 90°, were tested using air as the test fluid. The experimental results of the tube with B-VRTs in a forward/backward arrangement were compared to those of a plain tube alone and a tube with typical twisted tapes (TT) for Reynolds numbers between 6,000 and 20,000. The results indicated that the tube with the B-VRT having forward facing ribs with α = 45° gave the best performance with Nusselt number ratio (Nu/Nup) of 2.27, a friction factor (f/fp) of 4.4, and an aerothermal performance factor (APF) of 1.38. For the range investigated, the B-VRT offered up to 31.9% higher Nusselt numbers than TT. The B-VRT with the smallest rib attack angle (α) of 45° offered higher aerothermal performance factors than the ones with rib attack angles (α) of 60°, 75°, and 90° by approximately 6.85%, 12.99%, and 20.2%, respectively. The results of the B-VRT with optimum geometry (α = 45°) were benchmarked against those reported in similar published papers. Evidently, the aerothermal performance factors the B-VRT were superior to those of most of other tube inserts, especially at low Reynolds numbers. Finally, within the range of parameters (α, y/W and Re) taken into consideration in this study, correlations of Nu and f were developed to estimate the heat transfer and pressure drop. The correlations for Nu, f, and APF showed acceptable prediction accuracies, with respective deviations of ±4%, ±5.4%, and ±4%.
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Numerical Methodology for Enhancing Heat Transfer in a Channel with Arc-Vane Baffles
(2025-03-01)
Thapmanee, Piphatpong
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Phila, Arnut
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Wongcharee, Khwanchit
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Maruyama, Naoki
;
Hirota, Masafumi
This study numerically investigates flow and heat transfer in a channel with arc-vane baffles at various radius-to-channel high ratios (r/H = 0.125, 0.25, 0.375, and 0.5) for Reynolds numbers between 6000 and 24,000, focusing on solar air-heater applications. The calculations utilize the finite volume method, and the SIMPLE algorithm is executed with the QUICK scheme. For the analysis of turbulent flow, the finite volume method with the Renormalization Group (RNG) k-ε turbulence model was used. The results show that arc-vane baffles create double vortices along the axial direction, promoting flow reattachment on the heated surface and enhancing heat transfer. Baffles with smaller r/H ratios strengthen flow reattachment, reduce dead zones, and improve fluid contact with the heat transfer surface. The baffles with the smallest r/H ratio achieve a Nusselt number ratio (Nu/Nu<inf>s</inf>) of 4.91 at Re = 6000. As r/H increases, the friction factor (f) and friction factor ratio (f/f<inf>s</inf>) rise due to increased baffle curvature and surface area. The highest thermal performance factor (TPF) of 2.28 occurs at r/H = 0.125 and Re = 6000, reflecting an optimal balance of heat transfer and friction losses. Arc-vane baffles with a r/H ratio of 0.125 yield a TPF exceeding unity, indicating potential energy savings. These findings provide valuable insights for optimizing baffle designs to enhance thermal performance in practical applications.
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Thermohydraulic performance evaluation of a heat exchanger mounted with oval inclined twisted rings
(2025-03-01)
Samruaisin, P.
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Chuwattanakul, V.
;
Thapmanee, P.
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Kumar, M.
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Naphon, P.
This research examines the effects of oval inclined twisted rings (I-TRs) on thermal performance characteristics. Heat transfer enhancement, friction factor, and thermal enhancement factor tests were conducted under uniform wall heat flux with Reynolds numbers (Re) varying from 6000 to 20,000. A systematic investigation was carried out to examine the influence of different pitch ratios (p/D) and oval-ring inclination angles (θ) on thermal enhancement factor (TEF). The experimental results reveal that the Nusselt number increases with decreasing pitch ratio (p/D) and inclination angle (θ) of the I-TRs. At p/D = 1.5, the Nusselt numbers are approximately 8.59 % to 18.78 % higher than those for I-TRs with p/D values of 2.0 and 2.5. At the smallest inclination angle, θ = 30°, the Nusselt numbers are approximately higher than those at θ = 45°, 60°, 75°, and 90° by around 1.56 %, 7.21 %, 13.74 %, and 27.14 %, respectively. At a p/D ratio of 1.5 and an inclination angle of θ = 30°, the resulting thermal enhancement factor (TEF) consistently exceeds unity across the entire Reynolds number (Re) range. In contrast, for other geometries and configurations, some TEF values fall below unity at higher Re. Within the studied range, the highest TEF of 1.12 is achieved at θ = 30°, p/D = 1.5, and Re = 6,000. The key finding suggests that the performance of the thermal system is highly dependent on both the configuration and operational conditions.
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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
;
Pramuanjaroenkij, Anchasa
;
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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Thermal performance enhancement of a circular tube fitted with inclined perforated disk inserts
(2026-03-01)
Mehta, Rajesh
;
Gupta, Anirudh
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Kumar, Nitin
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Eiamsa-ard, Smith
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Thianpong, Chinaruk
Heat exchangers are crucial devices in industries, and enhancing their thermal performance while controlling pressure losses remains a significant challenge. This paper examines the idea that inclined perforated disk (IPD) inserts can be effectively used to improve heat transfer in circular tubes with constant heat flux conditions at acceptable levels of hydraulic penalties. Turbulent airflow with Reynolds numbers (Re) ranging from 5000 to 21,000 was examined in experiments, and three perforation indices (PI = 0.21, 0.24, and 0.27) were tested to determine the effects of hole density on thermal and hydraulic performance. Evidence showed that the Nusselt number (Nu) had been improved by over 86 % compared to plain tubes, with the thermal enhancement factor (TEF) reaching as high as 1.53 at PI = 0.27 and Re = 5000. Particle swarm optimization (PSO) and neural network modelling multi-objective optimization were used to test the results of the experiment and determine the best operating conditions at PI = 0.21. The paper has demonstrated that inclined perforated disk inserts can form a viable passive method for enhancing the efficiency of heat exchangers, as the swirl and jet flow patterns created by the perforations effectively break the thermal boundary layer, thereby increasing the rate of convective heat transfer.
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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
;
Chokphoemphun, Suriya
;
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.

Chuwattanakul, Varesa

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