Chuwattanakul, Varesa

Preferred name

Alternative Name

Chuwattanakul, V.

Main Affiliation

School of Engineering

varesa.ch@kmitl.ac.th

Now showing 1 - 9 of 9

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Effects of spiral start number and depth ratio of corrugated tube on flow and heat transfer characteristics in turbulent flow region
(2019-08-01)
Kongkaitpaiboon, V.
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Promthaisong, P.
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Chuwattanakul, V.
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Wongcharee, K.
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Eiamsa-ard, S.
Influence of spirally-corrugated tubes on heat transfer (Nu), pressure loss (f) and thermal enhancement factor (TEF) characteristics was numerically investigated. The physical models of spirally-corrugated tubes and also a straight circular tube were built for the comparative study. The predictions were performed for the spirally-corrugated tubes with spiral start numbers (N) of 2, 3, 4 and 5 and depth ratios (DR = e/D) of 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14 and 0.16 at Reynolds numbers of 5000, 8000, 14000 and 20000. The numerical results show that the spiral corrugated tubes created two types of flow structures: main swirl flows (appear around the core) and secondary swirl flows (appear near tube wall) which facilitate heat transfer between the fluid and the tube walls. The overall heat transfer depends on the competition between two effects: the positive effect of the stronger swirl intensity by increasing start number and the negative effect of the difficulty of fluid transfer into grooves by increasing depth ratio. For the investigated range, the corrugated tubes yield Nusselt numbers and thermal performance factors varying from 0.82 to 2.16 times and 0.66–1.2 times of the straight circular tube, respectively. The highest thermal enhancement factor (TEF) of 1.2 is achieved by using the tube with spiral start number of 4 having moderate depth ratio of 0.08 at Re = 5000.
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Intensification of Thermal Performance of a Heat Exchanger Tube with Knitted Wire Coil Turbulators Installed
(2025-12-01)
Wongcharee, K.
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Shoon Wai, T.
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Maruyama, N.
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Hirota, M.
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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/m<sup>2</sup> 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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Prediction of heat transfer and fluid flow in a cross-corrugated tube using numerical methods, artificial neural networks and genetic algorithms
(2022-03-01)
Eiamsa-ard, S.
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Chuwattanakul, V.
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Safikhani, H.
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Promthaisong, P.
In this paper, multi-objective optimization of geometric parameters of spirally-cross-corrugated (SCC) tubes is carried out using numerical methods, genetic algorithms (GAs), and artificial neural networks (ANNs). First, the turbulent flow is numerically characterized in various SCC tube geometries using a finite volume method with the realizable k−ε turbulence model. In this approach, the heat transfer coefficient and friction factor f in tubes are calculated. First, two parameters (corrugation pitch-to-diameter ratio (PR = p/D) and corrugation depth-to-diameter ratio (DR = e/D)) are examined in a turbulent flow regime that affects the strength of quadruple longitudinal vortex flows and thermal characteristics. At the final step, using the obtained polynomials for neural networks, multi-objective genetic algorithms (NSGA II) are employed for Pareto based multi-objective optimization of flow parameters in such tubes. This analysis considers two conflicting parameters, f Re and Nusselt number Nu with respect to three design variables, Reynolds number Re, values of PR and DR. Some interesting and important relationships between the parameters and variables mentioned above emerge as useful optimal design principles involved in the heat transfer of such tubes through Pareto based multi-objective optimization. Such important optimal principles would not have been obtained without the use of a combination of numerical techniques, ANN modeling, and the Pareto optimization.
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Influence of a double vortex chamber on temperature reduction in a counter-flow vortex tube
(2021-12-01)
Samruaisin, P.
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Chuwattanakul, V.
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Pimsarn, M.
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Promthaisong, P.
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Saysroy, A.
This article reports the effect of double vortex-chambers with multiple inlet snail entries of N = 1, 4 and 6 nozzles on the energy separation referred to cold gas exit temperature difference (ΔT<inf>c</inf>) in a counter-flow vortex tube type. The experimental work focused on ascertaining the effects of entry air pressure (P<inf>i</inf> = 2, 3 and 4 bar), distance ratios between the two vortex-chamber to the vortex tube diameter (l/D = 0.875–1.125) and the cold gas mass ratio (μ<inf>c</inf>) in a vortex tube. It was found that cold gas exit temperature difference (ΔT<inf>c</inf>) increased with increasing inlet air pressure (P<inf>i</inf>) and number of inlet nozzles (N), and decreasing l/D. Among the studied conditions, the double vortex-chamber operated at the highest P<inf>i</inf> of 4 bar, N = 6, the smallest l/D = 0.875 and μ<inf>c</inf> = 0.38 gave the highest cold gas exit temperature difference (ΔT<inf>c</inf>) of 31.5 °C. In addition, the deep learning optimization technique was also developed to predict the temperatures for different combination of parameters used in this study. It was found that the optimal models provide maximum R<sup>2</sup> value of 0.99317.
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Turbulent heat transfer enhancement in round tubes by inserting triple twisted-tapes
(2015-01-01)
Eiamsaard, S.
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Promthaisong, P.
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Chuwattanakul, V.
Turbulent flow characteristics and heat transfer performances in a round tube equipped with triple twisted tapes are investigated numerically. Effects of the triple twisted tapes at different twist ratios on the heat transfer and thermal performance characteristics are reported. The results of velocity and temperature fields, and the local heat transfer coefficients as well as the flow structure in tube with tape inserts are also given. A round tube wall is subjected to a constant wall temperature condition. Thermal field, heat transfer and fluid flow characteristics are studied using computational fluid dynamics (CFD) analysis. Computations, based on a finite volume method, are carried out by utilizing the Renormalized Group (RNG) k-e turbulence model. The investigation is carried out for triple twisted tapes with y/W = 2.0, 3.0 and 4.0 in round tubes for laminar air flow with Reynolds numbers between 500 and 2000. It is found that the use of triple twisted tapes with smallest twist ratio of y/W =2.0 results in the highest heat transfer and friction factor while the use of the tapes with the largest twist ratio (y/W = 4.0) results in the highest thermal performance. The highest thermal performances based on the constant pumping power criterion of the tubes equipped triple twisted tapes with y/W = 2.0, 3.0 and 4.0 are 2.43, 2.63 and 2.73, respectively.
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Influence of three-start spirally twisted tube combined with triple-channel twisted tape insert on heat transfer enhancement
(2016-04-01)
Eiamsa-ard, S.
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Promthaisong, P.
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Thianpong, C.
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Pimsarn, M.
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Chuwattanakul, V.
In the present article, heat transfer enhancement by three-start spirally twisted tube combination with triple-channel twisted tape is studied numerically using RNG k-ε turbulence model. Influences of the tape width ratio (w/D = 0.1, 0.25, 0.34 and 0.5) and tube/tape arrangement (belly-to-belly and belly-to-neck arrangements) are described. The numerical results of a twisted tube without tape and a circular plain tube are also given for comparison. The results are reported in terms of velocity field, temperature field, turbulent kinetic energy, local Nusselt number distribution, average Nusselt number, pressure loss and thermal performance factor. It is found that heat transfer and friction factor increase with tape width ratio. At a given tape width, the systems in belly-to-neck arrangement are more efficient for heat transfer enhancement than the ones in belly-to-belly arrangement. The three-start spirally twisted tubes with twisted tapes in belly-to-neck arrangement at w/D = 0.1, 0.25 and 0.34 give higher Nusselt numbers than the twisted tube without tape up to 1.2%, 21% and 36%, respectively. The twisted tubes with triple-channel twisted tape in belly-to-belly arrangement provide higher Nusselt numbers than the twisted tube without tape up to 1.23%, 6.7%, 10% and 17%, respectively. The superior heat transfer of the combined devices in belly-to-neck arrangement (especially at large w/D) is attributed to the stronger interaction between the swirling flows induced by the tubes and those induced by the tapes. Moreover, the systems in belly-to-neck arrangement cause lower friction loss than the ones in belly-to-belly arrangement. Thus, the systems in belly-to-neck arrangement yield higher thermal performance factors. Among the studied cases, the twisted tube combined with triple-channel twisted tape in belly-to-neck arrangement at w/D = 0.34 possesses the maximum thermal performance of 1.32 at Reynolds number of 5000.
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Thermal performance of heat exchanger tube installed with triple twisted-tapes
(2020-09-01)
Samutpraphut, B.
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Promthaisong, P.
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Wongcharee, K.
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Eiamsa-Ard, S.
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Chuwattanakul, Varesa
A current study deals with the numerical analysis of heat transfer intensification, flow-thermal fields, local heat transfer distribution, friction factor and thermal performance behavior of the heat exchanger tubes installed with triple twisted tapes. Each set of triple twisted tapes consists of three twisted tapes having an identical twist ratio. Twisted tapes of interest have three different twisted ratios (y/w = 1.0, 1.5 and 2.0). Simulation was performed for the turbulent flow with Reynolds numbers (Re) ranging from 5000 to 20,000. Numerical results indicate that the use of triple twisted-tapes leads to heat transfer enhancement. Nusselt number (Nu) and friction factor (f) increase while thermal performance factor () decreases with decreasing twist ratio of triple twisted tapes. The Nusselt numbers of the tubes installed with triple twisted-tapes having twist ratios of 1.0, 1.5 and 2.0 are higher than those of the plain tube by around 3.34-4.45, 2.75-3.65 and 2.56-3.41 times, respectively. Friction factors (f) of the tubes installed triple twisted-tapes with twist ratios of 1.0, 1.5 and 2.0 are increased up to 46.1-49.7, 24.16-26.04 and 15.86-17.09 times, respectively, as compared to those of the plain tube. The maximum thermal performance factors of 1.21, 1.23 and 1.32 are obtained by using triple twisted tapes with y/w = 1.0, 1.5 and 2.0 at the Reynolds number of 5000.
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Heat transfer mechanism in turbulent channel flow with V-tapered-baffles: Effect of convergence and divergence direction V-baffles
(2026-01-01)
Chokphoemphun, S.
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Phila, A.
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Promthaisong, P.
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Chamoli, S.
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Maruyama, N.
Solar air heaters are equipment that is utilized in a variety of applications including engineering and agriculture. Improving the transfer performance of heat exchangers is necessary to benefit from efficient energy consumption. The purpose of this work is to examine the effect of novel design V-tapered-baffles on the thermal performance of solar air heaters. The experiment was conducted with the expectation of a constant wall heat flux. In turbulent flow, air serves as the testing fluid with a Reynolds number range of 6,000 to 24,000. Two V-tapered-baffle types were employed in the experiment: convergent (C-VB) and divergent (D-VB) direction V-baffles, which were employed with fixed baffle pitch length of 60 mm and four different convergent and divergent edge baffle heights of 0, 3, 6, and 9 mm. The experimental results are compared with traditional V-baffles (T-VB) and the smooth surface channel. The investigation discovered that installing V-baffles provided a better thermal performance factor than traditional V-baffles. The important factor is that the V-baffles can reduce the friction factor by about 11–50 % compared to the traditional V-baffles under the same conditions. The maximum thermal enhancement factor values for the C-VB and D-VB were 2.19 and 2.13, respectively.
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3D numerical analysis of thermal-hydraulic behaviors of turbulent flow inside twisted square ducts
(2020-05-01)
Promthaisong, P.
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Chuwattanakul, V.
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Eiamsa-ard, S.
Heat transfer, local distributions of Nusselt number, flow structure, and friction characteristics of twisted square ducts are presented. Numerical analysis was carried out to investigate the influence of the twist ratio (TR = p/D = 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, and 6.0) on the thermal-hydraulic performance of twisted square ducts under constant wall heat flux condition for Reynolds numbers based on the hydraulic diameter of the twisted square duct ranging from 3000 to 20 000. The straight square duct was also analyzed for comparison. The numerical results showed that the twisted square ducts were more efficient in heat transfer than the straight square ducts because the swirl flow helped to increase fluid mixing and reduce thermal layer boundary thickness. The decrease of the twist ratio led to the increase in the Nusselt number and friction factor due to the higher frequency of swirl flow. As compared to the straight square duct, the twisted square ducts with TR = 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, and 6.0 improved heat transfer by 52, 49.82, 45.85, 42.22, 39.54, 35.41, and 31.77 %, respectively. Among the studied twisted ducts, the ones with twist ratio TR = 3.5 offered the maximum thermal enhancement factor of 1.42 at Re = 3000. In addition, the results also revealed that the twisted square ducts are thermo-hydraulically superior to the straight square ducts.

Chuwattanakul, Varesa

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