Jedsadaratanachai, Withada

Preferred name

Alternative Name

Jedsadaratanachai, W.

Main Affiliation

School of Engineering

withada.je@kmitl.ac.th

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Turbulent forced convection in a heat exchanger square channel with wavy-ribs vortex generator
(2015-08-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Turbulent forced convective heat transfer and flow configurations in a square channel with wavy-ribs inserted diagonally are examined numerically. The influences of the 30° and 45° flow attack angles for wavy-ribs, blockage ratio, R<inf>B</inf> = b/H = 0.05-0.25 with single pitch ratio, R<inf>P</inf> = P/H = 1 are investigated for the Reynolds number based on the hydraulic diameter of the square channel, Re = 3000-20000. The use of the wavy-ribs, which inserted diagonal in the square channel, is aimed to help to improve the thermal performance in heat exchange systems. The finite volume method and SIMPLE algorithm are applied to the present numerical simulation. The results are presented on the periodic flow and heat transfer profiles, flow configurations, heat transfer characteristics and the performance evaluations. The mathematical results reveal that the use of wavy-ribs leads to a higher heat transfer rate and friction loss over the smooth channel. The heat transfer enhancements are around 1.97-5.14 and 2.04-5.27 times over the smooth channel for 30° and 45° attack angles, respectively. However, the corresponding friction loss values for 30° and 45° are around 4.26-86.55 and 5.03-97.98 times higher than the smooth square channel, respectively. The optimum thermal enhancement factor on both cases is found at R<inf>B</inf> = 0.10 and the lowest Reynolds number, Re = 3000, to be about 1.47 and 1.52, respectively, for 30° and 45° wavy-ribs.
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Thermohydraulic Performance Improvement in Heat Exchanger Square Duct Inserted with 45° Inclined Square Ring
(2020-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Thermal performance development, heat transfer structure, and flow behavior in the heat exchanger square duct equipped with a 45° inclined square ring are investigated numerically. The effects of flow blockage ratios and spacing ratios for the inclined square ring on fluid flow and heat transfer are considered. The Reynolds number (Re = 100-2000, laminar regime) based on the hydraulic diameter of the square duct is selected for the present work. The numerical domain of the square duct inserted with the 45° inclined square ring is solved with the finite volume method. The SIMPLE algorithm is picked for the numerical investigation. The heat transfer characteristics and flow topologies in the square duct inserted with the inclined square ring are plotted in the numerical report. The heat transfer rate, pressure loss, and efficiency for the square duct placed with the inclined square ring are presented in forms of Nusselt number, friction factor, and thermal enhancement factor, respectively. As the numerical results, it is detected that the heat transfer rate of the heat exchanger square duct inserted with the inclined square ring is around 1.00-10.05 times over the smooth duct with no inclined square ring. Additionally, the maximum thermal enhancement factor for the heat exchanger square duct inserted with the inclined square ring is around 2.84.
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Numerical Simulation and Optimization of Enhanced Heat Transfer in Helical Oval Tubes: Effect of Helical Oval Tube Modification, Pitch Ratio, and Depth Ratio
(2018-11-26)
Promthaisong, Pitak
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Jedsadaratanachai, Withada
;
Eiamsa-ard, Smith
Flow and heat transfer behaviors in the helical oval tube, alternate-twisted-direction helical oval tube and regularly spaced helical oval tubes were numerically investigated. The helical oval tubes with eight oval tube depth ratios (0.03, 0.04, 0.05, 0.06, 0.07, 0.10, 0.15, and 0.20) and nine oval tube pitch ratios (0.6, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0) were examined in turbulent regime, Reynolds number ranged from 5000 to 20,000. The computational results showed that fully developed periodic flow and heat transfer in helical oval tubes commenced at around entrance length to characteristic diameter of 8–9. The decreasing depth ratio and increasing pitch ratio helped to reduce the pressure loss of the tube heat exchanger. The maximum thermal performance of 1.30 was obtained by the use of the helical oval tube with depth ratio of 0.05 and pitch ratio of 0.6 at the lowest Reynolds number of 5000. At similar conditions, typical helical oval tubes offered better heat transfer rate and thermal performance than helical oval tubes with alternate axes and regularly spaced helical oval tubes.
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Thermal characteristics in turbulent channel flows with V-baffle vortex generators
(2014-01-01)
Kaewkohkiat, Y.
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Jedsadaratanachai, W.
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Eiamsa-Ard, P.
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Promvonge, P.
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Eiamsa-Ard, S.
Experimental work has been performed to examine the effects of V-baffle vortex generators on the heat transfer and friction characteristics in a channel under a constant heat flux boundary condition. In the experiments, V-baffles at different pitch ratios (PR=P/e = 4.0, 6.0 and 8.0) were carried out. Measurements were carried out for a channel of one aspect ratio, AR = W/H = 4.0 and duct height, H= 40 mm with baffle height, e = 8 mm. Experiments were conducted for the Reynolds number range of 6000 to 22,000. The distributions of temperature and local Nusselt number on bottom channel wall were observed with thermochromic liquid crystal (TLC) sheet. Isothermal friction factors were also taken and presented. The obtained results demonstrate that heat transfer increases with the increase of Reynolds number, whereas friction factor (f) shows the opposite trend. Experimental results also show that the channels with V-baffle at the highest pitch ratio (PR = 8.0) provide highest heat transfer than others. © 2014 Asian Institute of Technology.
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Thermal performance assessment for laminar forced convection with downstream Reformed-V and Reformed-Double-V generators
(2014-01-01)
Jedsadaratanachai, Withada
;
Boonloi, Amnart
Thermal assessments for laminar flow in an isothermal wall square channel over downstream Reformed-V (RV) and Reformed-Double-V (RDV) generators inserted diagonally are presented numerically in three dimensional. The RV and RDV are designed to comfort for forming and installing in the heat exchanger channel. The effect of RV and RDV height is investigated in terms of blockage ratio, b/H, BR = 0.05-0.30 for Reynolds number based on the hydraulic diameter of the square channel, Re = 100-1200. The SIMPLE algorithm, finite volume method and the periodic condition are used in the current computational domain. The mathematical results show that the uses of RV and RDV provide higher heat transfer rate than the smooth square channel with no generators. The RV gives higher on both heat transfer rate and friction factor values than the RDV case for all BR and Re values. The maximum heat transfer rate and friction factor are found around 20.5 and 420 times over the smooth square channel, respectively, at BR = 0.30 for RV case. The optimum thermal enhancement factor, TEF, is found at BR = 0.1, Re = 2000 around 2.95 for RDV case.
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IMPACT OF THREE DIFFERENT DOUBLE BAFFLE DESIGNS ON THE THERMAL PERFORMANCE OF SQUARE DUCTS
(2022-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
CFD analyses of flow characteristics and heat transfer topology in a heat exchanger duct (HXD) placed with three various configurations of the double V-baffles (DVB) are reported. Parameters of interest are DVB height ratios (b/H = 0.05 – 0.25), gap spacing ratios (g = 0.05 – 0.40), flow directions (+x,-x), and DVB configurations (Type I, II and III). Laminar flow with Reynolds numbers (based on the inlet conditions) between 100 – 2000 is measured. The present problem is solved with the finite volume method (a commercial program). Fluid flow and heat transfer characteristics in the tested duct are described. Thermal assessments of the tested duct are also presented. Simulation results showed that the installation of the DVB in the HXD results in higher heat transfer rate due to the creation of the vortex flow and the disturbance of the thermal boundary layer (TBL). Different flow structures and heat transfer behavior are observed when gap spacing ratios, flow directions and DVB shapes are changed. In addition, the type II DVB provides the highest TEF of 3.55 at b/H = 0.10, g/H = 0.25 for the-x flow direction.
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Numerical Investigations of Laminar Air Flow and Heat Transfer Characteristics in a Square Channel Inserted with Discrete X-V Baffles (XVB)
(2023-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
Thermal performance enhancement in a square channel heat exchanger (HX) using a passive technique is presented. Vortex turbulator insertion in a square channel HX as a passive technique is selected for thermal improvement. The vortex turbulator of interest is discrete X-V baffles (XVB). The discrete XVBs are inserted in the square channel with the main aim of generating vortex flow. The vortex flow generated can support the enhanced convective heat transfer coefficient and also enhance HX performance. Effects of baffle configuration (type A and B),bafflesize(w/H= 0.05, 0.10, 0.15 and 0.20), baffle distance (e/H = 1, 1.5 and 2) and flow direction (±xairflow paths) on fluid flow and thermal topologies are numerically investigated by using a commercial code. As shown by the numerical results, the predicted flow configuration with the discrete XVB insertions, which include impinging and vortex streams, is found through the HX channel. The perturbing thermal boundary layer and greater air blending are also found through the HX channel inserted with the discrete XVB. These mechanisms promote and augment the convection heat transfer coefficient, heat transfer rate and rise thermal potentiality. The maximum Nusselt number of the channel with the baffles inserted is 11.01 times upper than that of the smooth channel, while the greatest thermal performance factor (TPF) is observed to be around 3.45.
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Investigations of Air-Flow Configuration, Heat Transfer Behavior and Thermal Performance in Heat Exchangers with XVB-Type Turbulence Generators Under Turbulent Flow Conditions
(2025-01-01)
Boonloi, Amnart
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Jedsadaratanachai, Withada
This study employs numerical modeling using the finite volume method to analyze airflow and thermal structures when vortex flow (VTF) generators are installed in heat exchanger square ducts (HX-SD). The VTF generator used in this study is the X-V baffle (XVB), which is designed to enhance heat transfer rates. The XVB is an evolution of the V-baffle, a type of VTF generator known for its efficiency in improving heat transfer. It features an X-shaped structure (considered in the cross-sectional (CS) plane, y-z plane) to further optimize the design. The present research investigates the effects of XVB thickness, represented by the thickness ratio (b) to the HX-SD height (H) or hydraulic diameter (Dh) (b/H), with B-R values ranging from 0.05 to 0.20. Additionally, three XVB configurations (Types A, B, and C) are examined, along with two airflow directions: AFD-VD (airflow direction – V-Downstream) and AFD-VU (airflow direction – V-Upstream). The investigation focuses on turbulent flow conditions, analyzing air velocity within a Reynolds number range of Re = 3,000 to 16,000. The results indicate that VTF is generated throughout the HX-SD due to the pressure difference caused by flow obstruction from the XVB in all cases examined. By enhancing air mixing and disrupting the thermal boundary layer (Th-BL), the induced VTF significantly increases the heat transfer rate. The maximum observed increase in heat transfer was 7.95 times higher than that of a smooth, empty duct.
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Three-Direction Type of Diffuser-Shaped Vortex Generator Development for the Wind Solar Tower
(2025-01-01)
Sudsanguan, Anan
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Boonloi, Amnart
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Jedsadaratanachai, Withada
This study explored the use of diffuser shapes to enhance the performance of a solar updraft tower. A diffuser-shaped vortex generator, a simple device requiring no structural modifications to the tower, was installed at the chimney outlet. The generator transformed crosswind into a vortex, increasing the updraft velocity. This study employed finite element methods and numerical models to validate the results alongside physical experiments. Both approaches focused on the crosswind velocity and vortex generator height to determine an optimal semi-opening angle for the diffuser shape. The experimental results revealed that an 8° diffuser-shaped vortex generator with a height of h<inf>vg</inf> = 2D achieved the greatest updraft enhancement, increasing the speed by 86.89% compared to the prototype tower. The enhancement was found to increase proportionally with the generator’s angle and height.
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Forced convection heat transfer, flow configuration and thermal performance in a square channel with modified v-shaped baffles
(2014-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
The influences of modified V-shaped baffle in a square channel for heat transfer and thermal performance enhancement are presented numerically in three Dimensional (3D). The V-shaped baffles are modified in order to comfortable to installation in the square channel. The plates are used for clamping on both the upper and lower V-shaped baffles resulting the modified V-shaped baffle like orifice plate called "V-shaped orifice tubulators, VOT". The effects of Blockage Ratios (BR = 0.05-0.20), flow attack angles (α = 20°, 30° and 45°) and flow directions (V-Downstream and V-Upstream) with a single Pitch Ratio (PR = 1) are investigated for Reynolds number based on the hydraulic diameter of the square channel (Dh), Re = 100-2000. The fully developed periodic flow and heat transfer are applied for the computational domain. The SIMPLE algorithm and the finite volume method are used in the current study. The numerical results show that the use of VOT not only increasing heat transfer rate, but also rise up very enlarge pressure loss due to reducing the flow area of the cross sectional area. In addition, the maximum thermal enhancement factors are found around 2.4 and 2.5 for BR = 0.10, a = 30° at the highest Reynolds number of V-Downstream and V-Upstream, respectively. © 2014 Science Publications.

Jedsadaratanachai, Withada

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