Jedsadaratanachai, Withada

Preferred name

Alternative Name

Jedsadaratanachai, W.

Main Affiliation

School of Engineering

withada.je@kmitl.ac.th

Now showing 1 - 10 of 18

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Convective heat transfer, friction factor and thermal performance in a round tube equipped with the modified V-shaped baffle
(2018-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Convective heat transfer, pressure loss and thermal performance in a heat exchanger tube inserted with the modified V-shaped baffle are investigated numerically. The influences of the flow attack angle (α = 20o, 30o and 45o), baffle height in term of blockage ratio (b/D = BR = 0.05, 0.10, 0.15, 0.20 and 0.25) and arrangement (The V-tip pointing downstream is called “V-Downstream”, while the V-tip pointing upstream is named “V-Upstream”.) on heat transfer and friction loss are presented for the Reynolds number in range 100 – 1200 (laminar region). The numerical study (finite volume method) is selected to solve the current investigation and to describe the mechanisms inside the heat exchanger tube. The flow visualizations and heat transfer characteristics in the heat exchanger tube are plotted in the numerical-result report. The results on heat transfer, friction factor and thermohydraulic performance of the test tube are compared with the smooth circular tube. It is found that the vortex strength in the heat exchanger tube is an important factor to enhance heat transfer rate and thermal performance. In addition, the maximum thermal enhancement factor is around 3.22 at α = 30o, BR = 0.2, Re = 1200 for V-Upstream arrangement.
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3D numerical investigation on laminar forced convection and heat transfer in a circular tube inserted with right triangular wavy surfaces
(2017-01-01)
Jedsadaratanachai, Withada
;
Boonloi, Amnart
Numerical investigations on flow and heat transfer characteristics in a circular tube heat exchanger inserted with right triangular wavy surfaces are reported. The configurations of the wavy surfaces; incline and V-shape, are studied with flow attack angles of 30°, 45° and 60° for the Reynolds numbers, Re = 100-2000. The numerical results are compared with the smooth circular tube. The mechanisms on flow and heat transfer in the tube heat exchanger with the wavy surface are presented. As the results, the wavy surface can generate the vortex flow and impinging flow through the test section that helps to improve the heat transfer rate and thermal performance. The impingement of the flow on the tube wall disturbs the thermal boundary layer that is an important factor to enhance the heat transfer rate. The V-Downstream wavy surface can create the highest strength of the impinging flow that leads to the highest heat transfer rate. In the range investigate, the augmentations are around 1.2-7.6 and 4-43.6 times above the smooth tube for the heat transfer and friction loss, respectively. In addition, the optimum thermal enhancement factor, TEF, is around 2.42 for the V-Downstream wavy surface at α = 30° and Re = 2000.
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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.
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Effect of location in transverse plane for 45-degree V-baffle on flow and heat transfer mechanisms in a square channel
(2018-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Numerical predictions on flow and heat transfer in a square channel heat exchanger placed with V-baffle are examined. The gap spacing between the V-baffle and channel wall is varied for all baffle heights. The laminar regime with Re = 100 - 1000 is considered. The numerical model for the square channel heat exchanger placed with V-baffle is validated. The preliminary result reveals that the computational domain has reliability to predict flow and heat transfer in the channel. The mechanisms on flow and heat transfer in the heat exchanger channel are illustrated at the numerical result section. The thermal performance analysis of the heating section when inserted with the V-baffle is also reported in forms of the Nusselt number ratio (Nu/Nu0 or NuR), friction factor ratio (f/f0 or fR) and thermal enhancement factor (TEF). As the results, it is found the gap spacing has extremely effect for flow structure and heat transfer behavior in the test section. The optimum gap spacing ratio may help to reduce the pressure loss or improves the heat transfer rate in the channel heat exchanger. The selection for the gap spacing ratio in the heating section at various baffle heights is also concluded. In addition, the gap spacing ratio around 5 - 10% is suggested for the range investigation.
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Numerical investigation of thermal profile and air-flow visualization in a tube heat exchanger with discrete X-V vortex inducers (DXVVI)
(2025-12-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
This study presents the implementation of discrete X-V vortex inducers (DXVVI) as a passive heat transfer enhancement technique in circular heat exchanger tubes. The DXVVI devices are introduced to improve the convective heat transfer coefficient, heat transfer rate, and thermal performance. Numerical simulations using a commercial CFD code were employed to investigate the flow structure and thermal behavior within the heat exchanger system. The DXVVI concept is developed based on a combination of the V-Orifice and V-shaped baffle, aiming to retain the thermal performance of the V-shaped baffle while maintaining the structural strength of the V-Orifice. The discrete configuration was selected to enhance turbulence levels and reduce pressure drop. Two DXVVI design groups, referred to as “GROUP 1” and “GROUP 2”, were proposed. Key parameters influencing the flow and thermal characteristics were investigated, including the pitch ratio (PRT), defined as the ratio of the longitudinal pitch or pitch distance (P) to the circular tube diameter (D), i.e., P/D, and the flow-blockage ratio (BKRT), defined as the ratio of the DXVVI thickness (b) to the circular tube diameter, i.e., b/D. The simulations were conducted under turbulent flow conditions with Reynolds numbers (Re) ranging from 3000 to 20,000, considering both co-flow (+x) and counter-flow (−x) directions. In GROUP 2, small gaps were introduced in various configurations to enhance turbulence intensity, increase the number of vortex cores, and further reduce pressure drop—leading to improved heat exchanger performance. The numerical model was validated using appropriate academic standards, confirming its reliability in predicting thermal and flow behaviors. The numerical results are performed in terms of fluid-flow structure (e.g., streamline plots in transverse planes and 3D flow visualizations) and thermal characteristics (e.g., fluid-temperature contours in cross-sectional planes and Nusselt number distributions on the tube surface). Performance evaluation was also carried out using dimensionless metrics, including the Nusselt number ratio (Nu/Nu₀), the friction factor ratio (f/f₀), and the thermal enhancement factor (TEF) under equal pumping power conditions. The best heat transfer rate augmentation was observed to be up to 8.07 times greater than the reference case (smooth tube). The highest TEF, equal to 3.14, was observed in GROUP 2 for configuration 5B5G5B with a pitch ratio (PRT) of 1.
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Numerical investigation on turbulent forced convection in heating channel inserted with discrete V-shaped baffles
(2016-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
The numerical examinations on flow visualization, heat transfer characteristic and performance improvement in a square duct inserted with discrete V-shaped baffles (DVB) are reported. The DVB is designed to reduce the pressure loss when compared with the V-shaped baffle. The influences of the flow blockage ratios (b/H, BR = 0.05-0.20), V-tip directions (V-Downstream and V-Upstream) are investigated for Reynolds number, Re = 3000-20,000, with a single pitch ratio and flow attack angle of 1 and 30°, respectively. As the results, the DVB can generate the vortex flow and impinging flow through the test section that assists to develop the thermal efficiency. The augmentations on the heat transfer coefficient and pressure drop are around 2.5-5.75 and 4-22.5 times above the smooth duct, respectively. The best thermal efficiency in forms of thermal enhancement factor, TEF, around 2.32 is detected at Re = 3000, BR = 0.10 and V-Upstream.
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Numerical assessments of flow pattern and heat transfer profile for the round tube equipped with different configurations of the dual-inclined baffle
(2021-10-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
Numerical studies of the heat exchanger tube (HXT) equipped with the dual-inclined baffle (DIB) on fluid streams and heat transfer profiles are reported. The DIB configurations can be separated into three types: 1. The DIB is inserted in the middle of the HXT called “type I″, 2. The DIB is placed on the HXT wall called “type II” and 3. The combination of the type I and II DIB called “type III”. The three DIB types are designed with the main purpose to create three different flow profiles. The influences of DIB height with a single pitch distance (P/D = 1) and DIB attack angle of 30° for heat transfer characteristics and fluid streams are discussed in a laminar flow region at Re = 100–2000 (considered at the entry condition). The numerical problem of the HXT inserted with the DIB is solved with a commercial code (the finite volume method). The computation domain is validated to confirm the reliability and accuracy of the simulated results. The flow configurations: streamlines in transverse planes (y-z planes), and heat transfer behaviors: temperature contours in transverse planes (y-z planes) and local Nusselt number contours (Nu<inf>x</inf>), in the HXT equipped with the DIB are proposed in the simulated-result section. The relations of the average Nusselt number ratio (Nu/Nu<inf>0</inf>), friction factor ratio (f/f<inf>0</inf>) and thermal enhancement factor (TEF) with the Reynolds numbers in the HXT inserted with the DIB are presented. As the simulated results, the equipment of the DIB in the HXT brings upper heat transfer rate and thermal performance than those of the smooth tube because of the creations of the vortex streams and impinging streams. The different flow profiles are detected when varying the DIB types that impact for the variations of the heat transfer profile. For the studied range, the increased heat transfer rate in the HXT installed with the DIB is observed to be around 1.03–17.46 times above the plain tube depended on the DIB type, DIB blockage and Reynolds number. Additionally, the maximal TEF of 3.70 is found for the type II DIB at b/D = 0.25 and Re = 2000.
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The effects of gap spacing ratio on flow structure and heat transfer characteristic for the v-orifice in the square channel heat exchanger
(2019-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
The variations of flow and heat transfer in the square channel heat exchanger inserted with various parameters of V-orifice are investigated numerically. The influences of flow directions (V-Downstream and V-Upstream), gap spacing ratios (g/H or GR = 0, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) and blockage ratios (b/H or BR = 0.05, 0.10, 0.15, 0.25 and 0.30) on flow topology and heat transfer behavior are reported. The laminar flow regime with the Reynolds number in the range 100 – 2000 is considered. The numerical results are presented in terms of flow and heat transfer structure in the heat exchanger channel. The thermal performance assessments in the square channel with V-orifice are also concluded. As the numerical results, the gap between the V-orifice and channel walls changes the flow and heat transfer mechanisms in the channel. The gap can reduce the friction loss in the channel and also helps to increase the turbulence of the flow. The optimum gap spacing ratio may help to increase the thermal performance of the square channel heat exchanger.
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Influences of the wavy surface inserted in the middle of a circular tube heat exchanger on thermal performance
(2015-09-22)
Jedsadaratanachai, Withada
;
Boonloi, Amnart
Numerical investigations on flow topology, heat transfer behavior and performance evaluation in a circular tube inserted with various configurations of wavy surfaces, Inclined wavy surface (IWS), V-downstream wavy surface (VDWS), V-Upstream wavy surface (VUWS) are presented. The effects of the flow attack angles; 20°, 30°, 45° and 60° are studied for the Reynolds numbers, Re = 100-2000. The numerical results are compared with the smooth circular tube with no wavy surface and the previous works. It is found that the IWS, VDWS and VUWS can produce longitudinal vortex flow and impinging jet of the fluid flow like inclined baffle, V-downstream baffle and V-Upstream baffle, respectively, but give lower friction loss. The flow phenomena created by the wavy surfaces help to augment the heat transfer rate and thermal performance in the test tube. In the range studied, the order of enhancement for heat transfer rate is around 1.40-3.75, 1.60-6.25 and 1.30-5.80 times higher than the smooth tube for IWS, VDWS and VUWS, respectively. Moreover, the maximum thermal performance, presented in terms of the Thermal enhancement factor (TEF), is found to be about 1.60, 2.40 and 2.10, respectively, for IWS, VUWS and VDWS.
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Flow topology, heat transfer characteristic and thermal performance in a circular tube heat exchanger inserted with punched delta winglet vortex generators
(2016-01-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
To improve the heat transfer rate and thermal performance, the punched delta winglet vortex generators, DWVGs, were inserted in the middle of the circular tube heat exchanger. The effects of the flow attack angles and the flow directions were investigated numerically for the Reynolds number Re = 100–2000. The finite volume method and the SIMPLE algorithm were used to study. The results are reported in terms of the flow structure, heat transfer behavior and thermal performance evaluation and also compared with the smooth tube with no vortex generators. As the numerical results, the use of the DWVGs in the tube can improve the heat transfer rate and thermal performance by creating the vortex flow through the tested section. The rise of the flow attack angle results in the increasing strength of the vortex flows. The flow attack angle of 25° performs the highest heat transfer rate and thermal performance, while the flow attack angle of 0o gives the reversed results. The computational results reveal that the optimum thermal enhancement factor is around 2.80 at Re = 2000, α = 25°, with the winglet tip pointing downstream. The correlations on both the Nusselt number ratio and friction factor ratio for the DWVG in the tube heat exchanger are presented.

Jedsadaratanachai, Withada

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