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Characterization of Heat Transfer Enhancement and Flow Topology in a Three-Start Spirally Corrugated Tube
(2025-12-01)
Du, Yuexiang
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Phila, Arnut
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Promthaisong, Pitak
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Chuwattanakul, Varesa
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Eiamsa-ard, Smith
The article provides a numerical analysis of the heat transfer characteristics and laminar periodic flow in a three-dimensional 3-start spirally corrugated tube. The working fluid is air, with a flow rate in terms of Reynolds numbers (Re) that ranges from 200 to 2,000. The investigation is conducted at six different pitch ratios (PR = 0.75, 1.0, 1.25, 1.5, 2.0, and 2.5) and five different depth ratios (DR = 0.02, 0.04, 0.06, 0.08, and 0.10). The results indicated that the spiral flow along the tube length was generated by the 3-start spirally corrugated tube. The swirl flow is divided into two components: the primary swirl flow, which is visible at the core, and the secondary swirl flow, which is visible at the near wall. These components contribute to the enhancement of fluid mixing, boundary layer disruption, and heat transfer on the tube wall. The Nusselt number (Nu) and friction factor (f) were increased as a result of the decrease in PR and the increase in Re and DR. The range of the Nu/Nu₀, f/f₀, and thermal performance factor (TPF) in a range analysis is 1.02 - 15.90, 0.97 - 5.52, and 0.73 - 2.33, respectively. At Re = 2,000, the corrugated tube with DR = 0.10 exhibited the greatest TPF of 2.33. Additionally, the results indicate that the 3-start spirally corrugated tube significantly improves heat transfer compared to the corresponding straight tube. The findings suggest that the structural characteristics of the flow path within the tube can be changed by a suitable PR and DR to optimize the overall heat transfer rate and thermal performance factor.
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3D numerical study on flow structure and heat transfer in a circular tube with V-baffles
(2015-02-01)
Jedsadaratanachai, Withada
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Jayranaiwachira, Nuthvipa
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Promvonge, Pongjet
A 3D numerical investigation has been carried out to examine periodic laminar flow and heat transfer characteristics in a circular tube with 45° V-baffles with isothermal wall. The computations are based on the finite volume method (FVM), and the SIMPLE algorithm has been implemented. The fluid flow and heat transfer characteristics are presented for Reynolds numbers ranging from 100 to 2000. To generate main longitudinal vortex flows through the tested section, V-baffles with an attack angle of 45° are mounted in tandem and in-line arrangement on the opposite positions of the circular tube. Effects of tube blockage ratio, flow direction on heat transfer and pressure drop in the tube are studied. It is apparent that a pair of longitudinal twisted vortices (P-vortex) created by a V-baffle can induce impingement on a wall of the inter-baffle cavity and lead a drastic increase in heat transfer rate at tube wall. In addition, the larger blockage ratio results in the higher Nusselt number and friction factor values. The computational results show that the optimum thermal enhancement factor is around 3.20 at baffle height of B = 0.20 and B = 0.25 times of the tube diameter for the V-upstream and V-downstream, respectively.
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Influences of the punched delta winglet vortex generators in a circular tube heat exchanger on thermo-hydraulic performance
(2015-01-01)
Jedasadaratanachai, Withada
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Boonloi, Amnart
Numerical investigations on flow topology, heat transfer behavior and thermal performance evaluation in a circular tube heat exchanger with the punched delta winglet vortex generators (PDWVG) inserted in the middle of the test section are presented. The effects of the flow attack angles that converging to the center of the tube; α = 0˚, 5˚, 10˚, 15˚, 20˚, 25˚, and flow directions; winglet tips pointing downstream and upstream, are investigated for the Reynolds numbers; Re = 100 – 2000. The finite volume method and SIMPLE algorithm are used for the current study. The results are presented in terms of flow configuration, heat transfer behavior and thermal performance assessments and also compared with the smooth tube with no PDWVG. As numerical results, the use of PDWVG inserted in the tube can help to improve heat transfer rate and thermal performance in the heat exchanger by creating the vortex flows through the test section. The rise of the flow attack angle and Reynolds number leads to increase in heat transfer, friction loss and thermal performance. The optimum TEF is around 2.33 at Re = 2000, α = 25˚ for winglet tip pointing downstream.
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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
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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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Laminar convection heat transfer in square channel fitted diagonally with 45° V-discrete baffles
(2014-01-01)
Tamna, Sombat
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Poonperm, Rachan
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Promvonge, Pongjet
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Thianpong, Chinaruk
This work presents a numerical investigation of laminar periodic flow and heat transfer in a constant heat flux-surfaced square-channel fitted diagonally with 45° V-discrete baffles. The computations are based on the finite volume method, and the SIMPLE algorithm has been implemented. The fluid flow and heat transfer characteristics are presented for Reynolds numbers based on the hydraulic diameter of the channel ranging from 200 to 1,200. Effects of different blockage ratios (BR=b/H), BR in range from 0.05-0.2 with pitch ratio of 1.0 on heat transfer and pressure loss in the channel are studied. It is apparent that vortex flows created by the 45° diagonal V-discrete baffle exist and help to induce impinging flows on wall leading to drastic increase in heat transfer rate over the smooth channel. In addition, the increase in the BR results in the rise of Nusselt number and friction factor values. The computational results reveal that the optimum thermal enhancement factor of the 45° V-discrete baffle is about 2.24 at BR=0.2. © (2014) Trans Tech Publications, Switzerland.
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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
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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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3D numerical study on laminar forced convection in V-baffled square channel
(2013-10-10)
Boonloi, Amnart
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Jedsadaratanachai, Withada
The article presents a mathematical study of fully developed periodic laminar flow visualization and heat transfer characteristics in an isothermal wall square-channel fitted with V-shaped baffles on one wall. The computations based on the finite volume method together with the SIMPLE algorithm have been performed. The investigation covers a range of Re based on the hydraulic diameter of the channel, Re = 100-1200. To create a pair of main streamwise vortex flows through the tested section, the V-baffles with the attack angle of 30° with the main flow direction are mounted in tandem and pointing downstream on the lower channel wall only. Effects of different baffle heights and pitches on heat transfer and pressure drop in the channel are examined and the results obtained are compared with smooth channel with no baffle. The numerical result shows that the presence of the V-baffle yields a significant heat transfer enhancement compared with the smooth channel. It is visible that the main vortex flows, a pair of streamwise twisted vortex (P-vortex) can induce impingement flows on the walls leading to a drastic increase in heat transfer rate over the channel. In addition, the increase in the baffle height leads to the rise in the heat transfer and pressure loss while that in the baffle pitch provides the opposite trend. The predicted results expose that the maximum thermal enhancement factors for the V-baffles with BR = 0.3, 0.3 and 0.4; and PR = 1, 1.5 and 2 are, respectively, about 2.44, 2.29 and 2.37 at higher Re. © 2013 Science Publication.
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Effect of twisted ratio on flow structure, heat transfer and thermal improvement in a circular tube with single twisted tape
(2013-01-01)
Jedsadaratanachai, Withada
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Boonloi, Amnart
The research presents a numerical analysis of laminar fully developed periodic flow and heat transfer in a constant temperature-surfaced circular tube with single twisted tape inserted. The twisted tape is introduced and inserted in the middle of the tested tube. The effects of twisted ratios (y/W = 1, 2, 3, 4, 5 and 6) are presented for Reynolds number (Re) values ranging from Re = 100 to 2000. The SIMPLE algorithm and periodic condition are used in the current study. The computational results are shown in the topology of flow, heat transfer and thermal improvement. It is found that the heat transfer in the circular tube with the twisted tape is more effective than that with no twisted tape inserted. The increase in the y/W ratio leads to decrease in the Nusselt number and friction factor. In addition, the numerical result shows that the reduction in the y/W ratio not only helps to create strong longitudinal vortex flows which enhance heat transfer, but also increase the pressure loss in the tested tube. The computed result reveals that the maximum value of the thermal enhancement factor, TEF is found to be 3.52 for using the twist tapes with y/W = 5 at the highest Reynolds number regime. © 2014 Science Publications.
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3D simulation of laminar flow and heat transfer in V-baffled square channel
(2012-01-01)
Promvonge, Pongjet
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Jedsadaratanachai, Withada
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Kwankaomeng, Sutapat
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Thianpong, Chinaruk
The article presents a numerical investigation on laminar flow and heat transfer characteristics in a three-dimensional isothermal wall square-channel fitted with inline 45̊ V-shaped baffles on two opposite walls. The computations based on the finite volume method with the SIMPLE algorithm have been conducted for the airflow in terms of Reynolds numbers ranging from 200 to 2000. The inline V-baffles with its V-tip pointing downstream and the attack angle (or half V-apex angle) of 45̊ relative to the flow direction are mounted repeatedly on the lower and upper walls. The baffled channel flow shows a fully developed periodic flow and heat transfer profile for BR=0.2 at x/D≊8 downstream of the inlet. Influences of different baffle height ratios (BR) and pitch ratios, (PR) on thermal behaviors for a fully developed periodic condition are investigated. It is apparent that the longitudinal counter-rotating vortex flows created by the V-baffle can induce impingement/attachment flows over the walls resulting in greater increase in heat transfer over the test channel. Apart from speeding up the fully developed periodic flow pattern, the rise of the BR leads to the increase in Nu/Nu <inf>0</inf> and f/f <inf>0</inf> values while that of the PR provides an opposite trend. The V-baffle performs better than the angled baffle at a similar condition. The V-baffle with BR=0.2 and PR=1.5 yields the maximum thermal performance of about 3.8 whereas the Nu/Nu <inf>0</inf> is some 14 times above the smooth channel at higher Re. © 2011 Elsevier Ltd.
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Numerical study of laminar heat transfer in baffled square channel with various pitches
(2011-01-01)
Jedsadaratanachai, Withada
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Suwannapan, Supattarachai
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Promvonge, Pongjet
The article presents a numerical analysis of laminar periodic flow and heat transfer characteristics in a constant temperature-surfaced square channel mounted with 30° angled baffles of various pitches. The computations were based on a finite volume method and the SIMPLE algorithm implemented. The fluid flow and heat transfer characteristics are presented for Reynolds number based on the channel hydraulic diameter ranging from 100 to 2000. The angled baffles were placed repeatedly on the lower and upper channel walls with in-line arrangement to generate a pair of streamwise counter - rotating vortex flows. Effects of different pitch ratios (PR=P/H) with a single baffle height ratio of 0.2 on heat transfer and pressure loss in the channel were examined. The baffled channel flow showed a fully developed periodic flow profile at about x/D≈7. The computation revealed that the pair of vortex flows created by the baffles exists and induces impingement/attachment flows on a side and the upper and lower walls leading to substantial increase in heat transfer rate over the test channel. The decrease in the PR led to the rise of friction factor only. The result showed that the optimum thermal performance enhancement factor of about 3.78 is found at PR=2.5. © 2011 Published by Elsevier Ltd.

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