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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
;
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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Effects of blockage ratio and pitch ratio on thermal performance in a square channel with 30° double V-baffles
(2014-11-01)
Jedsadaratanachai, Withada
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Boonloi, Amnart
This article presents flow configurations and heat transfer characteristics in an isothermal square channel with 301 double V-baffles. The influences of blockage ratios (b/H, BR=0.05-0.25) and pitch ratios (L/H, PR=1-2) for Reynold numbers, Re=100-1200 are investigated numerically. The 30° double V-baffles are placed on both two opposite walls of the square channel with in-line arrangement and each V-tip pointing downstream. The numerical results are presented in four parts; accuracy validations, flow structures, heat transfer behaviors and performance evaluations. It is found that the use of the double V-baffles performs higher heat transfer rate and pressure loss than the smooth channel with no baffle. The rise of the blockage ratio and reducing the pitch ratio lead to the increase in heat transfer rate and pressure loss. The optimum thermal enhancement factor is found to be about 3.2 at PR=1, BR=0.10 and Re=1200.
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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
;
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 flow and heat transfer in square channel with 30° inline angled baffle turbulators
(2010-08-01)
Promvonge, Pongjet
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Jedsadaratanachai, Withada
;
Kwankaomeng, Sutapat
The article presents a numerical investigation on periodic laminar flow and heat transfer behaviors in a three-dimensional isothermal wall square-channel fitted with 30°-angled baffles on two opposite channel walls. The computations based on the finite volume method with the SIMPLE algorithm have been conducted for the fluid flow in terms of Reynolds numbers ranging from 100 to 2000. To generate a pair of streamwise counter-rotating vortex (P-vortex) flows through the tested channel, the angled baffles with the attack angle of 30° are mounted periodically and inline arrangement on the lower and upper channel walls. Effects of different baffle heights and three pitch ratios on heat transfer and flow behaviors in the channel are examined. It appears that P-vortex flows help to induce impinging flows over the baffle leading end side and the inter-baffle cavity walls resulting in drastic increase in heat transfer rate over the test channel. The computational results reveal that the maximum thermal enhancement factors for the baffle with PR = 1, 1.5 and 2 are found to be about 3.6, 3.8 and 4.0 at BR = 0.2, 0.2 and 0.15, respectively. © 2010 Elsevier Ltd. All rights reserved.

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