Kwankaomeng, Sutapat
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Kwankaomeng, Sutapat
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Kwankaomeng, S.
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sutapat.kw@kmitl.ac.th
10 results
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Item type:Publication, Numerical investigation of laminar heat transfer in a square channel with 45° inclined baffles(2010-02-01); ; A numerical investigation of laminar periodic flow and heat transfer in a three-dimensional isothermal-wall square channel fitted with 45° inclined baffles on one channel wall is carried out in the present work. The finite volume method is introduced and the SIMPLE algorithm has been implemented for all computations. The fluid flow and heat transfer characteristics are presented for Reynolds numbers ranging from 100 to 1200. The 45° baffle mounted only on the lower channel wall has a height of b and an axial pitch length (L) equal to channel height (H). Effects of flow blockage ratios, BR = b/H = 0.1-0.5, on heat transfer and pressure loss in the square channel are examined and also compared with the typical case of the transverse baffle (or 90° baffle). It is found that apart from the rise of Reynolds number, the increase in the blockage ratio with the attack angle (α) of 45° results in considerable increases in the Nusselt number and friction factor values. The use of the 45° baffle can help to generate a streamwise main vortex flow throughout the channel leading to fast and chaotic mixing of flow between the core and the wall regions. In addition, the computational results reveal that the significant increase in heat transfer rate is due to impingement jets induced by a longitudinal vortex pair (P-vortex) of flow, appearing on the upper, lower and baffle trailing end side walls. The appearance of vortex-induced impingement flows created by the baffles leads to the maximum thermal enhancement factor of about 2.2 at BR = 0.4 and Re = 1200. The enhancement factor of the 45° baffle investigated is found to be higher than that of the 90° baffle for all Reynolds numbers and baffle heights. © 2009 Elsevier Ltd. All rights reserved. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Periodic laminar flow and heat transfer in a channel with 45° staggered V-baffles(2010-08-01); A numerical investigation has been carried out to examine periodic laminar flow and heat transfer characteristics in a three-dimensional isothermal wall channel of aspect ratio, AR=2 with 45° staggered V-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 100 to 1200. To generate two pair of main streamwise vortex flows through the tested section, V-baffles with an attack angle of 45° are mounted in tandem and staggered arrangement on the lower and upper walls of the channel. Effects of different baffle heights on heat transfer and pressure drop in the channel are studied and the results of the V-baffle pointing upstream are also compared with those of the V-baffle pointing downstream. It is apparent that in each of the main vortex flows, a pair of streamwise twisted vortex (P-vortex) flows can induce impinging flows on a sidewall and a wall of the interbaffle cavity leading to drastic increase in heat transfer rate over the channel. In addition, the rise in the V-baffle height results in the increase in the Nusselt number and friction factor values. The computational results reveal that the optimum thermal enhancement factor is around 2.6 at baffle height of 0.15. times of the channel height for the V-baffle pointing upstream while is about 2.75 at baffle height of 0.2. times for the V-baffle pointing downstream. © 2010 Elsevier Ltd. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Numerical study of laminar flow and heat transfer in square channel with 30° inline angled baffle turbulators(2010-08-01); ; 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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Heat transfer in square duct fitted diagonally with angle-finned tape-Part 2: Numerical study(2012-05-01); ; Thiangpong, ChinarukA numerical work has been conducted to examine turbulent flow and heat transfer characteristics in a three-dimensional isothermal-fluxed square-duct fitted diagonally with 30°-angle finned tapes. The computations are based on the finite volume method with the SIMPLE algorithm implemented. The air flow and heat transfer characteristics in the duct are presented for Reynolds number (Re) in a range of 4000 to 20,000. In the current study, a straight tape with 30°-angled fins mounted repeatedly on both sides is inserted diagonally into the test duct to generate a pair of longitudinal counter-vortices in assisting chaotic flow mixing in the duct including vortex-induced impingement (VI) effect. Effects of fin blockage ratio (BR= b/. H) and pitch ratio (PR= L/. H) on heat transfer and pressure drop behaviors in the duct are investigated and the results of the finned tape insert are compared with available measurements. The computation reveals that predicted results from the finned tape insert are in good agreement with measured data. The study indicates that the vortex flow can help to induce impingement/reattachment flows (VI effect) on the duct walls leading to drastic increase in the heat transfer rate over the duct. The rise of the BR and the reduction of the PR results in the increase in Nusselt number and friction factor values. The maximum thermal performance is found to be 1.95 for using the finned tape at BR= 0.2 and PR= 1 whereas the Nusselt number ratio is about 4.5 at lower Re. © 2012 Elsevier Ltd. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Numerical heat transfer study of turbulent square-duct flow through inline V-shaped discrete ribs(2011-12-01); ; A numerical work has been conducted to examine turbulent periodic flow and heat transfer characteristics in a three dimensional square-duct with inline 60° V-shaped discrete thin ribs placed on two opposite heated walls. The isothermal-flux condition is applied only to the upper and lower duct walls while the two sidewalls are insulated, similar to internal passage cooling of gas turbine blades. The computations are based on the finite volume method with the SIMPLE algorithm for handling the pressure-velocity coupling. Air is the working fluid with the flow rate in terms of Reynolds numbers ranging from 10,000 to 25,000. The numerical result is validated with available square-rib measured data and found to agree well with measurement. The computation reveals that the ribbed duct flow is fully developed periodic flow and heat transfer profiles at about x/ D=7-11 downstream of the inlet. Effects of different rib height to duct diameter ratios, BR, on thermal characteristics for a periodic ribbed duct flow are investigated. It is found that a pair of counter-rotating vortices (P-vortex) caused by the rib can induce impingement/attachment flows on the walls leading to greater increase in heat transfer over the test duct. In addition, the rise of BR values leads to the increase in heat transfer and friction loss. The maximum thermal performance is around 1.8 for the rib with BR=0.0725 where the heat transfer rate is about 4.0 times above the smooth duct at lower Reynolds number. © 2011 Elsevier Ltd. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Heat transfer in square duct fitted diagonally with angle-finned tape-Part 1: Experimental study(2012-05-01); ; Thiangpong, ChinarukThe paper presents an experimental study on turbulent flow and heat transfer characteristics in a square duct fitted diagonally with 30° angle-finned tapes. The tested duct has a square section and uniform heat-fluxed walls and the flow rate of air used as the test fluid is presented in terms of Reynolds number from 4000 to 23,000. The angle-finned straight tape in the present work is newly invented without previous investigations available. The insertion of the finned tape is performed with three ratios of fin pitch to duct height (PR= P/. H) at the fin attack angle of 30° with respect to the main flow direction. The finned tape inserted diagonally in the duct is expected to generate a longitudinal vortex flow pair through the heated duct. Influences of five fin-to-duct height ratios (BR= b/. H= 0.1-0.3) for each fin pitch on thermal and flow friction characteristics of the inserted duct are investigated. The experimental result shows that at smaller fin pitch spacing, the finned tape with BR= 0.3 provides the highest heat transfer and friction factor but the one with BR= 0.2 and PR= 1.0 yields the best thermal performance. The thermal performance of the newly invented finned tape turbulator is found to be much higher than that of the wire coil/twisted tape turbulator. © 2012 Elsevier Ltd. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Numerical prediction on laminar heat transfer in square duct with 30° angled baffle on one wall(2010-08-01); A numerical investigation on periodic laminar flow and heat transfer behaviors in a three-dimensional isothermal wall square duct fitted with 30° angled baffles on lower duct wall only is presented. The computations based on a finite volume method with the SIMPLE algorithm have been conducted for the fluid flow in terms of Reynolds numbers ranging from 100 to 2000. The angled baffles with attack angle of 30° are mounted periodically on the lower duct wall to generate a longitudinal vortex flow through the tested duct. Effects of different baffle height and three pitch length ratios on heat transfer and flow characteristics in the duct are investigated. The study shows that the longitudinal vortex flow created by the baffle helps to induce impinging flows over the baffle trailing end sidewall and the inter-baffle cavity wall resulting in drastic increase in heat transfer rate over the test duct. The computational results reveal that the Nusselt number ratio and the maximum thermal enhancement factor values for using the angled baffle are, respectively, found to be about 7.9 and 3.1 at Re=2000, BR=0.3 and PR=1.5. © 2010 Elsevier Ltd. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Thermal behavior in solar air heater channel fitted with combined rib and delta-winglet(2011-07-01); ; Effects of combined ribs and delta-winglet type vortex generators (DWs) on forced convection heat transfer and friction loss behaviors for turbulent airflow through a solar air heater channel are experimentally investigated in the present work. Measurements are carried out in the rectangular channel of aspect ratio, AR=10 and height, H=30mm. The flow rate is presented in the form of Reynolds numbers based on the inlet hydraulic diameter of the channel ranging from 5000 to 22,000. The cross-section shape of the rib placed on the absorber plate to create a reverse-flow is an isosceles triangle with a single rib height, e/H=0.2 and rib pitch, P<inf>l</inf>/H=1.33. Ten pairs of the DW with its height, b/H=0.4; transverse pitch, P<inf>t</inf>/H=1 and three attack angles (α) of 60°, 45° and 30° are introduced and mounted on the lower plate entrance of the tested channel to generate longitudinal vortex flows. The experimental results show that the Nusselt number and friction factor values for combined rib and DW are found to be much higher than those for the rib/DW alone. The larger attack angle of the DW leads to higher heat transfer and friction loss than the lower one. In common with the rib, the DW pointing upstream (PU-DW) is found to give higher heat transfer rate and friction loss than the DW pointing downstream (PD-DW) at a similar operating condition. In comparison, the largest attack angle (α=60°) of the PU-DW yields the highest increase in both the Nusselt number and friction factor while the lowest attack angle of the PD-DW provides the best thermal performance. © 2011 Elsevier Ltd. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 3D simulation of laminar flow and heat transfer in V-baffled square channelThe 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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Laminar periodic flow and heat transfer in square channel with 30° inclined baffles(2010-12-06); ; A numerical investigation has been carried out to study laminar flow and heat transfer characteristics in a three-dimensional isothermal wall square-channel with 30° staggered angled-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 100 to 1200. To generate a pair of stream wise counter-rotating vortex (P-vortex) flows through the tested channel, the baffles (like rectangular winglet) with the attack angle of 30° are mounted in tandem and staggered arrangement on both upper and lower walls of the test channel. Effects of different baffle heights at a single pitch ratio (PR=3) on heat transfer and pressure loss in the channel are studied. It is found that P-vortex flows created by the 30° baffle exist and help to induce impinging jets on a side wall and the upper and lower wall leading to drastic increase in heat transfer rate over the test channel. In addition, the increase in the baffle height results in the rise of Nusselt number and friction factor values. The computational results reveal that the optimum thermal enhancement factor of the baffle is about 2.9 at height of 0.15 times of the channel height.