Promvonge, Pongjet

Preferred name

Promvonge, Pongjet

Alternative Name

Promvonge, P.

Main Affiliation

School of Engineering

pongjet.pr@kmitl.ac.th

Now showing 1 - 10 of 23

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Numerical study on heat transfer of turbulent channel flow over periodic grooves
(2008-08-01)
Eiamsa-ard, Smith
;
Promvonge, Pongjet
A numerical investigation of turbulent forced convection in a two-dimensional channel with periodic transverse grooves on the lower channel wall is conducted. The lower wall is subjected to a uniform heat flux condition while the upper wall is insulated. To investigate turbulence model effects, computations based on a finite volume method, are carried out by utilizing four turbulence models: the standard k - ε, the Renormalized Group (RNG) k - ε, the standard k - ω, and the shear stress transport (SST) k - ω turbulence models. Parametric runs are made for Reynolds numbers ranging from 6000 to 18,000 with the groove-width to channel-height ratio (B/H) of 0.5 to 1.75 while the groove pitch ratio of 2 and the depth ratio of 0.5 are fixed throughout. The predicted results from using several turbulence models reveal that the RNG and the k - ε turbulence models generally provide better agreement with available measurements than others. Therefore, the k - ε model is selected to use in prediction of this complex flow. In addition, the results of the heat transfer coefficient, friction factor, skin friction coefficient and thermal enhancement factor are also examined. It is found that the grooved channel provides a considerable increase in heat transfer at about 158% over the smooth channel and a maximum gain of 1.33 on thermal performance factor is obtained for the case of B/H = 0.75. This indicates that the reverse/re-circulation flow in a channel with transverse grooves can improve the heat transfer rate. © 2008 Elsevier Ltd. All rights reserved.
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Turbulent convection in round tube equipped with propeller type swirl generators
(2009-04-01)
Eiamsa-ard, Smith
;
Rattanawong, Sarawut
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Promvonge, Pongjet
This article is aimed at studying the heat transfer, friction loss and enhancement efficiency behaviors in a heat exchanger tube equipped with propeller type swirl generators at several pitch ratios (PR). The investigation is performed for the Reynolds number ranging from 4000 to 21,000 under a uniform heat flux condition. The experiments are also undertaken for several blade numbers of the propeller (N = 4, 6, and 8 blades) and for different blade angles (θ = 30°, 45°, and 60°). The influences of using the propeller rotating freely, on heat transfer enhancement, pressure loss, and enhancement efficiency, are reported. In the experiments, the swirl generator is used to create a decaying swirl in the tube flow. Average Nusselt numbers are determined and also compared with those obtained from other similar cases. The experimental results indicate that the tube with the propeller inserts provides considerable improvement of the heat transfer rate over the plain tube around 2.07 to 2.18 times for PR = 5, blade angles θ = 60° and N = 8. The use of the propeller leads to maximum enhancement efficiency up to 1.2. Thus, because of strong swirl or rotating flow, the propellers and their blade numbers become influential upon the heat transfer enhancement. The increase in friction factor from using the propeller is found to be 3-18 times over the plain tube. Correlations for Nusselt number (Nu) and friction factor (f) for the inserted tube are provided and the performance evaluation criterion to access the real benefits in using the swirl generators of the enhanced tube is also determined. © 2009 Elsevier Ltd. All rights reserved.
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Heat transfer characteristics in a tube fitted with helical screw-tape with/without core-rod inserts
(2007-02-01)
Eiamsa-ard, Smith
;
Promvonge, Pongjet
Effects of insertion of a helical screw-tape with or without core-rod in a concentric double tube heat exchanger on heat transfer and flow friction characteristics are experimentally investigated. The heat exchanger has the outer and the inner tube diameters of 50 mm (D<inf>o</inf>) and 25 mm (D) where the cold and the hot waters used as the test fluids are in shell and tube sides, respectively. The stainless steel helical screw-tape has the geometrical dimensions of width (W) 17 mm with the clearance to the tube wall (D - W) / 2 = 4 mm. Thus, the insertion of the screw-tape in the tube is considered as a loose-fit. In the experiment, the loose-fit helical tape with or without core-rod, is inserted in the inner tube of the heat exchanger and the hot water enters the tube based on its Reynolds number in a range of 2000 to 12,000. The experimental results show that the increases in average Nusselt number of using the loose-fit, helical tape with and without core-rod are found to be 230% and 340%, respectively, over the corresponding plain tube. It is worth noting that for the loose-fit, helical tape without core-rod, the friction factor is around 50% less than that for the one with core-rod while the Nusselt number is about 50% higher. Furthermore, the enhancement efficiency of the helical screw-tapes varies between 1.00 and 1.17, 1.98 and 2.14, for the tapes with and without core-rod, respectively. © 2006 Elsevier Ltd. All rights reserved.
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Turbulent flow heat transfer and pressure loss in a double pipe heat exchanger with louvered strip inserts
(2008-02-01)
Eiamsa-ard, Smith
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Pethkool, Somsak
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Thianpong, Chinaruk
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Promvonge, Pongjet
In the present work, heat transfer and friction characteristics were experimentally investigated, employing louvered strips inserted in a concentric tube heat exchanger. The louvered strip was inserted into the tube to generate turbulent flow which helped to increase the heat transfer rate of the tube. The flow rate of the tube was in a range of Reynolds number between 6000 and 42,000. The turbulent flow devices were consisted of (1) the louvered strips with forward or backward arrangements, and (2) the louvered strip with various inclined angles (θ = 15°, 25° and 30°), inserted in the inner tube of the heat exchanger. In the experiment, hot water was flowed through the inner tube whereas cold water was flowed in the annulus. The experimental data obtained were compared with those from plain tubes of published data. Experimental results confirmed that the use of louvered strips leads to a higher heat transfer rate over the plain tube. The increases in average Nusselt number and friction loss for the inclined forward louvered strip were 284% and 413% while those for the backward louvered strip were 263% and 233% over the plain tube, respectively. In addition, the use of the louvered strip with backward arrangement leads to better overall enhancement ratio than that with forward arrangement around 9% to 24%. © 2007 Elsevier Ltd. All rights reserved.
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Enhancement of heat transfer in a tube with regularly-spaced helical tape swirl generators
(2005-01-01)
Eiamsa-ard, Smith
;
Promvonge, Pongjet
Influence of helical tapes inserted in a tube on heat transfer enhancement is studied experimentally. A helical tape is inserted in the tube with a view to generating swirl flow that helps to increase the heat transfer rate of the tube. The flow rate of the tube is considered in a range of Reynolds number between 2300 and 8800. The swirling flow devices consisting of: (1) the full-length helical tape with or without a centered-rod, and (2) the regularly-spaced helical tape, are inserted in the inner tube of a concentric tube heat exchanger. Hot air is passed through the inner tube whereas cold water is flowed in the annulus. The experimental data obtained are compared with those obtained from plain tubes of published data. Experimental results confirmed that the use of helical tapes leads to a higher heat transfer rate over the plain tube. The full-length helical tape with rod provides the highest heat transfer rate about 10% better than that without rod but it increased the pressure drop. To overcome this, different free-spacing ratio (s = L <inf>s</inf>/L<inf>h</inf>) of 0.5, 1.0, 1.5, and 2.0 were examined. It was found that the space ratio value should be about unity for Re < 4000. The regularly-spaced helical tape inserts at s = 0.5 yields the highest Nusselt number which is about 50% above the plain tube. © 2004 Elsevier Ltd. All rights reserved.
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Experimental investigation of heat transfer and flow friction in a circular tube fitted with regularly spaced twisted tape elements
(2006-12-01)
Eiamsa-ard, Smith
;
Thianpong, Chinaruk
;
Promvonge, Pongjet
Experimental investigation of heat transfer and friction factor characteristics in a double pipe heat exchanger fitted with regularly spaced twisted tape elements, were studied. The inner and outer diameters of the inner tube are 50.6 and 25.8 mm, respectively and cold and hot water were used as working fluids in shell side and tube side. The twisted tapes were made of the stainless steel strip with thickness of 1 mm and the length of 1500 mm. They were inserted in the test tube section in two different cases: (1) full-length typical twisted tape at different twisted ratios (y = 6.0 and 8.0), and (2) twisted tape with various free space ratios (S = 1.0, 2.0, and 3.0). The results, obtained from the tube with twisted tape insert, were compared with those without twisted tape. The results show that the heat transfer coefficient increased with twist ratio (y). Whereas the increase in the free space ratio (S) would improve both the heat transfer coefficient and friction factor. The results from each case were correlated for Nusselt number and friction factor. Subsequently, the predicted Nusselt number and friction factor from the correlations were plotted to compare with the experimental data. It was found that Nusselt number was within ± 15% and ± 10% for friction factor. © 2006 Elsevier Ltd. All rights reserved.
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Performance assessment in a heat exchanger tube with alternate clockwise and counter-clockwise twisted-tape inserts
(2010-03-01)
Eiamsa-ard, Smith
;
Promvonge, Pongjet
The article presents an experimental study of turbulent heat transfer and flow friction characteristics in a circular tube equipped with two types of twisted tapes: (1) typical twisted tapes and (2) alternate clockwise and counterclockwise twisted tapes (C-CC twisted tapes). Nine different C-CC twisted tapes are tested in the current work; they included the tapes with three twist ratios, y/w = 3.0, 4.0 and 5.0, each with three twist angles, θ = 30o, 60o and 90o. The experiments have been performed over a Reynolds number range of 3000-27,000 under uniform heat flux conditions, using water as working fluid. The obtained results reveal that the C-CC twisted-tapes provide higher heat transfer rate, friction factor and heat transfer enhancement index than the typical twisted-tapes at similar operating conditions. The results also show that the heat transfer rate of the C-CC tapes increases with the decrease of twist ratio and the increase of twist angle values. Depending on Reynolds number, twist ratio and twist angle values, the mean Nusselt numbers in the tube fitted with the C-CC twisted tapes are higher than those with the typical ones and the plain tube around 12.8-41.9% and 27.3-90.5%, respectively. The maximum heat transfer enhancement indexes of the C-CC twisted tapes with θ = 90o for y/w = 3.0, 4.0 and 5.0, are 1.4, 1.34 and 1.3, respectively. In addition, correlations of the Nusselt number and the friction factor for using the C-CC twisted tapes are also determined. Both predicted Nusselt number and friction factor are within ±15% and ±15% deviation compared to the experimental data. © 2009 Elsevier Ltd. All rights reserved.
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Numerical investigation of the thermal separation in a Ranque-Hilsch vortex tube
(2007-03-01)
Eiamsa-ard, Smith
;
Promvonge, Pongjet
The application of a mathematical model for the simulation of thermal separation in a Ranque-Hilsch vortex tube is presented in this paper. The modelling of turbulence for compressible, swirling flows used in the simulation is discussed. The work has been carried out in order to provide an understanding of the physical behaviors of the flow, pressure, temperature in a vortex tube. A staggered finite volume approach with the standard k-ε turbulence model and an algebraic stress model (ASM) is used to carry out all the computations. To investigate the effects of numerical diffusion on the predicted results, the second-order upwind (SOU) and the QUICK numerical schemes are used and compared with the first-order upwind and the hybrid schemes. The computations show that the differences of results obtained from using the various schemes are marginal. In addition, results predicted by both turbulence models generally are in good agreement with measurements but the ASM performs better agreement between the numerical results and experimental data. The computations with selective source terms of the energy equation suppressed show that the diffusive transport of mean kinetic energy has a substantial influence on the maximum temperature separation occurring near the inlet region. In the downstream region far from the inlet, expansion effects and the stress generation with its gradient transport are also significant. © 2006 Elsevier Ltd. All rights reserved.
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Heat transfer distribution and flow characteristics in a channel with perforated-baffles
(2022-11-01)
Eiamsa-ard, Smith
;
Sripattanapipat, Somchai
;
Saysroy, Anucha
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Promvonge, Pongjet
;
Maruyama, Naoki
The current paper reports the prediction of heat transfer performance of a channel with a modified perforated-baffle in a square wings (SW-PB) form. Numerical results include flow/temperature field, local heat transfer distribution, and thermal performance of a channel installed with the transverse solid baffle (TB), perforated-baffle (PB), and perforated-baffle with square wings (SW-PB). The simulation results demonstrated that TB brought a large recirculation flow, PB induced small recirculation and SW-PB produced several impinging jets as well as recirculation flows. Heat transfer rates given by PB were lower than those provided by TB and SW-PB by around 6.8% and 7.3%, respectively which were accompanied by lower friction losses by about 11.8% and 3.6%, respectively. Although, SW-PB gave higher heat transfer, the assessment of thermal performance factor (TPF) showed that the benefit from lower friction losses was more important. Under the same pumping power, TPFs assisted by SW-PB were higher than that assisted by PB and TB by 6.0% and 3.3%, respectively. The highest TPF of 1.2 was captured by SW-PB at Re = 9,000.
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Thermal characteristics in a heat exchanger tube fitted with dual twisted tape elements in tandem
(2010-01-01)
Eiamsa-ard, Smith
;
Thianpong, Chinaruk
;
Eiamsa-ard, Petpices
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Promvonge, Pongjet
The paper presents a comparative investigation of enhanced heat transfer and pressure loss by insertion of single twisted tape, full-length dual and regularly-spaced dual twisted tapes as swirl generators, in a round tube under axially uniform wall heat flux (UHF) conditions. The investigation encompassed the Reynolds number based on the inlet tube diameter (D) ranging from 4000 to 19,000. The experiments are performed using single twisted tapes and full-length dual twisted tapes with three different twist ratios (y/w = 3.0, 4.0 and 5.0) and also regularly-spaced dual twisted tapes with three different space ratios (s/D = 0.75, 1.5 and 2.25). The effects of major parameters on heat transfer and friction factor are discussed and the results from both single and dual twisted tape inserts are compared with those from the plain tube. The result shows that the heat transfer of the tube with dual twisted tapes is higher than that of the plain tube with/without single twisted tape insert. For both single twisted tape and full-length dual twisted tapes, Nusselt number (Nu) and friction factor (f) tend to increase with decreasing twist ratio (y/w). The average Nusselt number and friction factor in the tube fitted with the full-length dual twisted tapes at y/w = 3.0, 4.0 and 5.0, are respectively 146%, 135% and 128%; and 2.56, 2.17 and 1.95 times of those in the plain tube. For the regularly-spaced dual twisted tapes, the heat transfer rate is decreased with increasing space ratio (s/D). The average Nusselt numbers in the tube fitted with the regularly-spaced dual twisted tapes (s/D) of 0.75, 1.5 and 2.25 are respectively, 140%, 137% and 133% of that in the plain tube. With the similar trend mentioned above, all dual twisted tapes with free spacing yield lower heat transfer enhancement in comparison with the full-length dual twisted tapes (s/D = 0.0). © 2009 Elsevier Ltd. All rights reserved.

Promvonge, Pongjet

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