KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 10

Some of the metrics are blocked by your
consent settings
Experimental investigation and ANN prediction of heat transfer enhancement in a heat exchanger tube utilizing twin corrugated twisted tapes
(2025-12-01)
Du, Y.
;
Wongcharee, K.
;
Thianpong, C.
;
Chuwattanakul, V.
;
Chamoli, S.
This report introduces a novel twin-corrugated twisted tape (TC-TT) insert designed to enhance heat transfer in exchanger tubes. The key innovation lies in the twin-corrugated structure, which generates a twin-swirl flow effect. The corrugated surface synergistically increases flow disturbance and expands the effective heat transfer area. The studied parameters were twist ratios (y/w = 3.0, 3.5, and 4.0) and corrugation angles (θ = 45°, 60°, 75°, and 90°) at 6,000 ≤ Re ≤ 20,000. The results show that using twin-corrugated twisted tapes increases the average Nusselt number by roughly 60–135% compared to a plain tube and by 16–35% compared to a conventional single-twisted tape, confirming the effectiveness of this structural modification. This enhancement is primarily due to the combination of double swirling-flows and enhanced effective heat transfer generated by the corrugated surface. Reducing the corrugation angle (θ) and twist ratio (y/w) led to increases in the Nusselt number (Nu), friction factor (f), and thermal performance factor (TPF). Within the studied range, the Nusselt number, friction factor, and thermal performance factor reached maximum values of 5.18, 0.153, and 1.44, respectively, at a twist ratio of 3.0, a corrugation angle of 45°, and Re = 6,000. Regression analysis was utilized to develop correlations for the Nu and f, considering the Re, Pr, y/w, and θ as influencing variables. The proposed correlations for predicting the friction factor and Nusselt number have errors within ±3% and ±2%, respectively. In addition, an artificial neural network (ANN) was developed for predicting the thermal performance values occurring below the experimental study range. The optimal state ANN model shows remarkable prediction accuracy with R<sup>2</sup> of 0.965.
Some of the metrics are blocked by your
consent settings
Multi objective optimization of TiO2/water nanofluid flow within a heat exchanger enhanced with loose-fit delta-wing twisted tape inserts
(2022-02-01)
Thianpong, C.
;
Wongcharee, K.
;
Safikhani, H.
;
Chokphoemphun, S.
;
Saysroy, A.
A hybrid technique by using TiO<inf>2</inf>/water nanofluid together with loose-fit delta-wing twisted tape (LTT-W) was employed for heat transfer enhancement. Experiments encompassed the TiO<inf>2</inf>-water nanofluids having concentration (φ) of 0.05%–0.15 vol% and the loose-fit delta-wing twisted tapes having two different wing arrangements (co- and counter arrangement) and three loose-fit ratios (c/D) of 0.0, 0.15, and 0.2. Experimental revealed that the system with combined enhancement technique gave considerably higher heat transfer than the one without enhancement technique. This can be attributed to the combined influences of swirling flow and higher thermal conductivity of the working fluid. Heat transfer rate and thermohydraulic performance rose with the decrease of loose-fit ratio and the rise of nanofluid concentration. The maximum thermohydraulic performance (TPF) of 1.36 was obtained at c/D = 0.0 and φ = 0.15%. The Multi-Objective Optimization (MOO) was also performed to study the optimal thermohydraulic performance by using GMDH models and NSGA II algorithms. The Pareto front, which contains very useful information, were extracted for both co and counter arrangements. The Pareto fronts have recognized very accurately, the best boundary of the experimental data with respect to the lowest friction factor and highest Nusselt number.
Some of the metrics are blocked by your
consent settings
Characterization of heat transfer and artificial neural networks prediction on overall performance index of a channel installed with arc-shaped baffle turbulators
(2021-08-01)
Promvonge, P.
;
Eiamsa-Ard, S.
;
Wongcharee, K.
;
Chuwattanakul, V.
;
Samruaisin, P.
Influences of baffle pitch ratio (p/w) and attached angle of arc-shaped baffles (AB) on the overall performance index (OPI) of a channel installed with AB have been carefully studied. In addition, an artificial neural network (ANN) model for predicting the OPI of the channel was reported. The arc-shaped baffle (AB) showed a significant effect on the augmented heat transfer and friction loss penalty as compared to a smooth channel. As the attached arc shaped angle (θ) increased, both Nusselt number and friction factor intensified. The Nusselt number values at θ = 90° were higher than those at θ = 20°, 40°, 60°, and 80° by up to 5.8%, 3.9%, 2.3% and 2.5%, respectively. The Nusselt number increased when the p/w was raised from 4.0 to 8.0 while the opposite trend was observed when the p/w was raised from 8.0 to 12.0. The maximum OPI of 1.43 was achieved by using the baffles with θ = 90° and pitch ratio of 8.0 at Re = 4000. For the development of ANN models for predicting the OPI, it was found that the best predictive performance was (R2) of 0.99843407 for ANN model of 3-50-50-1 with Tanh-Tanh activation function at epoch of 1200.
Some of the metrics are blocked by your
consent settings
Silver–water nanofluid flow and convective heat transfer in a microfin tube equipped with loose-fit twisted tapes
(2020-06-01)
Samruaisin, P.
;
Wongcharee, K.
;
Chuwattanakul, V.
;
Eiamsa-ard, S.
Heat transfer enhancement and performance of compact heat exchangers have been extensively studied in the past century for the purpose of promoting energy efficiency. Microfin tubes in single/two/multiple-phase flow heat exchangers into which twisted tape swirl generators are installed can promote heat transfer with a moderate pressure loss penalty. This article reports on the enhanced heat transfer of silver–water nanofluids in a microfin tube into which loose-fit twisted tapes are installed in a counter-flow arrangement. The experiments were carried out using nanofluids with various silver concentrations (0.007–0.03 vol%), loose-fit twisted tapes with clearance ratios (c/D) of 0.0 (tight-fit), 0.05, 0.075 and 0.1, for a twist ratio, y/W, of 2.0. The results indicate that the heat transfer rate (Nu) and pressure drop (f) increase with a decrease in clearance ratio (c/D) and increase in silver (Ag) nanoparticle concentration. Additionally, the thermal performance factor tends to increase with the decrease in Reynolds numbers.
Some of the metrics are blocked by your
consent settings
Effects of spiral start number and depth ratio of corrugated tube on flow and heat transfer characteristics in turbulent flow region
(2019-08-01)
Kongkaitpaiboon, V.
;
Promthaisong, P.
;
Chuwattanakul, V.
;
Wongcharee, K.
;
Eiamsa-ard, S.
Influence of spirally-corrugated tubes on heat transfer (Nu), pressure loss (f) and thermal enhancement factor (TEF) characteristics was numerically investigated. The physical models of spirally-corrugated tubes and also a straight circular tube were built for the comparative study. The predictions were performed for the spirally-corrugated tubes with spiral start numbers (N) of 2, 3, 4 and 5 and depth ratios (DR = e/D) of 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14 and 0.16 at Reynolds numbers of 5000, 8000, 14000 and 20000. The numerical results show that the spiral corrugated tubes created two types of flow structures: main swirl flows (appear around the core) and secondary swirl flows (appear near tube wall) which facilitate heat transfer between the fluid and the tube walls. The overall heat transfer depends on the competition between two effects: the positive effect of the stronger swirl intensity by increasing start number and the negative effect of the difficulty of fluid transfer into grooves by increasing depth ratio. For the investigated range, the corrugated tubes yield Nusselt numbers and thermal performance factors varying from 0.82 to 2.16 times and 0.66–1.2 times of the straight circular tube, respectively. The highest thermal enhancement factor (TEF) of 1.2 is achieved by using the tube with spiral start number of 4 having moderate depth ratio of 0.08 at Re = 5000.
Some of the metrics are blocked by your
consent settings
An Impingement Cooling Using Swirling Jets Induced by Helical Rod Swirl Generators
(2018-07-26)
Eiamsa-Ard, S.
;
Nuntadusit, C.
;
Wongcharee, K.
;
Chuwattanakul, V.
The heat transfer performance of swirling impinging jets (SIJs) was investigated and compared with that of the conventional jet (CIJ). The swirling jets were induced by helical rod inserts (HRs) fitted with pipe nozzles. The helical rod inserts with two different rod diameter to nozzle diameter ratios (d/D) of 0.46 and 0.64 were employed for comparison. Jet-to-plate distance to nozzle diameter ratio (L/D) was varied from 1 to 5 while Reynolds number was fixed at 20,000. The temperature and Nusselt number distributions on the impinged plate were measured and evaluated using thermochromic liquid crystal (TLC) sheet and image processing technique. The experimental results showed that the swirling jet (SJ) at d/D=0.64 gave higher average heat transfer rate than the SJ at d/D=0.46 up to 6.41% and the conventional jet (CJ) up to 35.05%. In addition, Nusselt number peak of swirling jets increased as jet-to-plate distance decreased.
Some of the metrics are blocked by your
consent settings
Influence of CuO/water nanofluid concentration and swirling flow on jet impingement cooling
(2017-11-01)
Wongcharee, K.
;
Chuwattanakul, V.
;
Eiamsa-ard, S.
CuO/water nanofluids were applied in swirling impinging jets for heat transfer enhancement. Swirling flow was induced by twisted tape inserts with twist ratios (y/w) of 1.43, 2.86 and 4.28. Impinging jets were injected at three different ratios of jet-to-plate spacing to nozzle diameter (H/d) of 2, 3 and 4. Nanofluids with CuO concentrations of 2.0%, 3.0% and 4.0% by volume were comparatively tested with water (a base fluid) for Reynolds numbers ranging from 1600 to 9400. Experimental results reveal that the nanofluids with concentrations of 2.0 and 3.0% by volume yield higher Nusselt numbers than the base fluid while the one with concentration of 4.0% shows opposite result. At the ratio of jet-to-plate spacing/nozzle diameter (H/d) of 2, Nusselt number slightly increases with decreasing twist ratio (y/w). However, at the ratios of jet-to-plate spacing/nozzle diameter (H/d) of 3 and 4, Nusselt number increases with increasing twist ratio. Over the studied range, the optimum condition is found at H/d = 2, y/w = 1.43, and nanofluid concentration of 2.0% by volume.
Some of the metrics are blocked by your
consent settings
Heat transfer of swirling impinging jets with TiO2-water nanofluids
(2017-01-01)
Wongcharee, K.
;
Chuwattanakul, V.
;
Eiamsa-ard, S.
An experimental work has been carried out to study the heat transfer of swirling impinging jets (SIJs) with TiO<inf>2</inf>-water nanofluids using thermochromic liquid crystal technique. Experiments were carried out at constant jet-to-target spacing ratio (L/D) of 1.0, 2.0, 3.0 and 4.0 for Reynolds numbers from 5000 to 20,000 by using nanofluids with TiO<inf>2</inf>concentrations of 0.5%, 1.0%, 1.5%, 2.0% and 2.5% by volume, twisted tapes with twist ratios (y/W) of 4.0, 5.0, 6.0 and 7.0. Conventional impinging jets (CIJs) and swirling impinging jets (SIJs) with pure water were also tested, for comparison. At similar operation conditions, swirling impinging jets (SIJs) offer superior heat transfer to conventional impinging jets. It is also found that the nanofluids with concentrations of 0.5%, 1.0%, 1.5% and 2.0% by volume give higher Nusselt numbers than the base fluid (water) while the one with concentration of 2.5% shows opposite result. Over the studied range, the optimum condition where the maximum Nusselt number is achieved at TiO<inf>2</inf>-water nanofluids with concentration of 2.0% by volume and y/W = 6.0.
Some of the metrics are blocked by your
consent settings
Heat transfer evaluation of turbulent flows through gear-ring elements
(2017-01-01)
Ruengpayungsak, K.
;
Wongcharee, K.
;
Thianpong, C.
;
Pimsarn, M.
;
Chuwattanakul, V.
Heat transfer and friction loss characteristics in tubular heat exchangers with gear-ring turbulators (GR-Ts) have been experimentally and numerically investigated. The GR-Ts with different free-space length ratios (SR = s/D = 1.0, 2.0 and 3.0) and tooth numbers (N = 8, 16 and 24), were experimentally tested under constant wall heat flux in turbulent flow (Reynolds numbers from 6000 to 20,000). Air was used as the working fluid. The behaviors in a plain tube and the tube with a conventional ring turbulators (N = 0) were also studied for comparison. The results show that utilizing tubes with GR-Ts leads to the increases of heat transfer coefficient and pressure loss as compared to those associated with the use of a plain tube. Heat transfer enhancement and friction increase with decreasing free-space length ratio (SR) and tooth number (N). Among the investigated inserts, the conventional ring turbulators (N = 0) with free-space length ratio, SR = 1.0 give the highest heat transfer rate and friction factor at 2.7 times and 15.5 times of those of the plain tube. However, the maximum thermal performance factor of 1.3 is obtained by using the GR-Ts with the largest free-space length ratio and maximum tooth number (SR = 3.0 and N = 24). At SR = 3.0, the GR-Ts with tooth numbers (N) of 0, 8, 16 and 24 yield thermal performance factors up to 1.24, 1.26, 1.28 and 1.3, respectively. The numerical results are given for a better understanding of flow and heat transfer characteristics associated with the use of GR-Ts.
Some of the metrics are blocked by your
consent settings
Turbulent heat transfer through a heat exchanger with porous twisted tape inserts
(2009-01-01)
Eiamsa-Ard, S.
;
Wongcharee, K.
;
Rattanawong, S.
;
Eiamsa-Ard, P.
;
Pimsarn, M.
In this present work, the influences of the porous twisted tape (PT) on the heat transfer and the pressure loss are studied experimentally. The comparative experiments are conducted in the tube fitted with the PT or typical twisted tape (TT) at different twist ratios, y/w = 4.0 and 5.0, in the Reynolds number ranging from 4800 to 16,000 under uniform heat flux conditions. In the experiments, the PT inserts generate swirls that modify the near wall velocity profile resulted in improvement of the heat transfer rate. The experimental results reveal that the heat transfer rates increase with decreasing twist ratio (y/w) for all twisted tapes used in the experiments. The heat transfer rates increase up to 71% with the help of the PT. The increases in average Nusselt numbers of using PT and TT are found to be 48% and 22%, respectively, over those of the corresponding plain tube. However, PT causes a considerable increase in friction factor. The mean increases of friction factors for PT and TT are respectively, about 3.14 and 2.45 times in comparison with that for the plain tube. Mean friction factor and Nusselt number for PT, are respectively 28% and 21% higher than those for TT. In addition, the empirical correlations of the Nusselt number and friction factor are also reported.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results