Pimsarn, Monsak

Preferred name

Pimsarn, Monsak

Alternative Name

Pimsarn, M.

Main Affiliation

School of Engineering

monsak.pi@kmitl.ac.th

Now showing 1 - 10 of 15

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Influence of divergence tapered V-baffles on heat transfer behaviors in a rectangular channel
(2026-05-15)
Keaitnukul, Warin
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Pingta, Supapat
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Phila, Arnut
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Wongcharee, Khwanchit
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Maruyama, Naoki
This study examines the effects of Divergence Tapered V-Baffle (henceforth DT-VB) regarding the heat transfer and friction loss behavior within the rectangle-shaped duct. The baffle attack angles (α) were set at 45°, 60°, 75°, and 90°. The experimental results indicated that as Reynolds numbers increased, the Nusselt numbers exhibited an upward trend, while the friction values showed a corresponding decrease. The Nusselt number improved consistently as the attack angle decreased, with baffles at a 60° attack angle producing the highest friction loss, followed by those at 45°, 75°, and 90°. Among the configurations tested, the 45° attack angle demonstrated the best thermal performance due to its relatively low friction loss and enhanced heat transfer. The highest thermal performance factor (TPF) of 2.13 was attained at a 45° attack angle and a Reynolds number of 6,000.
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Thermal characterization in a circular tube fitted with inclined horseshoe baffles
(2015-01-22)
Promvonge, Pongjet
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Tamna, Sombat
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Pimsarn, Monsak
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Thianpong, Chinaruk
In the present study, the influence of inclined horseshoes baffles placed repeatedly in a tubular heat exchanger on heat transfer rate, friction factor and thermal enhancement factor are experimentally determined. The horseshoe baffle elements with an inclination angle of 20° were inserted periodically into the test tube at three different baffle-pitch ratios (P<inf>R</inf> = 0.5, 1.0 and 2) and -width or blockage ratios (B<inf>R</inf> = 0.1, 0.15 and 0.2). The experiment was conducted in the test tube having a uniform heat-fluxed wall by varying turbulent airflow to obtain Reynolds number in a range of 5300-24,000. The experimental results revealed that the tube fitted with inclined horseshoes baffles provides considerable improvement of the heat transfer rate over the plain tube around 92-208% while the friction factor is increased at about 1.76-6.37 times. To access the real benefits for the inclined horseshoes baffles inserted in plain tube, thermal performance factor is examined and found to be in the range of 1.34-1.92 at which the maximum obtained at P<inf>R</inf> = 0.5 and B<inf>R</inf> = 0.1 is considerably higher than that for published inserted devices. Correlations for Nusselt number and friction factor for the oblique horseshoe-baffled tube are also proposed.
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Turbulent heat transfer in a microfin tube with twisted tape insert
(2012-12-01)
Eiamsa-Ard, Smith
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Kongkaitpaiboon, Vichan
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Eiamsa-Ard, Petpices
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Pimsarn, Monsak
The purpose of the present study is to investigate experimentally the heat transfer, turbulent flow friction and thermal performance factor characteristics in a microfin tube with a twisted tape insert. In the experiment, heat transfer augmentation is expected from both the turbulence of flow near the tube wall produced by fin surface and the swirling flow generated by the twisted tape. Effect of the twisted tape at different twist ratios of y/W = 3, 4 and 5 on the heat transfer enhancement characteristics is also reported. In the experimental set-up, cold water was passed through the uniform heat flux tube in a range of Reynolds number between 5000 and 17000. The experimental results obtained are compared with those from plain tubes. The results show that the thermal performance from using the microfin tube fitted with twisted tape is considerably higher than that from the microfin tube alone. The Nusselt numbers and friction factors are found to be, respectively, 3.0, 4.0 and 5.0 times over the microfin tube alone for the microfin tube combined with twisted tape. In addition, the results demonstrate that as the twist ratio (y/W) decreases, the twisted tape will give better heat transfer enhancement. The microfin tube combined with twisted tape provides higher thermal performance factor than those the microfin tube alone around 172%, 142% and 124%, respectively, for y/W = 3, 4 and 5. The results were correlated in the form of Nusselt number as a function of Reynolds number, Prandtl number and twist ratio.
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Heat transfer evaluation of turbulent flows through gear-ring elements
(2017-01-01)
Ruengpayungsak, K.
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Wongcharee, K.
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Thianpong, C.
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Pimsarn, M.
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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.
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Heat transfer enhancement in a channel with rib-groove turbulators
(2010-04-01)
Kaewkohkiat, Y.
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Kongkaitpaiboon, V.
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Eiamsa-Ard, S.
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Pimsarn, M.
This paper presents the effects of the rib-groove turbulators on the heat transfer and friction characteristics in a rectangular channel. The experiments encompass the Reynolds number range from 1800 to 10,000; pitch ratios (PR=P/e) 6.6-13.3 by using air as the working fluid. The obtained results demonstrate that heat transfer rate in term of Nusselt number (Nu) increases with the increase of Reynolds number, whereas friction factor (f) shows the opposite trend. Both Nusselt number and friction factor increase with decreasing pitch ratio. It is also observed that heat transfer rate and friction factor for the channels with rib-groove turbulators are higher than those for the smooth channel under similar test conditions. In addition, the correlations for heat transfer rate in term of Nusselt number (Nu) and friction factor (f) for channel with rib-groove turbulators are also presented. © 2010 American Institute of Physics.
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Performance of a heat exchanger with compound inclined circular-rings and twisted tapes
(2022-09-01)
Pimsarn, M.
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Samruaisin, P.
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Thianpong, C.
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Ruengpayungsak, K.
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Eiamsa-Ard, P.
Optimization was done of the aerothermal performance factor (η) of a tube into which a combination of inclined circular-rings (ICRs) and twisted-tapes (TTs) were installed. The key contribution of this research is determination of the appropriate ICR and TT sizes to produce the best heat exchanger performance. An ICR's purpose is to produce counter-rotating vortices, whereas the TT's role is to create swirl flow within a tube to improve turbulence and transfer cold fluid from the core region to the heated-wall zone. The influence of circular-ring inclination angle (α = 30o, 45o, 60o and 90o), number of twisted tapes (H = 2, 4, and 6) and twist ratios (TR = 1.0, 2.0, and 3.0) on heat transfer and pressure losses were assessed to determine an optimum η condition. The heat transfer and friction factor tend to increase with H values and decreasing TR. The heat transfer of ICRs together with TTs is higher than in a plain tube by up to 128.7% and 155.3%, respectively, while it is better than the transverse circular-ring (α = 90o) and twisted-tape by up to 116.9% and 146.5%, respectively. Furthermore, due to moderate heat transfer and low pressure losses, a maximal η of 1.66 was achieved for α = 30o, H = 2 and TR = 3.0 within the examined range.
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Intensification of thermo-hydraulic performance in heat exchanger tube inserted with multiple twisted-tapes
(2018-05-25)
Piriyarungrod, N.
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Kumar, Manoj
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Thianpong, C.
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Pimsarn, M.
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Chuwattanakul, V.
The present work presents the thermo-hydraulic characteristics in the heat exchanger tube inserted with multiple-twisted tapes (M-TT). Multiple-twisted tapes consisted of a larger twisted tape and small twisted tapes which were placed along with the larger twisted tape. The study encompassed 6 different twist ratios of the small twisted tapes (y/w = 2.5, 5, 10, 15, 20 and 25) and 5 different numbers of the small twisted tapes (N = 2, 3, 4, 5 and 6). Experiments were conducted under uniform wall heat flux condition by using air as the testing fluid for Reynolds numbers from 6000 to 20,000. A large single twisted tape in a tight-fit form (T-TT) and that in a loose-fit form (L-TT) were tested as the reference cases for comparison. The experimental results found that the use of multiple-twisted tapes (M-TT) with N = 3, 4, 5 and 6 leads to the considerable increases in heat transfer enhancement and friction factor as compared to those of single twisted tape. For multiple twisted tapes (M-TT), Nusselt number (Nu), friction factor (f) and thermo-hydraulic performance factor (η) increase with increasing number (N) and decreasing twist ratio (y/w) of small twisted tapes. The maximum thermo-hydraulic performance factor of 1.2 is obtained by the use of M-TT with N = 6 and y/w = 2.5. In addition, the numerical work on flow and thermal behaviors was also performed for a better understanding of heat transfer mechanisms.
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Heat transfer characterization in a tubular heat exchanger with V-shaped rings
(2017-01-05)
Chingtuaythong, Witoon
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Promvonge, Pongjet
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Thianpong, Chinaruk
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Pimsarn, Monsak
This article presents the influence of V-shaped rings (or V-ring) placed in a uniform heat-fluxed tube on heat transfer and flow resistance characteristics. In the current experiment, the V-ring elements with attack angle of 30° are inserted into the tube with four relative ring-pitches (R<inf>P</inf> = P/D = 0.5, 1.0, 1.5 and 2.0) and three ring blockage ratios (R<inf>B</inf> = e/D = 0.1, 0.15 and 0.2). Air as the test fluid flows through the tube for Reynolds number of about 5000–25,000. The experimental results reveal that the V-ring can considerably enhance the heat transfer rate up to 5.8 times above the plain tube whereas the friction factor is up to 82 times. The increase in R<inf>B</inf> leads to higher heat transfer and friction loss while the increment in R<inf>P</inf> provides the reversing trend. The thermal enhancement factor of the V-ring is in the range of 1.36–1.63 where its maximum regarded as the optimum point is at R<inf>B</inf> = 0.1 and R<inf>P</inf> = 1.0. In comparison with other vortex-flow devices, the V-ring yields much higher thermal performance than the published inclined rings, wire-coils and twisted tapes. Nusselt number and friction factor correlations for the V-ring are also determined.
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Influence of bed height and drying temperature on shrimp drying characteristics using a fluidized-bed dryer
(2023-08-01)
Nanan, K.
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Eiamsa-ard, S.
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Chokphoemphun, S.
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Kumar, Manoj
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Pimsarn, M.
The aim of this work was to study shrimp drying in a fluidized-bed dryer to develop a process that performs better than traditional (sun dried) shrimp production. In these experiments, the influence of shrimp size (small, medium and large), bed height (h/D = 0.33, 0.66 and 1.0) and air temperature (60, 70 and 80 °C) on the drying rate were studied under a constant blower power. The experimental results showed that the moisture content of boiled shrimp decreased with an increased drying temperature due to the consequently higher temperature differential between the hot air and the shrimp. When the bed height (h/D) was reduced, shrimp moisture removal increased, but it also increased when shrimp size decreased. Moreover, the production rate of dried shrimp under a bed height h/D = 1.0 and drying temperature of 80 °C yielded the highest dried shrimp production rate of 4.83, 4.21 and 3.72 kg/h for small, medium and large shrimps, respectively.
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Thermal evaluation of flow channels with perforated-baffles
(2023-05-01)
Eiamsa-ard, Smith
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Phila, Arnut
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Wongcharee, Khwanchit
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Pimsarn, Monsak
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Maruyama, Naoki
The influences of perforated-baffles on the local Nusselt number (Nu) and thermo-hydraulic behaviors were comprehensively studied using thermochromic liquid crystal sheet. The perforated-baffles were designed in two forms: perforated-baffle (PB) and perforated-baffle with square wings (SW-PBs). Transverse solid baffles (TBs) were also tested for an assessment. All baffles had an identical height of 12 mm (e/H = 0.3). Experimental results showed that SW-PBs offered better Nu than PBs. It is also seen that PBs and SW-PBs caused lower pressure loss than TBs by around 20.49% and 13.98%, respectively. The reduction of friction loss was primarily due to the baffle perforation. In addition, the PBs yielded the thermal performance factors (TPF) up to 1.01 at the lowest Reynolds number of 6000.

Pimsarn, Monsak

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