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 68

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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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A study on dynamic response of functionally graded sandwich beams under different dynamic loadings
(2018-08-14)
Songsuwan, Wachirawit
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Pimsarn, Monsak
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Wattanasakulpong, Nuttawit
In this research, free and forced vibration of functionally graded sandwich beams is considered using Timoshenko beam theory which takes into account the significant effects of transverse shear deformation and rotary inertia. The governing equations of motion are formulated from Lagrange's equations and they are solved by using The Ritz and Newmark methods. The results are presented in both tabular and graphical forms to show the effects of layer thickness ratios, boundary conditions, length to height ratios, etc. on natural frequencies and dynamic deflections of the beams. According to the numerical results, all parametric studies considered in this research have significant impact on free and forced behaviour of the beams; for example, the frequency is low and the dynamic deflection is large for the beams which are hinged at both ends.
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Optimum airflow to reduce particle contamination inside welding automation machine of hard disk drive production line
(2015-03-01)
Thongsri, Jatuporn
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Pimsarn, Monsak
Welding automation machine (WAM), used for welding minute components to the head gimbal assembly (HGA) of a hard disk drive (HDD), needs to operate in a strictly clean environment. In today’s HDD factories, to prevent airborne particle contamination to the WAM, Fan Filter Units (FFUs) are installed on top of it to supply clean air and blow away outside airborne micro particles, keeping the microenvironment clean. Furthermore, the mass of the clean air should also carry away harmful particles generated inside the microenvironment. In this research, numerical simulation of airflow inside a WAM was performed in order to verify these cleaning functions of the airflow. A transition shear stress transport turbulence model was employed to simulate airflow from the FFUs through and out of the microenvironment. The simulation results showed that the airflow from the FFUs truly performs the two cleaning functions as intended. Moreover, they also revealed that the optimum air speed, the speed resulting in the lowest particle counts, is in the range of 0.35–0.55 m/s. Our findings can be useful for developers who may use FFUs to reduce particle counts in the environment of other types of industrial machinery.
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Tooth profile modifications for optimum dynamic load in spur gears based on pseudo-interference stiffness estimation method
(2005-01-01)
Pimsarn, Monsak
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Kazerounian, Kazem
A systematic methodology combining optimization, three dimensional analytical rigid body dynamics and a novel method, namely, Pseudo-Interference Stiffness Estimation method (PISE) []- [2], is proposed to dramatically reduce gear design time and improve the spur gear system dynamic performance. The main aim of this methodology is to search for the profiles of tooth crowning and shaving that eventually lead to the optimum dynamic tooth load in the gear mesh. An example of the detailed design study is numerically investigated. The results show that the dynamic tooth load can be reduced to up to 50 percent of its original value. However, this reduction is only valid at the operating ranges of the design load and design speed. It is also found that the effect of profile modification on the dynamic response of the gear system was mostly observed to be a reduction in the peak dynamic tooth load at the resonance speed. Later, the investigation of gear tooth durability was conducted to validate an improvement of gear life. The rating factors given in AGMA publication, Hertzian contact stress, bending fatigue stress, flash temperature and PV index are employed in gear durability determination. The results show that, with the reduction of 50 percent in dynamic tooth load, the reductions in PV index, bending fatigue, Hertzian contact stress, and flash temperature can be achieved up to 64, 58, 28 and 39 percent, respectively. Copyright © 2005 by ASME.
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Performance assessment in a heat exchanger tube with opposite/parallel wing twisted tapes
(2015-01-01)
Eiamsa-Ard, S.
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Pimsarn, M.
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Thianpong, C.
The thermohydraulic performance in a tube containing a modified twisted tape with alternate-axes and wing arrangements is reported. This work aims to investigate the effects of wing arrangements (opposite (O) and parallel (P) wings) at different wing shapes (triangle (Tri), rectangular (Rec), and trapezoidal (Tra) wings) and on the thermohydraulic performance characteristics. The obtained results show that wing twisted tapes with all wing shape arrangements (O-Tri/O-Rec/O-Tra/P-Tri/P-Rec/P-Tra) give superior thermohydraulic performance and heat transfer rate to the typical twisted tape. In addition, the tapes with opposite wing arrangement of O-Tra, O-Rec, and O-Tri give superior thermohydraulic performances to those with parallel wing arrangement of P-Tra, P-Rec, and P-Tri around 2.7%, 3.5%, and 3.2%, respectively.
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Numerical analysis of the influence of press-fitting on the fatigue life of railway axle
(2024-05-17)
Nwe, Theingi
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Pimsarn, Monsak
This study investigated the influence of press-fitting on the stress concentration and fatigue life of axles. Models of finite element analysis (FEA) with and without the press-fitting effect were developed using Abaqus software. These models were used to analyze the axle strength and profile the stress histories under various loads and running conditions, such as bending load, wheel-rail contact force, lateral force, and press-fitting force. Their combined loads were responsible for the axle fracture. Also, the prediction of fatigue life was extended to a three-dimensional stress state under fully reversed cyclic loading and variable overload spectra using commercial Fe-safe software with a strain-based Brown-Miller Morrow fatigue algorithm. With the press-fitting effect, the maximum von Mises stress at the groove notch transition zone of the axle was 6% higher than without the press-fitting effect. Press-fitting reduced the fatigue life of an axle by 37% compared to the ones without press-fitting, and the most damage happened at the same node as the maximum von Mises stress.
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Heat Transfer Analysis in a Channel Mounted with In-Line Downward-Facing and Staggered Downward-Facing Notched Baffles
(2025-09-01)
Phila, A.
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Keaitnukul, W.
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Kumar, M.
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Pimsarn, M.
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Chokphoemphun, S.
This study presents a comprehensive analysis of heat transfer enhancement, flow resistance, and thermal performance in rectangular channels equipped with three baffle configurations: conventional transverse baffles (TBs), in-line downward-facing notched baffles (IDF-NBs), and staggered downward-facing notched baffles (SDF-NBs). The influence of the pitch-to-baffle height ratio (P/e), ranging from 2.0 to 10, was examined across Reynolds numbers from 6000 to 24,000. Results indicate that a P/e ratio of 6.0 consistently yielded the highest Nusselt numbers across all configurations. While the TB configuration produced significant heat transfer at P/e= 6.0, it experienced a substantial friction penalty, with its best thermal enhancement factor (TEF = 1.168) observed at P/e = 8.0. The IDF-NB configuration achieved optimal performance at P/e = 6.0 with a TEF of 1.257, offering a better balance between heat transfer and flow resistance. The SDF-NB arrangement outperformed all other cases, delivering the highest Nusselt number (Nu = 116.9), TEF (1.362), and improved flow reattachment, primarily due to enhanced mixing from the staggered layout. These findings demonstrate that the staggered notched baffle configuration at P/e = 6.0 offers the most effective thermal performance enhancement among the configurations studied.
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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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Numerical simulation of two-dimensional laminar unsteady flow past a right trapezoidal cylinder at low Reynolds number: Study of sharpening angle, time step, grid independence and domain size
(2018-08-14)
Lamtharn, Sodsai
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Pimsarn, Monsak
Numerical simulation of two-dimensional laminar unsteady flow past a right trapezoidal cylinder at low Reynolds number (Re = 100), zero of the flow approaching angle and sharpening angle of the right trapezoidal of 22.5° with a side ratio B/A = 1 are carried out to provide moreapplicable data for engineering design of barred tee in aspect of structural integrity. A finite volume method, non-uniform meshing with second-order implicit time discretization into eight-node quadratic quadrilateral finite elements is employed. An incompressible flow SIMPLEC code with constant fluid properties is used. The convective terms using a third-order QUICK scheme. The numerical simulation result is compared against the published results of flow past a square cylinder. The effect of sharpening angle on the response of the right trapezoidal cylinder is investigated. A special study of the effects of flow on significant factor for time step, grid independence, blockage ratio, domain size, upstream and downstream extents, size domain next to cylinder and size domain extent are performed systematically. The Strouhal number and RMS lift coefficients of fully saturated flow are calculated. The result shown that increasing of sharpening angle, the Strouhal number is negligible changed whilst the RMS lift coefficients significantly increased.
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A Two-Dimensional Computational Study of a Single Right Trapezoidal Cylinder Subjected to Unsteady Laminar Flow Regime at Low Reynolds Number
(2020-07-27)
Lamtharn, Sodsai
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Pimsarn, Monsak
A right trapezoidal cross-section cylinder is used as guided bars for a barred tee in the long pipeline and piping system to protect the moving of pigs across the branched pipe. The cylinder must have the integrity to withstand to fluid flows-induced vibration which concerns the synchronization between vortex shedding frequency of fluid flows with a natural frequency of the cylinder. Therefore, this article aims to numerically investigate the vortex shedding frequency responses which are in terms of Strouhal number, flow force coefficients and in order to provide additional data for use in the absence of more applicable data for engineering design of the single right trapezoidal cylinder in structural integrity point of view. In this study, the simulation of the single right trapezoidal cylinder immersed in the uniform oncoming laminar flow regime with low Reynolds number; Re = 100, was performed. There are various sharpening angles in this study; defined as angle which is measured from virtual line parallel with height base side to slant side or (90°- acute angle°) of the cylinder, in the range of 0°, 15°, 22.5°, 40° and 60°, accompanying with the cylinder side ratio (B/A) which is the ratio of the longest base side-to-height base side, in the range of 1, 2, 3, 4, 5, 6 and 7. In the simulation, the Direct Numerical Simulation (DNS) with a finite volume method, an incompressible flow and constant fluid properties were employed. The computational results were validated against the published data. The effect of the sharpening angle and side ratio on the response of the single right trapezoidal cylinder were presented and discussed. The Strouhal number and flow force coefficients at fully ten cycle of saturated flow have been calculated. The simulated results show that increasing of sharpening angle, the Strouhal number slightly increases whilst the root mean square lift coefficients significantly increases. Additionally, as the side ratio increases, the Strouhal number and the root mean square lift coefficients decreases.

Pimsarn, Monsak

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