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 18

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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
;
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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Tooth profile modifications for optimum dynamic load in spur gears based on pseudo-interference stiffness estimation method
(2005-01-01)
Pimsarn, Monsak
;
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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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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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
;
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.
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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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Thermal performance assessment of turbulent flow through dimpled tubes
(2010-12-01)
Nivesrangsan, Pornchai
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Pethkool, Somsak
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Nanan, Kwanchai
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Pimsarn, Monsak
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Eiamsa-rd, Smith
This paper presents the heat transfer augmentation and friction factor characteristics by means of dimpled tubes. The experiments were conducted using the dimpled tubes with two different dimpled-surface patterns including aligned arrangement (A-A) and staggered arrangement (S-A), each with two pitch ratios (PR = p/D<inf>i</inf> = 0.6 and 1.0), for Reynolds number ranging from 9800 to 67,000. The experimental results achieved from the dimpled tubes are compared with those obtained from the plain tube. Evidently, the dimpled tubes with both arrangements offer higher heat transfer rates compared to the plain tube and the dimpled tube with staggered arrangement shows an advantage on the basis of heat transfer enhancement over the dimpled tube with aligned arrangement. The increase in heat transfer rate with reducing pitch ratio is due to the higher turbulent intensity imparted to the flow between the dimple surfaces. The mean heat transfer rate offered by the dimpled tube with staggered arrangement (S-A) at the lowest pitch ratio (PR = 0.6), is higher than those provided by the plain tube and the dimpled tube with aligned arrangement (AA) at the same PR by around 127% and 8%, respectively. The empirical correlations developed in terms of pitch ratio (PR), Prandtl number (Pr) and Reynolds number, are fitted the experimental data within ±8% and ±2% for Nusselt number (Nu) and friction factor (f), respectively. In addition, the thermal performance factors under an equal pumping power constraint of the dimple tubes for both dimpled-surface arrangements are also determined. © 2010 by ASME.
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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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Study of fatigue crack initiation location of wheel and rail under rolling contact using finite element method
(2018-08-14)
Jaifu, Apichai
;
Raeon, Suthep
;
Pimsarn, Monsak
The rail transit system is widely used for freight and passenger transportation. Due to the fact that its economic worthiness and high safety mode. Maintenance and damage prevention of wheel and rail are important factors affecting the safety of the system. The previous studies show that the most damage of wheel and rail is fatigue cracking, which is caused by the contact stress resulting from wheel and rail interaction. This article presents the study of the fatigue crack initiation location of wheel and rail under rolling contact at the wheel speed of 80 km/h using Finite Element Method (FEM). The three dimensional finite element models were created using the UIC60E1 wheel profile and BS100 rail profile. The Dang Van criteria was applied to analyse the fatigue crack initiation location in case of the wheel's position was changed along the rail lateral direction while the rail inclination angle was also varied at 0, 1/40, 1/30 and 1/20, respectively. The analysing results show that the fatigue crack initiation, determined by the Dang Van stress ratio, tends to increase when the wheel is moved from gauge side to field side. Additionally, the fatigue crack damage is likely to decrease when the rail inclination increases up to the inclination of 1/30 and the fatigue crack initiation locations were found underneath the wheel and rail surfaces. The obtained result can be a primary guideline for maintenance planning.

Pimsarn, Monsak

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