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Analysis of Indoor PM2.5 Contaminants Based on Outdoor Wind Velocity Through Different Infiltration Types
(2025-01-01)
Oo, Ghaim Man
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Kotmool, Komsilp
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Mongkolwongrojn, Mongkol
Nowadays, indoor PM2.5 concentrations have become a significant factor affecting indoor air quality (IAQ) and a major public concern, particularly with the rise of haze in Thailand and globally, as PM2.5 can penetrate human lungs. This research analyzes the dispersion of PM2.5 from outdoors to indoors using a fluid dynamics simulation framework that combines the Eulerian approach for continuous flow, the Lagrangian approach for particulate matter dispersion, and the RNG k-ε turbulent model for airflow. The study is aimed at protecting indoor environments from harmful exposure to PM2.5 from outdoor contaminants and improving IAQ. Primarily, three different infiltration types and shapes are studied to determine the minimum optimal positive room pressure, based on the impact of ambient wind velocity on indoor PM2.5 concentrations from outdoor pollutants. A minimum optimal pressure of 3.6 Pa and 27 air changes per hour (ACH) is sufficient to achieve a PM2.5-free indoor environment for all infiltration models. Furthermore, higher wind speeds can reduce indoor PM2.5 concentrations due to the increased momentum of particles. This research technique is implemented in the practical field study conducted within the laboratory room of the 55-Year Chalermprakiat Building. As a result, the investigated room, with an infiltration area of 0.06 m<sup>2</sup> and a rate of 0.0036 m<sup>3</sup>/s, will be certified as a clean room by achieving an optimal minimum pressure of approximately 0.01 Pa. This research will help achieve cleaner and safer indoor environments for any building by leveraging the optimal minimum pressure of cleanroom technology, provided that the infiltration rate and ambient wind velocity are accurately determined.
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Case Study on the design optimization of the positive pressure operating room
(2024-12-01)
Oo, Ghaim Man
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Kotmool, Komsilp
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Mongkolwongrojn, Mongkol
Ventilation systems of operating rooms (ORs) are significantly important in preventing postoperative wound infections that can cause morbidity and mortality after surgery in or out of the hospital. This study aims to identify the optimum overpressure for efficient operation while reducing the risk of surgical site infections (SSIs) based on the actual OR with the help of computational fluid dynamics. The species transport model, Lagrangian discrete phase model, and turbulent standard k-ε model are mainly used for the transient numerical study to improve the performance of the OR and reduce SSI cases. Four OR schemes were initially calculated for the best location of the patient on the surgical table. The results revealed that the modified position 90˚ is the best location with the minimum CO<inf>2</inf> and BCP concentrations. The investigated operating room could host up to ten surgical members with the optimum overpressure of 5.89 Pa and 0.56 m/s of supply velocity under the standard cleanliness level. Modifying the supply surface area will enhance the performance of the operating room by providing a cleaner zone and maintaining the desired room pressure, even with a low airflow rate. This optimization scheme could guide practical applications in all positively pressurized operating rooms to address issues related to overpressure effects.
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Effects of Crosswind on Pantograph–Catenary Wear Using Nonlinear Multibody System Dynamic Algorithms
(2023-09-01)
Daocharoenporn, Siripong
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Mongkolwongrojn, Mongkol
In this study, a multibody system (MBS) computational framework is developed to determine the exact location of the contact point and wear prediction resulting from the pantograph–catenary interaction. The railroad vehicle models in the MBS computational framework comprise rigid-body railroad vehicles, rigid-body pantograph systems, and flexible catenary systems. To avoid incremental rotation, the nonlinear finite element absolute nodal coordinate formulation is used to model a flexible catenary system in the MBS computational framework. To avoid co-simulation processes, the rigid-body railroad vehicle and the pantograph and flexible catenary systems were integrated into the MBS algorithms. The pantograph–catenary interaction is modeled using an elastic contact formulation developed to include the effect of pantograph–catenary separation and sliding contact. The proposed MBS approach evaluates the location of the contact point, contact force, and normal wear rate (NWR) from the mechanical and electrical contributions. This investigation considers the vibration caused by a crosswind scenario and determines the numerical result in the case of a steady crosswind scenario. The steady crosswind scenario contains the advantage of pantograph–catenary aerodynamic design, and the vibration of the catenary system remains significant after the excitation of a steady crosswind. In the case of a steady crosswind, the higher value of the steady crosswind effect significantly increases the mean contact force and the NWR from the mechanical contribution. After crosswind load disturbances, the mean contact force decreases, but the standard deviation of the contact force increases. Therefore, the NWR from the electrical contribution increases significantly. However, the total NWR increases with the crosswind velocity.
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Analysis of parametric optimization on the design of negative pressure room
(2023-01-01)
Oo, Ghaim Man
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Kotmool, Komsilp
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Mongkolwongrojn, Mongkol
Negative pressure rooms are crucial for the prevention of the dispersion of infectious diseases. Using the ANSYS-Fluent finite volume method (FVM), standard k (Formula presented.) ϵ turbulent, species transport, and discrete phase model with the transient condition, this research aims to reduce the amount of airborne contamination inside the negative pressure room. In the current design, both 10 area ratios and static supply pressures (Formula presented.) 1–(Formula presented.) 30 Pa are considered. The optimum condition is reached at an area ratio of 9 and 13 Air change per hours (ACHs) with a 96% reduction in CO<inf>2</inf> concentration and an exhaust velocity of 3 m/s and a minimum power consumption of 247 W at a supply pressure of ((Formula presented.) 10) Pa. The effective direct airflow pattern is observed as a safe environment by analyzing the streamlines and velocity vector distributions. To prevent the infectious viruses spread, the particle tracking of coughed droplets is analyzed so that 100% of aerosol particles can be extracted within 3 s. The door-opening effect showed that the desired negative pressure could be maintained even if the door opened for a long time. This work will benefit the design engineers for any intended negative pressure room and provide a secure working environment for the medical personnel.
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Effect of bearing materials on journal bearings under TEHL with lubricant based on Carreau model
(2020-02-17)
Gunnuang, Waleephan
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Aiumbhornsin, Chatchai
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Wongsa-Ngam, Jittraporn
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Mongkolwongrojn, Mongkol
This work presents a transient analysis of journal bearings under thermal elastohydrodynamic lubrication (TEHL) based on the Carreau model. The effects of the elastic modulus of the bearing liner have been investigated using numerical simulations. A time-dependent modified Reynolds equation and an adiabatic energy equation based on the Carreau model have been formulated and numerically solved to examine the performance of the journal bearings. The results show that the minimum film thickness and the friction coefficient both increase with decreasing bearing liner elastic modulus. In contrast, the dimensionless load carrying capacity, dimensionless maximum film temperature, and dimensionless maximum film pressure all decrease with decreasing bearing liner elastic modulus. The stability regions tend to decrease in size for journal bearings under TEHL, especially for journal bearings composed of soft materials.
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Pantograph/catenary wear using multibody system dynamic algorithms
(2020-01-01)
Daocharoenporn, Siripong
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Mongkolwongrojn, Mongkol
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Kulkarni, Shubhankar
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Shabana, Ahmed A.
In this investigation, computational multibody systems (MBS) algorithms are used to develop detailed railroad vehicle models for the prediction of the wear resulting from the pantograph/catenary dynamic interaction. The catenary wear is predicted for different motion scenarios that include constant-speed curve negotiation, and acceleration and deceleration on a tangent (straight) track. The effect of the vehicle vibration in these different motion scenarios on the contact force is further used to study the wear rates of the contact wire. The wear model used in this investigation accounts for the electrical and the mechanical effects. The nonlinear finite element (FE) absolute nodal coordinate formulation (ANCF), which is suitable for implementation in MBS algorithms, is used to model the flexible catenary system, thereby eliminating the need for using incremental rotation procedures and co-simulation techniques. The pantograph/catenary elastic contact formulation employed in this study allows for separation between the pantograph panhead and the contact wire, and accounts for the effect of friction due to the sliding between the pantograph pan-head and the catenary cable. The approach proposed in this investigation can be used to evaluate the electrical contact resistance, contribution of the arcing resulting from the pan-head/catenary separation, mechanical and electrical wear contributions, and effect of the pantograph mechanism uplift force on the wear rate.
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Prediction of the pantograph/catenary wear using nonlinear multibody system dynamic algorithms
(2019-05-01)
Daocharoenporn, Siripong
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Mongkolwongrojn, Mongkol
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Kulkarni, Shubhankar
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Shabana, Ahmed A.
In this investigation, computational multibody system (MBS) algorithms are used to develop detailed railroad vehicle models for the prediction of the wear resulting from the pantograph/catenary dynamic interaction. The wear is predicted using MBS algorithms for different motion scenarios that include constant-speed curve negotiation and acceleration and deceleration on a tangent (straight) track. The effect of the vehicle vibration in these different motion scenarios on the contact force is further used to study the wear rates of the contact wire. The wear model used in this investigation accounts for the electrical and the mechanical effects. The nonlinear finite element (FE) absolute nodal coordinate formulation (ANCF), which is suitable for implementation in MBS algorithms, is used to model the flexible catenary system, thereby eliminating the need for using incremental-rotation procedures and co-simulation techniques. In order to obtain efficient solutions, both the overhead contact line and the messenger wire are modeled using the gradient-deficient ANCF cable element. The pantograph/catenary elastic contact formulation employed in this study allows for separation between the pantograph panhead and the contact wire, and accounts for the effect of friction due to the sliding between the pantograph panhead and the catenary cable. The approach proposed in this investigation can be used to evaluate the electrical contact resistance, contribution of the arcing resulting from the panhead/catenary separation, mechanical and electrical wear contributions, and the effect of the pantograph mechanism uplift force on the wear rate. Numerical results are presented and analyzed to examine the wear rates for different motion scenarios.
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Effects of slider geometry change on helium filled HDD
(2014-01-01)
Mongkolwongrojn, Mongkol
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Kuanoon, Kunchit
This paper describes the static characteristics of helium filled hard disk drive for a s two rails flat slider gas bearing. Numerical scheme based on the finite difference with multigrid multi-level technique were implemented for the ultra-low flying height sliders. The effect of slider geometry change in both crown and camber on flying height have been examined in this research work. The results show that the flying height change is significantly with a few nanometers change in crown and camber. The flying height of helium filled magnetic flat slider head equal to 3.5 nm at trailing edge. The spacing for helium filled hard disk drive is lower than 4 nm when compared with conventional air filled hard disk drive. The increase of slider crown, the flying height increases rapidly but the increase of slider camber, the flying height decreases continuously. © (2014) Trans Tech Publications, Switzerland.
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Theoretical analysis of flying characteristics for air-helium filled HDD
(2014-01-01)
Mongkolwongrojn, Mongkol
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Kuanoon, Kunchit
This paper presents the flying characteristics of air-helium filled hard disk drive for a self-acting two rails flat slider bearing. Numerical scheme based on the finite difference with multigrid multi-level technique were implemented for the ultra-low flying height sliders. The characteristics of air-helium filled HDD have been examined in this research work. The results shown that the change of flying height is significantly for various fraction of air-helium filled, at various operating conditions such as temperature velocity and mass of slider. Increase of velocity, flying height increase. Increase both the temperature and the mass load, flying height decrease. Increasing of fraction in helium gas, the flying height decreases rapidly for 40% to 60% of fraction in helium filled. The flying height for air-helium filled magnetic flat slider head equal to 1.3 nm at trailing edge with mass load 12 mN and velocity 20 m/s. The spacing for helium filled hard disk drive is lower than 3 nm when compared with conventional air filled hard disk drive. © (2014) Trans Tech Publications, Switzerland.
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Effect of nanoparticle additives on rough surface cylinder in line contact under TEHL with non-Newtonian lubricant
(2014-01-01)
Mongkolwongrojn, Mongkol
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Rattapasakorn, Sountaree
This paper presents the results of a transient analysis of thermal elastohydrodynamic lubrication (TEHL) of a rough cylinder on a rough flat surface in line contact with non-Newtonian lubricant blended with Al2O 3 nanoparticles. The simultaneous systems of time-dependent modified Reynolds equation, elasticity equation and energy equation with initial conditions were solved numerically using multigrid multilevel with full approximation technique. In this study, the effect of Al2 O3 nanoparticle additives, surface roughness and sudden overload on TEHL of two surfaces in line contact were examined. The minimum film thickness and the pressure spike increase slightly with an increase in nanoparticle concentration. For TEHL with Al2 O3 nanoparticle additives, the film temperature increases very little due to thermal enhancement of nanofluids.

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