• Journal of computational fluids engineering
• /
• v.20 no.3
• /
• pp.87-93
• /
• 2015

In this study, a numerical analysis was performed to simulate the thermal-hydraulic response of the secondary side of a steam generator(SG) model equipped with an orifice-type SG outlet flow restrictor to a main steam line break(MSLB) at a pressurized water reactor(PWR) plant. The SG analysis model includes the SG upper steam space and the part of the main steam pipe between the SG outlet and the broken pipe end. By comparing the numerical calculation results for the present SG model to those obtained for a simple SG model having no flow restrictor, the effects of the flow restrictor on the thermal-hydraulic response of SG to the MSLB were investigated.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.9
• /
• pp.1429-1432
• /
• 2006

Polyaromatic hydrocarbons were separated by a capillary supercritical fluid chromatographic (SFC) column and detected by a UV detector at the wavelength of 280 $\mu$m. The temperature-controlled restrictor was designed for UV detection. The temperature-controlled restrictor is a 20 cm length of deactivated fused silica of 7 mm i.d. which is held right after UV detector of the capillary SFC. The temperature of the restrictor will control the flow rate of the supercritical carbon dioxide mobile phase through the capillary column in SFC. Thus as the pressure in the column is increased from 1500 psi to 4000 psi during a pressure program, the temperature of 7 $\mu$m fused-silica tube can be varied from 100 to 350 ${^{\circ}C}$ to maintain a constant flow rate.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.932-937
• /
• 2002

The polyimide nozzle and silicon restrictor inside a thermal micro actuator have been fabricated using state of the art laser micromachining methods. Numerical models of fluid dynamics inside the actuator chamber and nozzle are presented. The models include fluid flow from reservoir, bubble formation and growth, ejection through the nozzle, and dynamics of refill through restrictor. Since high tapered nozzle and restrictor are very important parameters for overall actuator performance design, a special setup for the beam delivery system has been developed. The effects of variations of nozzle thickness, diameter, taper angles, and restrictor shapes are simulated and some results are compared with the experimental results. It is fecund that the fluid ejection through the thinner and high tapered nozzle is more steady, fast, and robust and the tapered restrictor shows more satisfying refill than the zero taper one.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.97-103
• /
• 2002

Vibration isolation technology using an air spring and laminated rubber bearing is widely used because it has excellent vibration isolation characteristics. In the part of that, we usually make use of the self-damped air suing. It is occupied two chambers, restrictor, diaphragm and load plate. Two chambers contain compressed air and the volume of chambers and the area of load plate give a definition of stiffness and load. The restrictor and the volume ratio of two chambers give a definition of damping ratio. The conventional model of restrictor is made of one orifice and it causes turbulent flow in the orifice at the region of large deflection. The stillness of air suing is larger and the damping is lower in the region of large deflection. In the multi-orifice case, the stiffness is similar to air spring with one orifice but damping ratio is larger than conventional air spring. And damping ratio is smaller than conventional air suing in small deflection region. Deflection is small in the region of high frequency so small damping is better than large damping. As a result, we can reduce the storage stiffness of air suing in the wide region of deflection and increase the damping ratio in the region of large deflection. After this, we will try to and the relation of Reynolds Number and Flow Resistance then we are going to make another restrictor for air spring to improve damping ratio and stiffness.

• Tribology and Lubricants
• /
• v.33 no.5
• /
• pp.187-201
• /
• 2017

This paper presents the impact of couple stress lubricant on performance of slot-entry hydrostatic/hybrid journal symmetric/asymmetric bearings. Reynolds Equation using Finite Element Technique has been solved for the flow of couple stress and Newtonian lubricants in bearings. The results have been computed for concentric design pressure ratio(${\beta}^{\ast}=0.5$), slot width ratio (SWR = 0.25) and chosen parameters of couple stress lubricant ${\bar{l}}=5$, 10, 15. It is observed that numerically simulated outcomes for slot-entry journal bearings, considering the influence of couple stress lubricant indicate a substantial improvement in the performance of the bearing.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.26 no.3
• /
• pp.320-327
• /
• 2017

The main function of an infuser is to ensure constant dosage of a drug. Elastomer drug infusers have been used widely owing to their economic advantages. The mechanism of the device is primarily based on the pressure created from the elastic material that contains the drugs. However, as the drug is infused and the internal pressure is reduced, the drug is not linearly infused at all times. This study involves investigating factors to improve the design of the infuser. The first factor is the range of proper deformation, which does not affect a significant amount of stress variation during infusion. The second is concerned with the flow restrictor and the associated design variables are recommended by employing finite element analysis and the factorial experiment technique. The last factor is related to the spring device connected to balloon. The results showed that the drug reservoir can compensate for unexpected pressure gradient drops.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.4
• /
• pp.377-385
• /
• 2013

To identify the effects of an outflow area on pool boiling heat transfer in a vertical annulus, three different flow restrictors were studied experimentally. For the test, a heated tube of smooth stainless steel and water at atmospheric pressure were used. Both annuli with open and closed bottoms were considered. To validate the effects of the outflow area on the heat transfer, the results of the annulus with the restrictor were compared with the data for the plain annulus without the restrictor. The reduction of the outflow area ultimately results in a decrease in the heat transfer. As the outflow area is very small, a slight increase in heat transfer is also observed. The major cause of this tendency is explained as the difference in the intensity of liquid agitation cause by the movement of coalesced bubbles. It is identified that the convective flow, pulsating flow, and evaporative mechanism are considered as the important mechanisms.

• Tribology and Lubricants
• /
• v.7 no.2
• /
• pp.51-60
• /
• 1991

For the accurate run-out of a light rotor shaft the sliding bearings supplied with externally pressurized air are effectively applied, and it is important to predict the static and dynamic characteristics of rotor-bearing system. In this study direct numerical method is applied to solve the perturbed Reynolds' equation. To solve it the perturbed dimensionless mass flow rate is used as the boundary condition under the inherently-compensated restrictor. The dynamic characteristics of a rotor supported in the externally pressurized air bearings are analyzed, and as a result the orbit of the journal center is calculated. The theoretical results are investigated and discussed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.1 s.256
• /
• pp.51-61
• /
• 2007

This paper presents numerical and theoretical studies of acoustic wave interactions in slightly compressible liquids within piezoelectrically driven inkjet print heads. The interconnected flow channels may cause jet crosstalk, resulting in poor printing quality. It should be reduced by modifying the channel structure with the acoustic wave interactions considered. Compressible gas flow driven by the sudden movement of a top wall in the channel is calculated using Flow3D and is validated with the narrow gap theory. Limited compressibility model of the Flow3D is employed to calculate pressure waves of slightly compressible ink flow. It is found that reducing restrictor width can damp out the jet crosstalk by inhibiting the pressure wave propagation. The degree of crosstalk has been quantified using the maximum values of cross-correlations between neighboring channels and a critical channel dimension for acceptable crosstalk has been proposed. This finding is verified by drop visualization experiments using silicon-micromachined piezo inkjet print heads that are fabricated by our group.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1992.10a
• /
• pp.249-254
• /
• 1992

Hydrostatic Bearings have been applied to ultra high precision machine tools and precision instruments, because of their low friction characteristic, high load carrying capacity and high moving accuracy at all range of speed. In regard to realizing the Hydrostatic Bearing, various restrictors such as capillary, orifice, diaphram valve, spool valve, and etc can be used. However, their stiffness and flexibility are not sufficient in practical use for ultra precision machine tool elements. In this study dynamic equations were derived and the dynamic characteristics were simulated for both orifice and flow control servo valve. Simulation was carried out on the condition that static and sinusoidal dynamic loads were applied to the table of CNC jig Boring machine. The simulation results indicate the improvement of the performance of the Bearing system when flow control servo valve has been used as restrictor of Hydrostatic Bearing.