• Journal of the Korean Society of Visualization
• /
• v.19 no.1
• /
• pp.12-17
• /
• 2021

A three-dimensional slope valve component is used for controlling micro volume of liquid on a centrifugal force-based microfluidic disk platform, also called a lab-on-a-disk. The modeling factor of the slope valve component is determined to centrifugal force for liquid passing the crest of a slope valve via variation of slope length and angle as well as the radius to start point of slope valve. The centrifugal force is calculated by the equilibrium equation of the capillary and gravitational forces according to the microchannel surface roughness and the liquid volume, respectively. As a result, the slope valve is analyzed by the minimum angular velocity for liquid passing at crest point and the ratio between the length of micro liquid and slope length to obtain the factors for optimal slope angle modeling.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2004.11a
• /
• pp.237-240
• /
• 2004

Sulfur Hexafluoride, SF6 is widely used for leak detection and as a gaseous dielectric in transformers, condensers and circuit breakers. SF6 gas is also effective as a cleanser in the semiconductor industry. This paper presents a numerical study of the sealing force of disk type seal in SF6 gas safety valve. The sealing force on the disk seal is analyzed by the FEM method based on the Taguch's experimental design technique. Disk seals in SF6 gas safety valve are designed with 9 design models based on 3 different contact length, compressive ratio and gas pressure. The calculated results of Cauchy stress and strain showed that the sealing characteristics of Teflon PTFE is more effective compared to that of FKM(Viton), which is related to the stiffness of the materials. And also, the contact length of the disk seal is important design parameter for sealing the SF6 gas leakage in the safety valve.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.06a
• /
• pp.857-858
• /
• 2008

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.630-635
• /
• 2001

The stem thrust required to unwedging a gate valve is influenced by the pressure and temperature when the valve is closed and by the changes in these conditions between closure and opening. "Pressure Locking" and "Thennal Binding" refer to situations where pressure and temperature effects cause the unwedging load to be much higher than normal. A model of these phenomena has been developed. The effects of pressure and temperature are analyzed to determine the change in this disk-to-seat "interference". Flexibilities or Stiffness of the disk and body strongly influence the unwedging thrust. Calculation and limited comparison to data have been performed for the RHR motor operated valve designs and scenario. Pressure changes can increase the unwedging thrust when bonnet pressure exceeds the pressure in the adjacent piping and temperature changes can increase the unwedging thrust when a temperature change after closure produces an increase in the disk-to-seat interference.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.75-78
• /
• 2002

In this paper, flow on the rear region of a butterfly valve was analysed by using numerical and experimental methods. The butterfly-valve disk angle is changed as 0-60 degree and the uniform flow velocity was fixed In this experiment. It was shown that the numerical results are similar to the experimental results. General discussions are given to the flow-pattern change upon the disk angle of the valve.

• The KSFM Journal of Fluid Machinery
• /
• v.7 no.1 s.22
• /
• pp.9-16
• /
• 2004

A three-dimensional numerical analysis was carried out on incompressible flows in butterfly valves by using commercial FLUENT/UNS code. Characteristics of complex flows including cavitation effect were investigated for different valve disk angles. The butterfly-valves that had different disk angles and different disk shapes were compared with each other in detail. This study focused on the flow analysis in the conventional butterfly valve and the newly designed butterfly valve in order to prevent cavitation. The newly designed valve shows great improvement on performance and endurance.

• Journal of Energy Engineering
• /
• v.11 no.1
• /
• pp.26-33
• /
• 2002

In this paper, incompressible and compressible flow characteristics around the butterfly valve have been investigated. In order to simplify the problem, a flat disk valve with various valve disk angles and pressure ratios is considered in the present calculations. It was found that as the disk angle increases, the stagnation point on the front surface of the disk moves to the center of the surface and the inflow velocity decreases. The maximum flow velocity occurs at the downstream of throat because of the formation of vents contracta. As the pressure ratio decreases, compressibility effects increase and the jet formed between the throttle body wall and the disk edge becomes supersonic. This flow also builds up as a shock cell structure. The increase of disk angle and pressure ratio makes the mass flow at the inlet decrease, while the increase of disk angle and the decrease of pressure ratio make the pressure loss coefficient increase.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.18 no.1
• /
• pp.29-35
• /
• 2009

Butterfly valve is a kind of rotational valve which opens and closes the flow of fluid on rotating the disk 90 degrees in the valve body. In this paper, butterfly valve design safety evaluation which is based on the international valve specifications is investigated. Both body and disk of the butterfly valve are considered under the normal and pressurized operating conditions. A finite element analysis is carried out to compute the distribution of the displacement, stress and safety factor by using ANSYS. On the basis of calculated design safety we offer the design modification and compare with them.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.1
• /
• pp.36-41
• /
• 2002

The cause and the elimination method for the chattering phenomena were investigated in a check valve attached to the exit of an auxiliary cooling water pump in a Korean nuclear powerplant. From the site experiment and the numerical calculation, the incident angle of the disk was so small that it was not able to produce the sufficient lifting force to overcome the gravitational component of the disk weight. Moreover, it turned out that the installation position was not symmetric for the secondary vortical flow generated inside the elbow so that the flow structure had strongly unstable flow characteristics. From this study, the tapping noise and the chattering phenomena were eliminated exactly by changing the incidence angle of the valve disk and the installation position of the calve body.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.1848-1853
• /
• 2000

Cause and the elimination method for the chattering phenomena were investigated the check valve attached exit of the auxiliary cooling water pump at a korean nuclear powerplant. From the site experiment and numerical calculation the incident angle of the disk was so small that it was not able to produce the lifting force to overcome the component of disk weight. Moreover, it turned out that the installed position was not symmetric for the secondary vortical flow generated inside the elbow, so that the flow structure had strongly unstable flow characteristics. From this technical support, the tapping noise and the chattering phenomena were eliminated exactly by changing the incidence angle of the valve disk and installed position of the check valve.