Chul-Kyu Kim

Optimal design of groove shape on passive micromixer using design of experiment technique

Passive micromixers are one of the parts used for the mixing of two or more fluids in micro-electro-mechanical system devices, and they have been developed for various types. Fluid mixing in microscale devices is essential in microfluidic applications; however, it is difficult to mix fluids in microchannels due to the slowness of the molecular diffusion process at the microscale. In this study, optimization of the groove shape geometries of a micromixer using response surface design was performed, and the mixing performance was investigated through a numerical analysis applied with the passive scalar method. The most useful parameters were determined to be the geometric parameters of optimization, such as groove depth, groove length, distance between grooves, and groove angle. Response surface design, a design of experiments technique, was applied to the optimization procedure. The mixing index and pressure drop are important factors for evaluating the micromixer performance. Through the response surface design, this study aims to affect the groove shape of a passive micromixer. Consequently, it was concluded that the groove length and distance between grooves improved the mixing performance and decreased the pressure drop. In addition, optimal models were proposed for the passive micromixer.

Experimental Study on the Internal Flow of a Ball Valve used for a Gas Pipeline

>> This paper presents the flow characteristics of a ball valve used for a gas pipeline. Understanding of the internal flow of a ball valve is an important to analyze the physical phenomena of the valve. Present experimental study was performed by IEC 60534-2-3, the international standard for an industrial control valve testing procedure. Pressure measured at upstream and downstream of the valve, flow-rate and gas temperature passing the inside of the gas pipeline were measured with respect to valve opening rates. Throughout the experimental measurement of the ball valve, empirical equation of the pressure drop between the ball valve according to the mass flow rates is successively obtained using a polynomial curve fitting method. In addition, flow coefficient for determining the valve capacity is also analyzed with respect to valve opening rates using the curve fitting method.

Assessment of Gas Leakage for a 30-inch Ball Valve used for a Gas Pipeline

>> The purpose of this study is to evaluate the gas leakage for a 30-inch ball valve. The ball valve was designed and manufactured for a natural gas transportation through a long-distance pipeline mainly installed in the permafrost region. The gas leakage assessment is based on the pressure testing criteria of international standards. Pressure conditions of the gas leakage test was employed 70 bar, 100 bar, and 110 bar. The amount of the gas leakage at each pressure condition was small and had a value under the pressure testing criteria, ISO 5208. Gas leakage with respect to the test pressure was predicted by the polynomial curve fitting using the experimental results. It is found that the gas leakage rate according to the pressure is proportion to a second order curve.

Optimization of Patterned Grooves Micromixer Using the Design of Experiments

Mixing independent fluid is of significantly important in microfluidics application, however, is difficult to mix solutions in microchannels. Efficient mixing was also hampered by comparatively slow molecular diffusion process at the micro-scale. In this study, in order to enhance the mixing efficiency, the configuration of patterned grooves micromixer is optimized using an approximate optimization technique. First of all, mixing characteristics analyzed by 3-D Computational Fluid Dynamics. The effective of geometrical parameters on the mixing performance of the staggered herringbone mixer with patterned grooves on the floor are numerical investigated. Groove parameters choose the most effective parameters such as the patterned groove of depth, the patterned groove of length, between grooves distance, and the patterned groove of angle. Design of experiments is applied to the optimization procedure. The optimum micromixer models in parameters region performed to generate using Design of experiments in effective parameters. A mixing index and a pressure drop values calculated at the cross-sections compared each models and proposed optimization of models.

Performance Evaluation of a Vertical Axis Wind Turbine Using Real-Time Measuring Wind Data

Recently, small vertical axis wind turbine has been in the limelight as an essential component of hybrid renewable energy system, based on many advantages, such as low noise and cut-in wind speed, cost and site flexibility, etc. Turbine performance is analyzed by introducing the effect of different time averaging steps using real-time measuring wind data. All measured data through wind master is stored in the computer every second using a data acquisition system. The test turbine is installed at the island, which is located near Seoul, South Korea. Vertical axis wind turbine (VAWT) having the rated power of 1.5 kW is installed. The performance of the VAWT is compared and analyzed using 10-, 20-, and 30-min averaged data. Numerical simulation has also been performed to compare the turbine performance with experimental results. From the comparisons between experimental and numerical simulation, it is found that performance of the tested wind turbine is slightly different according to the different time-averaged data. Turbine performance analyzed by using 10-min time-averaged data, which has relatively lower standard deviation, has a good agreement to the result of numerical simulation.

Characteristics of Flow Induced Noise from a Ball Valve Used for a Gas Pipeline Using an Acoustic Camera

Received 9 January, 2017 Revised 19 January, 2017 Accepted 28 February, 2017 Abstract >> The present study describes flow induced noise generated from a ball valve used for a gas pipeline. Noise generation from a ball valve mainly induces by interference between unstable(or fluctuating) leakage flow and pipe wall when the ball valve is working closed or opened. To measure the positions of the noise source and the amplitude of noise with respect to measuring frequencies, a commercial acoustic camera is introduced. Noise characteristics generated by the ball valve have been performed by four valve opening rates: 30, 50, 70 and 100 percents. It is noted that 100 percent opening rate means that the valve is fully opened. Throughout the experimental measurements using the acoustic camera, the location of the noise source and the noise amplitude with respect to the frequencies for the test ball valve are clearly evaluated. It is found that the dominant frequencies come from the fluctuating flow at the downstream of the ball valve for four opening rates are observed between 3,000Hz and 3,200Hz. Maximum noise amplitude comes from the ball valve reaches 75dB at the valve opening rate of 50 percent.

Evaluation of Numerical Model of a Ball Valve used for a Gas Pipeline

>> This paper presents on the evaluation of numerical analysis model of a ball valve used for a gas pipeline. The ball valve has important role to control the gas flow of the pipeline as well as safety operation to prevent gas explosion at the emergency. For the validation of numerical simulation, the computational domains are introduced three different types: a hexahedron chamber connected to a pipeline outlet without considering the geometry of pressure tubes, a pipeline only considered the geometry of pressure tubes, and a pipeline connected both of the a hexahedron chamber and pressure tubes. The commercial code, SC/Tetra, is introduced to solve the three-dimensional steady-state Reynolds-averaged Navier-Stokes analysis in the present study. The valve flow coefficient and valve loss coefficient with respect to the valve opening rate of 30%, 50%, and 70% are compared with experimental results. Throughout the numerical analysis for the three analysis domains, pressure computed along the pipeline is affected by computational domains. It is noted pressure obtained by the computational model considering both of the a hexahedron chamber and pressure tubes has a relatively good agreement to the experimental data.

Experimental study for flow characteristics and performance evaluation of butterfly valves

The industrial butterfly valves have been applied to transport a large of fluid with various fields of industry. Also, these are mainly used a control of fluid flux to the water and waste-water pipeline. Present, butterfly valves are manufacturing for multiplicity shape of bodies and discs with many producers. However, appropriate performance evaluation was not yet accomplished to compare about these valves through experiments. This study is performed the experiment of flow characteristics and performance of manufactured 400A butterfly valves for the water and waste pipeline, and compared experimental results. We performed experiments that were controlled fixed a differential pressure condition (1 psi) and the range of the flow rate conditions (500 m3/hr ~ 2500 m3/hr), and also opened the disc of valves to a range of angle from 9 degree to 90 degree. We investigated and compared the valve flow coefficient and the valve loss coefficient of results through experiments with each butterfly valve.