• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.378-385
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• 2004

Viscous-driven pumping is a very promising type in microscale applications. However, there exist a few disadvantages such as low efficiency and small volume flow rate. In the present study, a pump with tandem rotating cylinders and its optimum synthesis are proposed fur enhancing pumping performance. First, using an unstructured grid CFD method, we investigate the effects of geometrical parameters and then the performance of the pump with tandem cylinders is evaluated. Next, an optimum design synthesis tool is constructed by combining the aforementioned CFD analysis model with the mathematical optimization model, namely, Modified Method of Feasible Directions (MMFD). This technique is used to optimize the geometrical parameters of the pump, fur maximizing pumping efficiency. From the optimization results, it is believed that the present optimum synthesis is robust and has a potential fur other microfluidic device design.

• Journal of computational fluids engineering
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• v.11 no.4 s.35
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• pp.75-80
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• 2006

Navier-Stokes simulation of the flow in a micro viscous pump is carried out. The micro viscous pump consists of a rotating circular rotor placed in a two dimensional channel. All simulation is carried out by using a finite volume approach, at the Reynolds number of 0.5, to study the performance of the micro viscous pump. Length of channel of the pump is varied to simulate the effects of the pumping load. Numerical solutions show that the net flow of the pump is realized by two counter rotating vortices formed on both sides of the rotor. The volume flow rate of the pump is decreased as length of the channel is increased, while the static pressure difference across the rotor is increased. The static pressure difference across the rotor is observed to be inversely proportional to the volume flow rate as inertia effects are negligibly small. The efficiency of the pump is found to reach a maximum when two counter rotating vortices on both sides of the rotor becomes to merge forming an outer enveloping vortex.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1256-1261
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• 2003

Since the viscous effect increases as the size of device decreases, viscous-driven micropump is a promising mechanism in microscale applications. In the present study, a dual-rotor type pump which contains two counter-rotating cylinders for improving performance characteristics is proposed. First, for flows in the single-rotor type pump, the present unstructured grid simulation method is validated by comparing its results to the previous results. Next, the performance of the dual-rotor type pump is evaluated by the parametric studies and is compared to that of the previous single-rotor type pump. The flow characteristics are qualitatively similar to those of single-rotor type pump. However, the performance of the micropump with tandem rotors is still better than that of previous pumping type, e.g. much larger flow rate, smaller driving region, higher efficiency, and wider operation range.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3386-3394
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• 1994

An experimental study has been performed on the flow over a rotating disk, where the diameter of the disk is 500 mm and the maximum vertical deviation of the upper surface is $50 \mu{m}$ for the whole range of the angular velocity up to 3400 rpm. The flow visualization experiment for the wall jet flow induced by impinging circular jet is carried out using schlieren system and measurements are made by 3-hole and 5-hole pitot tubes. Schlieren photographs show that as the rotating speed increases the wall jet flow becomes more stable and the size of the largest eddies becomes smaller. Measurements for impinging jet flow on the stationary disk verify the accuracy of the present experiment, and those for free rotating disk flow display the existence of transition region from laminar to turbulent flows. Measurements for impinging jet flow on the rotating disk exhibit the interaction between the wall jet and the viscous pumping effect, which explains the decay in size of turbulent eddies illustrated by the schlieren photographs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1889-1896
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• 2003

In the microfluidic applications, viscous-driven pumping mechanism is a promising one since the viscous effect increases significantly as the size of device decreases, relative to the inertial effect. However, there exist a few drawbacks we have to improve such as low efficiency and small volume flow rate. In the present study, an optimum design synthesis is proposed to enhance the performance characteristics of the micropump with single rotating cylinder. First, the unstructured grid CFD method is described and validated by comparing its results to the previous results. Next, an automated optimum design synthesis tool is constructed by combining the aforementioned CFD analysis model with the mathematical optimization model. This technique is used to improve the performance characteristics of newly designed viscous-driven pump. The presented results show that the fluid dynamic optimization tool is robust and may be applied to other microfluidic device design applications.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2725-2730
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• 2007

Turbo-type molecular drag pumps ( MDPs ) are used in the liquid crystal display ( LCD ), semiconductor and other thin film industries. Siegbahn ( disk-type ) molecular drag pumps are used as high-pressure stages in the hybrid-type turbomolecular pumps, where they can operate in the viscous, the transition and the free molecular flow regime. In this study is performed to investigate the pumping characteristics of three-stage disk-type molecular drag pump ( DTDP ) in the molecular transition flow region. The experiments are measured using five vacuum pressure gauges in the positions for rotors of DTDP. The test is performed with nitrogen gas ( $N_2$ ).

• Advances in concrete construction
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• v.11 no.3
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• pp.231-238
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• 2021

The present work aims at investigating the effects of using various fine mineral additions as partial replacement to Portland cement on the tribological properties of concrete. To achieve this goal, concrete mixtures were prepared with different percentages (10, 20 and 30%) of limestone fillers (LF) and natural pozzolana (NP), and (20, 40 and 60%) of blast furnace slag (BFS). The interface yield stress (τ0) and viscous constants (η) that allow characterizing friction at the concrete-pipe wall interface were determined using a rotational tribometer. In addition, the compositions of the boundary layers that formed in the pumping pipes of the different concretes under study were also identified and analyzed. The experimental results obtained showed that the concretes studied have a linear tribological behavior that can be described by the Bingham model. Furthermore, the use of different mineral additions, especially limestone fillers and blast furnace slags, even at high rates, had a beneficial effect on the optimization of the volume of paste present in the boundary layer, which made it possible to significantly reduce the viscous constant of concrete. However, a maximum rate of 10% of natural pozzolana was recommended to achieve tribological properties that are favorable to the pumpability of concrete.

• Food Science and Biotechnology
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• v.14 no.5
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• pp.566-571
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• 2005

Process of screw-pumping system (SPS) was optimized for mass production of encapsulated bifidus. SPS entrapment device was composed of feeding component, with optimized nozzle size and length of 18G (0.91 cm) and 4 mm, respectively, screw pump, and 37-multi-nozzle. Screw component had five wing turns [radius (r)=26 to 15 mm] from top to bottom of axis at 78-degree angle from middle of the screw, and two wings were positioned at screw edge to push materials toward nozzle. For nozzle component, 37 nozzles were attached to 20-mm round plate. Air compressor was attached to SPS to increase productivity of encapsulated bifidus. This system could be operated with highly viscous (more than 300 cp) materials, and productivity was higher than $1128\;{\pm}\;30\;beads/min$. Viability of encapsulated bifidus was $5.45\;{\times}\;10^8\;cfu$/bead, which is superior to that of encapsulated bifidus produced by other methods ($2.51{\times}10^8\;cfu$/bead). Average diameter of produced beads was $2.048\;{\pm}\;0.003\;mm$. Survival rate of SPS-produced encapsulated bifidus was 90% for Simulator of the Human Intestinal Microbial Ecosystem test and 88% in fermented milk (for 14 days). These results show SPS is effective for use in development of economical system for mass production of viable encapsulated bifidus.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2672-2677
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• 2007

An investigation of low Reynolds number flow in nozzles and diffusers which are widely used in the valveless micropump is presented. Flow characteristics in the nozzle and diffuser are explained in view of viscous effect and flow oscillation induced by pumping membrane. These calculation results show that the rectification property of valveless micropump is due to a flow separation in the diffuser and the separation is largely originated from the flow oscillation. Under the assumptions of steady flow velocity profile and flow separation in the diffuser, simplified analytical models are provided to see the dependency of rectification on the micropump geometry. Geometric parameters of channel length, nozzle throat, chamber size, and converging/diverging angle are depicted through the analytical models in low Reynolds number flow, and the prediction and experimental results are compared. This theoretical study can be used to determine the optimum geometry of valveless micropump.

• The KSFM Journal of Fluid Machinery
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• v.9 no.6 s.39
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• pp.29-34
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• 2006

Propeller type pump has been widely used for pumping water in agricultural and manufacturing industry. Since a propeller type pump contains a screw impeller inside a circular casing, the numerical analysis becomes complex. However, the accurate prediction of viscous flow is essential for computing hydrodynamic performances. To analysis the flow and the performance of the propeller type pump, the present work has solved 3D incompressible RANS equations on the multiblocked grid. From the present calculation, small amount of flow separation was shown near hub and the flow was recovered to nearly uniform inflow after one diameter downstream. Torque and thrust coefficient were computed and compared with experiments.