• Membrane and Water Treatment
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• v.8 no.1
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• pp.35-50
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• 2017

The theoretical membrane gas absorption module treatments in a hollow fiber gas-liquid membrane contactor using Happel's free surface model were obtained under countercurrent-flow operations. The analytical solutions were obtained using the separated variable method with an orthogonal expansion technique extended in power series. The $CO_2$ concentration in the liquid absorbent, total absorption rate and absorption efficiency were calculated theoretically and experimentally with the liquid absorbent flow rate, gas feed flow rate and initial $CO_2$ concentration in the gas feed as parameters. The improvements in device performance under countercurrent-flow operations to increase the absorption efficiency in a carbon dioxide and nitrogen gas feed mixture using a pure water liquid absorbent were achieved and compared with those in the concurrent-flow operation. Both good qualitative and quantitative agreements were achieved between the experimental results and theoretical predictions for countercurrent flow in a hollow fiber gas-liquid membrane contactor with accuracy of $6.62{\times}10^{-2}{\leq}E{\leq}8.98{\times}10^{-2}$.

• Advanced Composite Materials
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• v.18 no.2
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• pp.135-152
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• 2009

Liquid molding processes, such as resin transfer molding, involve resin flow through a porous medium inside a mold cavity. Numerical analysis of resin flow and mold filling is a very useful means for optimization of the manufacturing process. However, the numerical analysis is quite time consuming and requires a great deal of effort, since a separate numerical calculation is needed for every set of material properties, part size and injection conditions. The efforts can be appreciably reduced if similarity solutions are used instead of repeated numerical calculations. In this study, the similarity relations for pressure, resin velocity and flow front propagation are proposed to correlate another desired case from the already obtained numerical result. In other words, the model gives a correlation of flow induced variables between two different cases. The model was verified by comparing results obtained by the similarity relation and by independent numerical simulation.

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.54-61
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• 2017

The purpose of this study is to develop standard reference materials for safety control of construction materials considering the required performance of standard materials including flow performance incorporating particles. The flow characteristics of concrete are very complicated depending on mixing proportions of constituent materials, admixtures, amount of mixing, type of mixer, time of mixing, temperature and so forth. Uncertainties and multidimensional properties of concrete have been evaluated through various studies but there are few researches for the development of standard reference material. In this study, based on the rheological concept, the flow performance of construction materials was evaluated to understand the properties of standard reference materials and was finally obtained representing materials which simulate the standard reference materials.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1244-1249
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• 2002

In this study, the physical characteristics of steel-wire sound absorbing materials with different thickness and bulk density is experimentally obtained in terms of the porosity and specific flow resistivity. Based on the experimental results, the following conclusions can be made. The porosities of steel-wire sound absorbing materials are smaller than those of general absorbing materials, which are inversely proportional to the volume densities. For the porosity measurement with a good accuracy, the dynamic correction based on the system compliance should be involved in porosity measurement. In addition, the flow condition for the precise measurement of the specific flow resistivity of steel-wire sound absorbing materials should be limited in the laminar flow region.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.557-565
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• 2022

The effect of flow configuration in ammonia-fed solid oxide fuel cell are investigated by using a three-dimensional numerical model. Typical flow configurations including co-flow and counter-flow are considered. The ammonia is directly fed into the stack without any external reforming process, resulting in an internal decomposition of NH3 in the anode electrode of the stack. The result showed that temperature profile in the case of counter-flow is more uniform than the co-flow configuration. The counter-flow cell, the temperature is highest at the middle of the channel while in the case of co-flow, the temperature is continuously increased and reached maximum value at the outlet area. This leads to a higher averaged current density in counter-flow compared to that of co-flow, about 5%.

• Progress in Superconductivity and Cryogenics
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• v.15 no.3
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• pp.35-39
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• 2013

In this paper, we present test results of developed 100 W class linear compressor for Stirling-type pulse tube refrigerator. The fabricated linear compressor has dual-opposed configuration, free piston and moving magnet type linear motor. Power transfer, efficiency and required pressure waveform are predicted with designed and measured specifications. In experiments, room temperature test with flow impedance is conducted to evaluate performance of developed linear compressor. Flow impedance is loaded to compressor with metering valve for flow resistance, inertance tube for flow inertance and buffer volumes for flow compliance. Several operating parameters such as input voltage, current, piston displacement and pressure wave are measured for various operating frequency and fixed input current level. Behaviors of dynamics and performance of linear compressor as varying flow impedance are discussed with measured experimental results. The developed linear compressor shows 124 W of input power, 86 % of motor efficiency and 60 % of compressor efficiency at its resonant operating condition.

• Membrane and Water Treatment
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• v.4 no.4
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• pp.251-263
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• 2013

The internal reflux effect on dialysis through the retentate phase of a countercurrently cross-flow rectangular module is investigated. Theoretical analysis of mass transfer in cross-flow devices with or without recycling is analogous to heat transfer in cross-flow heat exchangers. In contrast to a device without reflux, considerable mass transfer is achievable if cross-flow dialyzers are operated with reflux, which provides an increase in fluid velocity, resulting in a reduction in mass-transfer resistance. It is concluded that reflux can enhance mass transfer, especially for large flow rate and feed-concentration operated under high reflux ratio.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.181-183
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• 2002

The accurate permeability for preform is critical to model and design the impregnation of fluid resin in the composite manufacturing process. In this study, the in-plane and transverse permeability for a woven fabric are predicted numerically through the coupled flow model which combines microscopic with macroscopic flow. The microscopic and macroscopic flow which are flows within the micro-unit and macro-unit cell, respectively, are calculated by using 3-D CVFEM(control volume finite element method). To avoid checker-board pressure field and improve the efficiency on numerical computation, A new interpolation function for velocity is proposed on the basis of analytic solutions. The permeability of plain woven fabric is measured through unidirectional flow experiment and compared with the permeability calculated numerically. Based on the good agreement of the results, the relationships between the permeability and the structures of preform such as the fiber volume fraction and stacking effect can be understood. The reverse and the simple stacking are taken in account. Unlike past literatures, this study is based on more realistic unit cell and the improved prediction of permeability can be achieved. It is observed that in-plane flow is more dominant than transverse flow in the real flow through preform and the stacking effect of multi-layered preform is negligible. Consequently, the proposed coupled flow model can be applied to modeling of real composite materials processing.

• Journal of Powder Materials
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• v.21 no.3
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• pp.235-240
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• 2014

The basis of the cobalt demand analysis by use was established via the investigation and analysis of the cobalt materials flow, and the overall cobalt metal material and parts industry structure in Korea was examined to determine the cobalt material flow. The markets of the cobalt material for machinery were studied, including their interrelations, via market and study trends, and relevant plans were examined. The results of the study indicated that the advanced core technology for advanced industry and technology-intensive industry development is required to structurally innovate the parts materials and basic materials industries and to upgrade the catch-up industry structure to the new frontier structure.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.176-179
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• 2001

When the preform is composed of more than two layers with different in-plane permeability in resin transfer molding, effective average permeability should be determined for the flow analysis in the mold. The most frequently used averaging scheme is the weighted average scheme, but it does not account for the transverse flow between adjacent layers. A new averaging scheme is proposed predicting the effective permeability of the multi-layered preform, which accounts for the transverse flow effect. The new scheme is verified by measuring the effective permeability of the multi-layered preforms and the difference in each flow front position.