• Journal of Advanced Marine Engineering and Technology
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• v.28 no.5
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• pp.818-826
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• 2004

The spray-induced mixing characteristics and thermal decomposition of aqueous urea solution into ammonia have been studied to design optimum sizes and geometries of the mixing chamber in SCR(Selective Catalytic Reduction) system. The cold flow tests about the urea-injection nozzle were performed to clarify the parameters of spray mixing characteristics such as mean diameter and velocity of drops and spray width determined from the interactions between incoming air and injected drops. Discrete particle model in Fluent code was adopted to simulate spray-induced mixing process and the experimental results on the spray characteristics were used as input data of numerical calculations. The simulation results on the spray-induced mixing were verified by comparing the spray width extracted from the digital images with the simulated Particle tracks of injected drops. The single kinetic model was adopted to predict thermal decomposition of urea solution into ammonia and solved simultaneously along with the verified spray model. The hot air generator was designed to match the flow rate and temperature of the exhaust gas of the real engines The measured ammonia productions in the hot air generator were compared with the numerical predictions and the comparison results showed good agreements. Finally, we concluded that the design capabilities for sizing optimum mixing chamber were established.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.1117-1125
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• 1996

A low-cost and precise metering device, which is suitable to automatic mixing of nutrient-solution for hydroponic culture, was developed for small-scale growers. The metering accuracy of the metering device developed was compared with commercial metering pumps. The mixing performance through the control of EC and pH was also evaluated. The accuracy of the metering device in terms of the full -scale error was $\pm$0.3% , which was much better compared to $\pm$2.45% and $\pm$1.38% for the two types of commercial metering pumps. The mixing system of nutrient-solution with the metering device showed a satisfactory control performance with the accuracies of $\pm$0.05mS/cm and$\pm$0.2pH for EC and pH, respectively.

• Journal of Biosystems Engineering
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• v.23 no.4
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• pp.365-372
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• 1998

This study was carried out to develop a nutrient-solution mixing-and-supplying system, which used a low-cost metering device instead of expensive metering pumps and a fuzzy logic controller. A low cost and precise overflow-type metering device was developed and evaluated by testing the flow discharge for the automatic nutrient-solution mixing-and-supplying system for snail-scale hydroponic sewers. The fuzzy logic controllers, which could predict and meet the desired values of EC and supply rate of nutrient solution were developed and verified by simulation and experiment. this fuzzy logic controller, whose algorithm consists of four crisp inputs, two crisp outputs and nine rules, was developed to predict the desired value of EC and supply rate of nutrient solution and two crisp inputs, one crisp output and nine rules used to control EC to the desired values. The nutrient-solution mixing-and-supplying system showed satisfactory EC control performance with the maximum overshooting of 0.035 mS/cm and the maximum settling time of 15 minutes in case of increasing 0.7 mS/cm. also, the accuracy of the overflow-type metering device in terms of the full-scale error was 2.29% when using solenoid valve only and 0.2% when using solenoid valve and flow control valve together.

• Bulletin of the Korean Chemical Society
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• v.20 no.8
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• pp.939-942
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• 1999

The tie lines delineating ion-exchange equilibria between NiFe2O4-NiCr2O4 spinel solid solution and Fe2O3-Cr2O3 corundum solid solution were determined at 900, 1000, and 1200 ℃ by electron microprobe and energy dispersive X-ray analysis of oxide phases, using the flux growth technique. Activities of the spinel components were calculated from the tie lines, assuming Temkin's ideal mixing in the corundum solid solution. The spinel phase could be expressed by a regular solution with negative deviations from ideality. The Gibbs free energies of mixing for spinel solid solution were discussed in terms of the cation distribution model, based on site preference energies and assuming random mixing on both tetrahedral and octahedral sites.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.425-432
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• 2002

This study was carried out to develop an automatic mixing system of nutrient solution for closed-loop hydroponics using ion electrodes. The results of the study are summarized as follows: 1. It appeared that ion-electrodes had not to be soaked into nutrient solution for a long time since it was much less durable than EC or PH sensors. Once ion-electrodes were soaked into real nutrient solution for a long time, they became unstable. 2. ion measurement modules, which were able to sample recirculated nutrient solution and easily wash and dry ion-electrodes, were developed in order to use ion-electrodes continuously. 3. The results of calibration tests on three kinds of ion electrodes presented that the time required to read measurement data was over 30 seconds. Using the calibration data the regression equations for the ion electrodes were developed. 4. An automatic nutrient-solution mixing system using the three kinds of ion electrodes was developed and then its accuracy was examined. The control errors of the mixing system using ion electrodes were in the range of 9.8 to 12%.

• Journal of computational fluids engineering
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• v.8 no.2
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• pp.16-23
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• 2003

A numerical study of the mixing of two fluids(pure water and a solution of glycerol in water) in a microchannel was carried out. By varying the glycerol content of the glycerol/water solution, the variation in mixing behavior with changes in the difference of the properties of the two fluids(e.g., viscosity, density, diffusivity) was investigated. The mixing phenomena were tested for three micromixers: a square mixer, a three-dimensional serpentine mixer, and a staggered herringbone mixer. The governing equations of continuity, momentum and solute mass fraction were solved numerically. To evaluate mixing performance, a criterion index of mixing of mixing uniformity was proposed. In the systems considered, the Reynolds numbers based on averaged properties were 1 and 10. For low Reynolds number (Re = 1), the mixing performance varied inversely with mass fraction of glycerol due to the dominance of molecular diffusion. The mixing performance by diffusion deteriorated due to a significant reduction in the residence time of the fluid inside the mixers.

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.109-115
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• 1998

Tri-cresyl phosphate(TCP) was synthesized by reaction of phosphorus chloride with mixed cresol(mixture of m-cresol, p-cresol, and others) in the presence of $AlCl_3$. Some of unwanted products and unreactants colored TCP. In order to separate TCP from these, vaccume distillation was carried twice, but colorless TCP could not be producted. Separation of unwanted materials by 2% NaOH solution was introduced before first and second distillation and optimal separation conditions such as NaOH concentration, mixing volume ratio, mixing time, and rpm were investigated for new batch separation and production of colorless TCP Optimal conditions were 2% NaOH solution, 35% mixing volume ratio of 2% NaOH solution, 1.5 hours of mixing time, and 20 rpm.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1841-1844
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• 2004

'Mixing Index($D_I$)'s generally used to measure the degree of mixing. A new method to calculate $D_I$ was proposed, when insoluble solution flows in micromixer. 'Vortex Index (${\Omega}_I$)'which indicate the degree of chaotic advection, is defined and formulated. A lots of arbitrary shaped microchannels were tested to calculate the $D_I$ and ${\Omega}_I$. And then a simple algebraic equation, $D_I=A{\Omega}_I+B$, was obtained. This equation may be used instead of partial differential equation, concentration equation.

• Clean Technology
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• v.23 no.1
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• pp.42-53
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• 2017

Numerical analysis was done to evaluate the fluid distribution inside of the mixing quencher to increase the reaction efficiency of the aqueous hydrogen peroxide solution in the scrubbing column which is used for simultaneous desulfurization and denitrification. Effective injection of the aqueous hydrogen peroxide ($H_2O_2$) solution in the mixing quencher has major effects for improving the reaction efficiency in the scrubbing column by enhancing the mixing of the aqueous $H_2O_2$ solution with the exhaust gas. The current study is to optimize the array of nozzles and the spray angles of the aqueous $H_2O_2$ solution in the mixing quencher by using the computational method. Main concerns of the analysis are how to enhance the uniformity of the $H_2O_2$ concentration distribution in the internal flow. Numerical analysis was done to check the distribution of the internal flow in the mixing quencher in terms of RMS values of the $H_2O_2$ concentration at the end of quencher. The concentration distribution of $H_2O_2$ at the end of is evaluated with respect to the different array of the nozzle pipes and the nozzle tip angles, and we also analyzed the turbulence formation and fluid mixing in the zone. The effect of the spray angle was evaluated with respect to the mixing efficiency in different flow directions. The optimized mixing quencher had the nozzle array at location of 0.3 m from the inlet duct surface and the spray angle is $15^{\circ}$ with the co-current flow. The RMS value of the $H_2O_2$ concentration at the end of the mixing quencher was 12.4%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.2 s.233
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• pp.232-238
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• 2005

The 'Mixing Index($D_I$)' is used as a conventional guidance measuring the degree of mixing for multiphase flows. For the case when insoluble solutions flow in a passive micromixer, a new method to calculate $D_I$ is proposed. The 'Vortex Index(${\Omega}_I$)' is suggested and formulated. We infer that ${\Omega}_I$ relates to the degree of chaotic advection. Various arbitrary shaped microchannels were tested to calculate the $D_I\;and\;{\Omega}_I$, and then a simple algebraic equation, $D_I=Aexp(B{\Omega}_I)$, is obtained. This equation may be used instead of the conventional partial differential equation, concentration equation, to estimate the degree of mixing.