• Journal of Korean Society on Water Environment
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• v.37 no.3
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• pp.168-174
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• 2021

Mixing is a very important unit in water treatment process. A mechanical stirring method is generally used for mixing, but recently, the use of pressurized water mixing method (pump diffusion flash mixer) has gained interest because it is more advantageous in terms of mixing time, noise, energy consumption, and maintenance. The following conclusions were obtained from the study of pressurized water mixing method by Computational Fluid Dynamics. Firstly, the mixing degree in the pipe increased as the density of water increased. Secondly, even if the relative velocity between flow rate in the pipe and the pressurized water was constant, the mixing degree decreased as the flow velocity in the pipe increased. Thirdly, the stronger the injection energy the higher the mixing degree. It was also found that the mixing degree was greatly affected by the injection velocity as compared to the injection flow amount. Finally, the required energy to achieve 95% mixing degree at the distance of 10 times diameter in big pipes of 500 mm to 3000 mm was 0.3 to 4.5 kJ. The result of this study could be used in the process design of injection with water purification chemicals, such as, ozone, chlorine, and coagulant.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3128-3133
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• 2007

The mixing method of water and chemicals is significant in a small-scale water supply system because drinking water should be supplied with a certain quantity of remaining chemicals maintained. In the present study, the concentration distribution and the mixing index were obtained from four models, which were to find out the optimal mixing method of water and chemicals. The two models brought the good mixing effects out of the four, one for providing chemicals from the center of water supply pipe and the other for setting up the semicircle block at the downstream of the chemicals-providing pipe. As a result, the mixing effect was found out to be increased due to the diffusion and the disturbance of flows. In conclusion, these results are expected to contribute to designing the optimal mixing system.

• Journal of computational fluids engineering
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• v.22 no.1
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• pp.1-7
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• 2017

The mixing of water and chemicals is an important process in the water purification plant. In this paper, we compare PDM(pump diffusion mixer) and hydraulic mixer at the basin in the mixing process. The proper flow rates are predicted and compared in both mixers using CFD technique. As a result, the flow rate of purifier chemical liquid should be 5% of that of water for the optimal performance of mixing process. The characteristics of the two mixing methods are compared with each other for strong and weak points on the operation of the purification system, discussed in the view point of CFD simulations.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.345-350
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• 2000

The objective of this study makes investigation into the effect on the properties of underwater antiwashout concrete. which is followed by mixing time and mixing quantity. There is an tendency that (the compressive strength of underwater antiwashout concrete made and cured in fresh water or sea water) is increase when dry mixing time, mixing quantity, total mixing time is increase as unit weight grows. The difference of compressive strength (in case of no dry mixing time and 60 second) is averagely 46.8kgf/㎠ in the fresh water and 35.6kgf/㎠ in sea water. it's considered that dry mixing is dispersed by underwater antiwashout admixture.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3021-3031
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• 1994

Experiments have been performed to find out the effect of the mixing port length of Y-jet atomizers on the spray performance, using air and water as the test fluids. Water and air flow rates and drop sizes were measured at each injection pressure condition for different mixing port length. The air flow rate was almost unaffected by the change of the mixing port length. However, the water flow rate was relatively susceptible to the change of the mixing port length. The mixing point pressure was very much influenced by the mixing port length. Variations of spatial distribution of Sauter Mean Diameter (SMD, $D_{32}$) and the cross-section-averaged SMD ($D_{32,m}$) with different mixing port length and air/water mass flow rate ratio were examined. Generally, when the mixing port length was reduced, the mean drop size decreased and became spatially even.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.1
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• pp.1-10
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• 1993

In order to investigate the environmental properties of set net grounds located in the coastal waters of Yeosu, oceanographic observations on the fishing grounds were carried out by the training ship of Yeosu Fisheries University from Jun. 1988 to Dec. 1990. The resultes obtained are summarized as follows; 1) The water mass in the fishing grounds were divided into the inner water (29.50-31.00$\textperthousand$), the mixed water (31.10-32.70$\textperthousand$) and the offshore water (32.70-34.30$\textperthousand$) according to the distribution of salinity from T-S diagram plotted all salinity data observed from Jun. 1988 to Dec. 1990. In spring the mixing water prevailed and in summer the inner and mixing water. But in autumn and winter the mixing and offshore waters prevailed. 2) The inner water which was formed by land water from the river of Somjin and the precipitation in the Yeosu district flowed southerly along the coast of Dolsando and spread south-easterly in the vicinity of Kumodo. The inner water and offshore water which supplied from the vicinity of Sorido and Yokchido formed the thermal front and halofront. 3) As the mixing water flowing from the western sea of Cheju to the southern coast of korea was low in temperature, the water mass of low temperature which appeared at the offshore bottom of Sorido in summer was considered not to be the Tsushima warm current. 4) As vertical mixing was made frequently in spring, autumn and winter, the differences in temperature and salinity between surface and bottom was respectively small. In summer, however, the mixing was not made because of the inner water expanded offshore through the space between surface and 10m layer and so a thermocline of $2.0^{\circ}C$/10m and halocline of 4.0$\textperthousand$/10m respectively in vertical gradient was formed. 5) In the vicinity of Dolsando and Kum a water low in salinity prevailed, but in the vicinity of Namhaedo and YoKchido the reverse took place. The inner and mixing waters formed at these arease was limited to the observation area not to spread widely.

• Journal of Integrative Natural Science
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• v.14 no.3
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• pp.99-106
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• 2021

A mixture of alcohol and water is commonly used as antifreeze, liquor, and the fundamental solvents for the manufacture of cosmetics, pharmaceuticals, and inks in our daily life. Since various properties of alcohol water mixtures such as density, boiling or melting point, viscosity, and dielectric constant are determined by their mixing ratio, it is very important to know the mixing ratio to predict their properties. One of simple method to find the mixing ratio is measuring the density of the mixtures. However, it is not easy to predict the mixing ratio from the density of the mixtures because the relationship between mixing ratio and density has not been established well. The relationship is dependent on the relative sizes of solute and solvent molecules, and their interactions. Recently, an empirical model to predict the density of glycerol water mixture from their mixing ratio has been introduced. The suggested model is simple but quite accurate for glycerol water mixture. In this article, we investigated the applicability of this model to different alcohol water mixtures. Densities for six different alcohol water mixtures containing various alcohols (e.g., ethylene glycol, 1,3-propane diol, propylene glycol, methanol, ethanol, and 1-propanol) were simulated and compared to experimentally measured ones to investigate the applicability of the model proposed for glycerol water mixtures to other alcohol water mixtures. The model predicted the actual density of all alcohol water mixtures tested in this article with high accuracy at various ratios. This model can probably be used to predict the mixing ratio of other alcohol water mixtures from their densities beyond 6 alcohols tested in this article from their densities.

• Journal of Environmental Science International
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• v.25 no.2
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• pp.231-238
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• 2016

In this study, we have investigated to find optimal pre-treatment flocculation condition by analyzing the floc growth rate with mixing conditions and the membrane permeation flux for pre-treatment step of the membrane process. The higher mixing intensity showed a constant floc size index (FSI) values, and lower mixing intensity increased the degree of dispersion of the FSI values. Results of comparing the distribution characteristics of the FSI value and the permeation flux were more effective in increasing flux when the FSI values were 0.2 or higher. The degree of dispersion of FSI was relatively large in 40 rpm mixing condition compared to 120 rpm. In 40 rpm mixing condition, it decreased the permeation flux compared to 120 rpm because various sizes of flocs were distributed. Coagulation-UF membrane process enhanced 30%~40% of the flux rate compare to UF alone process, and the coagulation-MF process increased up to 5% of the flux rate compare to MF alone process. Pre-treatment, that is, coagulation process, has been found to be less effects on relatively larger pore size for MF membrane. For UF membrane, the flux was a little bit same when applying only the rapid mixing process or rapid mixing with slow mixing processes together. In case of MF membrane, the flux was improved when rapid mixing process applied with slow mixing process together.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.2
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• pp.243-252
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• 2007

Effects of alum dosage on the particle growth were investigated by monitoring particle counts in a rapid mixing process. Kaolin was used for turbid water sample and several other chemicals were added to adjust pH and ionic strength. The range of velocity gradient and mixing time applied for rapid mixing were $200{\sim}300sec^{-1}$ and 30~180 sec, respectively. Particle distribution in the synthetic water sample was close to the natural water where their turbidity was same. The number of particles in the range of $10.0{\sim}12.0{\mu}m$ increased rapidly with rapid mixing time at alum dose of 20mg/L, however, the number of $8.0{\sim}9.0{\mu}m$ particles increased at alum dose of 50mg/L. The number of $14.0{\sim}25.0{\mu}m$ particles at alum dose of 20mg/L was 10 times higher than them at alum dose of 50mg/L. Dominant particle growth was monitored at the lower alum dose than the optimum dose from a jar test at an extended rapid mixing time(about 120 sec). The number of $8.0{\sim}14.0{\mu}m$ particles was lower both at a higher alum doses and higher G values. At G value of $200sec^{-1}$ and at alum dose of 10-20mg/L, residual turbidity was lower as the mixing time increased. But at alum dose above 40mg/L and at same G value, lower residual turbidity occurred in a short rapid mixing time. Low residual turbidity at G value of $300sec^{-1}$ occurred both at lower alum doses and at shorter mixing time comparing to the results at G value of $200sec^{-1}$.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.3
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• pp.370-377
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• 2005

Dispersion of coagulant should be completed in a fraction of a second before the metal hydroxide precipitate has form. For the reason so-called pump diffusion flash mixing (PDFM) have been proposed, and PDFM is one of reasonable methods to quickly disperse the hydrolyzing metal salts. In this study, therefore, we attempt to understand the difference of removal characteristics of natural organic matter (NOM) between pump diffusion flash mixing (PDFM) and conventional rapid mixing (CRM) for coagulation in a water treatment system, and to enhance the removal of NOM through the improved mixing process. DOC and turbidity removal by PDFM higher than those by CRM, while SUVA value of water treated by PDFM was high as compared with that by CRM. Hydrophilic NOM was more effectively removed by PDFM than CRM, since charge neutralization effect increased by quick dispersion of coagulant. The DBP formation potentials due to NOM was effectively reduced by the improved mixing (i.e., PDFM) for coagulation and could be controlled through decrease in concentration of precursor rather than reduction of activity with disinfectant.