• 태양에너지
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• 제9권1호
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• pp.30-35
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• 1989

This paper dealt with an experiments on temperature vairation in the heat storage zone due to change of vertical location (height) of sink diffuser and flow extraction in small saltless solar pond ($0.5{\times}0.5{\times}1.0M$), and the honeycomb device for this experimental purpose consisted of one-tired, sealed, and air filled by honeycomb panels. As results of experiments, 1) The storage zone was formed under lower region below the honeycomb device. 2) The higher vertical location of sink diffuser was placed, the more mixing phenomenon increased in the pond at steady flow extraction. 3) The more flow extraction increased, the more mixing phenomenon decreased at constant heat exchanger and variable flow extraction.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 가을 학술발표회 논문집
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• pp.629-634
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• 2002

Demands for the automatic measurement on angle and depth of equipment were arisen for the better construction in deep mixing method and grouting method. Civil, geotechnical, electronic, and communication experts worked together for the development of automatic measuring devices using wire and wireless transmitting-receiving set. The results on the development of automatic devices in an industrial installation will be presented.

• Nuclear Engineering and Technology
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• 제42권4호
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• pp.382-393
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• 2010

Thermal mixing by steam jets in a pool is dominantly influenced by a turbulent water jet generated by the condensing steam jets, and the proper prediction of this turbulent jet behavior is critical for the pool mixing analysis. A turbulent jet flow induced by a steam jet discharged through a vertical upward single hole into a subcooled water pool was subjected to computational fluid dynamics (CFD) analysis. Based on the small-scale test data derived under a horizontal steam discharging condition, this analysis was performed to validate a CFD method of analysis previously developed for condensing jet-induced pool mixing phenomena. In previous validation work, the CFD results and the test data for a limited range of radial and axial directions were compared in terms of profiles of the turbulent jet velocity and temperature. Furthermore, the behavior of the turbulent jet induced by the steam jet through a horizontal single hole in a subcooled water pool failed to show the exact axisymmetric flow pattern with regards to an overall pool mixing, whereas the CFD analysis was done with an axisymmetric grid model. Therefore, another new small-scale test was conducted under a vertical upward steam discharging condition. The purpose of this test was to generate the velocity and temperature profiles of the turbulent jet by expanding the measurement ranges from the jet center to a location at about 5% of $U_m$ and 10 cm to 30 cm from the exit of the discharge nozzle. The results of the new CFD analysis show that the recommended CFD model of the high turbulent intensity of 40% for the turbulent jet and the fine mesh grid model can accurately predict the test results within an error rate of about 10%. In this work, the turbulent jet model, which is used to simply predict the temperature and velocity profiles along the axial and radial directions by means of the empirical correlations and Tollmien's theory was improved on the basis of the new test data. The results validate the CFD model of analysis. Furthermore, the turbulent jet model developed in this study can be used to analyze pool thermal mixing when an ellipsoidal steam jet is discharged under a high steam mass flux in a subcooled water pool.

• 수산해양기술연구
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• 제35권3호
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• pp.237-241
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• 1999

It was investigated that the condition of fishing ground gave what kind of effect school type in relation to the property for the target school after the vertical temperature profile and school type were observed when tuna purse seiner for tuna purse seine was operated in the western pacific Ocean around the equator between December 12, 1993 and January 26, 1994. The results are as follows;1. This study divided fish schools associated with drift objects, a one targeted-operation, and the pelagic migrating fish schools that are another one for the property. The total of 23 operations were complected including 6 that targeted fish schools associated with drift objects and 17 that targeted pelagic migrating fish schools. It was known that the main operation was conducted on pelagic migrating fish school.2. Average and standard deviation of the depth of the surface mixing layer was 86.0m and 13.8m for fish schools associated with drift objects. 61.6m and 13.0m for pelagic migrating fish schools, respectively. The average depth of the surface mixing layer of the pelagic migrating fish schools was lower when compared to the fish schools associated with drift objects however the concentration of standard deviation was higher than those fish schools associated with drifted objects. Accordingly, it was assumed that the effect of vertical temperature profile for pelagic migrating fish school was higher than the fish schools associated with drift objects.

• 한국전산유체공학회지
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• 제21권3호
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• pp.24-30
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• 2016

In the water purification plant, the mixture of water and chemical from the mixing basin enters the flocculation basin. The rotating flocculators are generally used for the efficient flocculation of dregs. In this paper, the performance of flocculators of a vertical paddle type, widely used in the typical flocculation basins, and a hydro-foil type, recently disseminated in the field, are compared with each other by use of the numerical method. Also the characteristics and the efficiency are analyzed with CFD techniques. The strain rate and the eddy viscosity are compared for two types to predict the mixing efficiency, and the maximum speed and its location are pursued from the computed data. The hydrofoil type shows that the eddy viscosity is enhanced 1.66 to 3.03 times larger than that of vertical paddle type, and also produced 1.87 to 1.95 times larger flocs for each stage. However, the rapid rotation of hydrofoil may chop the floc to small size due to the higher turbulence intensity. From the result of computation, the strong and weak points of each type have been analyzed for the decision making.

• 한국정밀공학회지
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• 제21권8호
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• pp.97-105
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• 2004

The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Table liner is one of grinding elements of vertical roller mill and is subjected to the cyclic bending stress by rollers and the centrifugal force by rotation of table. It demands $4{\times}10^7$ expense of life but has $4{\times}10^6~-8{\times}10^6$ cycle. It fractures at the edge of grinding path of outside roller The repair expense fur it amounts to 30% of total maintenance of vertical roller mill. Therefore, this study shows the fracture mechanism of table liner of vertical roller mill using HDM and fatigue analysis

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.163-169
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• 2003

The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Table liner is one of grinding elements of vertical roller mill and is subjected to the cyclic bending stress by rollers load and the centrifugal force by rotation of table. It demands $4{\times}10^7$ cycle but has $4{\times}10^6{\sim}8{\times}10^6$ cycle. It fractures at the edge of grinding path of outside roller. The repair expense for it amounts to 30% of total maintenance of vertical roller mill. Therefore, this study shows the fracture mechanism of table liner for vertical roller mill using HDM and fatigue analysis

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1130-1135
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• 2004

The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Vertical roller mill is subjected to the cyclic bending stress by rollers load. It demands $4{\times}10^7$ cycle but has $4{\times}10^6{\sim}8{\times}10^6$ cycle. It fractures at the edge of grinding path of outside roller. The repair expense for it amounts to 30% of total maintenance. Therefore, this study shows optimal design for vertical roller mill using DOE and neural network.

• 한국대기환경학회지
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• 제16권2호
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• pp.141-150
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• 2000

In order to genralize the vertical dispersion of plume at long distances on mesoscale over complex terrain dispersion coefficients data have been obtained systematically according to lapsed time after release by using a composite turbulence water tank that simulates convective boundary layer. Dispersion experiments have been carried out for various combined conditions of thermal turbulence intensity mechanical turbulence intensity and plume release height at slightly to moderately unstable conditions. Results of tracer dispersion experiments conducted using water tank camera and image processing system have been converted into atmospheric dispersion data through the application of similarity law. The equation $\sigma$z/Zi=aX/(b+c X2)0.5 where $\sigma$2; vertical dispersion coefficient zi : mixing height X : dimen-sionaless downwind distance was confirmed to be an appropriate and general equation for expressing $\sigma$2 variation with turbulence intensity and plume release height, The value of "a" was found to be principally affected by mechanical turbulence intensity and that of "b" by mechanical turbulence intensity and release height. It was confirmed that the magnitude of "c" varies with release height. Results of water tank experiments on the relationship of $\sigma$2 vs downwind distance x have been compared with actual atmospheric dispersion data such as CONDORS data and Bowne's nomogram Operating conditions of a composite turbulence water tank for simulating the field turbulence situations of CONDORS experiments and Bowne's $\sigma$2(x) nomogram for suburban area have also been investigated in terms of water temperature difference between convection water tank and bottom plate heating tank grid plate stroke mixing water depth length scale and velocity scale. Moreover the effect of mechanical turbulence intensity on vertical dispersion has been discussed in the light of release height and downwind distance. height and downwind distance.

• 대기
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• 제32권4호
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• pp.307-322
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• 2022

A drone has recently got attention as an instrument for weather observation in lower atmosphere because it can produce the high spatiotemporal resolution weather data even though the weather phenomenon is inaccessible. Sea fog is a weather phenomenon occurred in lower atmosphere, and has observational limitations because it occurs on the sea. Therefore, goal of this study is to analyze the vertical structures about inflow, development and dispersion of sea fog using the high-resolution weather data with the meteorological sensor-equipped drone. This study observed sea fogs in the west coast of the Korean peninsula from March to October 2021 and investigated one sea fog inflowed into the coast on June 8th 2021. θ_e - q_v diagrams (θ_e: equivalent potential temperature, q_v: water vapor ratio) and vertical wind structures were analyzed. At inflow of sea fog, moist adiabatically stable layer was formed in 0-300 m and prevailing wind was switched from south-southwesterly to west-southwesterly under 120 m. Both changes are favorable for sea fog on the location. θ_e and q_v plummeted in a layer 0-183 m. The inflowed sea fog developed from 183 m to 327 m by mixing with ambient atmosphere on top of sea fog. Also, strong mechanical turbulence near ground drove a vertical mixing under stable layer. At dispersion of sea fog, as θ_e on ground gradually increased, air condition was changed to neutral. Evaporation occurred on both bottom and top in sea fog. These results induced dissipation of sea fog.