• Journal of computational fluids engineering
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• v.14 no.3
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• pp.69-75
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• 2009

The objective of this study is to investigate the suitable design for a domestic Circulating water pump(CWP), which is used in cooling-water intakes for the unit 3 and 4 of Yeonggwang nuclear power plant. All the simulations are performed, using CFD method with a commercial code STAR-CCM+ version 3.02. After modeling a present design of the pump, the flow around the rotating blade was calculated by using quasi-static method and sliding mesh method with the almost same condition as an actual state. Based on fundamental simulations with various depth of sea water, the reference pressure for the boundary condition of the present study was decided. To verify the reliability of the calculation results, the suction flow rate of the data was compared with that of the experimental data. As a result of this comparison, it is confirmed that two results are fairly consistent. For the improvement of the suction flow rate, computational analysis was done by changing a flow channel and blade shapes. It is shown that the suction flow rate of the new pump was improved.

• Journal of the Korean Society of Visualization
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• v.21 no.3
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• pp.23-32
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• 2023

This study aims to explore the heat transfer and flow phenomena inside an instant water heater and the influence of the design parameters of the water heater on the heating performance was investigated by 3-D numerical simulations considering heat convection. The design parameters are the heating ceramic dimension, the power of the heating device, and the water flow rate. The results show that a reasonable space for the heating device is required to optimize the heating performance. It is desirable to design higher heating device as possible for a given electric power. There exists a critical water flow rate that best meets the heating performance. The change in electric power has no impact on the flow phenomena and heating performance.

• The Journal of the Korea Contents Association
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• v.17 no.2
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• pp.535-542
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• 2017

There is a big difference of discharge rate between drought and flood period in Korea since the importance of water resources management has come to the fore. To know a river characteristics, it needs to estimate river discharge accurately. River discharge is calculated using the measured velocity of cross section and the estimated area of watercourse as input parameters into continuity equation. Generally, flow rate over a river is estimated from the relation equation between level and discharge, in this case, there are weakness for only the equal depths and the equal discharge estimated. In the present study, therefore, water surface slope was estimated using measured water level of Seongseo water level observation station and measured water level using ADVM at Gangchang Bridge. And then, we developed the discharge calculation equation using water surface slope. A method to easily calculated flow rate from the measured depth of the two points that are suggested by reflecting water surface slope because natural stream is unsteady flow, not uniform flow or not steady flow.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.339-342
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• 2004

It is research about special quality of ozone gas concentration and dissolved ozone concentration that show according to change of flow rate when liquefied ozone gas in water. If increase flow rate of ozone gas, ozone concentration increases being proportional and amount to fixed flow rate, dissolved ozone concentration was measured low. When ozone concentration How rate 1000 [ppm], dissolved ozone concentration smelted to flow rate 1.5[Q] for 28 [min] is $0.1740{\sim}0.8020[mg/l]$. Could know that half-life is most short by 3 minutes 8 seconds in flow rate 1.5 [Q]. And ozone smelted 20 minutes later after half-life measurement became disjointing all.

• Solar Energy
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• v.8 no.2
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• pp.46-56
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• 1988

This investigation concerns thermal stratification of the water due to the temperature difference (${\Delta}T=T_{\infty}-T_i$) between the mean temperature of the water in the test tank (1m wide, 1m high, 2.1m long) and the temperature of the inflow water into the tank; flow rate of circulating water and height of the sink diffuser in the test tank. The additional objectives was to observe a stratification phenomena near an interface by measuring the velosities and the temperature difference and investigate an availabilities of the better effective hot water through establishing thermocline near an interface around the bottom of the tank. Following results were obtained through the experiments. 1. When the flow rate was constant and the temperature difference (${\Delta}T=T_{\infty}-T_i$) between the mean temperature of the flow in the test tank and the temperature of the inflow water increased by 5.6, 9.5, 13.5($^{\circ}C$), obtained the better effective advantage of hot water and the stress near an interface increased gradually. 2. When the ${\Delta}T=T_{\infty}-T_i$ was constant and flow rate increased by 4.0, 4.8, 6.4, 8.0 (LPM), obtained the better effective advent age of hot water and the mean stress near an interface increased gradually. 3. When the height of the sink diffuser was 25cm from tank bottom in comparison with 50cm, obtained the better effective advantage of hot water and the mean stress near an interface increased.

• Solar Energy
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• v.19 no.4
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• pp.33-43
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• 1999

The study on ice thermal storage system is to improve total system performance and increase the economical efficiency in actual all-conditioning facilities. To obtain the high charging and discharging efficiencies in ice thermal storage system, the improvement of thermal stratification is essential, therefore the process flow must be piston flow in the cylindrical type. With the relation of the aspect ratio(H/D) in the storage tank, the stratification is formed better as inlet flow rate is smaller. If the inlet and the outlet port are settled at the upside and downside of the storage tank, higher storage rate could be obtainable. In case that the flow directions inside the thermal storage tank are the upward flow in charging and the downward in discharging, thermal stratification is improved because the thermocline thickness is maitained thin and the degree of stratification increases respectively. In the charging process, in case of inlet flow rate the thermal stratification has a tendency to be improved with the lower flow rate and smaller temperature gradient in case of inlet temperature, the large temperature difference between inflowing water and storage water are influenced from the thermal conduction. The effect of the reference temperature difference is seen differently in comparison with the former study for chilled and hot water. In the discharging process, the thermal stratification is improved by the effect of the thermal stratification of the charging process.

• Korean Journal of Agricultural Science
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• v.35 no.2
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• pp.225-235
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• 2008

The objective of this study is to evaluate the hydrological feasibility of heightening the Dae-ah reservoir in order to save instream flow at the Bong-dong station situated in the Mankyoung river. The results are summarized as follows. Firstly, from the Dong-sang and Dae-ah cascaded reservoir's water balance analysis, water supply indexes of the Dae-ah reservoir were analyzed to have the rate of water supply divided by watershed area of 1207.4 mm, the rate of water supply divided by rainfall of 95.8%, the rate of water supply divided by inflow of 153.1%, the rate of water supply divided by storage capacity of 236.1%, and the rate of inflow divided by storage capacity of 200.6%. Secondly, from the Dae-ah and Kyoung-cheon paralleled reservoir's water balance analysis, flow durations at the Bong-dong station were analyzed to have the Q95 (the 95th high flow) of $28.95m^3/s$, the Q185 (the 185th high flow) of $2.00m^3/s$, the Q275 (the 275th high flow) of $2.00m^3/s$, and the Q355 (the 355th high flow) of $0.82m^3/s$. Thirdly, in case of heightening the full water level of the Dae-ah reservoir of 10m, from the Dong-sang and Dae-ah cascaded reservoir's water balance analysis, water supply indexes of the Dae-ah reservoir were analyzed to have the rate of water supply divided by watershed area of 1220.7 mm, the rate of water supply divided by rainfall of 96.8%, the rate of water supply divided by inflow of 154.6%, the rate of water supply divided by storage capacity of 160.0%, and the rate of inflow divided by storage capacity of 137.0%. Fourthly, in case of heightening the full water level of the Dae-ah reservoir of 10m, from the Dae-ah and Kyoung-cheon paralleled reservoir's water balance analysis, flow durations at the Bong-dong station were analyzed to have the Q95 of $28.09m^3/s$, the Q185 of $1.79m^3/s$, the Q275 of $1.79m^3/s$, and the Q355 of $0.82m^3/s$. The conclusion appeared not to have the hydrological feasibility of heightening the Dae-ah reservoir from the reason that increased storage capacity does not increase water supply amount any more because of the high rate of the water supply divided by inflow.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.2
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• pp.83-90
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• 1985

The thesis is established on the basis of model tests on the central core dam. With variations in the upstream water level, the quantity of seepage in the downstream boundaries were obtained for each specific water level. Seepage alignment and equipotential lines to these occasions were also researched and measured. By making use of the resulting data from the experiment, the flow velocities and seepage quantity computed to the flow rate of each element of flownets by the Finite Element Method was compared with the values produced by experiments and approximate theoretical formula. Further to this, transitions of water level related thereto was also examined in the thesis. During the high water level, seepages shown by the experiment were larger than that of the F.E.M. Meanwhile, the in-between differences were found to be quite small during the low water level. In the flow rate of each element with which the flow-nets are constructed, flow velocities of the X and Z axis were faster on account of the variations in water level. Flow velocities of the Y axis were extremely small enough to be disregarded.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.73-88
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• 2014

Various studies on the critical flow models for sub-cooled and/or saturated water were reviewed, especially on Fauske, Moody, and Henry for basic theoretical models; Zaloudek for insight into physical phenomena for a critical flow in an orifice type flow path; Sozzi & Sutherland for a critical flow test of saturated and sub-cooled water at high pressure for orifice and nozzles; and a Marviken test on a full-scale critical flow test. In addition, critical flow tests of sub-cooled water for the break simulators in integral effect test (IET) facilities were also investigated, and a hybrid concept using Moody's and Fauske's models was considered by the authors. In the comparison of the models for the selected test data, discussions of the effect of the diameters, predictions of the critical flow models, and design aspects of break simulator for SBLOCA scenarios in the IET facilities were presented. In the effect of diameter on the critical flow rate with respect to all dimensional scales, it was concluded that the effect of diameter was found irrespective of diameter sizes. In addition, the diameter effect on slip ratio affecting the critical flow rate was suggested. From a comparison of the critical flow models and selected test data, the Henry-Fauske model of the MARS-KS code was found to be the best model predicting the critical flow rate for the selected test data under study.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4329-4337
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• 2022

Jet impinging device is designed for decay heat removal on horizontal fuel rods in a low temperature heating reactor. An experimental system with a fuel rod simulator is established and experiments are performed to evaluate water film covering capacity, within 0.0287-0.0444 kg/ms mass flow rate, 0-164.1 kW/m² heating flux and 13.8-91.4℃ feeding water temperature. An effective method to obtain the film coverage rate by infrared equipment is proposed. Water film flowing patterns are recoded and the film coverage rates at different circumference angles are measured. It is found the film coverage rate decreases with heating flux during single-phase convection, while increases after onset of nucleate boiling. Besides, film coverage rate is found affected by Marangoni effect and film accelerating effect, and surface wetting is significantly facilitated by bubble behavior. Based on the observed phenomenon and physical mechanism, dry-out depth and initial dry-out rate are proposed to evaluate film covering potential on a heating surface. A model to predict film coverage rate is proposed based on the data. The findings would have reliable guide and important implications for further evaluation and design of decay heat removal system of new reactors, and could be helpful for passive containment cooling research.