• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.28-35
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• 2016

The in-situ thermal response test for the design of a ground heat exchanger of geothermal heat pumps have difficulty in predicting the outlet temperature according to the variation of conditions due to the expense and time. This paper suggests a 3-D CFD analysis method to predict the heat transfer performance of vertical type ground heat exchanger, which is mostly used in national, and the outlet temperature and the slope of two in-situ thermal response tests were compared to test the proposed CFD reliability. The results of CFD analysis showed that the outlet temperature was predicted to within $0.5^{\circ}C$ of the actual value and the slope was predicted to within 1.6%. The reliability of the CFD analysis method was confirmed using this process, and the outlet temperature prediction of the two in-situ thermal response tests was obtained by changing ${\pm}20%$ of the flow rate and the effective thermal conductivity conditions, respectively. The results of CFD analysis showed that the outlet temperature of Case 1 was 28.0 (-20%) and $29.6^{\circ}C$ (+20%) for the flow rate variation and $29.6^{\circ}C$ (-20%) and $28.0^{\circ}C$ (+20%) for the effective thermal conductivity variation, and the outlet temperature of Case 2 was 28.4 (-20%) and $29.8^{\circ}C$ (+20%) for the flow rate variation and $29.7^{\circ}C$(-20%) and $28.4^{\circ}C$(+20%) for the effective thermal conductivity variation.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.137-143
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• 2013

This study is to develop the production method of stepwise dilution gas for the evaluation of complex odor concentration by orifice tube. The basic orifice tube for 10 and 30 times of dilution sample was made at first, and with the combination of the basic orifice tubes we can continuously manufacture the stepwise dilution sample gas for air dilution sensory test ; 10, 30, 100, 300, 1,000, 3,000 times etc. The hole size of orifice tube was 0.84 mm for 10 times of dilution sample, and was 0.34 mm for 30 times. Dilution sample gas made with the basic orifice tube have an excellent reproducibility, 2%RSD. In addition, over 90% of correlation was shown between the sample made by the orifice tube and the sample by the syringe dilution method. Because there was no concentration drift of dilution gas with changes of connected pump flow, the basic orifice tube could be mounted directly with a vacuum suction box, and could be used simply as a tool for the evaluation of odor, especially on site.

• Journal of Bio-Environment Control
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• v.6 no.1
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• pp.48-54
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• 1997

Among the various vegetables eggplant and gourd family can stand against high temperature environmental condition, about 35$^{\circ}C$. However, most of greenhouse farmers are giving up crop cultivation during hot summer season due to extreme temperature, 4$0^{\circ}C$ or above, condition of greenhouse interior. To improve this inferior crop growth condition, for nozzle system was installed in the pet greenhouse and the effect of fog system was investigated in order to determine fog water amount and the required fog nozzle numbers according to house volumes. MEE fog nozzle was selected for this Investigation which can produce water particle size of 27${\mu}{\textrm}{m}$ with water amount of 100$m\ell$ at pumping pressure of 70kg/$\textrm{cm}^2$. House cooling test was conducted in the pet greenhouse with one minute fogging and one minute air ventilation without stopping. It maintained 32$^{\circ}C$ at the house interior when the atmosphere and the house temperature were 35 and 4$0^{\circ}C$, respectively. And, an experimental equation was developed through calculating the changes of relative humidity and temperature with psychrometric equation which revealed the moisture transfer pattern between the house air and fog system. It showed that the required water fogging amounts to reduce 1$0^{\circ}C$, 40 to 3$0^{\circ}C$, needs 80.7$\ell$ for 1-2W(8,350㎥) and 99.9$\ell$ for 3-2G-3S(10,330㎥) type greenhouse with particle size of 27${\mu}{\textrm}{m}$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3518-3524
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• 2015

Spatial and time variation of the precipitation in Korea is high, therefore, more than 2/3 of the annual precipitation is concentrated during the rainy season. Climate change also causes the intensive rainfall in the area of dense population, thus the occurrence frequency of the heavy flood in the impervious area has been increased. Therefore, the structural food mitigation measures such as the construction of the higher design frequency stormwater pipes, pumping stations, and/or detention ponds. The flood bypass tunnel or retention storage is also one of the efficient structures to mitigate flood damage in the urban area. However, the economic feasibility has been controversial because the flood bypass tunnel might be used once or twice a year. To solve the problem, the multi-functional tunnel for the urban traffic and flooding bypass has been considered. In this study, the design criteria of the road and water tunnel has been analysed and the composite design criteria is proposed for the multi-functional tunnel which is expected to be constructed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.748-757
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• 2007

This paper is intended to solve the technical problem that fails in large-capacity induction motor starting due to serious voltage drop during starting period. One induction motor that is established already can reach in steady-state using reactor starting method but the voltage magnitude of PCC (point of common coupling) has dropped down a little. When the same capacity induction motor is installed additionally in the PCC, where the existing induction motor is operating, voltage drop becomes more serious by starting of additional induction motor. As a result, the additional induction motor fails in starting. Therefore, voltage compensation method is proposed so that all of two induction motors can be started completely. First, modeling technique is described in order to implement starting characteristics of large induction motor. And then, this paper proposes strategic starting scheme by proper voltage compensation that use no-load transformer tap control (NLTC) and step voltage regulator (SVR) for starting of two large induction motors successfully and improving the feeding network voltage profile during the starting period. The induction motor discussed in this paper is the pumped induction motor of 2500kVA capacity that is operating by KOWACO (Korea Water Resources Corporation). Modeling and simulation is conducted using PSCAD/EMTDC software.

• Resources Recycling
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• v.9 no.4
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• pp.28-36
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• 2000

This study describes to analyze the characteristics for separation and recovery of both the dried particles and the purified solvent from the waste solvent through the vaporization process by the continuous and instantaneous vacuum drying system. The vacuum drying system for the waste solvents recovery consists of a feeding pump, a double pipe heat exchanger, a vacuum spray chamber, and a condenser. The vacuum drying system heats the waste solvent to the vapor in the double pipe heat exchanger and the expanded vapor is sprayed at the end of the tube. The vaporized solvent in the condenser are recovered. The particles in the waste solvent are separated and dried from the vapor in the vacuum spray chamber. Performance evaluation of the vacuum drying system was conducted using the mixture of the dried pigment particles and benzene or alkylbenzene as test samples. For the mixture of 10 wt% pigment particles an 90% benzene, the recovery efficiency of benzene was 88% with the purity of 99% and the recovery efficiency of dried particles was 94% with the moisture of 1.1 wt%. The size of pigment particles was decreased from $6.5\mu\textrm{m}$ to $5.6\mu\textrm{m}$ in diameter due to high speed spraying and dispersion in the vacuum drying system during drying process. Therefore, the vacuum drying system showed to be an effective method for separating particles and solvent in the waste solvent.

• Journal of Korea Water Resources Association
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• v.45 no.12
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• pp.1213-1226
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• 2012

Evolutionary algorithms, which are frequently used in an automatic calibration of watershed runoff simulation models, are unconstrained optimization algorithms. An additional method is required to impose constraints on those algorithms. The purpose of the study is to modify the SCE-UA (shuffled complex evolution-University of Arizona) to impose constraints by a penalty function and to improve performance of the automatic calibration module of the SWMM (storm water management model) linked with the SCE-UA. As indicators related to peak flow are important in watershed runoff event simulation, error of peak flow and error of peak flow occurrence time are selected to set up constraints. The automatic calibration module including the constraints was applied to the Milyang Dam Basin and the Guro 1 Pumping Station Basin. The automatic calibration results were compared with the results calibrated by an automatic calibration without the constraints. Error of peak flow and error of peak flow occurrence time were greatly improved and the original objective function value is not highly violated in the automatic calibration including the constraints. The automatic calibration model with constraints was also verified, and the results was excellent. In conclusion, the performance of the automatic calibration module for watershed runoff event simulation was improved by application of the penalty function to impose constraints.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.5
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• pp.287-293
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• 2005

In this work, to develop soil inoculant which maintains stable viable cells and normalized quality, studies on micro-encapsulation with bacteria and yeast cells were performed by investigating materials and methods for micro-encapsulation as well as variation and stability of encapsulated cells. Preparation of capsule was conducted by application of extrusion system using micro-nozzle and peristaltic pump. K-carragenan and Na-alginate were selected as best carrier for gelation among K-carageenan, Na-alginate, locust bean gum, cellulose acetate phthalate (CAP), chitosan and gelatin tested. Comparing the gels prepared with Bacillus sp. KSIA-9 and carriers of 1.5% concentration, although viable cell of K-carragenan and Na-alginate was six times higher than those of other, Na-alginate was finally selected as carrier for gelation because it is seven times cheaper than K-carragenan. The gel of 1.5% Na-alginate was also observed to have the best morphology with circular hardness polymatrix and highest viable cell. When investigating the stability of encapsulated cells and the stabilizer effect, free cells were almost dead within 30 or 40 days whereas encapsulated cells decreased in 10% after 30 days and 15-30% even after 120 days. As stabilizer for maintaining viable cell, both 1% starch and zeolite appeared to possess the level of 70-80% cell for bacteria and yeast until after 120 days.

• Fire Science and Engineering
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• v.31 no.5
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• pp.63-69
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• 2017

This study describes the development of a long-distance hose for ultra-high pressure operation, which can be used in conjunction with an ultra-high pressure pump and can be effectively applied to the fire suppression of high-rise buildings and a long, large tunnels. Also, it has phosphorescent properties, which can help to secure the withdrawal route of the fire-fighters when they are threatened by the fire. We developed an ultra-high pressure hose aiming at a pressure of 3 MPa and a flow rate of 2000 lpm and developed an ultra-high pressure fire hose that can withstand this very high pressure by using a double jacket, triple polyurethane coating and warf (Wp) of 52. In order to ensure the performance of the developed ultra-high pressure hose, its structure, appearance, leakage at high pressure, length and elongation were inspected by a certified certification agency, who also subjected it to a peeling test, friction test, breaking pressure test and free fall test. Also, it was studied in addition to the luminescent high-pressure hose for fire-fighting. In the phosphorescence test, the luminance measurement value was more than the reference value of the luminance test after 40 minutes, which confirmed that its performance was satisfactory for fire-fighting products. In the future, if such an ultra-high pressure fire hose were commercialized and applied in the field, it could contribute to securing improved fire suppression and safer exit from fires, as compared to the fire hoses currently used in the suppression of fires in skyscraper buildings and long tunnels.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.163-170
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• 1998

The ultimate goal of total artificial heart is permanent substitute for a failed heart in a patient without any other therapeutic modality. Until now, infection has been the main problem related to the mechanical circulatory support system. The best way to solve this catastrophic complication and to improve the quality of life of TAH patients in terms of tethering must be implantation of TAH totally. The EH-TAH has been developed in NCVC from 1987 for this purpose. The system consists of an energy converter and pumps, which are designed to be placed in abdomen and pericardial space separately for a good anatomical fit. To evaluate the anatomical fit and hemodynamic performance of the EH-TAH, in vivo test was done. General condition of the animal and hemodynamic status had been stable until the TAH stopped on the 11th pumping day. The estimated cardiac output was about 7.7L/min. The values of mean aortic pressure, left and right atrial pressure were 93$\pm$10, 19$\pm$3 and 15$\pm$4 mmHg, respectively. The correlation coefficient between left and right atrial pressure was 0.96, which represents the dynamic function of the interatrial shunt in controlling left-right imbalance of cardiac output. During pumping days, the temperature on the surface of actuator had been maintained at 39.7$\pm$0.4$^{\circ}C$, less than 1$^{\circ}C$ higher than the rectal temperature. The TAH stopped on the 11th day due to mechanical problems. We concluded that the EH-TAH possessed satisfactory basic performance including anatomic fit and hemodynamic adequacy, although there were several mechanical problems to be solved yet.