• Journal of Biosystems Engineering
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• 제30권1호
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• pp.17-24
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• 2005

An efficient microbial control system was introduced into a garlic peeling system using pressurized water in order to improve the quality and the shelf-life of peeled garlic. High microbial density of the spoiled peeled garlic and the water used for peeling and washing indicated that an efficient microbial control system is necessary far the peeling system. Though Pseudomonas spp. and Penicillium spp. were closely related to the spoilage of peeled garlic, the spoilage of peeled garlic was thought to be caused mainly by nonspecific increase in microbial density. The shelf-life of the garlic peeled by pressurized water was longer than that of the garlic peeled by pressurized air, and the degree of damage had great effect on the shelf-life of peeled garlic. Ozonated water was effective in decreasing the microbial contamination and in increasing the shelf-life of peeled garlic. Based on the findings of the study, following improvements were made to the garlic peeling system using pressurized water; 1) the water circulation system was modified in order to completely separate the water for washing from the water for garlic peeling, 2) filtration and cooling equipments were introduced into the circulation system of the water for peeling, and 3) an ozone generator which could continuously supply ozonated water (dissolved ozone concentration of 0.4 ppm) was attached to the circulation system of the water for washing.

• 한국기후변화학회지
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• 제9권1호
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• pp.75-80
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• 2018

The problem of water shortages and water related disasters caused by climate change has increased the seriousness of water problems and the importance of water treatment technology capable of securing clean water is expanding. In this study, we analyzed not only the water pollutant generated by the filtration system technology of various water treatment technologies but also the indirect greenhouse gas emissions generation, and analyzed the influence on the environment. The subjects of study are Fabric Filter, Reverse Osmosis System and Pressurized Microfiltration Device which are widely used for water treatment and we analyzed the impact on the environment using the Life Cycle Assessment (LCA) method using the electricity amount necessary for use, the water purification efficiency, the throughput per ton and the cost. The amount of greenhouse gas generated when the Pressurized Microfiltration Device operates for 1 year is $2.15E+04kg\;CO_2-eq$., Fabric Filter is $3.29E+04kg\;CO_2-eq$., and Reverse Osmosis System is $1.68E+05kg\;CO_2-eq$. As a result of analyzing the amount of greenhouse gas generated at the time of purifying 1 ton of the Pressurized Microfiltration Device and the conventional filtration system, the Pressurized Microfiltration Device was $20.5g\;CO_2-eq$., Fabric Filter was $34.7g\;CO_2-eq$., and Reverse Osmosis System was $191.7g\;CO_2-eq$. The amount of greenhouse gas generated was calculated to be 41.0% less than that of the Fabric Filter by the Pressurized Microfiltration Device and 89.3% less than the Reverse Osmosis System. From the viewpoint of climate change, it is necessary to select a filtration system that takes climate change into account, not from the viewpoint of water quality removal efficiency and economic efficiency according to future water treatment applications, and it is necessary to select a water treatment filtration system more researches and improvements will be made for.

• 한국물환경학회지
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• 제37권3호
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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.

• 제어로봇시스템학회논문지
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• 제14권3호
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• pp.221-225
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• 2008

This paper presents a self-tuning controller for pressurized water reactor (P.W.R.). This self-tuning controller includes two substantial steps, such as parameter identification and control-law building in each cycle. Extended least square algorithm is used for parameter identification, Kalman filter is used for state estimation, and discrete Riccati equation is used for optimal control. Effectiveness of this algorithm is shown through computer simulation and sensitivity analysis.

• Nuclear Engineering and Technology
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• 제48권1호
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• pp.72-86
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• 2016

A steam explosion may occur during a severe accident, when the molten core comes into contact with water. The pressurized water reactor and boiling water reactor ex-vessel steam explosion study, which was carried out with the multicomponent three-dimensional Eulerian fuel-coolant interaction code under the conditions of the Organisation for Economic Co-operation and Development (OECD) Steam Explosion Resolution for Nuclear Applications project reactor exercise, is presented and discussed. In reactor calculations, the largest uncertainties in the prediction of the steam explosion strength are expected to be caused by the large uncertainties related to the jet breakup. To obtain some insight into these uncertainties, premixing simulations were performed with both available jet breakup models, i.e., the global and the local models. The simulations revealed that weaker explosions are predicted by the local model, compared to the global model, due to the predicted smaller melt droplet size, resulting in increased melt solidification and increased void buildup, both reducing the explosion strength. Despite the lower active melt mass predicted for the pressurized water reactor case, pressure loads at the cavity walls are typically higher than that for the boiling water reactor case. This is because of the significantly larger boiling water reactor cavity, where the explosion pressure wave originating from the premixture in the center of the cavity has already been significantly weakened on reaching the distant cavity wall.

• 환경위생공학
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• 제23권4호
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• pp.13-21
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• 2008

With the rise in membrane applications, residuals management has become a growing challenge for membrane system. The primary residuals of MF/UF (microfiltration/ultrafiltration) system results from the wastes generated during backwashing. Many regulatory agencies, utilities, and water process engineers are unfamiliar with the characteristics and methods for treatment and disposal of membrane residuals. Therefore, this study was performed to investigate the backwash residuals water quality from the pressurized system with and without pre-coagulation, and to suggest approaches for the backwash residuals treatment. Pressurized MF system was installed at Guui water intake pumping station and operated with raw water taken from the Han River. We compared performances with and without the recycling backwash residuals at flux conditions, 50 LMH and 90 LMH with and without pre-treatment (coagulation). Based on the results, recycling of backwash residuals in pressurized system with pre-coagulation showed applicability of backwash residuals managements. Moreover, the recovery rate also increased up to over 99%.

• KSBB Journal
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• 제18권3호
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• pp.202-206
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• 2003

역미셀과 가압이산화탄소를 이용한 난백 lysozyme의 추출실험에서 일정한 압력의 이산화탄소를 유기용액에 가하였을 때 lysozyme의 추출율과 그 때 형성되는 역미셀의 크기, 즉 역미 셀 내부의 수분함량 ($W_{0}$)를 알아보았다. 이산화탄소로 가압된 상태에서도 수용액에서 유기용액으로의 lysozyme의 추출 경향은 실험조건인 수용액의 이온강도, pH, 유기용액의 계면활성제의 농도를 달리 하였을 때 기존의 다른 연구와 유사한 경향을 나타내었으며, 이산화탄소의 압력을 102 bar까지 증가시켰을 때 가장 높은 추출율을 나타내었다. 또한 이때 역미셀 내부의 수분함량 ($W_{0}$)을 측정한 결과, lysozyme의 추출율과 역미셀 내부의 수분함량은 비례함을 확인할 수 있었다.

• 한국물환경학회지
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• 제28권2호
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• pp.292-299
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• 2012

The objective of this study is to develop a novel method for evaluating forward osmosis (FO) membrane performances using a non-pressurized FO system. Basic membrane performance parameters including water (A) and solute (B) permeability coefficients and unique parameter for FO membrane such as the support layer structural parameter (S) were determined in two FO modes (i.e., active layer faces feed solution (AL-FS) and active layer faces draw solution (AL-DS)). Futhermore, these parameters were compared with those determined in a pressurized reverse osmosis (RO) system. Theoretical water flux was calculated by employing these parameters to a model that accounts for the effects of both internal and external concentration polarization. Water flux from FO experiment was compared to theoretical water fluxes for assessing the reliability of those parameters determined in three different operation modes (i.e., AL-FS FO, AL-DS FO, and RO modes). It is demonstrated that FO membrane performance parameters can be accurately measured in non-pressurized FO mode. Specifically, membrane performance parameters determined in AL-DS FO mode most accurately predict FO water flux. This implies that the evaluation of FO membrane performances should be performed in non-pressurized FO mode, which can prevent membrane compaction and/or defect and more precisely reflect FO operation conditions.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2017년도 학술발표회
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• pp.265-269
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• 2017

Because of abrupt changes for velocity in water, transient flow is occurred in practical life. To reduce and avoid the high or low pressure of pipe network system, various surge protection facilities are used to prevent the risk in pipe network system. Especially, we focused on study not only preventing positive and negative pressure but also selecting adequate equipment for high pressurized pipelines. Several critical cases were considered by undertaking a steady state hydraulic study and transient dynamic simulation and we suggested that the surge vessel of various surge protection system was recommended to control high and low pressures on pipeline system in perspective.

• 방사성폐기물학회지
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• 제20권3호
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• pp.357-364
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• 2022

The safety of a KTC-360 transport cask, a large-capacity pressurized heavy-water reactor transport cask that transports CANDU spent nuclear fuel discharged from the reactor after burning in a pressurized heavy-water reactor, must be demonstrated under the normal transport and accident conditions specified under transport cask regulations. To confirm the thermal integrity of this cask under normal transport and accident conditions, high-temperature and fire tests were performed using a one-third slice model of an actual KTC-360 cask. The results revealed that the surface temperature of the cask was 62℃, indicating that such casks must be transported separately. The highest temperature of the CANDU spent nuclear fuel was predicted to be lower than the melting temperature of Zircaloy-4, which was the sheath material used. Therefore, if normal operating conditions are applied, the thermal integrity of a KTC-360 cask can be maintained under normal transport conditions. The fire test revealed that the maximum temperatures of the structural materials, stainless steel, and carbon steel were 446℃ lower than the permitted maximum temperatures, proving the thermal integrity of the cask under fire accident conditions.