• Progress in Superconductivity and Cryogenics
• /
• v.15 no.3
• /
• pp.49-52
• /
• 2013

An experiment to investigate the natural circulation of a cryogen has been performed. The study is motivated mainly by our recent development of cryogenic cooling system for prototype superconducting cyclotron without any circulating pump. In the natural circulation loop system, a cooling channel is attached on the outer surface of the aluminium block and the liquid nitrogen passes through inside of the channel to cool the block indirectly. A cryocooler as a heat sink is located at the top to re-condense cryogenic vapor coming from the aluminium block in which electrical heater is installed as a heat source. The main dimensions are determined using the relevant analysis and the natural circulation loop is successfully fabricated. The temperature distributions in the loop are measured during initial cool-down process and in steady state, from which the modified Grashof numbers are calculated and compared with the existing correlation estimated with one-dimensional analysis for steady state flow.

• Nuclear Engineering and Technology
• /
• v.52 no.12
• /
• pp.2789-2802
• /
• 2020

Small Modular Reactors (SMRs) are attracting wide attention due to their outstanding performance, extensive studies have been carried out for lead-based fast reactors (LFRs) that cooled with Lead or Lead-bismuth (LBE), and small modular natural circulation LFR is one of the promising candidates for SMRs and LFRs development. One of the challenges for the design small modular natural circulation LFR is to master the natural circulation thermal-hydraulic performance in the reactor primary circuit, while the natural circulation characteristics is a coupled thermal-hydraulic problem of the core thermal power, the primary loop layout and the operating state of secondary cooling system etc. Thus, accurate predicting the natural circulation LFRs thermal-hydraulic features are highly required for conducting reactor operating condition evaluate and Thermal hydraulic design optimization. In this study, a thermal-hydraulic analysis code is developed for small modular natural circulation LFRs, which is based on several mathematical models for natural circulation originally. A small modular natural circulation LBE cooled fast reactor named URANUS developed by Korea is chosen to assess the code's capability. Comparisons are performed to demonstrate the accuracy of the code by the calculation results of MARS, and the key thermal-hydraulic parameters agree fairly well with the MARS ones. As a typical application case, steady-state analyses were conducted to have an assessment of thermal-hydraulic behavior under nominal condition, and several parameters affecting natural circulation were evaluated. What's more, two characteristics parameters that used to analyze natural circulation LFRs natural circulation capacity were established. The analyses show that the core thermal power, thermal center difference and flow resistance is the main factors affecting the reactor natural circulation. Improving the core thermal power, increasing the thermal center difference and decreasing the flow resistance can significantly increase the reactor mass flow rate. Characteristics parameters can be used to quickly evaluate the natural circulation capacity of natural circulation LFR under normal operating conditions.

• 한국전산유체공학회:학술대회논문집
• /
• 1999.11a
• /
• pp.152-157
• /
• 1999

For the simulation of the blood flow in coronary artery, the system modeling of coronary hemodynamics is combined with CFD technique. The blood flow in coronary artery interacts with the global coronary circulation. Especially in case of the coronary artery with stenosis, the interaction plays an important role in the hemodynamics of the circulation. In this study we present a combined numerical approach using both the CFD technique for flow simulation and the global system model of coronary circulation. We use a lumped parameter model for the global simulation of coronary circulation whereas the finite element method is employed to compute the viscous flow field in stenosed coronary artery, The time variation of the pressure drop due to stenosis is obtained from the proposed numerical method. Numerical results shows that the flow resistance and pressure drop due to stenosis has a relatively large value in systole.

• Journal of Environmental Impact Assessment
• /
• v.21 no.1
• /
• pp.133-142
• /
• 2012

Convection Current Circulation System(CCCS) in stratified reservoir controls development of anaerobic condition and algal bloom during summer. In order to increase the CCCS effectiveness, we analyze diverse design parameters to make optimize the flow pattern in reservoir. In this study, we interpret the internal flow with installation and operation condition of CCCS based on CFD in reservoir. Design variables of CCCS is reservoir depth, stratification strength, distance of between CCCS and so on. Since reservoir depth and stratification strength in variables is depending on natural phenomenon, we evaluated current circulation effect by distance of CCCS and proposed the optimal design condition using CFD simulation. Flow and diffusion changes in water body was assessed by temperature and dye test. Changes in water floor temperature at 40m intervals was slowly descending over 37 hours. Dye diffusion simulation at 60m intervals, the radius of the spread between two devices were overlapped after 12 hours.

• Proceedings of the Korean Institute of Interior Design Conference
• /
• 2002.04a
• /
• pp.105-110
• /
• 2002

This study aims for the research of the local circulation in a kitchen to minimize the kitchen work load and to produce a more efficient kitchen system. This study analized the real behavior and circulation in the kitchen area and this focused on the kitchen of the working women in a dual-income family. Through the analisis, this study raised an idea that the work in the kitchen area is not in sequence, but random while the tradition idea of the kitchen system is arranged by cooking programe. Therefore, this became a reason to increase the kitchen work load ratter than the layout of the kitchen system, the cooking style and menu affected on the more kitchen load. To reduce the kitchen work load, the designeer should shorten the circulation in the kitchen area. And this is possible through the decrease distance between the sink and a kiting zone and through the wide kitchen table which is between the sink and a kiting zone.

• Journal of Chest Surgery
• /
• v.7 no.1
• /
• pp.73-78
• /
• 1974

Influences on organ function were studied in animals during prolonged extracorporeal circulation with a bubble type of oxygenator. More than six hours of total cardiopulmonary bypass was performed under mild hypothermia by means of an extracorporeal circulation system in five dogs. Obtained results were summarized as follows. 1. The renal function was not so impaired seriously until four hours of extracorporeal circulation. However, there was more serious impairment of renal function in this study when extracorporeal circulation was carried out for a period of five hours or more. 2. There was gradual hepatic damage during extracorporeal circulation and the damage was more significant after bypass for a period of five to six hours. 3. There was a significant decrease in serum K during bypass, irrespective of the pump oxygenator prime with a high K solution. The reason for this is complex and due to many factors, however, it was evidently related to serum glucose levels during extracorporal circulation.

• Journal of Korean Library and Information Science Society
• /
• v.9
• /
• pp.145-178
• /
• 1982

This is a survey of the circulation system for students in college & university libraries in Korea. The survey used a questionnaire with 14 questions on 6 items concerning the various aspects of the circulation system in 82 libraries responded among 85 college & university libraries as of 1981. The survey results discovered many problems needing improvement. The following list describes the measures needed to better the problems found in the survey results of 82 libraries. 1. 67.1% of the libraries shows the restricted volumes loaning less than 2 volumes, and 81.7% of the libraries shows the loan periods less than a week, but it is desirable to extend them, when comparing with the size of holdings and the higher educational system at present. 2. It is desirable that the number of a staff in charge of circulation works places one person per average 75-85 books borrowed a day, when calculating an adequate number of the staff on the basis of the correlation between books borrowed a day and number of the staff. 3. 59.8% of the libraries does not have reserved book system, but it is desirable to take it for increasing reliability about the circulation services. 4. More than half of the libraries takes a method of a public announcement on a notice-board for claims of overdue books, but it is desirable to send a claim notice to the individual in viewpoint of keeping their privacies. 5. More than half of the libraries to take the open access system uses a call slip, but it is desirable not to use it in viewpoint of simplicity and economical efficiency of the charging system, because of demanding the unnecessary records. 6. Most of libraries shows many problems of the charging system, especially in factors of the records and filing system, but it is desirable to improve it on the basis of 4 basic factors of the charging system, that is, simplicity, economical efficiency, promptitude and accuracy.

• Journal of the Society of Naval Architects of Korea
• /
• v.48 no.1
• /
• pp.93-97
• /
• 2011

When freezing is present on ballast water, it can impose additional loads on the hull and effect on stabilization of ship. The anti-icing techniques of ballast water, therefore, are key criteria for ship safety. The existing anti-icing techniques of ballast tank are hull heating, water circulation and air bubble system etc. In this research, anti-icing performance tests for the ballast water using micro-bubble system and sea water circulation system have been carried out at two temperature conditions($-10^{\circ}C$ and $-25^{\circ}C$). Ambient temperature, sea water temperature and temperature of the inner parts of the ballast tank are measured and also ballast water conditions are checked during the model test. The applied anti-icing techniques of ballast water, such as micro-bubble system and sea water circulation system show good performance in the low temperature conditions.

• Korean Journal of Organic Agriculture
• /
• v.17 no.3
• /
• pp.307-326
• /
• 2009

The present study suggests a concept of resources circulation type agriculture and a concept of a livestock zone related to it and evaluated economical efficiency about a possibility of the resources circulation type livestock zone based on the concept. As a result, when the resources circulation type livestock zone is operated in an area of 1,300ha, it was evaluated that the profit of 11,244 hundred thousand won per year is generated, compared to the conventional agriculture. When light and heat expenses and roughage of Hanwoo production, production of TMR forage as well as income of the energy and composting business of livestock manure at the recycling center were considered in addition to that, it was judged that the present zone development bushiness has enough business feasibility. However, it is necessary that the support regulations, etc. is constructed so that all produced compost byproducts are used at farmhouses and the system related to facility investment assurance and assistance of operating expenses is maintained. It is thought that the complement of a system is also necessary so that energy or power generation expenses can be operated in the same conditions as other new & renewable energy, and the nation's purchase of carbon credits(CDM) is investigated and systemized in the early period, and construction of a revitalization plan of the business through budget securing of the Ministry of Agriculture and Forestry related to the trade of CDM and carbon emission rights is also a business that should be urgently developed. In the future, the change of an outside environment will further promote use of the energy. Also, as people, who don't know agriculture. farm village, increase day by day because of population concentration in a city, an opportunity that can new added value through experience tourism or educational programs utilizing them is increasing. Accordingly, if programs utilizing social characteristics, such as utilization as a space of tourism. leisure. experience, system construction of bio-energy and system construction that Micro Grid or Smart Grid as a dispersed storage and generation system is stabilized, are constructed, it can be said that revitalization or success conditions of the zone is further achieved.

• The Journal of the Korea Contents Association
• /
• v.5 no.1
• /
• pp.65-71
• /
• 2005

With the rapid improvement of the internet and information technology, digital contents containing knowledge and information resource is circulated through the internet. A circulation system based on a standardized identifier is required to share this kind of information, generated from seminars and workshops conducted in the area of science and technology and saved in the form of digital video contents. The main objective of this study is on constructing an information circulation system based on the KOI identifier to effectively share the digital video contents produced from seminars and workshops related to the area of science and technology. Furthermore, the overview and status of a standardized identifier, and the functional aspects of the system such as the methods to apply the KOI identification system on the subject and its slides of digital video contents, a digital video contents management system, a centralized identifier management system, and the methods applied for the search of digital video metadata have been suggested to support construction of the information circulation system.