• Nuclear Engineering and Technology
• /
• 제37권6호
• /
• pp.537-556
• /
• 2005

A primary-pipe rupture accident is one of the design-basis accidents of a High-Temperature Gas-cooled Reactor (HTGR). When the primary-pipe rupture accident occurs, air is expected to enter the reactor core from the breach and oxidize in-core graphite structures. This paper describes an experiment and analysis of the air ingress phenomena and the method fur the prevention of air ingress into the reactor during the primary-pipe rupture accident. The numerical results are in good agreement with the experimental ones regarding the density of the gas mixture, the concentration of each gas species produced by the graphite oxidation reaction and the onset time of the natural circulation of air. A hydrogen production system connected to the High-Temperature Engineering Test Reactor (HTTR) Is being designed to be able to produce hydrogen by themo-chemical iodine-Sulfur process, using a nuclear heat of 10 MW supplied by the HTTR. The HTTR hydrogen production system is first connected to a nuclear reactor in the world; hence a permeation test of hydrogen isotopes through heat exchanger is carried out to obtain detailed data for safety review and development of analytical codes. This paper also describes an overview of the hydrogen permeation test and permeability of hydrogen and deuterium of Hastelloy XR.

• 설비공학논문집
• /
• 제3권4호
• /
• pp.297-305
• /
• 1991

Recently, automotive air conditioning system manufacturers have been made a great efforts on the system compactness and high efficiency. This growing interest comes improvements in evaporator thermal performance, one of the most important factors affecting the performance of air conditioning system. In order to improve design of compact type evaporator, this study executes performs to develop a computer program for evaporator thermal performance prediction of automotive air conditioning system. The brief summaries of this study are as follows: 1) To predict the overall thermal performance of serpentine type evaporator, the new simulating method is developed. 2) The calculations are performed as functions of oil mass concentration and refrigerant two-phase distribution at inlet manifold of evaporator. 3) The validity of this simulating program is confirmed by comparing the predicted thermal performance results to experimental results of practical available evaporator. 4) Based on these results, suggestions are made to improve the thermal performance of evaporator.

• 기본간호학회지
• /
• 제18권1호
• /
• pp.63-70
• /
• 2011

Purpose: This study was done to examine the effects of aroma inhalation therapy on pain post tonsillectomy. Method: A non-equivalent control group pre- and post-test design was used. The research instruments used in this study were a pain perception measurement and vital signs (systolic & diastolic blood pressure and pulse rate levels). Twenty-five patients in the experimental group went through aroma inhalation therapy for ten minutes after the tonsillectomy. The aroma inhalation therapy used was a blended oil, a mixture of Lavender and Loman chamomile in the ratio of 2:1. The 25 patients in the control group did not receive the therapy. Before and after the experiment, both groups were tested for pain (pain perception and vital signs). Collected data were processed with the SPSS WIN. Ver. 14.0 program and analyzed using frequencies, percentages, ${\chi}^2$-test, Fisher's exact test, t-test and ANCOVA. Results: Pain perception of patients was not significantly reduced. However systolic and diastolic blood pressure and pulse rate were significantly reduced. Conclusion: The results of the study indicate that aroma inhalation is a partially effective nursing intervention to reduce the post-operative tonsillectomy pain.

• 설비공학논문집
• /
• 제21권4호
• /
• pp.243-251
• /
• 2009

Refrigerant mixtures provide an opportunity to adjust their properties to fit design criteria and a possibility to create new blends that can improve heat transfer characteristics. Therefore, mixture of $CO_2$ and propane is chosen which may be a promising refrigerant and has good environmental compatibility. This paper presents measured heat transfer coefficient data during evaporation process of $CO_2$/propane mixtures flowing upward in vertical smooth and. micro-fin tubes. Smooth and micro-fin tubes with outer diameters of 5 mm and length of 1.44in were selected as test tubes. The tests were conducted at mass fluxes of 212 to $656kg/m^{2}s$, inlet temperatures of -10 to $30^{\circ}C$, heat fluxes of 15 to $60\;kW/m^2$ and for several compositions (75/25, 50/50, 25/75 wt%). Among $CO_2$/propane refrigerant mixtures, the heat transfer characteristics are much better than that of any compositions when the composition is 75/25 (wt%).

• Computers and Concrete
• /
• 제20권6호
• /
• pp.645-654
• /
• 2017

Continuing from previous studies of sustainable concrete containing environmentally friendly materials and existing modeling approach to predicting concrete properties, this study developed an estimation methodology to predicting the strength of sustainable concrete using an advanced case-based reasoning approach. It was conducted in two steps: (i) establishment of a case database and (ii) development of an advanced case-based reasoning model. Through the experimental studies, a total of 144 observations for concrete compressive strength and tensile strength were established to develop the estimation model. As a result, the prediction accuracy of the A-CBR model (i.e., 95.214% for compressive strength and 92.448% for tensile strength) performed superior to other conventional methodologies (e.g., basic case-based reasoning and artificial neural network models). The developed methodology provides an alternative approach in predicting concrete properties and could be further extended to the future research area in durability of sustainable concrete.

• Nuclear Engineering and Technology
• /
• 제53권10호
• /
• pp.3196-3206
• /
• 2021

For the Korean design of the PCCS (passive containment cooling system) in an innovative PWR, the overall thermal resistance around a condenser tube is dominated by the heat transfer coefficient of steam condensation on the exterior surface. It has been reported, however, that the calculated heat transfer coefficients by thermal-hydraulic system codes were much lower than measured data in separate effect tests. In this study, a new empirical model of steam condensation in the presence of a noncondensable gas was implemented into the MARS-KS 1.4 code to replace the conventional Colburn-Hougen model. The selected correlation had been developed from condensation test data obtained at the JERICHO (JNU Experimental Rig for Investigation of Condensation Heat transfer On tube) facility, and considered the effect of the Grashof number for naturally circulating gas mixture and the curvature of the condenser tube. The modified MARS-KS code was applied to simulate the transient response of the containment equipped with the PCCS to the large-break loss-of-coolant accident. The heat removal performances of the PCCS and corresponding evolution of the containment pressure were compared to those calculated via the original model. Various thermal-hydraulic parameters associated with the natural circulation operation through the heat transport circuit were also investigated.

• Advances in concrete construction
• /
• 제10권6호
• /
• pp.515-526
• /
• 2020

Cold-mixed asphalt mixture is a widely recommended asphalt pavement materials with potentially economic and environmental benefits. Due to the reduction of natural non-renewable mineral resources, powder minerals with similar properties are considered as new mineral fillers in asphalt mixtures. This study explored the feasibility of using cement to replace natural limestone powder (LP) in emulsified asphalt concrete modified by styrene-butadiene styrene copolymer. The experimental tests, including compressive strength, Marshall stability as well as moisture susceptibility test, were used to investigate the mechanical properties, the Marshall stability, flow value, as well as the moisture damage. In addition, the influence of material composition on the performance of asphalt concrete is explained by the microstructure evolution of the pore structure, the interface transition zone (ITZ), and the micromorphology. Due to mineralogical reactivity of cement, its replacement part of LP improved the mechanical properties, Marshall stability, but it will reduce the moisture susceptibility and flow value. This is because with the increase of the cement substitution rate, the pore structure of the asphalt concrete is refined, the width of ITZ becomes smaller, and the microstructure is more compact. In addition, asphalt concrete with a larger nominal particle size (AC-16) has relatively better performance.

• 열처리공학회지
• /
• 제35권1호
• /
• pp.27-32
• /
• 2022

Microbubble technology has been widely applied in various industrial fields. Recently, research on many types of microbubble application technology has been conducted experimentally, but there is a limit in deriving the optimal design and operating conditions. Therefore, if the computational fluid dynamics (CFD) analysis of multiphase flow is used to supplement these experimental studies, it is expected that the time and cost required for prototype production and evaluation tests will be minimized and optimal results will be derived. However, few studies have been conducted on multiphase flow CFD analysis to interpret fluid flow in microbubble generators using swirl flow. In this study, CFD simulation of multiphase flow was performed to analyze the air-water mixing process and fluid flow characteristics in a microbubble generator with a dual-chamber structure. Based on the simulation results, it was confirmed that a negative pressure was formed on the central axis of rotation due to the strong swirling flow. And it could be seen that the air inside the suction tube was introduced into the inner chamber of the microbubble generator. In addition, as the high-speed mixed fluid collided with external water sucked by the negative pressure near the outlet, a large amount of microbubbles was ejected due to the shear force between the two flows flowing in opposite directions.

• Computers and Concrete
• /
• 제32권2호
• /
• pp.185-206
• /
• 2023

This article aimed to explore the optimization of mineral admixtures and retarding admixture for high-performance concrete. In essence, fresh concrete can be regarded as a mixture in which both coarse and fine aggregates are suspended in a cement-based matrix paste. Based on this view, the test procedure was divided into three progressive stages of binder paste, mortar, and concrete to explore their rheological behavior and mechanical properties respectively. At each stage, there were four experimental control factors, and each factor had three levels. In order to reduce the workload of the experiment, the Taguchi method with an L9(3⁴) orthogonal array and four controllable three-level factors was adopted. The test results show that the use of the Taguchi method effectively optimized the composition of high-performance concrete. The slump of the prepared concrete was above 18 cm, and the slump flow was above 50 cm, indicating that it had good workability. On the other hand, the 28-day compressive strength of the hardened concretes was between 31.3-59.8 MPa. Furthermore, the analysis of variance (ANOVA) results showed that the most significant factor affecting the initial setting time of the fresh concretes was the retarder dosage, and its contribution percentage was 62.66%. On the other hand, the ANOVA results show that the most significant factor affecting the 28-day compressive strength of the hardened concretes was the water to binder ratio, and its contribution percentage was 79.05%.

• Journal of Animal Science and Technology
• /
• 제47권6호
• /
• pp.1081-1086
• /
• 2005

본 시험은 혼파유형별로 초지의 건물수량과 품질을 비교 검토하여 집약적인 경운초지에 적합한 혼파유형을 제시하고자 1999년 9월부터 2002년 12월까지 충남대학교 생명과학대학내 부속 초지시험포장에서 수행하였다. 공시된 혼파유형은 관행 혼파초지(orchardgrass 50%+tall fescue 20% + perennial ryegrass 10% + Kentucky bluegrass 10% + white clover 10%), 다초종 혼파초지(orchardgrass 40% + tall fescue 20% + perennial ryegrass 10% + Kentucky bluegrass 10% + redtop 10% + alfalfa 5% + red clover 5%) 및 단순 혼파초지(orchardgrass 80% + red clover 20%)의 3유형을 두어 시험하였다. 얻어진 시험결과는 다음과 같다. 3년 평균 ha당 건물수량은 혼파유형에 따라 차이를 보여, 다초종 혼파초지가 13,070kg/ha로 다른 관행(11,206kg)이나 단순 혼파초지(11,291kg)에 비하여 높은 결과를 나타내었다(p<0.05). 화학적성분 및 건물소화율(DMD)은 혼파휴형에 따라 차이를 보였는데, CP 함량은 다초종과 단순 혼파초지가 관행 혼파초지에 비하여 높았으며(p<0.05), 섬유소 물질의 함량은 대체적으로 관행 혼파초지에서 높은 결과를 나타내었다. 그러나 DMD는 다초종 혼파초지가 다른 혼파초지에 비하여 높은 결과를 나타내었다(p<0.05). 3년 평균 조단백질CPDM) 수량과 가소화건물(DDM) 수량은 다초종 혼파초지가 관행이나 다른 혼파초지에 비하여 높은 결과를 나타내었다(p<0.05). 이상의 결과를 종합해 볼 때, 혼파유형에 따라 건물수량과 품질이 달라지고 있음을 확인할 수 있었으며, 다초종 혼파초지가 관행이나 단순 혼파초지에 비하여 건물수량과 품질을 높이는데 효과적이라 하겠다.