• Title/Summary/Keyword: two-zone model

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Performance Prediction of Centrifugal Pumps using Two Zone Model (두영역모델을 사용한 원심펌프의 성능예측)

  • Choi, Young-Seok;Shim, Jae-Hyeok;Kang, Shin-Hyoung
    • 유체기계공업학회:학술대회논문집
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    • 1998.12a
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    • pp.33-41
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    • 1998
  • In this study, the performance prediction programs for centrifugal pumps are developed. To estimate the losses in the centrifugal pump impellers, two-zone model and TEIS(two elements in series) model are applied to the program. The basic concept of two zone model considers the primary zone that is an isentropic core flow and the secondary zone that is non-isentropic region at the impeller exit. The flows through two different zones mixed out at the impeller exit and the mixing process occurs with an increase in entropy, a decrease in total pressure. The level of the core flow diffusion in a impeller was calculated using TEIS(two elements in series) model. The effects of various parameters which are used in this program on the prediction of head and efficiency are discussed. The correlation curves to select the effectiveness of the primitive TEIS model were suggested according to the specific speed of the centrifugal pumps.

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Performance Prediction of Centrifugal Pumps using a Two Zone Model (두영역모델을 사용한 원심펌프의 성능예측)

  • Choi, Young-Seok;Shim, Jae-Hyeok;Kang, Shin-Hyoung
    • The KSFM Journal of Fluid Machinery
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    • v.2 no.1 s.2
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    • pp.56-63
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    • 1999
  • In this study, the performance prediction programs for centrifugal pumps are developed. To estimate the losses in the centrifugal pump impellers, a two-zone model and TEIS(two elements in series) model are applied to the program. The basic concept of a two zone model considers the primary zone that is an isentropic core flow and the secondary zone that has a non-isentropic region at the impeller exit. The flow goes through two different zones and is mixed out at the impeller exit and the mixing process occurs with an increase in entropy, a decrease in total pressure. The level of the core flow diffusion in an impeller was calculated using TEIS(two elements in series) model. The effects of various parameters which are used in this program on the prediction of head and efficiency are discussed. The correlation curves used to select the effectiveness of the primitive TEIS model were suggested according to the specific speed of the centrifugal pumps.

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Development of the Two-Zone Model to Estimate the Air Quality in Indoor Environments (실내 공기질 평가를 위한 2구획 모델의 개발)

  • 조석호;양성환;이봉헌;정성욱;이병호
    • Journal of Environmental Science International
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    • v.7 no.6
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    • pp.745-751
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    • 1998
  • The well-mixed room model has been traditionally used to predict the concentrations of contaminants in indoor environments. However, this is inappropriate because the flow fields in many indoor environments distribute contaminants non-uniformly, due to imperfect air mixing. Thus, some means used to describe an imperfectly mixed room are needed. The simplest model that accounts for imperfect air mixing is a two-zone model. Therefore, this study on development of computer program far the two-zone model is carried out to propose techniques of estimating the concentration of contaminants in the room. To do this, an important consideration is to divide a room into two-zone, i.e. the lower and upper zone assuming that the air and contaminants are well mixed within each zone. And between the zones the air recirculation is characterized through the air exchange parameter. By this basic assumption, the equations for the conservation of mass are derived for each zone. These equations are solved by using the computational technique. The language used to develope the program is a VISUAL BASIC. The value of air exchange coefficient($f_12$) is the most difficult to forecast when the concentrations of contaminants in an imperfectly mixed room are estimated by the two-zone model. But, as the value of $f_12$ increases, the air exchange between each zone increases. When the value of $f_12$ is approximately 15, the concentrations in both zone approach each other, and the entire room may be approximately treated as a single well-mixed room. Therefore, this study is available for designing of the ventilation to improve the air quality of indoor environments. Also, the two-zone model produces the theoretical base which may be extended to the theory for the multi-zone model, that will be contributed to estimate the air pollution in large enclosures, such as shopping malls, atria buildings, atria terminals, and covered sports stadia.

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Off-design Performance Prediction of Centrifugal Pumps by Using TEIS model and Two-zone model (TEIS 모델과 두 영역 모델을 이용한 원심 펌프의 탈 설계 성능 예측)

  • Yoon, In-Ho;Baek, Je-Hyun
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.574-579
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    • 2000
  • In this study. an off-design performance prediction program for centrifugal pumps is developed. To estimate the losses in an impeller flow passage, two-zone model and two-element in series(TEIS) model are used. At impeller exit. the mixing process occurs with an increase in entropy. In two-zone model. there are both primary zone and secondary zone for an isentropic core flow and an average of all non-isentropic streamtubes respectively. The level of the core flow diffusion in an impeller was calculated by using TEIS model. While internal losses in an impeller an automatically estimated by using the above models, some empirical correlations far estimating external losses. far example, disk friction loss, recirculation loss and leakage loss are used. In order to analyze the vaneless diffuser flow. the momentum equations for the radial and tangential directions are used and solved together with continuity and energy equations.

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Sensitivity Analysis on Off-Design Performance of Centrifugal Compressor Due to the Parameters of Two-zone Model and TEIS Model (두영역 모델과 직렬두요소 모델의 변수에 의한 원심 압축기 탈설계 성능의 민감도 분석)

  • Yoon, Sung-Ho;Baek, Je-Hyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.6
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    • pp.834-844
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    • 2000
  • In this study, an off-design performance analysis procedure is developed based on Two-zone model and TEIS model. In Two-zone model, there are both primary zone and secondary zone for an isentropic core flow and an average of all non-isentropic streamtubes respectively. The level of the core flow diffusion in an impeller is calculated by using TEIS model which regards the impeller as two successive rotating elements in series. At impeller exit, the mixing process occurs with an increase in entropy, that is to say, a decrease in total pressure. In loss models including Two-zone and TEIS model, some empirical parameters have a great influence on overall performance curve. So these parameters' influences on the overall performance curve are investigated and compared with experimental data.

Finite Element Modeling of Fracture Process Zone in Concrete (콘크리트 파괴진행영역의 유한요소모델링)

  • 송하원;변근주
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1995.04a
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    • pp.35-41
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    • 1995
  • Fracture Mechanics does work for concrete, provided that a finite nonlinear zone at fracture front is being considered. The development of model for fracture process zone is most important to describe fracture phenomena in concrete. The fracture process zone is a region ahead of a traction-free crack, in which two major mechanisms, microcracking and bridging, play important rules. The toughness due to bridging is dominant compared to toughness induced by microcracking, so that the bridging is dominant mechanism governing the fracture process of concrete. In this paper the bridging zone, which is a part of extended macrocrack with stresses transmitted by aggregates in concrete, is model led by a Dugdale-Barenblatt type model with linear tension-softening curve. Two finite element techniques are shown for the model of fracture process zone in concrete.

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A mathematical steel panel zone model for flanged cruciform columns

  • Saffari, Hamed;Sarfarazi, Sina;Fakhraddini, Ali
    • Steel and Composite Structures
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    • v.20 no.4
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    • pp.851-867
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    • 2016
  • Cruciform sections are an appropriate option for columns of orthogonal moment resisting frames for equal bending strength and stiffness about two main axes and the implementation is easier for continuity plates. These columns consist of two I-shaped sections, so that one of them is cut out in middle and two generated T-shaped sections be welded into I-shaped profile. Furthermore, in steel moment frames, unbalance moment at the beam-column connection leads to shear deformation in panel zone. Most of the obtained relations for panel zone strength derived from experimental and analytical results are on I-shaped columns with almost thin flanges. In this paper, a parametric study has been carried out using Finite Element Method (FEM) with effective parameters at the panel zone behavior. These parameters consist of column flange thickness, column web thickness, and thickness of continuity plates. Additionally, a mathematical model has been suggested to determine strength of cruciform column panel zone and has been shown its accuracy and efficiency.

Parameter Study of TEIS Model, Two-zone Model, and Stanitz's Equations (직렬 두요소 모델, 두 영역 모델, Stanitz 방정식에 대한 변수 연구)

  • Yoon, Sung-Ho;Baek, Je-Hyun
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.580-585
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    • 2000
  • Recently TEIS model, Two-zone model aid Stanitz equations are often used for off-design performance prediction of centrifugal compressor and pump. The prediction results often agree well with experimental data. However these models and equations have some important variables which have a great influence on overall performance prediction me. But no systematic study about these variables has been performed. So, in this paper, a systematic study about these variables influence on overall performance prediction owe is peformed. Finally the meaning of the variables and the research to be undertaken are discussed.

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Accidents involving Children in School Zones Study to identify the key influencing factors (어린이보호구역내 어린이 교통사고 발생에 미치는 영향요인 분석)

  • Park, Sinae;Lim, Junbeom;Kim, Hyungkyu;Lee, Soobeom
    • International Journal of Highway Engineering
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    • v.19 no.2
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    • pp.167-174
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    • 2017
  • PURPOSES: This study aims to analyze the impact of the implementation of a school zone traffic safety improvement project on the number of accidents involving children in these zones. METHODS : To analyze the correlation between school zone traffic safety features of roads in the zone and the number of accidents involving children, we developed an occurrence probability model of traffic accidents involving children by using a binary logistic regression model with SPSS 23.0 software. Two separate models were developed for two zones: interior block and arterial road. RESULTS :The model depicted that in the case of the interior block, shorter sidewalk width, speed bump, and an elevated crosswalk were key factors affecting the occurrence of accidents involving children. In the case of arterial roads exceeding a width of 12 m, the speed limit, roadside barriers, and red paving of road surfaces were found to be the key factors. CONCLUSIONS:The results of this study can serve as the elementary research data to help improve the effectiveness of school zone traffic safety improvement projects and school zone road repair projects in future.

Evaluation of Adhesive Properties Using Cohesive Zone Model : Mode I (Cohesive Zone Model을 이용한 접착제 물성평가 : 모드 I)

  • Lee, Chan-Joo;Lee, Sang-Kon;Ko, Dae-Cheol;Kim, Byung-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.5
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    • pp.474-481
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    • 2009
  • Fracture models and criteria of adhesive with two parameters, namely $G_C$ and ${\sigma}_{max}$, have been developed to describe the fracture process of adhesive joints. Cohesive zone model(CZM) is a representative two parameter failure criteria approach. In CZM, ${\sigma}_{max}$ is a critical, limiting maximum value of the stress in the damage zone ahead of the crack and is assumed to have some physical significance in adhesive failure. Based on CZM and finite element analysis method, the relationship between fracture load and adhesive properties, as $G_{IC)$ and $({\sigma}_{max})_I$, was investigated in adhesively bonded joint tensile test and T-peel test. The two parameters in tensile mode loading were evaluated by using the relationship. The value of $G_{\IC}$ evaluated by proposed method showed close agreement with analytical solution for tapered double cantilever beam(TDCB) test which proposed in an ASTM standard.