• Title/Summary/Keyword: stack effect

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Evaluation of the Alternatives to Minimize Stack Effect Problems with Elevators in Tall Complex Buildings (초고층 복합건축물 엘리베이터에서의 연돌현상 저감방안 평가)

  • Yu, Jung-Yeon;Song, Kyoo-Dong;Cho, Dong-Woo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.2
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    • pp.118-125
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    • 2009
  • The purpose of this study is to evaluate the stack effect reduction alternatives in tall complex buildings in cold climates. The main problems in tall buildings occur in elevators. Such problems as elevator doors that do not close and exhaust airflows result in excessive pressure differences across elevator doors due to stack effect. Under the expected conditions causing these pressure differences, Field measurements are performed in three tall buildings. Each result of the measurements is analyzed in architectural design aspects. With these analysis, building design guidelines are proposed and analyzed by field measurements and computer simulations.

Effect of stack configuration on the performance of 10W PEMFC stack (10W급 고분자 전해질 연료전지 스택의 구조적 차이에 다른 운전 특성 비교)

  • Yim, Sung-Dae;Kim, Byung-Ju;Sohn, Young-Jun;Yoon, Young-Gi;Yang, Tae-Hyun;Kim, Chang-Soo;Kim, Young-Chai
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.286-286
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    • 2009
  • A small PEM fuel cell has two different stack configurations such as active and passive stacks. The active stack has a distintion of high power density although it makes system complex by using alr blower and related BOPs resulting in large system volume. On the contrary, passive stack has an advantage of compact system because it doesn't need air supplying devices although it reveals relatively low stack power density. In this study we fabricated two 10W PEMFC stacks with different stack configurations, active and passive stacks, and tested their performance and stability. The active stack consists of 13cells with an active area of $5cm^2$. The passive stack has 12cells with an active area of $16cm^2$. When we compared the stack performance of those stacks, the active stack showed higher power density compared to the passive stack, particularly at high voltage regions. However, at low voltage and high current regions, the passive stack performance was comparable to the active stack. The stack stability was largely dependent on the fuel humidity, particularly for active stack. At low humidity conditions, the active stack performance was decreased continuously and the cell voltage distribution was not uniform showing seriously low cell voltage at center cells mainly due to the cell drying. The passive stack showed relatively stable behavior at low humidity and the stack performance was largely dependent on the atmospheric conditions.

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Field Experiment on Influence of Stack Effect to Pressure Differential System for Smoke Control (연돌효과가 급기가압 제연시스템에 미치는 영향에 대한 현장실험)

  • Kim, Jung-Yup
    • Fire Science and Engineering
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    • v.22 no.3
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    • pp.194-200
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    • 2008
  • In order to design and operate successfully the pressure differential system for smoke control which uses difference of pressure between compartments of building, architectural factors affecting the pressure field of building should be examined and the stack effect is one of the important factors. The field experiments on pressure field in two buildings of 21 stories and 31 stories in summer and winter season with regard to on/off condition of the pressure differential system are carried out to evaluate the influence of stack effect to evacuation and smoke management of high-rise building. In winter season when the stack effect increases, as the pressure differential system starts to operate, the pressure in upper stair rises largely due to the combination effect of the air infiltration from lobby to stair and the stack effect.

A Study on the Effect of Processor Stack Frame Mechanism on Secure Programming in C Language (C 언어에서 프로세서의 스택관리 형태가 프로그램 보안에 미치는 영향)

  • 이형봉;차홍준;노희영;이상민
    • The KIPS Transactions:PartC
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    • v.8C no.1
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    • pp.1-11
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    • 2001
  • There are several traditional factors of software quality. Some of them are such as correctness, reliability, efficiency, compatibility, portability, etc. In addition to them, security is required as another factor of software quality nowadays because some application programs are used as a way to attack information systems by stack frame manipulation. Each processor has its own peculiar stack frame mechanism and C language uses the characteristics of them. This paper explains the concept of security problem caused by stack frame manipulation, and the stack frame mechanism of Pentium, Alpha and SP ARC processor in detail. And then it examines the effect of stack frame mechanism on the security of programs in C language.

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Solving the Problems Caused by Stack Effect in a High-rise Residential Building through Field Measurement and Simulation; Case Study (실측과 시뮬레이션을 통한 초고층 주거건물에서의 연돌효과 문제의 해결)

  • Koo Sung-Han;Jo Jae-Hun;Yeo Myoung-Souk;Kim Kwang-Woo
    • Journal of the Korean housing association
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    • v.16 no.4
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    • pp.73-80
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    • 2005
  • A high-rise residential building experienced stack effect problems during the winter such as difficulties in opening residential entrance doors and whistling noise from elevator doors generated by airflow. Field measurements were carried out on the building and the problems were verified by the analysis of the measurement results from three points of view: the total stack pressure difference, pressure distribution on each floor, and the location of the neutral pressure level. Based on the analysis of the three key parameters, possible solutions were proposed, such as zoning vertical shafts, lessening the airflow from the entrance doors on basement floors and lobby floor by installing vestibules, improving the airtightness of exterior walls, and installing separation doors where the problems occur. Simulations of proposed solutions were conducted and the effects of reducing the pressure difference were evaluated. Stack effect problems in a high-rise residential building were verified through field measurements and could be mitigated by the solutions which were drawn from the analysis of the field measurements and the simulation results.

A Numerical Study on the Stack Effect and the Neutral Plane of a Single Simplified Shaft (단일 단순수직통로의 연돌효과와 중성대에 관한 수치해석 연구)

  • Jeon, Heung-Kyun;Choi, Young-Sang;Choo, Hong-Lok
    • Fire Science and Engineering
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    • v.23 no.5
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    • pp.143-152
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    • 2009
  • The numerical analyses for each single simplified shaft with three type openings were carried out by using computational fluid dynamics model for the calculation of the pressure difference and the location of the neutral plane and the visualization of stack effect. As the height of shaft heighten, the pressure difference of stack effect is much deviated against the theoretical value. For the Type A models shorter than 30 m height of shaft and the Type B models longer than 30m, the simulation results for the location of the neutral plane are well agreed to the theoretical values with 5% less deviations just after the beginning of simulation (t = 10s). For the Type B models longer than 30m with multiple openings, therefore, it is possible to calculate the location of the neutral plane by using a CFD model. The phenomenon of the air flow of stack effect can be easily understood with the visualization of stack effect.

Effect of Flue Gas Heat Recovery on Plume Formation and Dispersion

  • Wu, Shi Chang;Jo, Young Min;Park, Young Koo
    • Particle and aerosol research
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    • v.8 no.4
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    • pp.161-172
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    • 2012
  • Three-dimensional numerical simulation using a computational fluid dynamics (CFD) was carried out in order to investigate the formation and dispersion of the plume discharged from the stack of a thermal power station. The simulation was based on the standard ${\kappa}{\sim}{\varepsilon}$ turbulence model and a finite-volume method. Warm and moist exhaust from a power plant stack forms a visible plume as entering the cold ambient air. In the simulation, moisture content, emission velocity and temperature of the flue gas, air temperature and wind speed were dealt with the main parameters to analyze the properties of the plume composed mainly of water vapor. As a result of the simulation, the plume could be more apparent in cold winter due to a big difference of latent heat capacity. At no wind condition, the white plume rises 120 m upward from the top of the stack, and expands to 40 m around from the stack in cold winter after flue gas heat recovery. The influencing distance of relative humidity will be about 100 m to 400 m downstream from the stack with a cross wind effect. The decrease of flue gas temperature by heat recovery of thermal energy facilitates the formation of the plume and restrains its dispersion. Wind speed with vertical distribution affects the plume dispersion as well as the density.

Influence of Stack Effect in High-Rise Buildings on Wind Effect in Jeju (Comparative Analysis of Seoul and Jeju) (제주지역 고층건축물에서의 바람의 영향이 굴뚝효과에 미치는 영향 분석 (서울과 제주지역간의 비교 분석))

  • Lim, Chae-Hyun
    • Fire Science and Engineering
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    • v.29 no.6
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    • pp.6-12
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    • 2015
  • This study used CONTAM modeling to analyzed analyze the stack effect in high-rise buildings for the terrain and weather conditions of Seoul and Jeju. The differential pressure caused by the stack effect is a function of the indoor and outdoor temperature difference and the height of the vertical shaft. Jeju is considered more stable than Seoul, because it is warmer than Seoul in winter. The differential pressure in Jeju is about 60% that of Seoul in for the same height of buildings in winter. However, Jeju is an island and the neutral plane is raised by over 56% by strong winds, although there is less differential pressure caused by the stack effect in Jeju than in Seoul. Due to the raised neutral plane, the region and magnitude of negative pressure in the lower part is larger in Jeju than in Seoul.

Analysis of Thermal Effect by Coolant Plate Number in High-Temperature Polymer Electrolyte Membrane Fuel Cell Stack (고온형 고분자 전해질 연료전지 스택 내부의 냉각판 수가 스택에 미치는 열 영향성의 수치적 연구)

  • Choi, Byung Wook;Ju, Hyun Chul
    • Transactions of the Korean hydrogen and new energy society
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    • v.26 no.2
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    • pp.127-135
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    • 2015
  • High-Temperautre Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC) with phosphoric acid-doped polybenzimidazole (PBI) membrane has high power density because of high operating temperature from 100 to $200^{\circ}C$. In fuel cell stack, heat is generated by electrochemical reaction and high operating temperature makes a lot of heat. This heat is caouse of durability and performance decrease about stack. For these reasons, heat management is important in HT-PEMFC. So, we developed HT-PEMFC model and study heat flow in HT-PEMFC stack. In this study, we placed coolant plate number per cell number ratio as variable and analysed heat flow distribution in stack.

The Influence of Zoning at Shafts of Super-tall Buildings on the Stack Effect and Stairwell Pressurization (초고층건물 샤프트의 수직구획이 연돌효과 및 급기가압 성능에 미치는 영향)

  • Kim, Beom-Kyue;Kim, Hak-Jung;Yeo, Yong-Ju;Leem, Chae-Hyun;Park, Yong-Hwan
    • Fire Science and Engineering
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    • v.26 no.5
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    • pp.92-98
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    • 2012
  • This study analyzed the effect of zoning on the distribution of pressure differentials caused by stack effect and air pressurization in a center core type of 80 story super-tall building. The results showed that maximum pressure difference more than 250 Pa can be generated by stack effect without zoning. Zoning of stairwell only resulted in 10 Pa reduction of maximum pressure difference, however, zoning of both stairwell and EV shaft especially at the same floor revealed 50 % reduction in stack effect. It was also analysed that the minimum required air flow rate occurred when the stairwell temperature reached 50 % of temperature difference between indoor and outdoor.