• Title/Summary/Keyword: Super-cooling

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Effects of Vertical Meteorological Changes on Heating and Cooling Loads of Super Tall Buildings

  • Song, Doosam;Kim, Yang Su
    • International Journal of High-Rise Buildings
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    • v.1 no.2
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    • pp.81-85
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    • 2012
  • Vertical meteorological conditions encountered by super tall buildings, such as wind speed, temperature and humidity, vary due to their height. Therefore, it is necessary to consider these environmental changes to properly estimate the heating and cooling loads, and to minimize the energy demands for HVAC in super tall buildings. This paper aims to analyze how vertical meteorological changes affect heating and cooling loads of super tall buildings by using numerical simulation. A radiosonde, which observes atmospheric parameters of upper air such as wind speed, wind direction, temperature, relative humidity and pressure, was used to provide weather data for the building load simulation. A hypothetical super tall building was used for the simulation to provide quantified characteristics of the heating and cooling loads, comparing the lower, middle and upper parts of the building. The effect of weather data on the heating and cooling loads in super tall building was also discussed.

A Building Heating and Cooling Load Analysis of Super Tall Building considering the Vertical Micro-climate Change (초고층 오피스 건물의 수직외부환경 변화가 건물부하에 미치는 영향)

  • Kim, Yang-su;Song, Doosam;Hwang, Suk-Ho
    • KIEAE Journal
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    • v.10 no.4
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    • pp.117-122
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    • 2010
  • In these days numerous super tall buildings are under construction or being planned in Middle East and Asian countries. Some of them are planned as an ultra high-rise building that goes over 600m tall, including Burj Khalifa, the tallest building in the world. External environment such as wind speed, temperature and humidity of the super tall building varies due to its vertical height. Therefore, it is necessary to consider these environmental changes to estimate building heating and cooling load. This paper analyzes how vertical microclimate difference affects building heating and cooling load in super tall building by simulation using radiosonde climate data. Besides, the correlation between air-tightness of building envelope and building load was analyzed for a super tall building.

Influence of the Cooling Rate on the Phase Precipitation of Super Duplex Stainless Steel (슈퍼 듀플렉스 스테인리스강의 응고·냉각 시 상석출에 미치는 냉각속도의 영향)

  • Jang, Eun Seok;Kim, Ki Young;Kim, Suk Jun
    • Journal of Korea Foundry Society
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    • v.35 no.2
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    • pp.23-28
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    • 2015
  • This work presents the effect of the cooling rate on the precipitation of super duplex stainless steel. Specimens of super duplex stainless steel with a specific composition were cooled at various cooling rates after being melted at $1550^{\circ}C$ in a directional solidification furnace. Ferrite (${\delta}$), Austenite (${\gamma}$), Sigma (${\sigma}$), and Chi (${\chi}$) phases were precipitated when the cooling rate was lower than 0.22 K/s. When the cooling rate was 0.22 K/s or faster, ${\sigma}$ and ${\chi}$ phases were not precipitated.

Multi-dimensional extreme aerodynamic load calculation in super-large cooling towers under typical four-tower arrangements

  • Ke, Shitang;Wang, Hao;Ge, Yaojun
    • Wind and Structures
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    • v.25 no.2
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    • pp.101-129
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    • 2017
  • Local transient extreme wind loads caused by group tower-related interference are among the major reasons that lead to wind-induced damage of super-large cooling towers. Four-tower arrangements are the most commonly seen patterns for super-large cooling towers. We considered five typical four-tower arrangements in engineering practice, namely, single row, rectangular, rhombic, L-shaped, and oblique L-shaped. Wind tunnel tests for rigid body were performed to determine the influence of different arrangements on static and dynamic wind loads and extreme interference effect. The most unfavorable working conditions (i.e., the largest overall wind loads) were determined based on the overall aerodynamic coefficient under different four-tower arrangements. Then we calculated the one-, two- and three-dimensional aerodynamic loads under different four-tower arrangements. Statistical analyses were performed on the wind pressure signals in the amplitude and time domains under the most unfavorable working conditions. On this basis, the non-Gaussian distribution characteristics of aerodynamic loads on the surface of the cooling towers under different four-tower arrangements were analyzed. We applied the Sadek-Simiu procedure to the calculation of two- and three-dimensional aerodynamic loads in the cooling towers under the four-tower arrangements, and the extreme wind load distribution patterns under the most unfavorable working conditions in each arrangement were compared. Finally, we proposed a uniform equation for fitting the extreme wind loads under the four-tower arrangements; the accuracy and reliability of the equation were verified. Our research findings will contribute to the optimization of the four-tower arrangements and the determination of extreme wind loads of super-large cooling towers.

Effect of the building envelope on heating and cooling load in super tall building considering the meteorological changes with height (높이별 기상변화를 고려한 초고층 건축물의 외피종류별 냉난방 부하특성 분석)

  • Choi, Jong-Kyu;Kim, Yang-Soo;Song, Doo-Sam
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.337-344
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    • 2012
  • Today, the number of super tall buildings are under construction or being planed in Middle East and Asian Countries. For example the burj Khalifa, the tallest building in the world, is completed in 2008 and the height of that is about 800m. Also, Lotte World Tower is under construction in Korea. External environmental conditions such as wind speed, air temperature, humidity and solar radiation around the super tall building differs according to the building height due to the vertical micro climate change. However, the meteorological information used for AC design of building is obtained typically from standard surface meterological station data(~2m above the ground). In this paper the effect of the building envelope on heating and cooling load in super tall building considering the meteorological changes with height was analyzed with simulation method. As results of this research, the guideline to select the building envelop alternatives for super tall building will be suggested in this paper.

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A Comparative Analysis of Energy Simulation Results and Actual Energy Consumption on Super High-rise Apartments (초고층 공동주택의 세대별 냉난방부하 시뮬레이션 결과 및 에너지 실사용량과의 비교 분석)

  • Suh, Hye-Soo;Kim, Byung-Seo
    • Journal of the Korean Solar Energy Society
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    • v.31 no.4
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    • pp.34-40
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    • 2011
  • Apartment Housing has been increasing steadily, particularly our current super high-rise apartment houses that represent the culture has become a trend in Korea. These super high-rise apartment houses' curtain wall system increases heating and cooling loads, it is expected to vary by each unit's thermal properties. In this study, measured indoor environment and energy simulation results were compared to actual energy consumption. As a result, the various factors that affect heating and cooling loads, such as direction, plan type and glazing area, influence each unit's load characteristic. In particular, according to the electricity costs savings behavior, the occupant's thermal discomfort is expected to be large in summer. Therefore, to reduce heating and cooling load for each unit requires a reasonable plan.

Experimental Study for Ice Formation around Two Horizontal Circular Tubes (수평 2열 원통관 주위의 동결형상에 관한 연구)

  • Yoon, J.I.;Kim, J.D.;Toyofumi, Kato;Oh, H.K.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.1
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    • pp.89-97
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    • 1995
  • Experimental study was performed for free convection and ice formation around two horizontal circular tubes which were placed vertically. Temperature and velocity distributions were visualized with real time holographic interferometry technique and tracer method. When water was cooled, super cooled region was formed around cooling pipe. It was found that flow induced by free convection always directed downwards when the coolant temperature was low, while it directed upwards when the coolant temperature was comparably high though it directed downwards initially. Flow phenomena with free convection were investigated in detail with varying cooling rate and length between cooling pipes. And growing process of dense ice was also investigated. Dendritic ice is suddenly formed within a supercooled region, and a dense ice layer begins to develop from the cooling wall.

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Compressibility Factor Effect on the Turbulence Heat Transfer of Super-critical Carbon Dioxide by an Elliptic-blending Second Moment Closure (타원혼합모형을 이용한 초임계상태 이산화탄소의 압축성계수에 의한 난류열전달 특성)

  • Han, Seong-Ho;Seo, Jeong-Sik;Shin, Jung-Kun;Choi, Young-Don
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.1 s.256
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    • pp.40-50
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    • 2007
  • The present contribution describes the application of elliptic-blending second moment closure to predict the gas cooling process of turbulent super-critical carbon dioxide flow in a square cross-sectioned duct. The gas cooling process under super-critical state experiences a drastic change in thermodynamic and transport properties. Redistributive terms in the Reynolds stress and turbulent heat flux equations are modeled by an elliptic-blending second moment closure in order to represent strongly non-homogeneous effects produced by the presence of walls. The main feature of Durbin's elliptic relaxation second moment closure that accounts for the nonlocal character of pressure-velocity gradient correlation and the near-wall inhomogeneity guaranteed by the elliptic blending second moment closure.

Effect of Two Step Austenitizing Treatment Conditions on the Microstructural Characteristics of ADI (ADI의 조직특성에 미치는 2단 오스테나이트화 처리조건의 영향)

  • Choi, S.L.;Yun, K.H.;Moon, W.J.;Kang, C.Y.;Kim, H.G.
    • Journal of the Korean Society for Heat Treatment
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    • v.11 no.1
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    • pp.46-53
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    • 1998
  • The variation of the mechanical properties, microstructures and the formation of retained austenite with heat treatment conditions in austempered ductile cast iron has been investigated. In the case of austempered ductile cast iron below 25mm diameter, it has been found that a pearlite structure are not obtained under a super cooled condition at range of $0.05^{\circ}C/sec{\sim}10^{\circ}C/sec$, and the matrix is precipitated in graphite, bainite and retained austenite. After austempering treatment the retained austenite is increased with decreasing cooling rate. The elongation increases with decreasing super cooling rate, and the optimum result has been shown to be the elongation of 15.6% at super cooling rate of $0.05^{\circ}C/sec$. The optimum result has been shown to be the tensile strength-elongation balance of $1656kgf/mm^2.%$ and it is more than doubled to as the casting state and continuous cooling condition.

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A study on the average wind load characteristics and wind-induced responses of a super-large straight-cone steel cooling tower

  • Ke, S.T.;Du, L.Y.;Ge, Y.J.;Zhao, L.;Tamura, Y.
    • Wind and Structures
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    • v.25 no.5
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    • pp.433-457
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    • 2017
  • As a novel typical wind-sensitive structure, the wind load and wind-induced structural behaviors of super-large straight-cone cooling towers are in an urgent need to be addressed and studied. A super large straight-cone steel cooling tower (189 m high, the highest in Asia) that is under construction in Shanxi Power Plant in China was taken as an example, for which four finite element models corresponding to four structural types: the main drum; main drum + stiffening rings; main drum + stiffening rings + auxiliary rings (auxiliary rings are hinged with the main drum and the ground respectively); and main drum + stiffening rings + auxiliary rings (auxiliary rings are fixed onto the main drum and the ground respectively), were established to compare and analyze the dynamic properties and force transferring paths of different models. After that, CFD method was used to conduct numerical simulation of flow field and mean wind load around the cooling tower. Through field measurements and wind tunnel tests at home and abroad, the reliability of using CFD method for numerical simulation was confirmed. On the basis of this, the surface flow and trail characteristics of the tower at different heights were derived and the wind pressure distribution curves for the internal and external surfaces at different heights of the tower were studied. Finally, based on the calculation results of wind-induced responses of the four models, the effects of stiffening rings, auxiliary rings, and different connecting modes on the dynamic properties and wind-induced responses of the tower structure were derived and analyzed; meanwhile, the effect mechanism of internal suction on such kind of cooling tower was discussed. The study results could provide references to the structure selection and wind resistance design of such type of steel cooling towers.