• Wind and Structures
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• 제28권1호
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• pp.1-17
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• 2019

Internal ring beams are primary components of new ring-stiffened cooling towers. In this study, numerical simulation of the internal flow field of a cooling tower with three ring beams under wind-thermal coupling effect is performed. The studied cooling tower is a 220-m super-large hyperbolic indirect natural draft cooling tower that is under construction in China and will be the World's highest cooling tower, the influence of peripheral radiators in operating cooling tower is also considered. Based on the simulation, the three-dimensional effect and distribution pattern of the wind loads on inner surface of the cooling tower is summarized, the average wind pressure distributions on the inner surface before and after the addition of the ring beams are analyzed, and the influence pattern of ring beams on the internal pressure coefficient value is derived. The action mechanisms behind the air flows inside the tower are compared. In addition, the effects of internal ring beams on temperature field characteristics, turbulence kinetic energy distribution, and wind resistance are analyzed. Finally, the internal pressure coefficients are suggested for ring-stiffened cooling towers under wind-thermal coupling effect. The study shows that the influence of internal stiffening ring beams on the internal pressure and flow of cooling towers should not be ignored, and the wind-thermal coupling effect should also be considered in the numerical simulation of cooling tower flow fields. The primary conclusions presented in this paper offer references for determining the internal suction of such ring-stiffened cooling towers.

• 융복합기술연구소 논문집
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• 제6권1호
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• pp.37-41
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• 2016

The serpentine internal passage is located in turbine blade and it shows the variety heat transfer distribution. Especially, the Coriolis force, which is induced by blade rotation, makes different heat transfer distribution of the leading and trailing surfaces of serpentine internal passage. The different heat transfer is one of the reasons why the serpentine cooling passage shows low cooling performance in the rotating condition. So, this study tried to design the advanced the serpentine passage to consideration of the Coriolis force. The design concept of advanced serpentine cooling is maximizing cooling performance using the Coriolis force. So, the flow turns from leading surface to trailing surface in advanced serpentine passage to match the direction of Coriolis force and rotating force. We performed numerical analysis using CFX and compared the existing and advanced serpentine internal passage. This design change is induced the high heat transfer distribution of whole advanced serpentine internal passage surfaces.

• 한국자동차공학회논문집
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• 제21권1호
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• pp.36-42
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• 2013

Recently, the automobile of the future will be able to substitute an electric vehicle for an internal combustion engine, so the following research is actively in the process of advancing. A traction motor is one of the core parts which compose the electric vehicle. Especially, it is difficult to connect cooling water piping to an in-wheel motor because the in-wheel motor is located within the wheel structure. This structure has disadvantage for closed type and air cooling, so the cooling design of motor housing and internal in-wheel motor is important. In this study, thermo-flow analysis of the in-wheel motor for vehicles was performed in consideration of ram air effect. In order to improve cooling efficiency of the motor, we variously changed geometries of housing and internal shape. As a result, we found that the cooling efficiency was most excellent, in case the cooling groove direction was same with air flow direction and arranged densely. Furthermore, we investigated the cooling performance enhancement with respect to variable geometries of internal in-wheel motor.

• Wind and Structures
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• 제29권4호
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• pp.235-246
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• 2019

Wind loading is one of important loadings that should be considered in the design of large hyperbolic natural-draught cooling towers. Both external and internal surfaces of cooling tower are under the action of wind loading for cooling circulating water. In the previous studies, the wind loads on the external surface attracted concernedly attention, while the study on the internal surface was relatively ware. In the present study, the wind pressure on the internal surface of a 220 m high cooling tower is measured through wind tunnel testing, and the effect of ventilation rate of the packing layer on internal pressure is a major concern. The characteristics of internal wind pressure distribution and its effect on wind-induced responses calculated by finite element method are investigated. The results indicate that the wind loading on internal surface of the cooling tower behaves remarkable three-dimensional effect, and the pressure coefficient varies along both of height and circumferential directions. The non-uniformity is particularly strong during the construction stage. Analysis results of the effect of internal pressure on wind-induced responses show that the size and distribution characteristics of internal pressure will have some influence on wind-induced response, however, the outer pressure plays a dominant role in the wind-induced response of cooling tower, and the contribution of internal pressure to the response is small.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.67-70
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• 2000

The tool life is not long enough under sever forming condition in warm forging. The tool life is affected by wear heat fatigue plastic deformation and so on. Especially wear is one of the most serious factors for tool life. To increase tool life we should consider various factors like processing design die design die materials lubrication and cooling system This study design to obtain the steady state temperature of die by FEM analysis under several conditions of cooling. There are four cooling conditions in this study no cooling internal cooling external cooling and both internal and external cooling. With above obtained temperatures tool life is predicted using Archard's model that is considered softening of die. The effect of internal cooling system is better than that of externally cooled die. To predict the die life the steady state temperature is calculated by using mean temperature of die. Considering only wear the die life much longer as the cooling effect is bigger. The more accurate die life will be predicted if we consider heat crack as well as wear.

• 설비공학논문집
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• 제23권12호
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• pp.836-842
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• 2011

It has been shown that the air-conditioning system with slab cooling storage is effective in cutting peak load and utilizing nighttime electric power. The stochastic properties of internal heat generation which has great influence on the cooling load are examined in this paper. Based on the measured cooling load and electric power consumption in an office building with slab cooling storage, stochastic time series models to simulate these random processes are investigated. Furthermore, a calculated result by an optimal control method of thermal analysis taking into account the internal heat is compared with the measured cooling load.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.479-497
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• 2019

In the current code design, the use of a uniform internal pressure coefficient of cooling towers as internal suction cannot reflect the 3D characteristics of flow field inside the tower body with different ventilation rate of shutters. Moreover, extreme weather such as heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind. In this study, the world's tallest cooling tower under construction, which stands 210m, is taken as the research object. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed iteratively using continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind speed and rainfall intensity on the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower body is analyzed. The combination of wind velocity and rainfall intensity that is most unfavorable to the cooling tower in terms of distribution of internal pressure coefficient is identified. On this basis, the wind/rain loads, distribution of aerodynamic force and working mechanism of internal pressures of the cooling tower under the most unfavorable working condition are compared between the four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the amount of raindrops captured by the internal surface of the tower decreases as the wind velocity increases, and increases along with the rainfall intensity and ventilation rate of the shutters. The maximum value of rain-induced pressure coefficient is 0.013. The research findings lay the basis for determining the precise values of internal surface loads of cooling tower under extreme weather conditions.

• 설비공학논문집
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• 제17권3호
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• pp.209-215
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• 2005

Since a transcritical $CO_2$ cycle shows lower performance than conventional air conditioners in the cooling mode operation, it is required to enhance the performance of the $CO_2$ cycle by applying advanced technologies and optimizing components. In this study, the cooling performance of a $CO_2$ system measured by varying refrigerant charge amount, compressor frequency, EEV opening and length of internal heat exchanger. As a result, the cooling COP of the basic system without internal heat exchanger was 2.1. The cooling performance of the modified cycle applying internal heat exchanger improved by $4-9\%$ over the basic cycle.

• Journal of Mechanical Science and Technology
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• 제18권6호
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• pp.990-1001
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• 2004

The retention of a molten pool vessel cooled by internal vessel reflooding and/or external vessel reactor cavity flooding has been considered as one of severe accident management strategies. The present numerical study investigates the effect of both internal and external vessel mixed cooling on an internally heated molten pool. The molten pool is confined in a hemispherical vessel with reference to the thermal behavior of the vessel wall. In this study, our numerical model used a scaled-down reactor vessel of a KSNP (Korea Standard Nuclear Power) reactor design of 1000 MWe (a Pressurized Water Reactor with a large and dry containment). Well-known temperature-dependent boiling heat transfer curves are applied to the internal and external vessel cooling boundaries. Radiative heat transfer has been considered in the case of dry internal vessel boundary condition. Computational results show that the external cooling vessel boundary conditions have better effectiveness than internal vessel cooling in the retention of the melt pool vessel failure.

• Architectural research
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• 제14권1호
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• pp.11-18
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• 2012

College of Architecture, Georgia Institute of Technology, Atlanta, GA, US Abstract The intermittent heating and cooling energy need calculation of the ISO 13790 monthly method was examined. The current ISO 13790 method applies a reduction factor to the continuous heating and cooling need calculation result to derive the intermittent heating and cooling for each month. This paper proposes a method for the intermittent energy need calculation based on the internal mean temperature calculation. The internal temperature calculation procedure was introduced considering the heat-balance taking into account of heat gain, heat loss, and thermal inertia for reduced heating and cooling period. Then, the calculated internal mean temperature was used for the intermittent heating and cooling energy need calculation. The calculation results from the proposed method were compared to the current ISO 13790 method and validated with a dynamic simulation using EnergyPlus. The study indicates that the intermittent heating and cooling energy need calculation method using the proposed model improves transparency of the current ISO 13790 method and draws more rational outcomes in the monthly heating and cooling energy need calculation.