• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.284-292
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• 2009

The stack-effect in high-rise buildings in winter causes many problems such as difficulties in opening or closing doors, infiltration, energy loss, noise and fire protection. Stack effect is influenced by temperature difference between the interior and exterior of building and the height of building. As an attenuation method for stack effect, the architectural methods are generally used. However, as though architectural methods were fully adopted, the problems are reported as ever in tall building. In this study, a new method to reduce stack effect will be suggested. As an active control method against the stack effect, E/V shaft natural cooling method is suggested. In this paper, the concept of E/V shaft natural cooling system and its reduction performance of stack effect by simulation and field measurement will be reported.

• 설비공학논문집
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• 제10권5호
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• pp.535-549
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• 1998

A numerical study for performance analysis of a counterflow type forced draft tower and natural draft cooling tower has been performed based on the method using the finite volume method with non-orthogonal body fitted and non-staggered grid system. For solving the coupling problem between water and air, air enthalpy balance, moisture fraction balance, water enthalpy balance, and water mass balance equations are solved with Navier-Stoke’s equations simultaneously. For the effect of turbulence, the standard k-$\varepsilon$ turbulent model is implied in this analysis. The predicted result of the present analysis is compared with the experimental data and the commercial software result to validate the present study, The predicted results show good agreement with the experimental data and the commercial software result. To investigate the influence of the cooling tower design parameters such as approach, range and wet bulb temperature, parametric studies are also peformed.

• Design & Manufacturing
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• 제16권2호
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• pp.46-52
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• 2022

As the consumer market in the eco-friendly vehicle industry grows, the demand for water pump in a electric car parts market. This study intend to propose a mathematical model that can verify the effect of improving thermal properties when a non-conductive cooling filler liquid is introduced into an electric vehicle water pump. Also, the pros and cons of the immersion cooling method and future development way were suggested by analyzing the cooling characteristics using on the derived analysis solution. Thermal characteristics analysis of electric water pump applied with non-conductive filler liquid was carried out, and the diffusion boundary condition in the motor body and the boundary condition the inside pump were expressed as a geometric model. As a result of analyzing the temperature change for the heat source of the natural convection method and the heat conduction method, the natural convection method has difficulty in dissipating heat because no decrease in temperature due to heat release was found even after 300 sec. Also, it can be seen that the heat dissipation effect was obtained even though the non-conductive filling liquid was applied at the 120 sec and 180 sec in the heat conduction method. It has proposed to minimize thermal embrittlement and lower motor torque by injecting a non-conductive filler liquid into the motor body and designing a partition wall thickness of 2.5 mm or less.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3086-3091
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• 2007

When a molten corium is relocated in a lower head of a reactor vessel, the ERVC (External Reactor Vessel Cooling) system is actuated as coolant is supplied into a reactor cavity to remove a decay heat from the molten corium during a severe accident. To achieve this severe accident mitigation strategy, the two-phase natural circulation flow in the annular gap between the external reactor vessel and the insulation should be formed sufficiently by designing the coolant inlet/outlet area and gap size adequately on the insulation device. For this reason, one-dimensional natural circulation flow tests were conducted to estimate the natural circulation flow under the ERVC condition of APR1400. The experimental facility is one-dimensional and scaled-down as the half height and 1/238 rectangular channel area of the APR1400 reactor vessel. As the water inlet area increased, the natural circulation mass flow rate asymptotically increased, that is, it converged at a specific value. And the circulation mass flow rate also increased as the outlet area, injected air flow rate, and outlet height increased. But the circulation mass flow rate was not changed along with the external water level variation if the water level was higher than the outlet height.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.308-311
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• 2008

As a severe accident mitigation strategy in a nuclear power plant, ERVC(External Reactor Vessel Cooling) has been proposed. Under ERVC conditions, where a molten corium is relocated in a reactor vessel lower head, a natural circulation two-phase flow is driven in the annular gap between the reactor vessel wall and its insulation. This flow should be sufficient to remove the decay heat of the molten corium and maintain the integrity of the reactor vessel. Preliminary experimental study was performed to estimate the natural circulation two-phase flow. The experimental facility which is one dimensional, the half height, and the 1/238 channel area of APR1400, was prepared and the experiments were carried out to estimate the natural circulation two-phase flow with varying the parameters of the coolant inlet area, the heat rate, and the coolant inlet subcooling. In results, the periodic circulation flow was observed and the characteristics were varied from the experimental parameters. The frequency of the natural circulation flow rate increased as the wall heat flux increased.

• Wind and Structures
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• 제11권6호
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• pp.479-496
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• 2008

In this paper, computer simulation of wind flow around a single cooling tower with louver support at the base in the KAZERUN power station in south part of IRAN is presented as a case study. ANSYS FLOTRAN, an unstructured finite element incompressible flow solver, is used for numerical investigation of wind induced pressure load on a single cooling tower. Since the effects of the wind ribs on external surface of the cooling tower shell which plays important role in formation of turbulent flow field, an innovative relation is introduced for modeling the effects of wind ribs on computation of wind pressure on cooling tower's shell. The introduced relation which follows the concept of equivalent sand roughness for the wall function is used in conjunction with two equations ${\kappa}-{\varepsilon}$ turbulent model. In this work, the effects of variation in the height/spacing ratio of external wind ribs are numerically investigated. Conclusions are made by comparison between computed pressure loads on external surface of cooling tower and the VGB (German guideline for cooling tower design) suggestions.

• 한국가시화정보학회지
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• 제16권3호
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• pp.52-58
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• 2018

In this study, an experimental facility has been built to measure the cooling performance of a piezoelectric fan. The facility is composed of a heat source made of $50{\mu}m$ Ni-Cr foil, a piezoelectric fan and a rotary fan for cooling the heat source. For two cases where the foil is vertical or horizontal, the surface temperature on the foil has been measured by an IR camera with and without cooling and the cooling performance of both fans has been analyzed. With cooling by both fans, the rotary fan lowers the surface temperature of the foil as a whole, while the piezoelectric fan lowers the surface temperature at the center of the foil locally. It is also found that the cooling effectiveness of the piezoelectric fan is higher on the horizontal foil than on the vertical foil because the natural convection interferes with the jet from the piezoelectric fan.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.266-271
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• 2003

The numerical study was carried out to effectively cool Induction motor applied to a washing machine. The outer rotor made of steel periodically spins up and down. The stator consists of the thin layered iron plates and copper coil. The effective cooling system is necessary to solve the reliability problem caused by the electric losses at the coil and the iron plate. Because the heat transfer rate of the natural convection in partially open space is generally low, thus it is necessary to enhance the heat transfer using rotating perforated plate. The flow phenomena around the motor are very complex due to the motor geometry and the outer rotor motion. The mixed convection takes place due to the slow rotation speed. The three dimensional flow simulation was performed using rotating reference frame technique and Boussinesq approximation but the radiation effect was neglected. It was found that the angle and direction of the cooling blades play an important role in the stator temperature.

• 대한기계학회논문집B
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• 제28권12호
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• pp.1484-1493
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• 2004

In this study, it induced to a conclusion below by experiment consideration to regarding an effective supercooling ends method of the flow cooling water in a tube of continuous ice making method and the static cooling water in a tube of continuous ice making method which used magneticfluid in a dynamic type ice storage system. Continuous ice making in a tube of the flow cooling water was shortened about 12 minutes until supercooling ends that case which gave vertical eccentricity rotation magnetic field 120rpm than did not provide magnetic field by experimental result that was tested to supercooling ends effect from shape control of magneticfluid. Continuous ice making method in a tube of the static cooling water compared with and reviewed the case that was not provided with the magnetic field and exposed cooling surface instantaneously by magnetic field. It confirmed that supercooling degree $\Delta$ $T_{c}$, $\Delta$ $T_{s}$, and $\Delta$ $T_{w}$ became lower because of heat transfering increasing by the occurrence of natural convection between after cooling starting progress time 1∼3 minutes if it did not give a magnetic field, and peformed the supercooling ends when natural convection occurred confirmed that refrigerating capacity was better. That relation $\Delta$ $T_{c}$, and $t_{e}$/($\Delta$ $T_{c}$-$\Delta$ $T_{s}$) after convection occurred, was not depended on $T_{b}$ and initial temperature if the depth of water and thickness of magneticfluid were regular and it was possible to verify conjecture of tp from $\Delta$ $T_{s}$ and $\Delta$ $T_{c}$.lar and it was possible to verify conjecture of tp from $\Delta$ $T_{s}$ and $\Delta$ $T_{c}$.c}$.>.

• Journal of Advanced Marine Engineering and Technology
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• 제39권4호
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• pp.449-455
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• 2015

전력용 변압기 용량의 증대와 고효율화에 따른 권선의 단위체적당 열발생량의 증가 및 이에 따른 절연성능의 저하는 전력용 변압기의 수명과 신뢰성에 큰 영향을 준다. 이러한 문제점은 방열기의 냉각성능을 증가시킴으로써 해결이 가능하다. 본 연구는 ONAF(Oil Natural Air Forced) 형식의 변압기의 방열기에 대해 공기의 강제대류를 일으키는 팬의 위치에 따른 냉각성능 평가를 통하여 냉각효과가 가장 큰 팬의 위치를 찾기 위한 것이다. 해석에는 유동해석 상용소프트웨어를 사용하였으며, 해석시간의 단축을 위하여 오일의 냉각유로를 단순화시켰고 팬의 지름을 일정하게 두고 팬의 위치를 다양하게 변화시켜가며 해석을 실행하였다. 해석 결과 팬의 수직적인 위치 변화는 냉각성능에 크게 영향을 주지 않았으나 팬이 변압기의 전방영역에 위치할 경우 후방영역의 배치보다 온도강하가 큰 것을 확인할 수 있었다.