• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1897-1902
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• 2003

An 1/21.6 scaled experimental facility was prepared utilizing the results of a scaling analysis to simulate the APRI400 reactor and insulation system. The behaviors of the boiling-induced two-phase natural circulation flow in the insulation gap were observed, and the liquid mass flow rates driven by natural circulation loop were measured by varying the wall heat flux, upper exit slot area and configuration. And non-heating experiments have also been performed and discussed to certify the hydraulic similarity of the heating experiments by injecting air equivalent to the steam generated in the heating experimental condition.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 추계학술발표대회 논문집
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• pp.190-195
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• 2008

The objective of this research is to determine overall heat transfer coefficients (K-value) of exterior wall, floor, and roof of Nakseonjae, a Korean traditional residence via field measurement of transient heat flow and temperature difference across each envelope component. Heat flow sensors and T-type thermocouple were attached on the internal and the external surface of each building component, and real-time measurement data were collected for the three consecutive summer days. The K-values determined in this research showed good agreement with other results from open literature. Peak and annual thermal loads of the traditional residence estimated by a commercial energy simulation program were compared with those for a current apartment house. The traditional house showed lower annual cooling load than that of the current building. It may caused by the fact that the traditional building has less air-tight envelopes and no fenestration passing direct solar radiation into the space.

• 태양에너지
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• 제10권3호
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• pp.13-18
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• 1990

표면 온도가 균일하지 않은 원통을 균속도 유동장에 가로 놓았을 경우, 표면에서의 열전달 특성은 표면이 등온이거나 일정한 heat flux가 주어졌을 때와는 판이하게 다르다. 본 연구에서는 공기의 균속도 유동장내에서 두가지 경우(step형 및 선형변화)의 비등은 경제조건이 원통면을 따라 원주방향으로 주어졌을 때 표면에서의 열전달 특성을 고찰하였다. Step형 변화는 원통형 태양로의 표면에서 관찰될 수 있다. Solar One(Califomia주의 Barstow시에 있는 태양로)의 경우, 작동유체(물)는 표면을 따라 원주방향과 수직으로 설치된 튜브를 따라 흐르면서 액체상태로부터 고온고압의 증기로 변한다. 이 과정에서 태양로 표면의 receiver panel은 그 위치에 따라, preheater, boiler, 그리고 superheater의 역할을 수행하며 표면의 온도도 균일하지 않은 분포를 나타낸다. 이와 같은 경우 표면의 평균 온도를 가지고 대류에 의한 열 손실을 계산하면 큰 오류를 범할 가능성이 있다.

• 대한기계학회논문집B
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• 제36권4호
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• pp.425-430
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• 2012

본 연구에서는 비상시 전기 공급용 MCFC 프리커버터의 천연가스(메탄)로부터 수소의 생산량을 증가시키는 경우를 수치적으로 해석하였다. 상용 코드를 사용하였으며 촉매는 다공성 매질로 시뮬레이션 하였다. 3가지 주요 화학반응인 수증기 개질반응(SR), 수성 가스 전환(WGS) 및 직접 수증기 개질 반응(DSR)은 사용자 부프로그램을 사용하여 해석하였다. 프리컨버터에서 10%의 연료전환율을 얻기 위해 요구되는 추가 열량을 벽면을 통해 공급하게 되면 프리컨버터의 벽면 부근에서만 매우 불균일한 온도 분포와 화학반응이 일어나는 것으로 분석되었다. 이와 같은 현상은 매우 작은 열전도율을 갖는 다공성 매질의 촉매와 흡열반응으로 설명되어질 수 있다. 해석결과 프리컨버터의 길이가 짧은 경우가 보다 균일한 연료전환율을 보여 주며, 촉매의 유지 보수 면에도 길이가 짧은 경우가 유리함을 보여 주었다.

• 설비공학논문집
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• 제13권4호
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• pp.242-251
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• 2001

Flow boiling heat transfer coefficients (HTCs) of R22, R134a, R407C, and R410A were measured for a horizontal plain tube. The test section was made of a copper tube of 8.8mm inner diameter and 1000mm length respectively. The refrigerant was heated by passing hot water through an annulus surrounding the test section. All tests were performed at a fixed refrigerant saturation temperature of $5^{\circ}C$ with mass fluxes of 100~300 kg/$m^2$,/TEX>s. HTCs were measured by two methods: the direct wall temperature measurement method and the indirect Wilson plot method. Experimental results showed that the Wilson plot method was affected greatly by the external test conditions and yielded inconsistent results. For the mass flux of 100kg/$m^2$,/TEX>s, HTCs were almost constant regardless of the quality for a given refrigerant HTCs of R134a and R407C were similar to those of R22 while those of R410A were 60% higher than those of R22. For the mass fluxes of 200 and 300kg/$m^2$,/TEX>s, HTCs of R407C were almost the same as those of R22, while HTCs of R134a and R410A were 12-13% and 20~23% higher than those of R22 respectively. For pure refrigerant, Shah\`s correlation yielded a good agreement with the measured data both qualitatively and quantitatively.

• 한국건축시공학회지
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• 제16권5호
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• pp.397-403
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• 2016

건축물의 에너지 절약기준이 강화됨에 따라 단열성능이 우수한 외단열 공법의 적용이 증가 추세에 있으나, 빈번한 화재사고로 외단열 화재확산 방지를 위한 규정이 강화되었다. 따라서, 기존 EPS 외단열 시스템의 단열성능을 확보하면서 화재안전성을 향상하기 위하여 불연성 단열재를 화재확산 방지구조로 적용한 EPS 외단열 시스템의 대형 화재시험을 ISO 13785-2에 의하여 수행하였고, 그 결과, 시간에 따른 시험체의 외형분석에서 EPS 단열재만 사용한 외단열 공법보다 우수한 화재확산 방지효과가 있는 것으로 판단되었고, 온도 및 열류량 측정결과에서도 하단부보다 상단부의 온도 및 열류량이 낮게 측정되어 차열효과가 있는 것으로 판단되었다.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.9-18
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• 2024

In-vessel retention through external reactor vessel cooling (IVR-ERVC) is a severe accident management (SAM) strategy that has been adopted and used in many nuclear reactors such as AP1000, APR1400, and light water reactor etc. Some reactor accidents have raised concerns about nuclear reactors among residents, leading to a decrease in residents' acceptability and many studies on SAM are being conducted. Experiments on IVR-ERVC are almost impossible due to its specificity, so fluid characteristics are analyzed through BALI experiments with similar condition. In this study, computational fluid dynamics (CFD) via Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) for BALI experiments were performed. Steady-state CFD analysis was performed on three turbulence models, and SST k-ω model was in good agreement with the experimental measurement temperature within the maximum error range of 1.9%. LES CFD analysis was performed based on the RANS analysis results and it was confirmed that the temperature and wall heat flux for depth was consistent within an error range of 1.0% with BALI experiment. The LES CFD analysis results were compared with those of the Lagrangian-based solver. LES matched the temperature distribution better than SOPHIA, but SOPHIA calculated the position of boundary between stratified layer and convective layer more accurately. On the other hand, Lagrangian-based solver predicted several small eddy behaviors of the convective layer and LES predicted large vortex behavior. The vibration characteristics near the cooling part of the BALI experimental device were confirmed through Fast Fourier Transform (FFT) investigation. It was found that the power spectral density for pressure at least 10 times higher near the side cooling than near the top cooling.