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Non-gray Radiation in the Entrance Regionof a Smooth Tube Taebeom Seo
서태범(Taebeom Seo) 한국태양에너지학회 1995 한국태양에너지학회 논문집 Vol.15 No.3
튜브 내의 입구영역에서 대루와 비회복사(mon-gray radiation)가 동시에 일어날 때의 열전달 특성을 수치해석적으로 연구하였다. 작동유체는 이산화탄소, 수증기, 질소의 혼합가스라 하였고, 유동은 속도장과 온도장이 동시에 발달하는 층류 유동으로 가정하였다. 복사전달방정식을 풀기 편하게 하기 위해 P-1 근사법이 사용되었고 혼합가스의 비회흡수계수(non-gray sbsorption coefficient)는 지수광폭밴드모형(exponential wide band model)을 이용해서 구하였다. 열전달 특성에 대한 온도조건의 영향을 조사하기 위해 튜브의 축방향에 대한 평균온도와 뉴셀트수(Nusselt number)의 변화를 몇 가지 다른 온도조건에 대해 나타내었다. 속도장과 온도장이 동시에 발달하는 경우의 뉴셀트수를 속도장은 완전히 발달되어 있고 온도장만 발달하는 경우의 뉴셀트 수와 비교하였다. 또한, 가스의 성분조성이 대류와 비회복사 뉴셀트수에 미치는 영향을 조사하였다. Non-gray radiation with convection in the entrance region of a smooth tube is numerically investigated. The fluid is a mixture of carbon dioxide, water vapor, and nitrogen to simulate combustion products of propane. The flow is assumed to be laminar and hydrodynamically and thermally developing. The P-l approximation is used to simplify the radiative transfer equation and the exponential wide band model is adapted to model the spectral absorption coefficients of non-gray gas mixture. The bulk mean temperature and Nusselt number variation along the tube axis are shown for several inlet and wall temperature pairs to show the effect of temperature on the heat transfer characteristics. Nusselt numbers for simultaneously developing flow are compared to those for thermally developing now. In addition, the effect of the mole fraction of the non-gray gases on convective and radiative Nusselt numbers is investigated.
집시형 태양열 흡수기의 Transient 열전달 특성에 대한 수치해석 연구
이주한(Juhan Lee),서주현(Joohyun Seo),오상준(Sangjune Oh),이진규(Jinkyu Lee),서태범(Taebeom Seo) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
A numerical and experimental studies are carried out to investigate the transient heat transfer characteristics of 5㎾th dish-type solar air receiver. Measured solar radiation and temperatures at several different locations are used as boundary conditions for numerical simulation. Many parameters' effects (reflectivity of the reflector, the thermal conductivity of the receiver body, transmissivity of the quartz window, etc.) on the thermal performance are investigated. Discrete Transfer Method is used to calculate the radiation heat exchange in the receiver. A transient heat transfer model is developed and the rate of radiation, convection and conduction heat transfer are calculated. Comparing the experimental and numerical results, good agreement is obtained. Using the numerical model, the transient heat transfer characteristics of volumetric air receiver for dish-type solar thermal systems are known and the transient thermal performance of the receiver can be estimated.
금속성 활성 촉매를 이용한 고온 태양열 메탄-이산화탄소 개질반응
신일융(Ilyoong Shin),김재익(Jaeik Kim),이진규(Jingyu Lee),서태범(Taebeom Seo) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Solar reforming of methane with CO₂ was successfully tested with a direct irradiated absorber on a parabolic dish capable of 5㎾th solar power. The new type of catalytically activated metallic foam absorber was prepared, and its activity was tested. Ni was applied as the active metal on the gamma?alumina coated Ni metal foam for the preparation of the catalytically-activated metal foam layer. Compared to conventional direct irradiation of the catalytically-activated ceramic foam absorber, this new metallic foam absorber is found to exhibit a superior reaction performance at the relatively low insolation or at low temperatures. In addition, unlike direct irradiation of the catalytically-activated ceramic foam absorber, metallic foam absorber has better thermal resistance, which prevents the emergence of cracks caused by mechanical or thermal shock. The total solar power absorbed reached up to 2.1㎾ and the maximum CH₄ conversion was almost 40%.