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저온재생기 2열원 2중효과 Parallel Flow Cycle의 특성해석
최국광(K.K.Choi),이동호(D.H.Rie) 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.17 No.3
본 연구는 저온재생기에서 용액 재생 열원으로 저온열을 보조열원으로 이용가능한 2열원 2중효용흡수 사이클특성을 규명하기 위한 방법으로 병렬 용액 순환형 2중 효용 흡수 사이클 해석을 수행한다. 본 해석은 저온 재생기에서 필요한 재생열의 일부를 태양열 또는 배열 등과 같은 저온 보조 가열원을 이용하여 열의 유용성 검증을 위한 기초 수단으로 가열원 입구 온도, 용액 순환량을 변화시켜 2중효용 parallel flow cycle의 특성을 규명한다. Cycle simulation of the double effect parallel flow mxle1 is applied to a lithium-Bromide/water system, with the objective of evaluation the possibilities of effectively utilizing waste-heat as a secondary heat source for the low-temperature generator. In this study, cycle simulation has been carried out to clarify the effect heat exchange in order to predict the performance of absorption refrigeration cycles using waste heat.
직육면체형 잠열축열조내 상변화물질의 열전달특성에 관한 연구
임장순(C.S.Yim),최국광(K.K.Choi),김준근(J.K.Kim),김영기(Y.K.Kim),김일겸(I.G.Kim),김동춘(D.C.Kim) 한국태양에너지학회 1995 한국태양에너지학회 논문집 Vol.15 No.3
본 연구는 상변화물질로써 무기염수화물계 물질인 피로인산나트륨(Na₄P₂O_7·10H₂O)이 채워져있는 직육면체형 잠열축열조 내에서 축열과정시 일어나는 상변화물질의 온도특성, 열전달현상, 축열량 등을 실험적으로 측정하고 그 결과들을 수치해석 결과들과 비교·검토한 것이다. 축열과정시 상변화물질인 피로인산나트륨은 용융상태가 액체상태가 아닌 gel상태이므로 액체상태에서의 주된 열전달현상으로 나타나는 자연대류 유동현상이 일어나지 않아 전도에 의한 열전달현상이 지배적인 것으로 나타났다. 무기염수화물계 상변화물질은 공극율(공기 함유율)이 작을수록 열용량이 커지므로 축열과정시 공극율이 큰 경우보다 온도가 서서히 상승되었으며, 실험으로 측정된 온도값과 수치해석적인 방법으로 계산된 온도감ㅅ은 최대 15%의 차이가 났다. This study presents experimental and numerical results of the temperature characteristics, the heat transfer phenomema, and the heat storage quantity during the heat storage process with sodium phyrophosphate decahydrate (Na₄P₂O_7·10H₂O)-Phase Change Material (PCM) in a latent heat storage tank (cubic type). It was proved that heat transfer by conduction was dominant because PCM (Na₄P₂O_7o 10H₂O) during heating processes was gel phase, not liquid phase. The gap ratio (rate of air content) of PCM became smaller, the thermal capacity of PCM became larger, therefore the temperature distribution of PCM slowly increased than that of large gap ratio. There was maximum 15% difference between measured temperatures and calculated temperatures.
충돌수분류(衝突水噴流)에 의한 Semi-cylinder면(面)에서의 열전달(熱傳達)에 관(關)한 실험적(實驗的) 연구(硏究)
염기찬,최국광,서정윤,Ohm, K.C.,Choi, G.G.,Seo, J.Y. 대한설비공학회 1988 설비저널 Vol.17 No.6
Local heat transfer coefficients were measured on semi-cylinders on which a circular water jet impinged in crossflow. The ratio of the semi-cylinder's diameter and the nozzle outlet diameter were varied parametrically, as were the Reynolds number and the supplementary water heights. The measurements showed that the circumferential distribution of the heat transfer coefficient peaked at the stagnation point. For a fixed supplementary water height, the peak heat transfer coefficient was not depend on the curvature of test specimen(d/D). Optimum height of supplementary water which brought about the augmentation of heat transfer at the stagnation point was S/D=1. The Nusselt number decreased as the circumferential distance or angle increased. The circumferential distribution of dimensionless heat transfer (Nu/Nus) was independent of d/D ($d/D{\geq}8.33$), but for the d/D<8.33, it was depended on d/D. At a fixed angle of specimen, dimensionless heat transfer (Nu/Nus) decreased as the ratio d/D increased. The extent of the decrease between d/D=6.67 and 8.33 was markedly greater than that between d/D=8.33 and 10, or d/D=10 and 11.67.
증기흡수시(蒸氣吸收時) 계면활성제액적간(界面活性劑液滴間)에 발생(發生)하는 마랑고니대류거동(對流擧動)의 가시화(可視化)
이동호,최국광,백목효부,서정윤,Rie, D.H.,Choi, K.K.,Kashiwagi, T.,Seo, J.Y. 대한설비공학회 1992 설비공학 논문집 Vol.4 No.2
In most absorption machines, absorption enhancement has been achieved by adding small amount of surfactant additive, which introduced the surface tension difference between absorbent and surfactant droplets in the vapor absorption. The aim of this study is to understand a basic mechanism of Marangoni convection and its effectiveness in the vapor absorption enhancement. In this study, nonflowing aqueous solution of LiBr 60 mass% was exposed to saturated water vapor under the condition that two dropwises surfactant were fixed on the absorbent surface. Our experiments achieved to visualize the enhanced heat and mass transfer phenomena by the effect of Marangoni convection through the laser holographic interferometry. Also, Marangoni convection behavior was obtained by using tracer method.
이종수,양한주,최국광,서정윤,Lee J.S,Yang H.J,Choi K.K,Seo J.Y 대한설비공학회 1987 설비저널 Vol.16 No.1
In this paper, the local effective thermal conductivities and calculated by using the actual temperature distribution in packed bed. The variations of these are investigated for radius and air stream direction, flow rate and particle diameter. The resulting local effective thermal conductivi-ties are classified in the inner zone of bed and vicinity zone of the wall surface. Also these are related to dimensionless axial direction position, radius direction position, and particle diameter and Reynolds number which uses particle diameter as the characteristic length. If these correla-tions are represented by function, the equation is showed in Eq. (3-4). This equation is well satisfied with experimental results within $\pm25\%.$
충돌수분류(衝突水噴流)에 의한 원통내면(圓筒內面)에서의 열전달증진(熱傳達增進)에 관한 연구(硏究)
엄기찬,우창기,최국광,서정윤,Ohm, K.C.,Woo, C.K.,Choi, G.G.,Seo, J.Y. 대한설비공학회 1990 설비공학 논문집 Vol.2 No.4
An experimental study of the heat transfer characteristics between circular water jet and cylindrical inner surface is presented. The ratios of the semi-cylinder's inner diameter and the nozzle outlet diameter were varied parametrically, as were the Reynolds number and the supplementary water heights. The measurements showed that cirucmferential distribution of the heat transfer coefficient peaked at the stagnation point and, there occurred a kind of a secondary maximum of heat transfer that moved toward to stagnation point as the ratio d/D increased. The local heat transfer coefficient increases as the Reynolds number becomes larger, and the rate of increase is subjected to the influence of d/D & position of angle. Also, optimum heights of supplementary water which brings about the augmentation of heat transfer are S/D=1 for the stagnation point, the position of $15^{\circ}$ & $30^{\circ}$ angle, but for the positions of $45^{\circ}$ angle (d/D=10~11.67), $60^{\circ}$ & $75^{\circ}$ angle, the heat transfer coefficients in the case of using supplementary water are smaller than simple jet (S/D=0).
수직관내(垂直管內)를 흘러내리는 액막식(液膜式) 흡수기(吸收器)의 흡수(吸收) 및 열전달특성(熱傳達特性)(제(第)2보(報) 열전달특성(熱傳達特性))
엄기찬,이동호,최국광,카시와기 타카오,서정윤,Ohm, K.C.,Rie, D.H.,Choi, G.G.,Kasiwagi, Takao,Seo, J.Y. 대한설비공학회 1993 설비공학 논문집 Vol.5 No.4
This is the second report of a three part study on the absorption and heat transfer characteristics of absorber, the correlation of refrigerating capacity and heating capacity. The 2nd report deals with the heat transfer characteristics of a vertical falling film type absorber of inner copper tube. The solute is LiBr-Water solution(60wt%) and the solvent is water vapor. The film Reynoles numbers are varied in the range of 35~130. The states of LiBr solution at the top of absorber are supercooled liquid and superheated liquid. The results are summarized as follows ; Heat transfer results reveal that for the absorption of falling film, the state of LiBr solution appears to be influential in determining the heat transfer. Thus, for the state of supercooled liquid, heat transfer coefficient decreases with increasing the film Reynolds number, but in the condition of superheated liquid, it increases conversely. The mass transfer coefficients that were presented in the 1st.report and heat transfer coefficients of this paper are presented as the dimensionless correlation. The optimum water flowrate which brings about maximum value of heat flux in the film exists, and that increases with increasing the cooling water temperature.
이광수(J.S.Lee),최국광(K.K.Choi) 한국태양에너지학회 1998 한국태양에너지학회 논문집 Vol.18 No.3
축류비가 5이고 형상비가 7인 長方形 노즐을 사용하여 연직 상향의 3차원 자유 충돌 수분류계를 구성하였다. 수평 충돌판에 상향의 장방형 충돌수분류가 충돌할 때, 보조수를 동반하지 않은 단일수분류 및 보조수를 동반하는 수분류에 대하여 노즐-충돌판 사이의 거리, 노즐출구 속도를 변수로하여 노즐의 긴변 방향과 짧은 변 방향에 대하여 전압 및 정압 분포를 측정하였다. 이때 충돌판상에서 정압이 영이 되는 국소 위치까지의 거리인 충돌 반폭을 구하고, 최고 압력을 나타내는 정체점을 기준으로 무차원 정압 분포식을 제시하였다. 또한 각 실험조건에서 정체점상에서의 충돌속도를 구하였으며, 충돌속도는 노즐-전열면간 거리가 증가함에 따라 감소하며 그 감쇄율은 삼차원 자유 분류의 특성감쇄 영역의 유동 특성을 갖는다. The purpose of this research is to investigate the characteristics of static and total pressure distribution' in the upward free water jet system impinged on a downward flat plate. The rectangular nozzle was used and its contraction and aspect ratio was five and about seven respectively. Experimental conditions considered were jet velocity, distance between nozzle and flat plate, height of supplementary water.<br/> It was founded that pressure distribution on the flat plate had the Gaussian curve when the pressure at stagnation point and impinging half width were chosen as the scaling parameters. The maximum pressure was shown at the stagnation point. The central impingement velocity decreased with the increment of distance between nozzle and flat plate, and its slop of decay was similar to that of chracteristics decay region in the three-dimensional free jet.