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직사각형 전도성 장애물을 갖는 밀폐공간내에서의 자연대류
추홍록(H.L.Choo),김병하(B.H.Kim),김현우(H.W.Kim),장충선(C.S.Jang) 한국태양에너지학회 1998 한국태양에너지학회 논문집 Vol.18 No.2
자연대류에서 정사각형 밀폐공간의 중랑에 고립된 전도성 장애물이 들어 있을 때 열전도도의 효과를 수치해석적으로 연구하였다. Pr=0.17, Ra=1.0x10⁴, 1.0x10^5, 1.0x10^6, 유체와 전도체의 열전도율비인 K^*=1.0, 6.6, 34.0 그리고 전도성 장애물의 비 ζ=0.5, 1.0, 2.0에서 수치연구를 수행하였다. 그 결과들은 유선, 등온선 그리고 Nusselt수로 나타내었다. Ra and K^* 값이 일정한 상태에서 평균 Nusselt수가 증가함에 따라 ζ가 증가하였다. ζ=1.0(장애물의 형상비)일 경우 Rayleight수에 관계없이 K^*(장애물의 열전도율비)가 증가할수록 평균 Nusselt수는 감소한다. 장애물의 크기와 열전도율비가 동일할 때 대류열전달 효과는 ζ=0.5인 경우보다 ζ=2.0일 때 더 향상되었다. The effect of the thermal conductivity of a centered, square, heat-conducting body on natural convection in a square enclosure was examined numerically. Numerical simulations was carried out for Pr=0.17, Ra=1.0x10⁴, 1.0x10^5, 1.0x10^6, K^*=1.0, 6.6, 34.0 and ζ=0.5, 1.0, 2.0. The results were reported in terms of streamlines, isotherms, Nusselt number. As the results, the mean Nusselt number increases with the increasing of ζ at a constant Ra and K^*. In the case of ζ =1.0(obstruction shape ratio), the mean Nusselt numbers were decreased as increasing of K^*(obstruction thermal conductivity ratio) with regardless of the Rayleigh number. When the constant obstruction size and thermal conductivity ratio, convective heat transfer effect was more enhanced at ζ =2.0 than ζ =0.5.
추홍록,상희선,이병화 한국산업안전학회 1998 한국안전학회지 Vol.13 No.4
The vortex tube is a simple device for separating a compressed gaseous fluid stream into two flows of high and low temperature without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air supply system. The phenomena of energy separation through the vortex tube was investigated experimentally. This study is focused on the effect of the diameter of cold end orifice diameter on the energy separation. The experiment was carried out with various cold end orifice diameter ratio from 0.22 to 0.78 for different input pressure and cold air flow ratio. The experimental results were indicated that there are an optimum diameter of cold end orifice for the best cooling performance. The maximum cold air temperature difference was appeared when the diameter ratio of the cold end orifice was 0.5. The maximum cooling capacity was obtained when the diameter ratio of the cold end orifice was 0.6 and cold air flow ratio was 0.7.
공기공급 시스템에 적용되는 Vortex Tubes 의 에너지 분리특성에 관한 연구(2) : 표면의 단열효과에 따른 영향 the effect of surface insulation
추홍록,유갑종,방창훈 한국산업안전학회 1999 한국안전학회지 Vol.14 No.1
The vortex tube is a simple device which splits a compressed gas stream into a cold stream and a hot stream without any chemical reactions. Recently, vortex tube is widely used to 1ocal cooler of industrial equipments and air supply system. In this study, the insulation effect of surface on the efficiency of vortex tube was performed experimentally. The experiment is carried out for nozzle area ratio of 0.194, diameter ratio of cold end orifice of 0.6 and input pressure ranging from 0.2Mpa to 0.5Mpa. The purpose of this study is focused on the effect of surface insulation of vortex tube with the variation of cold air mass flow ratio. The results indicate that the temperature difference of cold and hot air are higher about 12% and 30% than that of not insulated vortex tube respectively. Furthermore, for the insulated vortex tube, the similarity relation for the prediction of cold end temperature as the function of cold air mass flow ratio and input pressure is obtained.
Vortex Tube 의 부분유입율과 저온 입 출구비가 에너지분리 특성에 미치는 영향
김정수,추홍록,상희선 한국산업안전학회 1998 한국안전학회지 Vol.13 No.3
The vortex tube is a simple device for separating a compressed fluid stream into two flows of high and low temperature without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air conditioner for special purpose. The phenomena of energy separation through the vortex tube were investigated to see the effects of cold flow inlet-outlet ratios and partial admission rates on the energy separation experimentally. The experiment was carried out with various cold flow inlet-outlet ratios from 0.28 to 10.56 and partial admission rates from 0.176 to 0.956 by varying input pressure and cold air flow ratio. To find best use in a given cold flow inlet-outlet ratio and partial admission rate, the maximum temperature difference of cold air was presented. The experimental results were indicated that there are an optimum range of cold flow inlet-outlet ratio for each partial admission rate and available partial admission rate.