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혼합날개가 부착된 6×6 봉다발 부수로에서의 열전달 향상을 위한 실험적 연구
변선준,신용철,민경호,방윤곤,채영종 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.2
The present experimental study investigates single-phase heat transfer coefficients downstream of support grid in 6×6 rod bundles. Support grid with Split mixing vanes enhance heat transfer in rod bundles by generating turbulence but this turbulence is confined to a short distance. Support grid with large scale vortex flow(LSVF) mixing vanes enhanced heat transfer to a longer distance. In this study, the experiments were performed at reynolds numbers of 50,000. The characteristics of the heat transfer enhancement of the Split mixing vane and those of the LSVF mixing vane were compared. The results showed that the characteristics of the heat transfer enhancement of rods by the Split mixing vane were limited to 10 Dh after the spacer grid, but those by the LSVF mixing vane were maintained until 15 Dh after the spacer grid. For the reynolds number of 50,000, the heat transfer enhancement effect was 3.0% greater when using the LSVF mixing vane than when using the Split mixing vane between the 1 ∼ 15 Dh interval after the spacer grid.
혼합날개를 이용한 6×6 봉다발 부수로에서의 열전달 향상 특성에 관한 실험적 연구
변선준,어재혁,윤정,정지영 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.5
In the present study, single-phase heat transfer characteristics for downstream flow in the support grid of 6×6 rod bundle were investigated. It has been known that a turbulence generation due to a support grid with split mixing vanes enhances heat transfer in rod bundle but its heat transfer enhancement actually affects to relatively shorter distance. On the other hand, it has been also turned out that a support grid with large scale vortex flow (LSVF) mixing vanes results in heat transfer enhancement to a longer distance. Based on the results of literatre survey, single-phase water heat transfer experiments were performed for Reynolds numbers at around 30,000, and the heat transfer enhancement effect with both i) the split mixing vanes and ii) the LSVF mixing vanes was compared in this study. The key results showed that the effect of heat transfer enhancement in rod bundle region by the split mixing vanes was maintained up to the length of 15Dh behind the spacer grid. For the Reynolds numbers at around 30,000, it was also observed that the effect using the LSVF mixing vanes was stronger at about 3% when compared to the case using the split mixing vanes only for the distance ranging from 1 to 15Dh behind the spacer grid.
혼합날개가 부착된 6×6 봉다발 부수로에서의 열전달 향상을 위한 실험적 연구
변선준,신용철,민경호,방윤곤,채영종 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.2
The present experimental study investigates single-phase heat transfer coefficients downstream of support grid in 6×6 rod bundles. Support grid with Split mixing vanes enhance heat transfer in rod bundles by generating turbulence but this turbulence is confined to a short distance. Support grid with large scale vortex flow(LSVF) mixing vanes enhanced heat transfer to a longer distance. In this study, the experiments were performed at reynolds numbers of 50,000. The characteristics of the heat transfer enhancement of the Split mixing vane and those of the LSVF mixing vane were compared. The results showed that the characteristics of the heat transfer enhancement of rods by the Split mixing vane were limited to 10 Dh after the spacer grid, but those by the LSVF mixing vane were maintained until 15 Dh after the spacer grid. For the reynolds number of 50,000, the heat transfer enhancement effect was 3.0% greater when using the LSVF mixing vane than when using the Split mixing vane between the 1 ∼ 15 Dh interval after the spacer grid.
SMART-ITL 안전주입배관 파단시 노심보충수탱크 주입성능에 관한 실험적 연구
변선준(Sun-Joon Byun),배황(Hwang-Bae),류성욱(Sung-Uk Ryu),전병국(Byong-Guk Jeon),유효봉(Hyo-Bong Ryu),민경호(Kyoung-Ho Min),방윤곤(Yun-Kon Bang),전우진(Woo-Jin Jeon),이성재(Sung-Jae Yi),박현식(Hyun-Sik Park) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
System-integrated modular advanced reactor (SMART) is an integral-type nuclear reactor which received its design certificate in 2012 for the first time in the world. Currently, to improve its safety level, passive safety systems are designed and their performance has been evaluated. In this study, to examine the injection characteristics of a core makeup tank, a small-break loss of coolant accident is simulated using the SMART integral test loop (SMART-ITL). The experimental results provide more understanding on the behaviors of core makeup tanks (CMTs) as well as supporting future licensing process.
백연저감 시스템용 Pilot 파형 열교환기 열전달 특성에 대한 실험적 연구
왕쩐후안,변선준,권영철 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.5
In this study, the heat transfer characteristics of pilot wave heat exchanger for white smoke reduction system was investigated. The performance of the wave and honeycomb heat exchanger combined with the first stage, second stage and third stage was tested using a calorimeter. Air and water inlet/outlet temperature and flow rate, pressure drop and dehumidification amount were measured to compare the heat transfer performance according to the type and the combination of heat exchanger. The heat transfer rate and dehumidification amount of the wave heat exchanger were higher than that of the honeycomb heat exchanger, and the pressure drop was low. As the stage increased, the heat transfer rate and the increase of the dehumidification amount were more pronounced, and the pressure drop linearly increased. The wave heat exchanger had a lower flow resistance than the honeycomb heat exchanger with the honeycomb structure and had a higher heat transfer effect due to the convection, so the water outlet temperature was higher in the wave heat exchanger.
레이놀즈응력 수송방정식 모형에 의한 폴리머 항력감소 난류 채널유동의 예측
신종근,변선준 한국기계기술학회 2018 한국기계기술학회지 Vol.20 No.5
An elliptic blending Reynolds stress transport equation model for Newtonian fluids has been extended to predict polymer-induced drag reduction FENE-P fluids. The conformation tensor equation which is related to the polymer stress is adopted from the model form of Resende et al., and the models of redistribution and dissipation rate terms for the Reynolds stress transport equation are considered by the elliptic blending equation. Also, the new model terms for viscoelastic turbulent transport and viscoelastic dissipation in the Reynolds stress transport equation are introduced to consider the polymer additives effect. The prediction results are directly compared to the DNS data to assess the performance of the present model predictions.
왕쩐후안,변선준,권영철 한국기계기술학회 2018 한국기계기술학회지 Vol.20 No.5
In this study, the fatigue and vibration analysis were performed by using Solidworks program to investigate the damage percentage, life cycle and vibration mode depending on the types and positions of load applied to the table (Cases 1, 2, 3, 4). The farther the point of action of the load was, the more the fatigue damage and stability of the table were greatly reduced. The life cycles of Case 1 and 4 were over 100,000 cycles and the fatigue damage was less than 70%. From the vibration analysis, five modes and natural frequencies of Case 1 were confirmed. As the natural frequency increases, the shape of the corresponding mode is predicted not to be deformed.
차재민,변선준,왕쩐후안,권영철 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.2
In the present study, the structural and fatigue analysis on the shape change of an automatic press are investigated for prediction of operation safety and reliability of the automatic press along the thickness(t) and length(L) of head, and corner shapes(case 1, 2, 3). The equivalent stress and deformation characteristics of the automatic press were studied by computerized analysis method for the bushing production of the seat frame. An external stress of 14.0 MPa was applied to predict the operation stability and the fatigue limit of the structure. As the thickness of the header increased and the length of the header decreased, the load stability applied by the piston improved and the maximum stress and deformation were reduced. In addition, due to the change in shape of the corners, the load applied at the cross-sectional area of the corners decreases, and then the maximum stress and deformation appearing in the header are reduced. That is, the change of corner shapes affects the equivalent stress and deformation. That is the change of corner shapes affects the equivalent stress and deformation. From the fatigue and vibration analysis, fatigue failure does not occur even when the number of alternating operation of the automatic press increases, and the natural frequency is predicted for dynamic characteristics.
파형 열교환기의 열전달 및 유동특성에 관한 전산해석 연구
왕쩐후안,변선준,차재민,권영철 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.4
In this study, the heat flow characteristics of wave heat exchanger was investigated by being applied to the white smoke reduction system. Through numerical analysis, the heat transfer and flow characteristics of the wave heat exchanger with the change of inlet condition of air-side and water-side were analyzed. To investigate the temperature, the absolute humidity, heat transfer rate, pressure drop and turbulence characteristics of the wave heat exchanger, the simulation analysis was conducted by using the commercial computational fluid dynamics software (Solidworks Flow Simulation) under uniform flow conditions. As the inflow rate of air decreased and the inflow temperature of water increased, the heat transfer coefficient of the wave heat exchanger decreased. When the experimental conditions of water-side were the same, the air outlet temperature and absolute humidity of the wave heat exchanger increased with increasing inflow rate of air. To reduce the white smoke, the air outlet temperature and absolute humidity of the wave heat exchanger must be reduced. Therefore, the lower the air velocity and the water inflow temperature into the wave heat exchanger, the more effective it is.