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안내덕트 내부 난류유동구조에 따른 열전달 특성변화 수치해석
유근종(Geun Jong Yoo),최훈기(Hoon Ki Choi),최기림(Kee Lim Choi) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.9
본 연구에서는 복합화력발전소 가스터빈 출구가스 안내덕트 내부의 가스유동장이 배열회수보일러 전열기구에 미치는 영향을 CFD기법을 이용하여 분석하였다. 안내덕트 내부 난류흐름의 경우, 유속의 편차가 크고 선회 효과 및 상승류 현상이 심한 특징을 가지고 있음으로 이와 같은 유동의 수치해석을 위해 2개 방정식 난류점성 모델 중 RNG k-? 모델을 사용하였으며 유동장의 영향을 가장 많이 받는 배열 회수보일러 최종과열기관의 열전달특성변화를 파악하기위하여 NTU 방식을 이용한 수치해석결과와, 산업계에서 적용하는 설계기법에 의한 결과를 비교하였다. Because of the instability of a flow pattern in the inlet transition square duct (hereinafter referred to as “transition duct”) of a heat recovery steam generator (hereinafter referred to as “HRSG”) in a combined cycle power plant, the Reynolds number in the first row of a tube bank is differs sharply from that in the sectional area of the transition duct. This causes differences in the heat flux in each tube in the tube bank. The computational fluid dynamics (CFD) predictions provide three-dimensional results for velocity, temperature, and other flow parameters over the entire domain of the duct and HRSG. A renormalization group theory (RNG) based k-? turbulent model is used for obtaining the results cited in this study. A porous media option is used for modeling the tube banks and the number of transfer units method is used for determining the heat transfer characteristics. This study describes a comparison between the numerical simulation results and actual design output.
유근종(Geun Jong Yoo),최훈기(Hoon Ki Choi),최기림(Kee Lim Choi),신병주(Byeong Ju Shin) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.7
Configuration of the inlet transition square duct (hereinafter referred to as "transition duct") for heat recovery steam generator (hereinafter referred to as "HRSG") in combined cycle power plant is limited by the construction type of HRSG and plant site condition. The main purpose of the present study is to analyze the effect of a variation in turbulent flow pattern by roof slop angle change of transition duct for horizontal HRSG, which is influencing heat flux in heat transfer structure to the finned tube bank. In this study, a computational fluid dynamics(CFD) is applied to predict turbulent flow pattern and comparisons are made to 1/12th scale cold model test data for verification. Re-normalization group theory (RNG) based k-ε turbulent model, which improves the accuracy for rapidly strained flow and swirling flow in comparison with standard k-ε model, is used for the results cited in this study. To reduce the amount of computer resources required for modeling the finned tube bank, a porous media model is used.
루프 환기구에 따른 보일러빌딩 내부 환기성능에 관한 수치적 연구
최훈기 ( Hoon Ki Choi ),유근종 ( Geun Jong Yoo ),이상헌 ( Sang Heon Lee ) 한국산업보건학회 (구 한국산업위생학회) 2016 한국산업보건학회지 Vol.26 No.3
Objectives: The objective of this paper is to find flow and heat transfer characteristics numerically in boiler buildings for three different ventilation window configurations. Methods: Turbulent natural convection flow in boiler buildings with a constant heating wall temperature was analyzed numerically . Governing equations were solved with standard finite-volume method using the SIMPLE algorithm. Conclusions: Flow and heat transfer characteristics are found for three different ventilation types. In the lower area under furnace, velocity and temperature distributions show similar patterns among the three different ventilation types. In the upper area over furnace, however, air flow is well mixed with lower peak temperatures for types B and C, which have roof ventilation windows, compared to type A which has side wall louvers only. Also, type B, with a single large roof window, shows better ventilation effect than does type C with its distribution roof windows.
최훈기(Hoon Ki Choi),유근종(Geun Jong Yoo) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.3
In this paper, hydraulic & thermal developing and fully developed laminar forced convection flow of a water-Al₂O₃ nanofluid in a circular horizontal tube with uniform heat flux at the wall, are investigated numerically. A single phase model employed with temperature independent properties. The thermal entrance length is presented in this paper. The variations of the convective heat transfer coefficient and shear stress are shown in the entrance region and fully developed region along different nanoparticles concentration and Reynolds numbers. Convective heat transfer coefficient for nanofluids is larger than that of the base fluid. It is shown that heat transfer is enhanced and shear stress is increased as the particle volume concentration increases. The heat transfer improves, as Reynolds number increases.
김철환 ( Chul Hwan Kim ),유근종 ( Geun Jong Yoo ),최훈기 ( Hoon Ki Choi ) 한국산업위생학회 2005 한국산업보건학회지 Vol.15 No.3
Ventilation effect is analyzed for boiler building with multiple heat sources. Air flow inside the boiler building is characterized as turbulent mixed convection. Analysis methodology is set up with two different k-ε type models (standard k-ε, RNG k-ε). Two different cases with high and low outside temperature are analyzed. In case of high outside temperature condition, mixed convection is well realized inside the boiler building. With different upper louver opening rate, air flow is also well established and proper opening rate is found to meet design limit in case of low outside temperature condition. Difference of analysis results for two different turbulence models are not significant. Therefore, analysis methodology with simple k-ε turbulence model is found to be reliable for the boiler building ventilation analysis. However, more simplified geometrical model is desired to expand its application.
환기현상의 수치적 해석을 위한 난류모델의 영향에 관한 연구
김철환(Chul Hwan Kim),유근종(Geun Jong Yoo),최훈기(Hoon Ki Choi),공영경(Yeong Kyung Kong),최유송(Yu Song Choi) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Ventilation is required to keep proper working condition inside building enclosure. Ventilation effect can be evaluated through numerical analysis before its implementation. Usual method of ventilation is mixed convection. Numerical analysis is performed with 3 different turbulence models of k-ε model, RNG k-ε model and Reynolds stress model. Also, 3 different wall functions are utilized in the analysis. Comparison of prediction results and experimental data show general agreement each other. The prediction performance with different turbulence models are shown similar each other.
배이석(Yee Seok Bae),유근종(Geun Jong Yoo),최훈기(Hoon Ki Choi) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
In engine room, a good enclosure system is necessary for reducing noise but installing enclosure system in engine room cause a bad influence upon the cooling performance because of poor ventilation. The cooling efficiency of enclosure system can be improved by changing speed of fan and flow path for ventilation of engine room. In this study, numerical analysis is performed to assess cooling effect of enclosure system using finite volume method. The RNG k-ε model is adopted for turbulence model along with heat exchanger model and porous media model for heat exchanger analysis and moving reference frame model for rotational fan. Cold flow analysis result proves reasonable agreement with experimental data. Analysis results show direct effect of velocity and temperature distribution on cooling ability of enclosure system. Compare with the engine room which has no enclosure system, the case with total enclosure system which has box hole flow path and 1570rpm of fan speed shows the proper cooling capacity.