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김찬중,Kim, Charn-Jung 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.5
In the cylindrical coordinate, the origin r = 0 plays a role of the singularity and thus much care is needed to treat near-origin region. This work presents a new numerical scheme which is derived from the exact solution under the one-dimensional assumption in the radial direction. It is shown that the near-origin region can be properly treated by the radial-exponential scheme, whereas the numerical results from the conventional exponential scheme deviate considerably from the exact solution. Over the region of small ($ {\delta}r_e/r_e$ the present radial-exponential scheme turns out to be almost the same as the exponential scheme.
김찬중(Charn-Jung Kim),이정희(Jung-Hee Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
A new modified model is presented for moving boundary problems occurring in the discretization<br/> process. The sum of a real mass flux and a pseudo mass flux has been considered as one term in the<br/> discretization process of the convection-diffusion flux. However, this paper deals with two mass fluxes<br/> separately to physically gain appropriate results. A one-dimensional numerical analysis on a moving<br/> boundary is performed to compare the present model with previous models. The boundary<br/> immobilization technique is employed with a coordinate transformation. The power-law scheme is<br/> adapted to discretize the governing equations. Present results are also compared with the analytic<br/> solutions in order to validate the present model. The differences between the results of previous models<br/> and the analytic solutions increase as moving time decrease or as moving distance increases. However,<br/> the results using the present model show a good agreement with the analytic solutions.
강정호(Jung Ho Kang),남진현(Jin Hyun Nam),김찬중(Charn-Jung Kim),송명호(Myung Ho Song) 한국전산유체공학회 2008 한국전산유체공학회 학술대회논문집 Vol.2008 No.-
The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.
고분자 연료전지의 다공성층 내에서의 액상수분 이동에 관한 공극-네트워크 해석 연구
강정호(Jung Ho Kang),이상건(Sang Gun Lee),남진현(Jin Hyun Nam),김찬중(Charn-Jung Kim) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
Water is continuously produced in polymer electrolyte membrane fuel cell (PEMFC), and is transported and exhausted through polymer electrolyte membrane (PEM), catalyst layer (CL), microporous layer (MPL), and gas diffusion layer (GDL). The low operation temperatures of PEMFC lead to the condensation of water, and the condensed water hinders the transport of reactants in porous layers (MPL and GDL). Thus, water flooding is currently one of hot issues that should be solved to achieve higher performance of PEMFC. This research aims to study liquid water transport in porous layers of PEMFC by using pore-network model, while the microscale pore structure and hydrophilic/hydrophobic surface properties of GDL and MPL were fully considered.
강정호(Jung Ho Kang),남진현(Jin Hyun Nam),김찬중(Charn-Jung Kim),송명호(Myung Ho Song) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.4
The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.
비엇갈림 격자계에서 CIP법을 이용한 캐비티내의 유동해석
이정희(Jung Hee Lee),강준(Joon Kang),임도균(Dokiun Im),김찬중(Charn Jung Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
In this study, we discuss CIP method, which can treat compressible/incompressible problem and<br/> multi-phase problem. We can apply this method to the general equations by using CCUP. In this<br/> paper, non-staggered grid arrangement and predictor-corrector method are used to enhance later<br/> development and the solution accuracy and convergence performance. To validate the numerical<br/> algorithm proposed in this paper, the two-dimensional unsteady flow in the driven cavity is simulated.<br/> The numerical results of this subject using the present algorithm are compared with other numerical<br/> results. As a result, it is prived that the present scheme gives stable and improved solutions, and the<br/> results even coarse grid are in good agreement with other result using a fine grid arrangement.
고에너지밀도용접 과정에서의 2차원 열유동에 대한 수치해석적 연구
박건중,장경천,김찬중,Park, Kun-Joong,Jang, Kyung-Chun,Kim, Charn-Jung 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.9
This work presents a two-dimensional quasi-steady state model to study the fluid flow and heat transfer in high-power density welding process of thin AISI-304 stainless steel plates. The enthalpy method and the finite volume method were used for a numerical analysis of the mushy region phase change as well as the heat flow at the weld pool and the heat-affected zone. The results show that the mushy region distributed around the weld pool becomes wider downstream and the surface heat losses by convection and radiation can be significant factors in welding process especially when a welding speed is relatively low.
목분 충진 고분자 용융체의 압출다이 내 유동 및 열전달에 관한 수치해석
고승환,박형규,송명호,김찬중,Ko, Seung-Hwan,Park, Hyung-Gyu,Song, Myung-Ho,Kim, Charn-Jung 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.2
A three-dimensional numerical analysis of the flow and heat transfer characteristic of wood-flour-filled polypropylene melt in an extrusion die was carried out. Used for this analysis were Finite Concept Method based on FVM, unstructured grid and non-Newtonian fluid viscosity model. Temperature and flow fields are closely coupled through temperature dependent viscosity and viscous dissipation. With large Peclet, Nahme, Brinkman numbers, viscous heating caused high temperature belt near die housing. Changing taper plate thickness and examining some predefined parameters at die exit investigated the effect of taper plate on velocity and temperature uniformities. In the presence of taper plate, uniformity at die exit could be improved and there existed an optimum thickness to maximize it.