• Journal of Mechanical Science and Technology
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• 제20권1호
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• pp.158-166
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• 2006

Extended Graetz problem in microtube is analyzed by using eigenfunction expansion to solve the energy equation. For the eigenvalue problem we applied the shooting method and Galerkin method. The hydrodynamically isothermal developed flow is assumed to enter the microtube with uniform temperature or uniform heat flux boundary condition. The effects of velocity and temperature jump boundary condition on the microtube wall, axial conduction and viscous dissipation are included. From the temperature field obtained, the local Nusselt number distributions on the tube wall are obtained as the dimensionless parameters (Peclet number, Knudsen number, Brinkman number) vary. The fully developed Nusselt number for each boundary condition is obtained also in terms of these parameters.

• 대한기계학회논문집
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• 제13권5호
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• pp.952-961
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• 1989

본 연구에서는 널리 사용되는 핀-관 직교류 열교환기의 정상 상태를 예측 하기 위하여 냉매의 상변화에 따른 유체의 물성치, 열전달계수 및 마찰계수의 변화와 관벽에서의 축방향 열전도를 고려한 모형을 세우고 이를 분석하여 열교환기의 종합적 인 특성을 규명하고자 한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.192.1-192
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• 2001

• Journal of Welding and Joining
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• 제17권5호
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• pp.77-82
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• 1999

Resistance spot welding process is completed in very short time and there are many factors affecting on the generation of heat. It is difficult to control these experimental factors and monitor distribution of the temperature and stresses in the experimental analysis case. and too much time and expense are required for the experimental trials to fine proper welding condition. So numerical analyses have been attempted steadily, but most numerical analyses on the resistance spot welding are mainly focused on thermal behavior. Therefore, in this paper, the numerical analysis of mechanical behavior as well as heat conduction is carried out for the spot welding process. For this numerical analysis, axial symmetric computer program for the spot welding analysis by F.E.M. has been developed considering heat conduction and thermal elastic-plastic theory. Material properties depending on temperature such as density, heat conductivity, heat expansion coefficient, specific heat, yield stress, elastic modulus, and specific resistance are considered. Using the results of temperature distribution obtained from heat conduction analysis, the thermal elastic-plastic analysis is carried out to clarify mechanical behavior of spot welded specimen. In order to evaluate the effect of residual stresses, numerical analyses are carried out under tension-shear load in two cases respectively; one with residual stress, the other without residual stresses.

• Journal of Welding and Joining
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• 제21권6호
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• pp.40-45
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• 2003

Steel members have advantages of resisting torsion and axial compression. In design, residual stresses at the welded joint of T-shape steel pipes are one of the most important points to be considered. In this paper, characteristics of residual stresses of welded joints are clarified by carrying out 3D non-steady heat conduction analysis and 3D thermal elastic-plastic FE-analysis. According to the results, the production mechanism of residual stresses at the welded joint of T-shape steel pipe is clarified. In this paper, circumferential stresses depended on thermal histories but axial and radial stresses were more dependent on geometrical shape than thermal histories. Residual stresses in the axial direction on the lower part of pipe member were tensile, controlled by geometrical shape. However, in case of middle part, residual stresses in all the directions were controlled by thermal histories.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.221-227
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• 2009

The study of the solidification process of welded metal is carried out using the finite element method, which is the basic study for optimal design. In the analysis of temperature, the welded zone is cooled as the result of heat conduction to the base metal and heat transfer to the circumference. In the early phase of the temperature in base metal zone is little changed. But after the rise in temperature the whole area is cooled gradually and uniformly with the lapse of 10 seconds, and a temperature change is hardly occurred in the radial direction but in the axial direction.

• Nuclear Engineering and Technology
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• 제29권5호
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• pp.406-416
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• 1997

A computational method is developed for predicting the steady-state temperature field in an LMR core. Detailed core-wide coolant temperature profiles are efficiently calculated using the simplified energy equation mixing model[1] and the subchannel analysis method. The $\theta$-method is employed for discretizing the energy equations in the axial direction. The interassembly coupling is achieved by interassembly gap flow. Cladding and fuel temperatures are calculated with the one-dimensional conduction model and temperature integrals of conductivities. The accuracy of the method is tested by performing several benchmark calculations for too LMR problems. The results indicate that the accuracy is comparable to the other methods based on ENERGY model. It is also shown that the implicit scheme for the axial discretization is more efficient than the explicit scheme.

• 한국진공학회지
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• 제17권5호
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• pp.400-407
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• 2008

본 연구에서는 축전 결합형 플라즈마원에 대한 전자기장의 2차원 공간 의존성을 계산하였다. 1차원 유체 방정식을 기반으로 축전 전기장과 전도 전류 밀도의 axial 방향 공간 의존성을 계산한 후, radial 방향으로는 맥스웰 방정식의 해를 ${\omega}r/c$에 대한 power series로 전개하여 전자기장의 2차원 공간 의존성을 계산하였다.

• 태양에너지
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• 제6권1호
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• pp.60-69
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• 1986

Two-dimensional finite difference numerical analysis is used to study conjugate natural convection heat transfer from a horizontal conducting tube with one vertical axial fin. By increasing dimensionless fin length ($L_F$), the mean total Nusselt number of the upward fin is slightly less than that of the downward fin at $L_F\;{\le}\;0.18$ and is higher than that of the downward fin at $L_F\;>\;0.18$. However comparing the upward fin and the downward fin with the no fin, the mean total Nusselt numbers of downward fin and upward fin at $L_F=0.30$ are increased approximately 4.01% and 5.51%, respectively. As Rayleigh number, Prandtl number and Biot number increase, the mean total and the mean tube Nusselt numbers are increased, but as wall thickness increases, the mean total and the mean tube Nusselt numbers are decreased. As the fin conduction parameter increases, the mean total Nusselt number is slightly increased because of increasing the mean fin Nusselt number.

• Tribology and Lubricants
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• 제11권5호
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• pp.150-155
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• 1995

In order to analyze the thermal effects of the rotor models, the finite element technique was used in this study. The length of the hat was investigated as a design parameter. At the start of each brake application the disk surface temperature rapidly increases to a maximum value and then decays due to external cooling and thermal conduction to the hat. The calculated results indicate that the long length of the hat shows the minimum deformation in axial direction, which is related to the thermal problems, coned wear, vibration and noise.