소형 공정열교환기 시제품의 고온구조해석

송기남,이형연,홍성덕,박홍윤,Song, Kee-nam,Lee, H-Y,Hong, S-D,Park, H-Y 한국압력기기공학회 2010 한국압력기기공학회 논문집 Vol.6 No.1

PHE(Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR(Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. Korea Atomic Energy Research Institute established the gas loop for the performance test of components, which are used in the VHTR, and they manufactured a PHE prototype to be tested in the loop. In this study, as part of the high-temperature structural-integrity evaluation of the PHE prototype, which is scheduled to be tested in the gas loop, we carried out high-temperature structural-analysis modeling, thermal analysis, and thermal expansion analysis of the PHE prototype. The results obtained in this study will be used to design the performance test setup for the PHE prototype.

소형 공정열교환기 시제품에 대한 탄소성 고온구조해석

송기남,이형연,홍성덕,박홍윤,Song, Kee-nam,Lee, H-Y,Hong, S-D,Park, H-Y 한국압력기기공학회 2011 한국압력기기공학회 논문집 Vol.7 No.2

PHE(Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR(Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. Korea Atomic Energy Research Institute established a small-scale gas loop for the performance test of components, which are used in the VHTR, and they manufactured a PHE prototype made of Hastelloy-X to be tested in the small-scale gas loop. Results from the elastic structural analysis on the PHE prototype were reported in the previous article. In order to investigate the macroscopic structural characteristics and behavior of the PHE prototype under the test condition of the small-scale gas loop far more in detail, elastic-plastic high-temperature structural-analysis of the PHE prototype was carried out in this study.

이종재료로 구성된 영역의 응력장 해석 개선방안 연구

송기남,Song, Kee-Nam 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.11

Displacement fields and interface stresses are obtained by modifying the potential energy functional with a penalty function which enforces the continuity of stresses at the interface of two-materials. Based on the displacement field and the interface stresses, a new methodology to generate a continuous stress field over the entire domain including the interface of the dissimilar materials has been proposed by combining the L$^{2}$ projection method of stress-smoothing and the Loubignac's iterative method of improving the displacement field. Stress analysis was carried out on two examples which are made of highly dissimilar materials. As a result of the analysis, it is found that the proposed method provides improved continuity of the stress field over the entire domain as well as predicting accurate nodal stresses at the interface. In contrast, the conventional displacement-based finite element method provides significant stress discontinuties at the interfaces. In addition, it was found that the total strain energy evaluated from the improved continuous stress field converge to the exact value as increasing the number of iterations in the proposed method.

변위형 유한요소 해에서 국부응력장 향상에 대한 연구

송기남,Song, Kee-Nam 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.2

An efficient and useful method to improve the local stress field in a displacement-formulated finite element solution has been proposed using the theory of conjugate approximations for a stress field and the Loubignac's iterative method for a displacement field. Validity of the proposed method has been tested through three test examples, to improve the stress field and displacement field in the whole domain and the local regions. As a result of analysis on the test examples, it is found that the stress field in the local regions are approximated to those in the whole domain within a few iterations which have satisfied the original finite element equilibrium equation. In addition, it is found that the local stress field are by far better approximated to the exact stress field than the displacement-based stress field with the reduction of the finite-element mesh-size.

판형 홀다운스프링 집합체의 탄성강성도 민감도 평가

송기남,Song, Kee-Nam 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.8

The previous elastic stiffness formulas of leaf type holddown spring assemblies(HDSs) have been corrected and extended to be able to consider the point of taper runout for the TT-HDS and all the strain energies for both the TT-HDS and the TW-HDS based on Euler beam theory and Castigliano'stheorem. The elastic stiffness sensitivity of the leaf type holddown spring assemblies was analyzed using the derived elastic stiffness formulas and their gradient vectors obtained from the mid-point formula. As a result of the sensitivity analysis, the elastic stiffness sensitivity at each design variable is quantified and design variables having remarkable sensitivity are identified. Among the design variables, leaf thickness is identified as that of having the most remarkable sensitivity of the elastic stiffness. In addition, it was found that the sensitivity of the leaf type HDS's elastic stiffness is exponentially correlated to the leaf thickness.

너비감소 판형 홀다운스프링 집합체의 탄성강성도 평가

송기남,Song, Kee-Nam 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.1

A formula for estimating the elastic stiffness of TW-HDS with a uniformly tapered width from w$_{0}$ to w$_{1}$ over the length, has been analytically derived based on Euler beam theory and Castigliano's theorem. Elastic stiffnesses of the TW-HDSs designed in the same dimensional design spaces as the KOFA HDSs have been estimated from the derived formula, in addition, a sensitivity study on the elastic stiffness of the TW-HDSs has been carried out. Analysis results show that elastic stiffnesses of the TW-HDSs have been by far higher than those of the KOFA HDSs, and that, as the effects of axial and shear force on the elastic stiffness have been 0.15-0.21%, most of the elastic stiffness is attributed to the bending moment. As a result of sensitivity analysis, the elastic stiffness sensitivity at each design variable is quantified and design variables having remarkable sensitivity are identified. Among the design variables, leaf thickness is identified as that of having the most remarkable sensitivity of the elastic stiffness.

공액근사개념과 Loubignac의 반복계산법을 이용한 국부응력장 개선에 대한 연구

송기남,Song, Kee-Nam 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.10

Based on the application of te theory of conjugate approximations and the Loubignac's iterative method in a local region, a method to improve the stress filed in a displacement-formulated finite element solution has been proposed. The validity of the proposed method has been tested through two examples : a thick cylinder under internal pressure loading and an infinite plate with a central circular hole subjected to uniaxial tension. As a result of analysis of the examples, it was found that the stress field obtained for the local region model by the proposed method approximates well for the whole domain model. In addition, it was found that because of a significant decrease in the computing time to obtain the improved stress field, the proposed method is efficient and useful for the detailed stress analysis in local regions.

경수로 핵연료 지지격자체 구조설계에 대한 소고

송기남,Song, Kee-nam 한국압력기기공학회 2011 한국압력기기공학회 논문집 Vol.7 No.3

A spacer grid, which supports nuclear fuel rods laterally and vertically with a friction grip, is one of the most important structural components in a PWR fuel. The form of grid strap and supporting parts such as grid spring and dimple is known to be closely related with the mechanical/structural performance of spacer grid and nuclear fuel assembly. In this study, reviewing various research results for enhancing the performance of the spacer grid, some structural design considerations and research directions on the spacer grid assembly are suggested for further study.

소형가스루프 시험조건에서 중형 공정열교환기 시제품의 고온구조해석

송기남,홍성덕,박홍윤,Song, Kee-nam,Hong, S-D,Park, H-Y 한국압력기기공학회 2012 한국압력기기공학회 논문집 Vol.8 No.1

A PHE (Process Heat Exchanger) in a nuclear hydrogen system is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR (Very High Temperature Reactor) to a chemical reaction that yields a large quantity of hydrogen. Korea Atomic Energy Research Institute has established a small-scale gas loop for the performance test on VHTR components and recently has manufactured a medium-scale PHE prototype made of Hastelloy-X. A performance test on the PHE prototype is scheduled in the gas loop. In this study, high-temperature structural analysis modeling, and macroscopic thermal and structural analysis of the medium-scale PHE prototype by imposing the established displacement boundary constraints in the previous research were carried out under the gas loop test condition. The results obtained in this study will be compared with performance test results.

소형가스루프 시험조건에서 소형 공정열교환기 시제품의 고온구조해석

송기남,홍성덕,박홍윤,Song, Kee-nam,Hong, S-D,Park, H-Y 한국압력기기공학회 2012 한국압력기기공학회 논문집 Vol.8 No.1

A PHE (Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR (Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. A small-scale PHE prototype made of Hastelloy-X is being tested in a small-scale gas loop at Korea Atomic Energy Research Institute. In order to properly evaluate the high-temperature structural integrity of the small-scale PHE prototype, it is very important to impose a proper constraint condition on its structural analysis model. For this effort, we tried to impose several constraint conditions on the structural analysis model and consequently fixed a proper and effective displacement constraints.