Numerical Simulation of Thermal Striping Phenomena in T-Junction Piping System Using Large Eddy Simulation

2008 ◽  
Author(s):  
Masa-Aki Tanaka ◽  
Hiroyuki Ohshima ◽  
Hideaki Monji
Keyword(s):  
Numerical Simulation ◽  
Heat Conduction ◽  
Three Dimensional ◽  
Piping System ◽  
Fluid Temperature ◽  
Numerical Schemes ◽  
Simulation Code ◽  
Simple Method ◽  
Thermal Striping ◽  
Les Model

In Japan Atomic Energy Agency (JAEA), simulation code “MUGTHES (MUlti Geometry simulation code for THErmal-hydraulic and Structure heat conduction analysis in boundary fitted coordinate)” has been developed to evaluate thermal striping phenomena that are caused by turbulence mixing of fluids in different temperature. MUGTHES employs Boundary Fitted Coordinate (BFC) system to treat complex geometries in power plants. And MUGTHES can deal with three-dimensional transient thermal-hydraulic problem coupled with three-dimensional transient heat conduction in the surrounding structure in consideration of conjugated heat transfer. In this paper, numerical schemes for thermal-hydraulic simulation employed in MUGTHES are described including LES model. A simple method to limit numerical oscillation is adopted in energy equation solving process. A new iterative method to solve Poisson equation in BFC system is developed for effective transient calculations. This method is based on BiCGSTAB method and SOR technique. As the code validation of MUGTHES, a numerical simulation in a T-junction piping system with LES approach was conducted. Numerical results related to velocity and fluid temperature distributions were compared with an existing water experimental data and the applicability of numerical schemes with LES model in MUGTHES to the thermal striping phenomenon was confirmed.

Numerical Investigation on Thermal Striping Phenomena in a T-Junction Piping System

2014 ◽  
Author(s):  
Masaaki Tanaka ◽  
Yasuhiro Miyake
Keyword(s):  
Numerical Simulation ◽  
Thermal Fatigue ◽  
Large Scale ◽  
Structural Integrity ◽  
Piping System ◽  
Simulation Code ◽  
Fine Mesh ◽  
Large Eddy ◽  
Thermal Striping ◽  
High Cycle Thermal Fatigue

Thermal striping phenomena caused by mixing of fluids at different temperature is one of the most important issues in design of Fast Breeder Reactors (FBRs), because it may cause high-cycle thermal fatigue in structure and affect the structural integrity. A numerical simulation code MUGTHES has been developed to investigate thermal striping phenomena and to estimate high cycle thermal fatigue in FBRs. In this study, numerical simulation for the WATLON experiment which was the water experiment of a T-junction piping system (T-pipe) conducted in JAEA was carried out to validate the MUGTHES and to investigate the relation between the mechanism of temperature fluctuation generation and the unsteady motion of large eddy structures. In the numerical simulation, the large eddy simulation (LES) approach with standard Smagorinsky model was employed as eddy viscosity model to simulate large-scale eddy motion in the T-pipe. The mesh as the same with the previous study as reference, the finer mesh and the coarser mesh arrangements were employed to estimate the Grid Convergence Index (GCI) for uncertainty quantification in the validation process. The modified method of the GCI estimation based on the least squire version could successfully quantify uncertainty. Through the numerical simulations, it was indicated that the fine mesh arrangement could improve the temperature distribution in the wake. It could be found that the thermal mixing phenomena in the T-pipe were caused by the mutual interaction of the necklace-shaped vortex around the wake from in the front of the branch jet, the horseshoe-shaped vortex and the Karman’s vortex motions in the wake.

Numerical Investigations of Arched Vortex Characteristics Generated at T-Junction Piping Systems

2004 ◽  
Author(s):  
Toshiharu Muramatsu
Keyword(s):  
Stokes Equations ◽  
Velocity Ratio ◽  
Navier Stokes ◽  
Fluid Temperature ◽  
Simulation Code ◽  
Navier Stokes Equations ◽  
Downstream Region ◽  
Piping Systems ◽  
Frequency Components ◽  
Thermal Striping

Thermohydraulic analyses for a fundamental water experiment simulating thermal striping phenomena at T-junction piping systems were carried out using a quasi-direct numerical simulation code DINUS-3, which is represented by instantaneous Navier-Stokes equations and deals with a modified third-order upwind scheme for convection terms. Calculated results were compared with experimental results on the flow patterns in the downstream region of the systems, the arched vortex structures under a deflecting jet condition, the generation frequency of the arched vortex, etc. in the various conditions; i.e., diameter ratio α, flow velocity ratio β and Reynolds number Re. From the comparisons, it was confirmed that (1) the DINUS-3 code is applicable to the flow pattern classifications in the downstream region of the T-junction piping systems, (2) the arched vortex characteristics with lower frequency components and their generation possibilities can be estimated numerically by the DINUS-3 code, and (3) special attentions should be paid to the arched vortex generations with lower frequency components of fluid temperature fluctuations in the design of T-junction systems from the viewpoints of the avoidances for the thermal striping.

Fatigue Damage Evaluation for Thermal Striping Phenomena Using Analytical Spectrum Method

2005 ◽  
Author(s):  
Satoshi Okajima ◽  
Shinsuke Sakai ◽  
Satoshi Izumi ◽  
Atsushi Iwasaki ◽  
Naoto Kasahara
Keyword(s):  
Fatigue Damage ◽  
Analytical Methods ◽  
Safety Margin ◽  
Closed Form Solution ◽  
Design Stage ◽  
Piping System ◽  
Damage Evaluation ◽  
Random Loading ◽  
Simple Method ◽  
Thermal Striping

It is well known that fatigue damage accumulates around T-junctions of piping system where two kinds of fluid with different temperatures are mixed. This phenomenon is called thermal striping, and simple method for evaluating the fatigue damage derived from this phenomenon is greatly important for both design and maintenance stages. However, the evaluation of the thermal stress derived from the thermal striping is rather difficult since the evaluation requires complicated analyses such as fluid mixing, heat transfer, and heat conduction. In addition, the closed-form solution to describe the stress-range distribution under random loading has not been established yet since the rainflow cycle-counting method is not suitable to the analytical treatment. Though numerical calculation may be available for the evaluation, it requires time-consuming work and is not practical for design stage. For this reason, an analytical method for evaluating the fatigue damage directly from stress power spectrum density (PSD) is desired. In this paper, the feasibility study to apply analytical methods to the evaluation of thermal-striping damage is examined. The analytical methods are applied to the fatigue damage evaluation from the stress PSD that was obtained by the thermal striping experiment. Finally, the applicability and problem of each method will be discussed. In order to apply the envelope PSD to design, the property of safety margin associated with the PSD is investigated too.

Development of Numerical Simulation Method for Melt Relocation Behavior in Nuclear Reactors: Validation of Applicability for Actual Core Support Structures

2016 ◽  
Author(s):  
Susumu Yamashita ◽  
Kazuyuki Tokushima ◽  
Masaki Kurata ◽  
Kazuyuki Takase ◽  
Hiroyuki Yoshida
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Computer Aided Design ◽  
Nuclear Power ◽  
Radiation Heat Transfer ◽  
Three Dimensional ◽  
Simulation Models ◽  
Simulation Method ◽  
Transfer Model ◽  
Simulation Code

In order to precisely investigate molten core relocation behavior in the Fukushima Daiichi nuclear power station, we have developed the detailed and phenomenological numerical simulation code named JUPITER for predicting the molten core behavior including solidification and relocation based on the three-dimensional multiphase thermal-hydraulic simulation models. At the moment, multicomponent analysis method which can be treated any number of component as a fluid or solid body, Zr-water reaction model and simple radiation heat transfer model were implemented and showed that multicomponent melt flow and its solidification were confirmed in the simplified core structure system. However, the validation of the JUPITER using high temperature molten material has not been performed yet. In this paper, in order to evaluate the validity of the JUPITER, especially, for high temperature melt relocation experiment, we compared between numerical and experimental results for that system. As a result, qualitatively reasonable result was obtained. And also we performed melt relocation simulation on actual core structures designed by three dimensional CAD (Computer-Aided Design) and then we estimated phenomena which might be actually occurred in SAs.

Numerical Simulation of a Dielectric Material Exposed to Short Pulsed Laser Radiation

2001 ◽  
Author(s):  
Richard A. Whalen ◽  
Gregory J. Kowalski
Keyword(s):  
Numerical Simulation ◽  
Heat Conduction ◽  
Time Scales ◽  
Thermal Transport ◽  
Dielectric Material ◽  
Index Of Refraction ◽  
Hyperbolic Heat Conduction ◽  
Focal Volume ◽  
Simulation Code ◽  
Radial Temperature

Abstract A numerical simulation code is developed to study laser beam propagation and the significance of self-focussing or defocusing effects on a manufacturing process. The solution method includes the thermally stimulated nonlinear optical effects caused by the temperature and intensity dependent index of refraction. The results demonstrate that radial temperature gradient magnitudes of 0.06 to 0.6°C produce significant changes in the focal volume of the beam. The magnitudes of the temperature changes are directly related to differences in the absorption coefficient. The thermal transport of the absorbed radiation is modeled using Fourier heat conduction for long time scales and Hyperbolic heat conduction for short time scales. The focal volume of the beam is significantly altered by the differences between these thermal transport mechanisms. These results were determined using a simulation of a Z-scan measurement technique.

Constructal Placement of High-Conductivity Inserts in a Slab: Optimal Design of “Roughness”

2001 ◽  
Vol 123 (6) ◽  
pp. 1184-1189 ◽  
Author(s):  
M. Neagu and ◽  
A. Bejan
Keyword(s):  
Numerical Simulation ◽  
Heat Conduction ◽  
Optimal Design ◽  
Contact Resistance ◽  
Rough Surface ◽  
Fundamental Problem ◽  
Three Dimensional ◽  
High Conductivity ◽  
Constant Thickness ◽  
Two Dimensional

This paper addresses the fundamental problem of how to facilitate the flow of heat across a conducting slab heated from one side. Available for distribution through the system is a small amount of high-conductivity material. The constructal method consists of optimizing geometrically the distribution of the high-conductivity material through the material of lower conductivity. Two-dimensional distributions (plate inserts) and three-dimensional distributions (pin inserts) are optimized based on the numerical simulation of heat conduction in a large number of possible configurations. Results are presented for the external and internal features of the optimized architectures: spacings between inserts, penetration distances, tapered inserts and constant-thickness inserts. The use of optimized pin inserts leads consistently to lower global thermal resistances than the use of plate inserts. The side of the slab that is connected to the high-conductivity intrusions is in effect a “rough” surface. This paper shows that the architecture of a rough surface can be optimized for minimum global contact resistance. Roughness can be designed.

Development of Thermal-Hydraulic Code Coupled With Heat Conduction in Structure for Thermal Striping Phenomena: Development of Calculation Module for Temperature Distribution in Structure

2007 ◽  
Author(s):  
Masa-Aki Tanaka ◽  
Hiroyuki Ohshima
Keyword(s):  
Heat Conduction ◽  
Structural Damage ◽  
Evaluation Method ◽  
Transient Heat Conduction ◽  
Transfer Model ◽  
Piping System ◽  
Thermal Interaction ◽  
Breeder Reactors ◽  
Finite Volume Approach ◽  
Thermal Striping

Thermal striping is one of the most important issues in terms of safety of Fast Breeder Reactors (FBRs). Thermal striping occurs where high temperature fluid mixes with low temperature one and it might cause structural damage. An analysis program (“MUGTHES”) for fluid-structure thermal interaction has been developed to evaluate the thermal striping phenomena and to establish the evaluation method. MUGTHES consists of two calculation modules for thermal-hydraulic analysis and for heat conduction analysis in structure and a conjugated heat transfer model that connects both modules. Thus, thermal-hydraulic field and temperature field in structure can be calculated simultaneously. Boundary Fitted Coordinate (BFC) system is employed to treat complex geometries in FBR plants. Governing equations in BFC system are discretized using the finite-volume approach to keep these conservation conditions in computation. In this paper, detailed description of the evaluation method of spatial differential terms in the equations was described. Numerical simulations were performed using fundamental problems related to one dimensional transient heat conduction in a cube and to radial transient heat conduction in a cylinder, in order to verify the discretization method in BFC system and the calculation method for thermal interaction between two calculation regions. In addition, numerical simulation of T-junction piping system was carried out to investigate characteristics of temperature fluctuation and to confirm the applicability of the program to a practical problem.

Numerical Simulations of Thermal-Mixing in T-Junction Piping System Using Large Eddy Simulation Approach

2011 ◽  
Author(s):  
Masaaki Tanaka ◽  
Satoshi Murakami ◽  
Yasuhiro Miyake ◽  
Hiroyuki Ohshima
Keyword(s):  
Numerical Simulations ◽  
Large Scale ◽  
Branch Pipe ◽  
Three Dimensional ◽  
Piping System ◽  
Thermal Mixing ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Thermal Striping ◽  
High Cycle Thermal Fatigue

Thermal striping phenomenon caused by mixing of fluids at different temperatures is one of the most important issues in design of fast breeder reactors (FBRs), because it may cause high-cycle thermal fatigue in structure. Authors have been developed a numerical simulation code MUGTHES to investigate thermal striping phenomena in FBRs and to give transient data of temperature in the fluid and the structure for an evaluation method of the high-cycle thermal fatigue problem. MUGTHES employs the boundary fitted coordinate (BFC) system and deals with three-dimensional transient thermal-hydraulic problems by using the large eddy simulation (LES) approach and artificial wall conditions derived by a wall function law. In this paper, numerical simulations of MUGTHES in T-junction piping system appear. Boundary conditions for the simulations are chosen from an existing water experiment in JAEA, named as WATLON experiment. The wall jet condition in which the branch pipe jet flows away touching main pipe wall on the branch pipe side and the impinging jet condition in which the branch pipe jet impinges on the wall surface on the opposite side of the branch pipe are selected, because significant temperature fluctuation may be induced on the wall surfaces by the branch pipe jet behavior. Numerical results by MUGTHES are validated by comparisons with measured velocity and temperature profiles. Three dimensional large-scale eddies are identified behind of the branch pipe jet in the wall jet case and in front of the branch pipe jet in the impinging jet case, respectively. Through these numerical simulations in the T-pipe, generation mechanism of temperature fluctuation in thermal mixing process is revealed in the relation with the large-scale eddy motion.

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