Study on High-Cycle Thermal Fatigue Evaluation for Thermal Striping in Mixing Tees with Hot and Cold Water (3) : Design Chart (4); Frequency Characteristics of Temperature Fluctuation by Rain Flow Method

2002 ◽  
Vol 2002 (0) ◽  
pp. 483-484
Author(s):  
Koichi TANIMOTO ◽  
Kenji OGURA ◽  
Kouji SHIINA ◽  
Toshihiko FUKUDA ◽  
Yasuhiko MINAMI ◽  
...  
Keyword(s):  
Thermal Fatigue ◽  
Temperature Fluctuation ◽  
Cold Water ◽  
Frequency Characteristics ◽  
Flow Method ◽  
Design Chart ◽  
Fatigue Evaluation ◽  
Thermal Striping ◽  
High Cycle Thermal Fatigue

Development of High Cycle Thermal Fatigue Evaluation Method Based on Time Interval of Peak-to-Peak of Fluid Temperature

2010 ◽  
Author(s):  
Nobuyuki Kimura ◽  
Jun Kobayashi ◽  
Hideki Kamide
Keyword(s):  
Thermal Stress ◽  
Thermal Fatigue ◽  
Temperature Fluctuation ◽  
Evaluation Method ◽  
Frequency Characteristics ◽  
Time Interval ◽  
Fluid Temperature ◽  
Cycle Number ◽  
The Core ◽  
High Cycle Thermal Fatigue

Hot and cold fluids are mixed at the core outlet of sodium cooled fast reactors. The temperature fluctuation causes high cycle thermal fatigue in structural components. The temperature fluctuation at the core outlet region does not have always a sinusoidal waveform but a sharp edged waveform. The temperature shows intermittent and sudden decrease and recovery like a spike form. It is necessary to take into account the spiky waveform of temperature fluctuation for the construction of an evaluation method of the high cycle thermal fatigue. The conventional method uses the amplitude and cycle number of waves without reference to the frequency of temperature fluctuation. In this study, the time interval of each wave based on the rainflow method was applied to consider frequency characteristics against the conversion from fluid temperature to thermal stress in structure. The thermal stress obtained from the new method was compared to the results of FEM analysis. It was found that the consideration of frequency characteristics of waves could evaluate the fatigue damage in structure. Furthermore, the frequency characteristics of waves in this method were expressed as the unified curve independent of the velocity. Hereby the new evaluation method could evaluate the thermal fatigue in the reactor.

Analysis of Turbulence Induced Thermal Mixing Effects on T-Junction Fluid-Structure Degradation

2015 ◽  
Author(s):  
Mohammed Hasan ◽  
Debashis Basu ◽  
Kaushik Das
Keyword(s):  
Thermal Fatigue ◽  
Power Plants ◽  
Cold Water ◽  
Thermal Structure ◽  
Degradation Mechanism ◽  
Cooling Water ◽  
Computational Method ◽  
Primary Coolant ◽  
Structure Degradation ◽  
Thermal Striping

Thermal striping generally is recognized as a significant long-term degradation mechanism in the primary cooling water circuit of nuclear power plants (NPPs). This phenomenon occurs by mixing of hot and cold water streams in the primary coolant loop. Depending on the flow configuration, the turbulent mixing process can lead to thermal striping, temperature fluctuations in the T-junction region, thermal fatigue, and crack generation in the associated structure. The objective of this study is to provide an in-depth look into the underlying physics for thermal fatigue to determine appropriate screening criteria and risk significance for the regulatory safety evaluation process. In addition, the structure of turbulence in the T-junction also is investigated. The computational method comprised of Large Eddy Simulation (LES) modeling to simulate turbulence and Proper Orthogonal Decomposition (POD) analysis to capture the coherent structures and turbulence scales. In addition, Conjugate Heat Transfer (CHT) analyses have been performed to predict the thermal field and temperature distribution in the solid piping material of the T-junction. Finally, the corresponding thermal stress in the solid pipe is estimated based on a simplified one-dimensional model to assess the thermal-structure degradation.

Thermal Fatigue Evaluation Method of Pipes by Equivalent Stress Amplitude

2012 ◽  
Author(s):  
Takafumi Suzuki ◽  
Naoto Kasahara
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Evaluation Method ◽  
Stress Amplitude ◽  
Equivalent Stress ◽  
Safety Margin ◽  
Evaluation Procedure ◽  
Fatigue Evaluation ◽  
High Cycle Thermal Fatigue ◽  
Equivalent Stress Amplitude

In recent years, reports have increased which are about failure cases caused by high cycle thermal fatigue both at light water reactors and fast breeder reactors. One of the biggest reasons of the cases is a turbulent mixing at a Tee-junction, where hot and cold temperature fluids are mixed, in a coolant system. In order to prevent thermal fatigue failures at Tee-junctions, The Japan Society of Mechanical Engineers (JSME) published the guideline S017-2003 (or JSME guideline) which is an evaluation method of high cycle thermal fatigue damage at a nuclear piping. It has some limitations in terms of its inconstant safety margin and its complexity in evaluation procedure, however. In order to solve these limitations, this paper proposes a new evaluation method of thermal fatigue damage with use of the “equivalent stress amplitude” which represents random temperature fluctuation effects on thermal fatigue damage. Because this new method makes methodology of evaluation clear and concise, it will contribute to improving the guideline for thermal fatigue evaluation.

Classification of Flow Patterns in Angled T-Junctions for the Evaluation of High Cycle Thermal Fatigue

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Shaoxiang Qian ◽  
James Frith ◽  
Naoto Kasahara
Keyword(s):  
Flow Pattern ◽  
Thermal Fatigue ◽  
Velocity Ratio ◽  
Branch Pipe ◽  
General Characteristic ◽  
Flow Patterns ◽  
Characteristic Equations ◽  
Piping Systems ◽  
Fatigue Evaluation ◽  
High Cycle Thermal Fatigue

Temperature fluctuations caused by the mixing of hot and cold streams at tee junctions may lead to high cycle thermal fatigue (HCTF) failure. It is necessary to evaluate the integrity of structures where the HCTF may occur. Therefore, the Japan Society of Mechanical Engineers (JSME) published “Guideline for Evaluation of High Cycle Thermal Fatigue of a Pipe (JSME S017),” in 2003, which provides the procedures and methods for evaluating the integrity of structures with the potential for HCTF. In JSME S017, one of the important procedures of thermal fatigue evaluation is to classify the flow patterns at tee junctions, because the degree of thermal fatigue damage is closely related to the flow pattern downstream of the mixing junction. The conventional characteristic equations for classifying flow patterns are only applicable to 90-deg tee junctions (T-junctions). However, angled tee junctions other than 90 deg (Y-junctions) are also used in chemical plants and refineries for reducing the pressure drop in the mixing zone and for weakening the force of the impingement of the branch pipe stream against the main pipe. The aim of this paper is to develop general characteristic equations applicable to both T- and Y-junctions. In this paper, general characteristic equations have been proposed based on the momentum ratio for all angles of tee junctions. Further, the validity of the proposed characteristic equations and their applicability to all angles of tee junctions have been confirmed using computational fluid dynamics (CFD) simulations. The results have also highlighted that the angle of the branch pipe has a significant effect on increasing the velocity ratio range for less damaging deflecting jet flow pattern, which is an important finding that could be used to extend the current design options for piping systems where HCTF may be a concern. In addition, categorization 3 is recommended as a more proper method for classifying flow patterns at tee junctions when evaluating the potential for thermal fatigue.

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