Experimental investigations of flow distribution in coolant system of Helium-Cooled-Pebble-Bed Test Blanket Module

2016 ◽  
Vol 103 ◽  
pp. 53-68
Author(s):  
M. Ilić ◽  
G. Schlindwein ◽  
R. Meyder ◽  
T. Kuhn ◽  
O. Albrecht ◽  
...  
Keyword(s):  
Flow Distribution ◽  
Experimental Investigations ◽  
Pebble Bed ◽  
Coolant System

scholarly journals Research on Influence of Different Simulation Methods of Bypass Flow in Thermal Hydraulic Analysis on Temperature Distribution in HTR-10

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Shiyan Sun ◽  
Youjie Zhang ◽  
Yanhua Zheng
Keyword(s):  
Temperature Distribution ◽  
Reactor Core ◽  
Flow Distribution ◽  
Maximum Temperature ◽  
Flow Ratio ◽  
Hydraulic Analysis ◽  
Bypass Flow ◽  
Pebble Bed ◽  
The Core ◽  
Thermal Hydraulic Analysis

In pebble-bed high temperature gas-cooled reactor, gaps widely exist between graphite blocks and carbon bricks in the reactor core vessel. The bypass helium flowing through the gaps affects the flow distribution of the core and weakens the effective cooling of the core by helium, which in turn affects the temperature distribution and the safety features of the reactor. In this paper, the thermal hydraulic analysis models of HTR-10 with bypass flow channels simulated at different positions are designed based on the flow distribution scheme of the original core models and combined with the actual position of the core bypass flow. The results show that the bypass coolant flowing through the reflectors enhances the heat transfer of the nearby components efficiently. The temperature of the side reflectors and the carbon bricks is much lower with more side bypass coolant. The temperature distribution of the central region in the pebble bed is affected by the bypass flow positions slightly, while that of the peripheral area is affected significantly. The maximum temperature of the helium, the surface, and center of the fuel elements rises as the bypass flow ratio becomes larger, while the temperature difference between them almost keeps constant. When the flow ratio of each part keeps constant, the maximum temperature almost does not change with different bypass flow positions.

Unsteady Steam Turbine Optimization Using High Fidelity CFD

2020 ◽  
Author(s):  
Vahid Iranidokht ◽  
Ilias Papagiannis ◽  
Anestis Kalfas ◽  
Reza Abhari ◽  
Shigeki Senoo ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Computational Cost ◽  
Flow Distribution ◽  
Fast Response ◽  
Test Facility ◽  
Experimental Investigations ◽  
Experimental Setup ◽  
Efficiency Gain ◽  
Flow Angle ◽  
Computational Optimization

Abstract This paper presents the computational methodology, and experimental investigations accomplished to enhance the efficiency of a turbine stage by applying non-axisymmetric profiling on the rotor hub wall. The experimental setup was a two-stage axial turbine, which was tested at “LISA” test facility at ETH Zurich. The 1st stage was considered to create the flow history for the 2nd stage, which was the target of the optimization. The hub cavity of the 2nd stage was designed with large dimensions as a requirement of a steam turbine. The goal was to optimize the interaction of the cavity leakage flow with the rotor passage flow to reduce the losses and increase efficiency. The computational optimization was completed using a Genetic Algorithm coupled with an Artificial Neural Network on the 2nd stage of the test turbine. Unsteady time-accurate simulations were performed, using in-house developed “MULTI3” solver. Besides implementing all geometrical details (such as hub and tip cavities and fully 3D blade geometries) from the experimental setup into the computational model, it was learned that the unsteady upstream effect could not be neglected. A novel approach was introduced by using unsteady inlet boundary conditions to consider the multistage effect while reducing the computational cost to half. The importance of this implementation was tested by performing a steady simulation on the optimized geometry. The predicted efficiency gain from steady simulations was 4.5 times smaller (and negligible) compared to the unsteady approach. Excluding the cavity geometry was also assessed in a different simulation setup showing 3.9% over-prediction in the absolute efficiency value. Comprehensive steady and unsteady measurements were performed utilizing pneumatic, Fast Response Aerodynamic (FRAP), and Fast Response Entropy (FENT) probes, on the baseline and profiled test cases. The end-wall profiling was found to be successful in weakening the strength of the hub passage vortex by a 19% reduction in the under-over turning. As a result, the blockage was reduced near the hub region leading to more uniform mass flow distribution along the span. The flow angle deviations at the higher span position were also corrected due to better control of the flow angles. Furthermore, the improvements were confirmed by reductions in entropy, Secondary Kinetic Energy, and pressure unsteadiness. The accurate computational implementations led to an excellent agreement between the predicted and measured efficiency gain.

Optimal Design and Operation of Microdevices for Chemical Production

2013 ◽  
Author(s):  
Osamu Tonomura
Keyword(s):  
Production Capacity ◽  
Flow Distribution ◽  
Experimental Investigations ◽  
Chemical Plants ◽  
Chemical Production ◽  
Flow Sensors ◽  
Term Operation ◽  
Fluid Properties ◽  
Uniform Flow Distribution

Microreactors engage the attention of researchers and engineers in the pharmaceutical and chemical industries as well as universities. When the production capacity of micro chemical plants is increased by numbering-up approach, it is important to realize the uniform flow distribution among the parallelized microreactors. In addition, a blocked microreactor needs to be identified as early as possible to achieve the stable long-term operation of micro chemical plants. However, it is not practical to install the sensors in all the microreactors from the viewpoint of cost or space. In this research, a system that can detect and diagnose a blocked microreactor by using just two flow sensors is developed. The effectiveness of the developed system is demonstrated by numerical and experimental investigations, and it is clarified that the developed method has high robustness to changes in the fluid properties and the microreactor characteristics such as pressure drop. The developed system will be applicable to various types of micro chemical plants with parallelized microreactors.

Unsteady Flow Physics and Performance Prediction of a 1-1/2 Stage Unshrouded High Work Turbine Using the Lattice Boltzmann Approach

2016 ◽  
Author(s):  
Ignacio Gonzalez-Martino ◽  
Sébastien Gautier
Keyword(s):  
Unsteady Flow ◽  
Lattice Boltzmann ◽  
Flow Distribution ◽  
Turbine Rotor ◽  
Flow Coefficient ◽  
Experimental Investigations ◽  
Experimental Measurements ◽  
Number Range ◽  
Eddy Simulation ◽  
High Work

A comparison between experimental measurements and simulations of a 1-1/2 stage unshrouded high work turbine are presented. The experimental investigations were conducted by the Turbomachinery Laboratory of ETH Zurich. The data was obtained from steady and unsteady probe measurements that were performed in four axial planes between stator and rotor rows. Simulations have be performed using the commercial CFD solver PowerFLOW based on the Lattice Boltzmann (LB) method to compute unsteady flow fields. The turbulent flow fluctuations are resolved up to a certain scale using a so-called Very Large Eddy Simulation (VLES) approach. One crucial aspect of the present study is the use a new non-isothermal version of the LB model that allows extending the Mach number range of the standard PowerFLOW scheme up to about 0.9. These unsteady simulations have been used to better understand the different flow structures observed in the experiments, and in particular the mechanisms of tip leakage across the blades of the unshrouded turbine rotor. In the present work, the complete 1-1/2 stage turbine with time-accurate moving rotor geometry has been simulated using the LB solver. This means that no blade reduction technique or almost-periodic flow hypothesis have been used in the simulation. The geometry was modified in order to close the rotor tip gap and do not consider its effects. A thorough comparison of these two simulations with the experimental data has been conducted and presented in the paper: averaged quantities along the turbine stage such as pressure drop, the degree of reaction, the loading coefficient, and the flow coefficient; averaged midspan inlet and exit angles for each turbine blade rows; and flow distribution at four axial planes between the rotor and stator rows. Moreover, a deep analysis of the unsteady flows in the blade channel has been performed in order to better understand the flow features observed in the experimental measurements. Finally, it has been be possible to analyze the interaction modes between turbine rows thanks to the simulation of the full 360° geometry and its time-accurate approach.

Experimental investigations on the thermal and mechanical behaviour of a binary beryllium pebble bed

2000 ◽  
Vol 49-50 ◽  
pp. 521-528 ◽  
Author(s):  
M. Dalle Donne ◽  
A. Goraieb ◽  
G. Piazza ◽  
F. Scaffidi-Argentina
Keyword(s):  
Mechanical Behaviour ◽  
Experimental Investigations ◽  
Pebble Bed

scholarly journals Bypass flow in small absorber sphere channels of the high-temperature gas-cooled reactor pebble-bed module

2017 ◽  
Vol 10 (3) ◽  
pp. 128-139 ◽  
Author(s):  
Ziping Liu ◽  
Zeguang Li ◽  
Jun Sun
Keyword(s):  
High Temperature ◽  
Network Model ◽  
Reactor Core ◽  
Flow Distribution ◽  
Maximum Temperature ◽  
Bypass Flow ◽  
Pebble Bed ◽  
Flow Network ◽  
Control Rod ◽  
High Temperature Gas

In the high-temperature gas-cooled reactor pebble-bed module, the helium bypass flow among graphite blocks cannot be ignored due to its effect on the temperature distribution as well as the maximum temperature in the reactor core. Bypass flow was previously analyzed in the discharging tube, in vertical gaps between graphite reflectors, and in control rod channels. The focus of this study is on the bypass flow that connects the small absorber sphere channels. Different from bypass flow connecting the control rod channels, there was no evident inlet or outlet flow paths into or out of the small absorber sphere channels at the top or bottom of the reactor core. Therefore, the bypass flow connecting the pebble bed with the small absorber sphere channels was mainly caused by the horizontal gaps, in which those gaps would also be irregular due to installation, thermal expansion, or irradiation of the graphite reflectors. After clarifying the resistant coefficients of those gaps by computational fluid dynamic tools, the bypass flow distribution was calculated by the flow network model including the flow in the reactor core, small absorber sphere channels, as well as horizontal gaps. Cases with various size combinations of gaps were adopted into the flow network model to test the sensitivity of bypass flow distribution to those parameters. Finally, the bypass flow in the small absorber sphere channels was concluded to be not significant in the reactor core.

Influence of Spacer Elements on Flow Distribution and Heat Transfer in Experimental Models of Fuel Assemblies

2018 ◽  
Author(s):  
O. Kashinsky ◽  
D. Kulikov ◽  
A. Kurdyumov ◽  
S. Lezhnin ◽  
P. Lobanov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Distribution ◽  
Experimental Models ◽  
Experimental Investigations ◽  
Rod Bundles ◽  
Spacer Grid ◽  
Flow Stabilization ◽  
Fuel Assemblies ◽  
Hexagonal Arrangement ◽  
Strong Disturbance

Experimental investigations of thermal hydraulic properties of coolant flow in experimental models of fuel assemblies (FA) were performed. FA models with 7, 19 and 37 pins in hexagonal arrangement were used as test sections. Friction loss coefficients of smooth rod bundles are presented and compared. Hydraulic resistance of spacing grids with different geometry is discussed. Comparison of obtained data with correlations of Rehme and Idelchik is carried out. Averaged heat transfer dependences on distance from spacer grid top end are presented and compared with different dependences. Experimental results for coolant velocity distribution in subchannels of experimental models were obtained using both Pitot pipe technique and laser Doppler annemometry (LDA). It was shown that a strong disturbance of the flow just behind the spacer grid is present. The flow stabilization occurs at relatively small distances from the spacer elements.

Integrated System CFD Modelling of the Flow Distribution Within a Pebble Bed Modular Reactor

2008 ◽  
Author(s):  
T. H. Huang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Distribution ◽  
Complex Model ◽  
Integrated System ◽  
Operating Conditions ◽  
Large Network ◽  
Cfd Modelling ◽  
Pebble Bed ◽  
Wide Range

The complex hydrodynamic phenomena of a Pebble Bed Modular Reactor (PBMR) are partly attributed to interconnecting flow paths. Modelling the hydrodynamic phenomena provides insight to the reactor over a wide range of operating conditions. The Systems Computational Fluid Dynamics (SCFD) approach combines the advantage of conventional Computational Fluid Dynamics (CFD) modelling in simulating the detailed flow interaction to the more robust solver applied in Flownex thermal-hydraulics software. Although this approach is inherently geometry-dependent, its application in a large network or complex model has seen a reduction in computational speed compared to the conventional CFD modelling approach, without compromising the integrity of the result. This expedites the design-analysis cycle and allows testing of a combination of design changes.

Unsteady Steam turbine optimization using high fidelity CFD

2021 ◽  
pp. 1-56
Author(s):  
Vahid Iranidokht ◽  
Ilias Papagiannis ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Shigeki Senoo ◽  
...  
Keyword(s):  
Computational Cost ◽  
Flow Distribution ◽  
Fast Response ◽  
Test Facility ◽  
Experimental Investigations ◽  
Experimental Setup ◽  
Efficiency Gain ◽  
Computational Optimization ◽  
Novel Approach ◽  
Measured Efficiency

Abstract This paper presents the computational methodology, and experimental investigations accomplished to enhance the efficiency of a turbine stage by applying non-axisymmetric profiling on the rotor hub wall. The experimental setup was a two-stage axial turbine, which was tested at “LISA” test facility at ETH Zurich. The goal was to optimize the interaction of the cavity leakage flow with the rotor passage flow to increase efficiency. The computational optimization was completed using a Genetic Algorithm coupled with an Artificial Neural Network. Unsteady time-accurate simulations were performed, using in-house developed “MULTI3” solver. Besides implementing all geometrical details from the experimental setup into the computational model, it was learned that the unsteady upstream effect could not be neglected. A novel approach was introduced by using unsteady inlet boundary conditions to consider the multistage effect while reducing the computational cost to half. Comprehensive steady and unsteady measurements were performed utilizing pneumatic, Fast Response Aerodynamic (FRAP), and Fast Response Entropy (FENT) probes, on the baseline and profiled test cases. The end-wall profiling was found to be successful in weakening the strength of the hub passage vortex by a 19% reduction in the under-over turning. As a result, the blockage was reduced near the hub region leading to more uniform mass flow distribution along the span. Furthermore, the improvements were confirmed by reductions in entropy, Secondary Kinetic Energy, and pressure unsteadiness. The accurate computational implementations led to an excellent agreement between the predicted and measured efficiency gain.

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