scholarly journals Computational fluid dynamics investigation of thermal-hydraulic characteristics in a simplified pebbled bed modular reactor core using different arrangements of fuel elements

2017 ◽  
Vol 10 (3) ◽  
pp. 119-127 ◽  
Author(s):  
Yuyu Bai ◽  
Nan Gui ◽  
Xingtuan Yang ◽  
Jiyuan Tu ◽  
Shengyao Jiang
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Temperature ◽  
Reactor Core ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Face Centered ◽  
Fuel Elements ◽  
High Temperature Gas

High-temperature gas-cooled reactor is a kind of advanced nuclear reactor in which the core is packed with spherical fuel elements. In high-temperature gas-cooled reactors, the operating temperature is higher than that in ordinary light water reactors. In an attempt to analyze the flow pattern and heat transfer situation to provide reference for the safe operation of the pebble bed reactors, a segment of simplified high-temperature gas-cooled reactor core is simulated with computational fluid dynamics method. Four kinds of arrangement, including simple cubic, body-centered cubic, face-centered cubic, and a combination structure of body-centered cubic and face-centered cubic, are studied, respectively. Based on the simulation results, higher heat transfer capability and lower pebble temperature are obtained in the case with the most compact arrangement. The drag coefficient ( Cd) for four arrangements with different inlet Reynolds number (Re) is obtained and relationship between Re and Cd is analyzed. In addition, a simulation with a broken fuel element in the body-centered cubic fluid domain has been performed. The results show that the presence of broken fuel may result in uneven flow, which will change the heat transfer condition. So it is better to avoid broken fuel element in a high-temperature gas-cooled reactor.

scholarly journals Computational Fluid Dynamics Applied to Study Coolant Loss Regimes in Very High Temperature Reactors

2021 ◽  
Vol 9 (2A) ◽  
Author(s):  
Uebert Gonçalves Moreira ◽  
Dany Sanchez Dominguez ◽  
Leorlen Yunier Rojas Mazaira ◽  
Carlos Alberto Brayner de Oliveira Lira ◽  
Carlos Rafael García Henández
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Temperature ◽  
Reactor Core ◽  
Normal Operation ◽  
Pebble Bed ◽  
Continuous Increase ◽  
High Temperature Reactors ◽  
Fuel Elements ◽  
Very High

The nuclear energy is a good alternative to meet the continuous increase in world energy demand. In this pers-pective, VHTRs (Very High Temperature Reactors) are serious candidates for energy generation due to its   inherently safe performance, low power density and high conversion efficiency. However, the viability of these reactors depends on an efficient safety system in the operation of nuclear plants. The HTR (High Temperature Reactor)-10 model, an experimental reactor of the pebble bed type, is used as a case study in this work to perform the thermohydraulic simulation. Due to the complex patterns flow that appear in the pebble bed reactor core CFD (Computational Fluid Dynamics) techniques are used to simulate these reactors. A realistic approach is adopted to simulate the central annular column of the reactor core. As geometrical model of the fuel elements was selected the BCC (Body Centered Cubic) arrangement. Parameters considered for reactor design are available in the technical report of benchmark issues by IAEA (TECDOC-1694). We obtain the temperature profile distribution in the core for regimes where the coolant flow rate is smaller than recommended in a normal operation. In general, the temperature distributions calculated are consistent with phenomenological behavior. Even without considering the reactivity changes to reduce the reactor power or other safety mechanisms, the maximum temperatures do not exceed the recommended limits for TRISO fuel elements.

Computational Fluid Dynamics Investigation of a High Temperature Waste Heat Exchanger Tube Sheet Assembly

2005 ◽  
Author(s):  
Michael A. Porter ◽  
Dennis H. Martens ◽  
Thomas Duffy ◽  
Sean McGuffie
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Temperature ◽  
Temperature Distribution ◽  
Carbon Steel ◽  
Gas Flow ◽  
Waste Heat ◽  
Thermal Reactor ◽  
Process Gas

Many modern Sulfur Recovery Unit (SRU) process waste heat recovery exchangers operate in high temperature environments. These exchangers are associated with the thermal reactor system where the tubesheet/tube/ferrule assemblies are exposed to gasses at temperatures approaching 3000°F. Because sulfur compounds are present in the process gas, the carbon steel tubesheet and tubes in the assembly will be deteriorated by sulfidation as the operating metal temperature rises above 600°F. Ferrule systems are used to protect the carbon steel from exposure to excessive temperatures. The temperature distribution in the steel tubesheet/tube/ferrule system is affected by process gas flow and heat transfer through the assembly. Rather than depend upon “assumed” heat transfer coefficients and fluid flow distribution, a Computational Fluid Dynamics (CFD) investigation was conducted to study the flow fields and heat transfer in the tubesheet assembly. It was found that the configuration of the ferrule installation has a large influence on the temperature distribution in the steel materials and, therefore, the possible sulfidation of the carbon steel parts.

scholarly journals Preliminary Analysis on Burnup Calculation of Several Arrangement of TRISO and Pebble inside an MCNP Model of HTR Core

2021 ◽  
Vol 2072 (1) ◽  
pp. 012008
Author(s):  
W Luthfi ◽  
Suwoto ◽  
T Setiadipura ◽  
Zuhair
Keyword(s):  
Reactor Core ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Average Deviation ◽  
Absolute Deviation ◽  
Hexagonal Close Packed ◽  
Simple Cubic ◽  
High Temperature Reactor ◽  
Face Centered ◽  
Burnup Calculation

Abstract Several studies related to simplifying the modeling of pebble bed High-Temperature Reactor core (HTR) has been developed before. From some calculation on several MCNP models with a fueled pebble to dummy ratio 57:43, using a combination of several types of TRISO (TRi-structural ISOtropic particle fuel) unit and Pebble unit is modeled to achieve its first criticality. In this paper, some MCNP model that uses 27000 pebbles with a 57:43 ratio and 100% fueled pebble is created to be used on burnup calculation and to compare its k-eff and nuclide inventory. From this burnup calculation, it could be seen that SC (Simple Cubic) TRISO unit has faster calculation time followed by the HCP (Hexagonal Close Packed) TRISO unit and then the FCC (Face-Centered Cubic) TRISO unit. The BCC (Body-Centered Cubic) pebble unit had some consistent deviation from another pebble unit, and it still needs more study to know more about the reason behind it. It could be seen that if there are some dummy pebbles inside the reactor, then the deviation would be higher than if there is just fueled pebble inside the reactor. On the 57:43 ratio, the absolute average deviation of k-eff on burnup calculation is lower than 2% and 10% for nuclide inventory (mass). On 100% fueled pebble, it’s below 0.15% on k-eff absolute deviation and below 8% on nuclide inventory deviation.

Design Considerations for Compact Ceramic Off-Set Strip Fin High Temperature Heat Exchangers

2005 ◽  
Author(s):  
Sundaresan Subramanian ◽  
Roald Akberov ◽  
Clayton Ray DeLosier ◽  
Yitung Chen ◽  
Anthony E. Hechanova ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Temperature ◽  
Heat Exchanger ◽  
Transfer Enhancement ◽  
Heat Exchanger Design ◽  
Temperature Heat ◽  
Overall Performance ◽  
Offset Strip Fin

This paper deals with the development of a three-dimensional numerical model to predict the overall performance of an advanced high temperature heat exchanger design, up to 1000°C, for the production of hydrogen by the sulfur iodine thermo-chemical cycle used in advanced nuclear reactor concepts. The design is an offset strip-fin, hybrid plate compact heat exchanger made from a liquid silicon impregnated carbon composite material. The two working fluids are helium gas and molten salt (Flinak). The offset strip-fin is chosen as a method of heat transfer enhancement due to the boundary layer restart mechanism between the fins that has a direct effect on heat transfer enhancement. The effects of the fin geometry on the flow field and heat transfer are studied in three-dimensions using Computational Fluid Dynamics (CFD) techniques. The pre-processor GAMBIT is used to create a computational mesh, and the CFD software package FLUENT that is based on the finite volume method is used to produce the numerical results. Fin dimensions need to be chosen that optimize heat transfer and minimize pressure drop. Comparison of the overall performance between two fin shapes (rectangular versus curved edges) is performed using analytical calculations (where available) as well as computational fluid dynamics techniques. The analytical calculations predict larger pressure losses than the numerical simulations. The model developed in this paper will be used to investigate the heat exchanger design parameters in order to find an optimal design.

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