Impact of system parameters on quenching heat transfer in the candidate materials for accident tolerant fuel-cladding in LWRs

2019 ◽  
Vol 129 ◽  
pp. 375-389 ◽  
Author(s):  
Jun-young Kang ◽  
Tong Kyun Kim ◽  
Gi Cheol Lee ◽  
HangJin Jo ◽  
Moo Hwan Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fuel Cladding ◽  
System Parameters

Study on onset of nucleate boiling with screw tube for fusion reactor application

2021 ◽  
Author(s):  
Ji Hwan Lim ◽  
Minkyu Park
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
Transfer Mechanism ◽  
High Heat Flux ◽  
Heat Transfer Mechanism ◽  
System Parameters ◽  
Smooth Tubes

Abstract The onset of nucleate boiling (ONB) is the point at which the heat transfer mechanism in fluids changes and is one of the thermo-hydraulic factors that must be considered when establishing a cooling system operation strategy. Because the high heat flux of several MW/m2, which is loaded within a tokamak, is applied under a one-side heating condition, it is necessary to determine a correlative relation that can predict ONB under special heating conditions. In this study, the ONB of a one-side-heated screw tube was experimentally analyzed via a subcooled flow boiling experiment. The helical nut structure of the screw tube flow path wall allows for improved heat transfer performance relative to smooth tubes, providing a screw tube with a 53.98% higher ONB than a smooth tube. The effects of the system parameters on the ONB heat flux were analyzed based on the changes in the heat transfer mechanism, with the results indicating that the flow rate and degree of subcooling are proportional to the ONB heat flux because increasing these factors improves the forced convection heat transfer and increases the condensation rate, respectively. However, it was observed that the liquid surface tension and latent heat decrease as the pressure increases, leading to a decrease in the ONB heat flux. An evaluation of the predictive performance of existing ONB correlations revealed that most have high error rates because they were developed based on ONB experiments on micro-channels or smooth tubes and not under one-side high heat load conditions. To address this, we used dimensional analysis based on Python code to develop new ONB correlations that reflect the influence of system parameters.

Design of a Thermostat for Precise Temperature Control From −190 Deg to +650 Deg C

1969 ◽  
Vol 91 (2) ◽  
pp. 168-172
Author(s):  
J. Ansari ◽  
W. Leidenfrost ◽  
R. Oldenburger
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Temperature Control ◽  
Hypothetical Case ◽  
Heat Transfer Medium ◽  
System Parameters ◽  
Set Up ◽  
Proportional Controller ◽  
Cylindrical Block ◽  
Selection Of

A proposed apparatus for controlling temperatures from −190 deg to +650 deg with an estimated accuracy of 0.001 deg C is described. The apparatus utilizes helium as the heat transfer medium. The selection of the gain constants of the controller depends upon the system parameters. The hypothetical case of a solid cylindrical block with an integral plus proportional controller is considered, the differential equations are set up, and a graphical scheme is presented for the selection of the controller constants.

Simulations of Heat Transfer Within the Fuel Assembly/Backfill Gas Region of Transport Packages

2005 ◽  
Author(s):  
Pablo E. Araya Go´mez ◽  
Miles Greiner
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Generation ◽  
Radiation Transport ◽  
Transport Processes ◽  
Two Dimensional ◽  
Measurable Effect ◽  
Fuel Cladding ◽  
Reactor Assembly ◽  
Horizontal Support

A two-dimensional computational model of a spent 7×7 Boiling Water Reactor assembly in a horizontal support basket was developed using the Fluent computational fluid dynamics package. Heat transfer simulations were performed to predict the maximum cladding temperature for assembly heat generation rates between 100 and 600W, uniform basket wall temperatures of 25 and 400°C, and with helium and nitrogen backfill gases. Different sets of simulations modeled conduction/radiation and natural convection/radiation transport across the gas filled regions to assess the importance of different transport processes. Simulations that included natural convection exhibited measurably lower cladding temperatures than those that did not only for nitrogen, at the lower basket wall temperature, and within an intermediate range of heat generation rates. Outside these conditions and for helium, conduction and radiation transport are sufficiently large so that natural convection has no measurable effect. Finally, the maximum cladding temperature is more sensitive to the assumed value of the fuel cladding emissivities when nitrogen is the backfill gas than when helium is used.

EFFECTS OF SYSTEM PARAMETERS ON THE TWO-PHASE FLOW AND HEAT TRANSFER BEHAVIOR IN A ROD BUNDLE

2019 ◽  
Author(s):  
Grant Garrett ◽  
Faith R. Beck ◽  
Yue Jin ◽  
Fan Bill Cheung ◽  
Stephen M. Bajorek ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
System Parameters ◽  
Rod Bundle ◽  
Flow And Heat Transfer ◽  
Heat Transfer Behavior ◽  
Transfer Behavior

scholarly journals POST CRITICAL HEAT TRANSFER AND FUEL CLADDING OXIDATION

2016 ◽  
Vol 4 ◽  
pp. 8 ◽  
Author(s):  
Vojtěch Caha ◽  
Jakub Krejčí
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Oxide Layer ◽  
Critical Heat Flux ◽  
Nuclear Reactor ◽  
Nuclear Reactors ◽  
Convection Flow ◽  
Fuel Cladding ◽  
Loss Of Coolant Accident ◽  
Nuclear Reactor Safety

The knowledge of heat transfer coefficient in the post critical heat flux region in nuclear reactor safety is very important. Although the nuclear reactors normally operate at conditions where critical heat flux (CHF) is not reached, accidents where dryout occur are possible. Most serious postulated accidents are a loss of coolant accident or reactivity initiated accident which can lead to CHF or post CHF conditions and possible disruption of core integrity. Moreover, this is also influenced by an oxide layer on the cladding surface. The paper deals with the study of mathematical models and correlations used for heat transfer calculation, especially in post dryout region, and fuel cladding oxidation kinetics of currently operated nuclear reactors. The study is focused on increasing of accuracy and reliability of safety limit calculations (e.g. DNBR or fuel cladding temperature). The paper presents coupled code which was developed for the solution of forced convection flow in heated channel and oxidation of fuel cladding. The code is capable of calculating temperature distribution in the coolant, cladding and fuel and also the thickness of an oxide layer.

Interaction of Heat Transfer by Conduction, Convection, and Radiation in a Radiating Fluid

1963 ◽  
Vol 85 (4) ◽  
pp. 318-328 ◽  
Author(s):  
R. Viskanta
Keyword(s):  
Heat Transfer ◽  
Energy Transport ◽  
Relative Role ◽  
Heat Transfer Characteristics ◽  
Temperature Variations ◽  
System Parameters ◽  
Heating And Cooling ◽  
Finite Distance ◽  
Parallel Surfaces

Consideration is given to the interaction of conduction, convection, and radiation in a fully developed laminar flow. The flat duct consists of two diffuse, nonblack, isothermal parallel surfaces a finite distance apart; the fluid between them emits and absorbs thermal radiation. The problem is formulated in terms of a nonlinear integro-differential equation, and the solution is obtained by a method employed by Barbier. Numerical examples show the influence of the system parameters such as the optical thicknesses, the ratio which determines the relative role of energy transport by conduction to that by radiation, the emissivity of the duct walls as well as the differences between heating and cooling on the temperature variations across the duct and on the heat-transfer characteristics. Two methods for obtaining approximate temperature distributions for optically transparent and opaque radiating media are outlined and the results discussed.

scholarly journals Optimization and Entropy Production: Application to Carnot-Like Refrigeration Machines

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 953 ◽  
Author(s):  
Camelia Stanciu ◽  
Michel Feidt ◽  
Monica Costea ◽  
Dorin Stanciu
Keyword(s):  
Heat Transfer ◽  
Second Law Of Thermodynamics ◽  
Operating Conditions ◽  
Optimum Operating ◽  
System Parameters ◽  
Linear Heat ◽  
Operation Conditions ◽  
Sensitivity Studies ◽  
Actual Operation ◽  
Magnitude Sensitivity

Several optimization models of irreversible reverse cycle machines have been developed based on different optimization criteria in the literature, most of them using linear heat transfer laws at the source and sink. This raises the issue how close to actual operation conditions they are, since the heat transfer law on the phase-change processes is dependent on ΔT3. This paper addresses this issue by proposing a general model for study and optimization of thermal machines with two heat reservoirs applied to a Carnot-like refrigerator, with non-linear heat transfer laws and internal and external irreversibility. The optimization was performed using First and Second Law of Thermodynamics and the Lagrange multipliers method. Thus, several constraints were imposed to the system, also different objective functions were considered, allowing finding the optimum operating conditions, as well as the limited variation ranges of the system parameters. Results show that the nature of the heat transfer laws affects the optimum values of system parameters for obtaining maximum performances and also their magnitude. Sensitivity studies with respect to system several parameters are presented. The results contribute to the understanding of the system limits in operation under different constraints and allow choosing the most convenient variables in given circumstances.

Empirical Analysis Using Advanced Similarity Methods

2002 ◽  
Author(s):  
John J. Wood ◽  
Kristin L. Wood ◽  
Wade O. Troxell
Keyword(s):  
Heat Transfer ◽  
Solid Mechanics ◽  
Large Range ◽  
System Parameters ◽  
Analysis Techniques ◽  
Domain Of Applicability ◽  
Development Cycle ◽  
Material Tests ◽  
Insight Into ◽  
Parameters Of Interest

Traditional dimensional analysis techniques for predicting the performance characteristics of a product can be greatly improved in both accuracy and domain of applicability by the infusion of empirical data, derived from material tests, into the equations that characterize the system parameters of interest. Advanced similarity methods are investigated which overcome the constraints associated with the traditional methods and provide increased analysis capability and improved insight into the phenomenon governing the problem. Such capability greatly increases the design toolbox available to product developers, across a large range of scale and application. It also significantly enhances a developer’s choices for prototype portioning during a development cycle. Solid mechanics and heat transfer applications are used to illustrate the basic utility of the methods.

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