Turbulent Friction Factor for a Rod Bundle in Consideration of a Subchannel Geometry

2002 ◽  
Author(s):  
Joo Hwan Park ◽  
Chang Joon Jeong ◽  
Myung Seung Yang ◽  
Dong Suk Oh
Keyword(s):  
Friction Factor ◽  
Measurement Data ◽  
Experimental Results ◽  
Flow Area ◽  
Theoretical Derivation ◽  
Turbulent Friction ◽  
Law Of The Wall ◽  
Rod Bundle ◽  
Two Parameters ◽  
Geometry Parameter

A generalized turbulent friction factor for a rod bundle was developed based on “Law of the Wall” for a tube. It was included two parameters which are one parameter of hydraulic diameter and flow area of a subchannel and rod bundle and another parameter (called geometry parameter hereinafter) of subchannel configuration and pitch-to-diameter ratio (P/D) for a single subchannel. The turbulent geometry parameter for a single subchannel has been used as a constant on the previous works but it was found to be dependent on subchannel shapes and P/D from the present work. Hence, it was modeled as a function of the subchannel shapes and P/D from 1.0 to 1.5. The turbulent geometry parameters for single subchannels were validated by the theoretical derivation of a triangular and square subchannel. Those are compared and agreed well with the previous measurement data for 4 kinds of subchannel types such as a triangular, a square, a wall and a corner subchannel. The present model of turbulent friction factor for a rod bundle included the turbulent geometry parameter has been compared with the various experimental results for circular tubes and hexagonal tubes with various rod numbers. The predicted turbulent friction factors for those rod bundles were agreed excellently with experimental results.

Analytical Prediction of Turbulent Friction Factor in Circular Pipe Under Supercritical Conditions

2012 ◽  
Author(s):  
Jinguang Zang ◽  
Xiao Yan ◽  
Shanfang Huang ◽  
Zejun Xiao ◽  
Yanping Huang
Keyword(s):  
Friction Factor ◽  
Viscous Sublayer ◽  
Circular Pipe ◽  
Main Role ◽  
Analytical Prediction ◽  
Flow Area ◽  
Algebraic Form ◽  
Supercritical Conditions ◽  
Turbulent Friction ◽  
Law Of The Wall

An analytical method was proposed for the prediction of the turbulent friction factor in a circular pipe under supercritical conditions. The friction factor equation was based on the new wall function by Van Direst transformation which is widely used in compressed flow. The law of the wall of two layers was used and integrated over the entire flow area to obtain the algebraic form of the turbulent friction factor. The new turbulent friction formula was first adjusted to Colebrook equation in isothermal flow at supercritical pressures. And then it was validated in heated supercritical flow by several existing correlations. Similar trends were found between them, which confirms the physical validity of the new frictional formula. The theoretical analysis also shows that the friction factor due to the variation of fluid property at supercritical pressures is mainly caused by the density and viscosity variation. In viscous sublayer, both the viscosity play the main role, while in turbulent sublayer, only the density do.

Experimental Study on the Effect of Localized Blockages on the Friction Factor of a 61-Pin Wire-Wrapped Bundle

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Mason Childs ◽  
Robert Muyshondt ◽  
Rodolfo Vaghetto ◽  
Duy Thien Nguyen ◽  
Yassin Hassan
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Flow Behavior ◽  
Fluid Pressure ◽  
Transition Flow ◽  
Flow Area ◽  
Number Range ◽  
Rod Bundle ◽  
Transition Flow Regime ◽  
Friction Factor Correlation

Abstract The thermal-hydraulic behavior of the flow in rod bundles has motivated numerous experimental and computational investigations. Previous studies have identified potential for accumulation of debris within the small subchannels of typical wire-wrapped assemblies with subsequent total or partial blockage of subchannel coolant flow. A test campaign was conducted to study the effects of localized blockages on the bundle averaged friction factor of a tightly packed wire-wrapped rod bundle. Blockages were installed within the bundle, and fluid pressure drop was measured across one wire pitch for a Reynolds number range of 500–17,200. The Darcy–Weisbach friction factor of the perturbed rod bundle geometry was compared with that of the unblocked bundle, as well as with the predictions of a well-established friction factor correlation. Differing effects based on blockage size and location for various flow regimes were studied. A number of conclusions can be made about the effects of the blockages on the friction factor, such as an increasing effect of the blockage on friction factor with an increase in Reynolds number, a change in flow behavior in the turbulent transition flow regime near Reynolds number 3000, differences in effect on friction factor for different types of subchannel blockage, and a nonlinear trend in friction factor variation with flow area impeded for edge subchannels. To this end, all data and quantified uncertainty produced in this study are made available for comparison and validation of advanced computational tools.

Analytic Prediction of the Friction Factor for Turbulent Flow in Internally Finned Channels

1981 ◽  
Vol 103 (3) ◽  
pp. 423-428 ◽  
Author(s):  
M. J. Scott ◽  
R. L. Webb
Keyword(s):  
Turbulent Flow ◽  
Friction Factor ◽  
Analytical Model ◽  
Analytical Models ◽  
Turbulent Friction ◽  
Law Of The Wall ◽  
Finned Tubes ◽  
Rectangular Channels ◽  
Factor Data ◽  
Analytic Prediction

This work develops an analytical model for the friction factor with turbulent flow in internally finned channels. Such channels are an important class of enhanced heat transfer surfaces. Until this work, no analytical models for the turbulent friction factor have been proposed. The present model assumes the validity of the Law of the Wall and applies the logarithmic velocity distribution to the interfin and core regions of the flow. Theoretically based friction factor equations are developed for internally finned circular tubes and rectangular channels. The model predicts Carnavos data for 21 internally finned tubes within ± 10 percent. Friction factor data were taken for five internally finned, rectangular channels. The analytical model predicts these data within ± 10 percent, except for the case of a very high fin.

Study on the Truck Scale Cheating Automatic Monitoring System Based on the GPRS

2013 ◽  
Vol 703 ◽  
pp. 240-243 ◽  
Author(s):  
Yan Jun Zhao ◽  
Shou Guang Cheng ◽  
Bin Qu
Keyword(s):  
Monitoring System ◽  
Measurement Data ◽  
Experimental System ◽  
Automatic Monitoring ◽  
Experimental Results ◽  
Pneumatic Conveying ◽  
Automatic Monitoring System ◽  
On Line ◽  
Conveying System

The truck scale is more and more applied on the weighing system. To seek illegal profits, many kinds of truck scale cheating method is found in the weighing system. To monitoring the truck scale cheating method, the truck scale cheating automatic monitoring system based on the GPRS is brought out in this paper. The truck scale cheating automatic monitoring system is designed. The monitoring system includes three parts: the monitoring terminal, the GPRS transmission module and the upper monitoring system. The truck scale measurement data of the sensors are collected by the monitoring terminal and sent to the upper monitoring system through the GPRS module. The experimental system is established on the pneumatic conveying system and the experiment is carried out. The experimental results show that the automatic monitoring system can on-line monitor the truck scale cheating method and improves the security of the truck scale weighing system.

A Brief Review on Validation for Heat Treatment Simulation

2021 ◽  
Author(s):  
Kyozo Arimoto
Keyword(s):  
Heat Treatment ◽  
Measurement Data ◽  
Strain Analysis ◽  
Experimental Results ◽  
Stress Distributions ◽  
Simulation Functions ◽  
Basic Functions ◽  
Hardness Prediction ◽  
Quenched Steel ◽  
Complex Phenomena

Abstract Heat treatment simulation has progressed to the stage where several commercial software are available. Validations of simulation functions using experimental results contributed to this realization. Organizing information on the validations may be effective for maintaining the functions and educating users about the nature of the phenomena. For this reason, the author here briefly reviews mainly his validation cases. Since experiments using specimens having relatively simple shapes can reveal the essence of complex phenomena, the results have been used in the validations. When the basic functions such as heat transfer, phase transformation, latent heat, and hardness prediction were comprehensively validated in the early stages of software development, the author used experimental results of the inverse hardening in quenched steel cylinders. After that, his validations of the software at the stage where adding stress and strain analysis functions, used effectively measurement data of length and diameter changes, and residual stress distributions in normally quenched steel cylinders. While, it was also worth to validate curving in long specimens cooled unevenly, which included a case of specimens with a similar cross-section to the Japanese sword. In addition, the author validated distortions and residual stresses in carburized and quenched, induction hardened, and also nitrided specimens.

scholarly journals Objective assessment for characterising the flatness of garment sewing stitches

2013 ◽  
Vol 13 (4) ◽  
pp. 110-117
Author(s):  
Jiang Hongxia ◽  
Liu Jihong ◽  
Chai Zhilei ◽  
Wang Chunxia ◽  
Zhang Mingxia
Keyword(s):  
Standard Deviation ◽  
Empirical Mode Decomposition ◽  
Objective Assessment ◽  
Window Size ◽  
Experimental Results ◽  
Classification Method ◽  
Average Area ◽  
Mode Decomposition ◽  
Two Parameters

Abstract In this paper, a novel classification method of assessing garment sewing stitch based on amended bi-dimensional empirical mode decomposition (ABEMD) has been introduced. Two parameters that characterise garment sewing stitch, average area and standard deviation, have been defined based on the grey value of pixels. Experimental results showed that when the window size is 512×128 pixels with regard to average area, the threshold can be decided as 6.00, 5.50, 5.30 and 4.00 for five different grades , respectively. Meanwhile, with regard to standard deviation, the threshold can be decided as 48.00, 40.00, 30.00 and 20.00, respectively. It is demonstrated that the parameters are effective in discriminating sewing stitch images in terms of the grades when used as inputs for the ABEMD. The performance of the algorithm on different garment status is significantly reliable.

Sensitivity Studies of Shear Stress Transport Turbulence Model Parameters on the Prediction of Seven-Rod Bundle Benchmark Experiments

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Cale Bergmann ◽  
S. Ormiston ◽  
V. Chatoorgoon
Keyword(s):  
Shear Stress ◽  
Turbulence Model ◽  
Turbulence Modeling ◽  
Sensitivity Study ◽  
Model Parameters ◽  
Rod Bundle ◽  
Shear Stress Transport ◽  
Sst Turbulence Model ◽  
Sensitivity Studies ◽  
Two Parameters

This paper reports the findings of a sensitivity study of parameters in the shear stress transport (SST) turbulence model in a commercial computational fluid dynamics (CFD) code to predict an experiment from the Generation IV International Forum Supercritical-Water-Cooled Reactor (GIF SCWR) 2013–2014 seven-rod subchannel benchmark exercise. This study was motivated by the result of the benchmark exercise that all the CFD codes gave similar results to a subchannel code, which does not possess any sophisticated turbulence modeling. Initial findings were that the CFD codes generally underpredicted the wall temperatures on the B2 case in the region where the flow was supercritical. Therefore, it was decided to examine the effect of various turbulence model parameters to determine if a CFD code using the SST turbulence model could do a better job overall in predicting the wall temperatures of the benchmark experiments. A sensitivity study of seven parameters was done, and changes to two parameters were found to make an improvement.

A theory of the lifted temperature minimum on calm clear nights

1993 ◽  
Vol 344 (1671) ◽  
pp. 183-206 ◽  
Keyword(s):  
Surface Temperature ◽  
Critical Rayleigh Number ◽  
Surface Cooling ◽  
Turbulent Friction ◽  
Temperature Boundary ◽  
Unstable Layer ◽  
Eddy Transport ◽  
Two Parameters ◽  
Rayleigh Benard ◽  
Temperature Boundary Condition

Numerous reports from several parts of the world have confirmed that on calm clear nights a minimum in air temperature can occur just above ground, at heights of the order of 12 m or less. This phenomenon, first observed by Ramdas & Atmanathan (1932), carries the associated paradox of an apparently unstable layer that sustains itself for several hours, and has not so far been satisfactorily explained. We formulate here a theory that considers energy balance between radiation, conduction and free or forced convection in humid air, with surface temperature, humidity and wind incorporated into an appropriate mathematical model as parameters. A complete numerical solution of the coupled air—soil problem is used to validate an approach that specifies the surface temperature boundary condition through a cooling rate parameter. Utilizing a flux-emissivity scheme for computing radiative transfer, the model is numerically solved for various values of turbulent friction velocity. It is shown that a lifted minimum is predicted by the model for values of ground emissivity not too close to unity, and for sufficiently low surface cooling rates and eddy transport. Agreement with observation for reasonable values of the parameters is demonstrated. A heuristic argument is offered to show that radiation substantially increases the critical Rayleigh number for convection, thus circumventing or weakening Rayleigh-Benard instability. The model highlights the key role played by two parameters generally ignored in explanations of the phenomenon, namely surface emissivity and soil thermal conductivity, and shows that it is unnecessary to invoke the presence of such particulate constituents as haze to produce a lifted minimum.

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