Application of EEMD-Multiscale Entropy Algorithm in the Signal Analysis of Narrow Channel Two-Phase Flow Under Rolling Motion

2021 ◽  
Author(s):  
Wenjun Chu ◽  
Yang Liu ◽  
Hongye Zhu ◽  
Xingtuan Yang ◽  
Liqiang Pan
Keyword(s):  
Signal Reconstruction ◽  
Rectangular Channel ◽  
Inertial Force ◽  
Narrow Channel ◽  
Multiscale Entropy ◽  
Compact Structure ◽  
Liquid Distribution ◽  
Multi Scale ◽  
High Heat Transfer ◽  
Eemd Method

Abstract The narrow rectangular channel has the advantages of compact structure and high heat transfer coefficient, and has been widely used in nuclear systems. However, the internal flow of the narrow channel will be affected by the non-inertial force when it is used in undulating conditions. Aiming at the visualized parallel narrow channel boiling experiment system, this study applies the EEMD method to the analysis of signals such as outlet pressure of the test section under rolling conditions. We utilize the features that the variance and energy of the empirical mode decomposition component will suddenly change in the low frequency band, and effectively realize the adaptive removal of signal noise and signal reconstruction under different rolling parameters. This paper also introduces the theory of multi-scale entropy to extract features of different time-scale signals obtained by EEMD method. The obtained signal energy moment and multi-scale entropy changes obviously with the gas-liquid distribution of the experimental section, which can be used as the basis for narrow channel flow pattern identification.

Stream-barb installations for narrow channel bends — a laboratory study

2004 ◽  
Vol 31 (3) ◽  
pp. 478-486 ◽  
Author(s):  
Troy Matsuura ◽  
Ronald Townsend
Keyword(s):  
Laboratory Study ◽  
Phase 1 ◽  
Rectangular Channel ◽  
Field Tests ◽  
Narrow Channel ◽  
Secondary Currents ◽  
Stream Bank ◽  
Low Profile ◽  
Bank Protection ◽  
Bed Scour

Phase 1 of an ongoing laboratory study of a novel form of stream-bank protection structure is described. "Barbs" are dike-like stone structures designed to protect the (usually unstable) outside-bank regions of channel bends. These low-profile structures point upstream into the flow and typically extend to about 1/4-way across the channel. By disrupting near-bank velocity gradients they promote sediment deposition along the eroding outside-bank region. Their presence also modifies the "helicoidal"-type flow pattern of the bend such that secondary currents, which would otherwise attack the outside-bank, are redirected towards the center of the channel. This novel form of bank protection structure is currently undergoing field tests on selected bends on a number of shallow "wide" streams in Illinois, USA. While initial results are encouraging, additional studies are necessary to develop design criteria for their wider application. In phase 1 of this study, the effectiveness of different arrangements of barb groups, in both 90° and 135° moveable-bed bend sections of a hydraulically "narrow" rectangular channel, are investigated. For each hydraulic condition considered, the channel-bed scour profiles generated by the different barb groups are compared to corresponding "reference" profiles generated in the absence of barbs. Judging the effectiveness of the different barb groups in promoting long-term stability of the outside-bank region is based on two criteria: (i) percent reduction achieved in scouring in the vicinity of the outside-bank and (ii) degree to which the channel thalweg (deepest portion) is moved from the outside-bank region towards the center of the channel.Key words: barb, channel bends, local scouring, bank erosion, bank protection, secondary currents.

A Critical Review of Drag Reduction in Channel Flows and Numerical Study of Forced Convective Transport in a Channel With Conducting-Lubricating (CO-LUB) Surfaces

2015 ◽  
Author(s):  
Jessica Reyes ◽  
Krishna Kota
Keyword(s):  
Heat Transfer ◽  
Drag Reduction ◽  
Liquid Flow ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Narrow Channel ◽  
Convective Transport ◽  
Bulk Liquid ◽  
Frictional Drag ◽  
Ansys Fluent

Addressing the traditionally contradictory problem of obtaining considerable drag reduction without negatively impacting heat transfer as much is an arduous scientific challenge. In this paper, prior efforts on frictional drag reduction and the associated issues are discussed in relevant detail, and the effectiveness of Conducting-Lubricating (CO-LUB) surfaces as one of the potential options to address this challenge for single phase forced convection of liquids is numerically pursued. CO-LUB surfaces have exceptionally high wetting characteristics, and when saturated with a liquid microlayer, provide remarkable lubrication to bulk liquid flow and simultaneously facilitate heat transfer by conduction through the microlayer. In the simulations, the side walls of a high aspect ratio rectangular channel were assumed as CO-LUB surfaces and flow and heat transfer of bulk liquid flow were modeled using ANSYS FLUENT 14.5. Volume-of-Fluid (VOF) method was used to model the two phases with a free surface interface, with water as the microlayer liquid and oil as the bulk liquid, in a narrow channel of 5 mm width and 50 mm length under laminar flow, constant wall heat flux conditions. The results were compared with a regular channel of the same dimensions (without CO-LUB surfaces) and it was found that pressure drop decreased remarkably by ∼23 times for some cases but without any heat transfer attenuation (actually, improved heat transfer performance was observed) leading to highly energy-efficient convective transport.

Optimization Design the Configuration Sizes of Multi-Layer Rectangle Micro-Channel Heat Sink

2013 ◽  
Vol 444-445 ◽  
pp. 1101-1106
Author(s):  
Li Feng Wang ◽  
Bao Dong Shao ◽  
He Ming Cheng ◽  
Ying He
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Optimization Design ◽  
High Heat ◽  
Micro Channel ◽  
Compact Structure ◽  
Total Thermal Resistance ◽  
High Heat Transfer ◽  
High Heat Transfer Coefficient

The configuration sizes of multi-layer rectangle micro-channel heat sink are optimized, which has been widely used to cool electronic chip for its high heat transfer coefficient and compact structure. Taking the thermal resistance and the pressure drop as goal functions, a binary-objective optimization model was proposed for the multi-layer rectangle micro-channel heat sink based on Sequential Quadratic Programming (SQP) method. The number of optimized micro-channel in width n1 and that in height n2 are 24 and 3, the width of optimized micro-channel Wc and fin Wf are 360 and 55μm, the height of optimized micro-channel Hc is 1000μm, and the corresponding total thermal resistance of the whole micro-channel heat sink is 1.5429 °C/W. The corresponding pressure drop is about 2.3454 Pa. When the velocity of liquid is larger than 0.3 m/s, the effect of change of velocity of liquid on the thermal resistance and pressure drop can be neglected.

Experimental Measurements and Numerical Simulations of Two-Phase Stratified, Wavy and Slug Flow in a Narrow Rectangular Channel

2005 ◽  
Author(s):  
Steven P. O’Halloran ◽  
B. Terry Beck ◽  
Mohammad H. Hosni ◽  
Steven J. Eckels
Keyword(s):  
Numerical Simulations ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Measurement Techniques ◽  
Narrow Channel ◽  
Experimental Measurements ◽  
Phase Flow ◽  
Two Phase ◽  
Two Fluids

Flow pattern transitions in two-phase flow are important phenomena for many different types of engineering applications, including heat exchangers. While two-phase flow is not understood as well as single-phase flow, advancements in both measurement techniques and numerical simulations are helping to increase the understanding of two-phase flow. In this paper, stratified/wavy flow is investigated, along with the transition from wavy to slug flow. For the experimental setup, a narrow channel with a length of 600 mm, height of 40 mm, and a width of 15 mm was fabricated using clear acrylic plastic, and water and air were the two fluids used for testing. The water in the channel was initially at rest, and the transition in flow patterns was created by increasing the velocity of air flowing over the water surface. Particle image velocimetry (PIV) was used to measure the velocity of the flow for stratified and wavy flow conditions, and also the velocity at the onset of slug flow. Along with the experimental measurements, computational fluid dynamics (CFD) simulations were conducted on a similar geometry using the volume of fluid (VOF) two-phase model. A commercial CFD software package was used for the simulations, and comparisons were made between the experimental measurements and numerical results. Favorable agreement was found between the experimental measurements and the numerical simulations. In particular, the transition from wavy to slug flow compared well to previously developed two-phase flow transition models, including the slug transition developed by Taitel and Dukler.

Analysis of Single Phase Flow and Temperature Fields in Rectangular Channel With Translation in Width

2010 ◽  
Author(s):  
Lei Luo ◽  
Wenzhen Chen ◽  
Zhiyun Chen ◽  
Jianli Hao
Keyword(s):  
Heat Exchange ◽  
Single Phase ◽  
Rectangular Channel ◽  
Reactor Core ◽  
Temperature Fields ◽  
Single Phase Flow ◽  
Compact Structure ◽  
Fuel Assemblies ◽  
Width Direction ◽  
New Type

Plate fuel assemblies will be widely applied in the future because of their simple and compact structure and excellent heat exchange capability. When the plate fuel assemblies are used in a ship reactor, the effect of the ship motion on the reactor core thermal hydrodynamic must be investigated. In this paper, aiming at the rectangular shape of coolant channels in the assemblies, the numerical simulation of the flow and heat exchange in a rectangular channel in horizontal translation is carried out. Using the CFD Software and UDF code, the simulation model of the channel in horizontal translation with and without acceleration along its width direction is built up, and the related characteristics is analyzed and discussed. The results and conclusions are applicable and useful for the new type ship PWR design.

Dimple Enhanced Heat Transfer in High Aspect Ratio Channels

2001 ◽  
Author(s):  
Srinath V. Ekkad ◽  
Hasan Nasir
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Rectangular Cross Section ◽  
Rectangular Channel ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
High Heat Transfer ◽  
Smooth Channel ◽  
Wide Range

Abstract Detailed heat transfer measurements are presented for a rectangular channel with dimples on one wall. Dimpled surfaces provide high heat transfer enhancement comparable to ribbed surfaces with reduced overall pressure drop. The heat transfer coefficients were measured using a transient liquid crystal technique. The effect of channel flow Reynolds number was investigated for a wide range from 10000 to 65000. The channel is a 25.4 mm × 101.6 mm (1” × 4”) rectangular cross-section with the dimples on one of the 101.6 mm wall. Heat transfer enhancement around three times that of a smooth channel were achieved for all flow conditions. The overall pressure drop through the dimpled section of the passage was also measured. The resulting thermal performance of the dimples surfaces is significantly higher compared to channels with protruding ribs.

Multi-Objective Optimization Design of Multi-Layer Rectangle Micro-Channel Heat Sink for Single-Phase Flow and Heat Transfer

2013 ◽  
Vol 709 ◽  
pp. 286-291 ◽  
Author(s):  
Li Feng Wang ◽  
Bao Dong Shao ◽  
He Ming Cheng
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Optimization Design ◽  
High Heat ◽  
Micro Channel ◽  
Compact Structure ◽  
Total Thermal Resistance ◽  
High Heat Transfer

The purpose of this paper is to optimize the structural sizes of multi-layer rectangle micro-channel heat sink, which has been widely used to cool electronic chip for its high heat transfer coefficient and compact structure. Taking the thermal resistance and the pressure drop as goal functions, a binary-objective optimization model was proposed for the multi-layer rectangle micro-channel heat sink based on Sequential Quadratic Programming (SQP) method. The number of optimized micro-channel in width n1 and that in height n2 are 21 and 7, the width of optimized micro-channel Wc and fin Wf are 340 and 130μm, the height of optimized micro-channel Hc is 415μm, and the corresponding total thermal resistance of the whole micro-channel heat sink is 1.3354 °C/W. The corresponding pressure drop is about 1.3377 Pa. When the velocity of liquid is larger than 0.3 m/s, the effect of change of velocity of liquid on the thermal resistance and pressure drop can be neglected.

scholarly journals An Adaptive Filtering Method for Bridge Vibration Signals Based on Improved CEEMDAN and Multi-Scale Permutation Entropy

2021 ◽  
Vol 8 (4) ◽  
pp. 163-168
Author(s):  
Dawei He ◽  
Boxin Wang ◽  
Xin Gao ◽  
Xia Wang
Keyword(s):  
Adaptive Filtering ◽  
Signal To Noise Ratio ◽  
Signal Reconstruction ◽  
Vibration Signal ◽  
Optimization Method ◽  
Permutation Entropy ◽  
Vibration Signals ◽  
Multi Scale ◽  
Long Span Bridge ◽  
Vibration Signal Analysis

Aiming at the serious noise of bridge vibration signals in complex environment, this paper proposed an adaptive filtering and denoising optimization method for bridge structural health monitoring. The method took CEEMDAN algorithm as the core, during the step-by-step decomposition of original signals, white noise with opposite signs was added in each stage, meanwhile multi-scale permutation entropy (MPE) was introduced to analyze the mean entropy of each intrinsic mode function (IMF) at different scales, and components with serious noise were eliminated to complete the first filtering; then, in order to optimize the remaining IMFs for signal reconstruction and ensuring the smoothness and similarity of filtering, an optimized reconstruction model was established to complete the second filtering. Compared with the CEEMDAN method, the proposed method could solve the problems of mode mixing and endpoint effect with good completeness, orthogonality, and signal-to-noise ratio. At last, the advantages and application value of the proposed method were verified again by the vibration signal analysis of a real long-span bridge structure.

CFD Study of the Condensation of Water Vapor on the Particles Flow in Rectangular Narrow Channel

2014 ◽  
Author(s):  
Daping Lin ◽  
Tao Zhou ◽  
Xu Yang ◽  
Xiaolu Fang
Keyword(s):  
Phase Transition ◽  
Temperature Field ◽  
Water Vapor ◽  
Liquid Phase ◽  
Liquid Layer ◽  
Rectangular Channel ◽  
Narrow Channel ◽  
Ansys Fluent ◽  
Thermophoretic Force ◽  
Condensation Point

This paper presents a CFD study of the flow and deposition of particles in vapor in a 1000mm by 20mm narrow rectangular channel. The temperature of the wall is set below the condensation point, so the vapor will change into the liquid phase near the wall. The flow and deposition of the particles in the condition when the phase transition of water occurs is simulated by ANSYS Fluent code. The result shows that the condensation of the water vapor will change the temperature field and the velocity of the flow in the channel. The particles will be forced to the wall due to the thermophoretic force. The condensation developing process will enhance the deposition of the particles while the developed liquid layer will stop the particles flow to the wall.

Study of Factors Influencing Non-Uniform Gas-Liquid Distribution in the Refrigerant Distributor in an Air Conditioner

2014 ◽  
Author(s):  
Eiji Ishii ◽  
Kazuki Yoshimura
Keyword(s):  
Grid Method ◽  
Particle Method ◽  
Liquid Films ◽  
Gas Flows ◽  
Air Conditioner ◽  
Liquid Interfaces ◽  
Liquid Distribution ◽  
Air Conditioners ◽  
Multi Scale ◽  
Liquid Flows

Factors that influence the non-uniform gas-liquid distribution in refrigerant distributors in air conditioners were studied. Gas-liquid flows in two-pass and multi-pass distributors were numerically simulated with a particle/grid hybrid method; droplets and liquid films were mainly simulated using a particle method, and gas flows were simulated using a grid method. Complex behaviors of multi-scale gas-liquid interfaces in the multi-pass distributor were simulated because droplets that were smaller than the grid size could be simulated without numerical diffusion through the gas-liquid interfaces. The effect of the connecting angle of the bend pipe was studied in the two-pass distributor, whereas the effects of the tube’s position relative the distributor inflow and the effect of gravity were investigated in the multi-pass distributor. The model was validated against multiple experimental data taken from an at-scale physical model. We found that keeping the liquid at the inlets of the multi-pass tubes was important for ensuring a uniform distribution.

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