scholarly journals CFD Investigation of the Effect of the Feed Spacer on Hydrodynamics in Spiral Wound Membrane Modules

2018 ◽  
Vol 23 (4) ◽  
pp. 80 ◽  
Author(s):  
Zhiming Han ◽  
Mitsuharu Terashima ◽  
Bing Liu ◽  
Hidenari Yasui
Keyword(s):  
Shear Stress ◽  
Friction Factor ◽  
Dead Zone ◽  
Three Dimensional ◽  
Flow Profile ◽  
Power Number ◽  
Contour Plots ◽  
Computational Fluid Dynamics Cfd ◽  
Membrane Modules ◽  
Spiral Wound

Spacers are designed to create a feed channel, but they are also obstacles to the flow in spiral wound membrane modules. The geometry of the feed spacer influences the flow pattern, which was investigated by using a three-dimensional Computational Fluid Dynamics (CFD) model. For the conventional feed spacer, unavoidable disadvantages were caused by its line contact with the membrane. The pillar-like feed spacer was designed to achieve area contact, which made it possible to enhance the porosity and minimize the adverse effects from the dead zone caused by the transverse filament. Through reductions in the connecting filament’s diameter, the channel porosity reached 0.979. Regarding the maximum porosity, the dimensionless power number was reduced by 47.31% at Reynolds number 150 in comparison with a previously studied commercial spacer. Furthermore, a modified friction factor, as a dimensionless parameter, was employed to investigate the shear stress at the membrane’s surface. At dimensionless power number 106, the enhancement of the modified friction factor increased by approximately 22.27% in comparison with the results of a previous study. Based on the numerical prediction, the homogenization of shear stress distribution, which changed the flow profile near the membrane, was featured through contour plots.

scholarly journals Impact of Modified Spacer on Flow Pattern in Narrow Spacer-Filled Channels for Spiral-Wound Membrane Modules

Environments ◽  
2018 ◽  
Vol 5 (11) ◽  
pp. 116
Author(s):  
Zhiming Han ◽  
Mitsuharu Terashima ◽  
Bing Liu ◽  
Hidenari Yasui
Keyword(s):  
Shear Stress ◽  
Flow Pattern ◽  
Friction Factor ◽  
Flow Direction ◽  
Dead Zone ◽  
Three Dimensional ◽  
Stress Contour ◽  
Directional Change ◽  
Low Shear Stress ◽  
Membrane Modules

A modified spacer, which was constructed with arched filaments and zigzag filaments, was designed to improve vortex shedding and generate a directional change in flow patterns of membrane modules, especially in the vicinity of the feed spacer filament, which is most affected by fouling. A unit cell was investigated by using a three-dimensional computational fluid dynamics (CFD) model for hydrodynamic simulation. The results of CFD simulations were carried out for the fluid flow in order to understand the effect of the modified spacer on vortices to the performance of arched filaments at different distances. From 2D velocity vectors and shear stress contour mixing, the flow pattern and dead zone flushing were depicted. The ratio of low shear stress area to the total area increased with the inlet velocity closed to 20%. The energy consumption with respect to flow direction for the arched filament was 80% lower than that in the zigzag filament. Compared with previous commercial spacers’ simulation, the friction factor was lower when the main flow was normal to the arched filament and the modified friction factor was close to the commercial spacers. The homogenization was realized through the flow pattern created by the modified spacer.

CFD SIMULATION OF SHEAR STRESS AND SECONDARY FLOWS IN URETHRA

2007 ◽  
Vol 19 (02) ◽  
pp. 117-127 ◽  
Author(s):  
Yang-Yao Niu ◽  
Ding-Yu Chang
Keyword(s):  
Shear Stress ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Normal Female ◽  
Urinary System ◽  
Stress Distributions ◽  
Computational Fluid Dynamics Cfd ◽  
Peak Value ◽  
Lower Urinary

In this work, a preliminary numerical simulation of the lower urinary system using Computational Fluid Dynamics (CFD) is performed. Very few studies have been done on the simulation of three-dimensional urine through the lower urinary system. In this study, a simplified lower urinary model with rigid body assumption is proposed. The distributions of urine flow velocity, wall pressure and shear stress along the urethra are simulated based on MRI scanned uroflowmetry of a normal female. Numerical results show that violent secondary flows appear on the cross surface near the end of the urethra when the inflow rate is increased. The oscillative variation of pressure and shear stress distributions are found around the beginning section of the urethra when flow rate is at the peak value.

scholarly journals CFD simulation of the aeration process and baffle influence in a full-scale commercial flat sheet module

2020 ◽  
Vol 81 (9) ◽  
pp. 2004-2010
Author(s):  
Yingchen Cao ◽  
Bowen Gu ◽  
Alexander Sonnenburg ◽  
Wilhelm Urban
Keyword(s):  
Shear Stress ◽  
Cfd Simulation ◽  
Full Scale ◽  
Membrane Module ◽  
Flat Sheet ◽  
Average Shear ◽  
Computational Fluid Dynamics Cfd ◽  
Membrane Modules ◽  
Aeration Process ◽  
A Minor

Abstract The goal of the present paper is to investigate the aeration process and the enhanced effect of baffles in a full-scale commercial membrane bioreactor (MBR) system configured with a flat sheet (FS) membrane module. Through a computational fluid dynamics (CFD) simulation, two aerated FS membrane modules for full-scale applications with 26 membrane sheets were simulated. The numerical results indicate that the presence of baffles and the distances between the baffle and the outmost membrane sheet have a minor influence on the area-weighted shear stress for full-scale MBRs. In addition, bubble size and the bottom distance between the aerator and membrane bottom do not affect the average shear stress of full-scale FS membrane modules much. However, an increase in air flow rate has a significant effect on the area-weighted shear stress. A large FS membrane module is recommended, as it could achieve the same cleaning effect as the small one with a lower specific aeration demand for membranes.

scholarly journals Computational Fluid Dynamics Modelling of the Heat Pump Drying of Banana: Preliminary Studies

2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Folasayo T Fayose ◽  
Zhongjie Huan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Temperature Distribution ◽  
Heat Pump ◽  
Three Dimensional ◽  
Velocity Gradients ◽  
Contour Plots ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamics Modelling ◽  
Heat Pump Drying

The distribution of local temperature, moisture and velocity gradients obtained in CFD calculations can be used to develop models for predicting the parameters in a drying process. This article reports a preliminary result on the efforts to characterizing the performance of a heat pump dryer using Computational Fluid Dynamics (CFD). A three dimensional, pressure based, transient, laminar, incompressible model of heat pump drying of banana slices using Ansys 14.5 (15), a CFD package- FLUENT was investigated. Turbulent cases were also examined. The geometry was considered as elemental volume with symmetrical walls while the banana slices were designed as solids with pores containing a mixture of water and air. Parameters/variable/geometry investigated include velocity, moisture and temperature distribution of the air within the dryer and of the banana slices. The result of the numerical simulation was validated with experimental results from a heat pump dryer and there were agreements. The model is successful in predicting the temperature profile and mass fraction of moisture. Keywords— Ansys, Banana, Computational Fluid Dynamics (CFD), Contour plots, Drying, Velocity and temperature distribution

scholarly journals X-ray computed tomography reveals that grain protrusion controls critical shear stress for entrainment of fluvial gravels

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 149-153 ◽  
Author(s):  
Rebecca A. Hodge ◽  
Hal Voepel ◽  
Julian Leyland ◽  
David A. Sear ◽  
Sharif Ahmed
Keyword(s):  
Computed Tomography ◽  
Shear Stress ◽  
Three Dimensional ◽  
Critical Shear Stress ◽  
Bedload Transport ◽  
Flow Profile ◽  
X Ray ◽  
Computed Tomography Scanning ◽  
X Ray Computed ◽  
Bed Stability

Abstract The critical shear stress (τc) for grain entrainment is a poorly constrained control on bedload transport rates in rivers. Direct calculations of τc have been hindered by the inability to measure the geometry of in situ grains; i.e., the shape and location of each grain relative to surrounding grains and the bed surface. We present the first complete suite of three-dimensional (3-D) grain geometry parameters for 1055 water-worked grains, and use these to parameterize a new 3-D grain entrainment model and hence estimate τc. The 3-D data were collected using X-ray computed tomography scanning of sediment samples extracted from a prototype scale flume experiment. We find that (1) parameters including pivot angle and proportional grain exposure do not vary systematically with relative grain size; (2) τc is primarily controlled by grain protrusion, not pivot angle; and (3) larger grains experience larger forces as a result of projecting higher into the flow profile, producing equal mobility. We suggest that grain protrusion is a suitable proxy for assessing gravel-bed stability.

Efficiency prediction for storage chambers using computational fluid dynamics

1996 ◽  
Vol 33 (9) ◽  
pp. 163-170 ◽  
Author(s):  
Virginia R. Stovin ◽  
Adrian J. Saul
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Particle Tracking ◽  
Critical Value ◽  
Complex Geometries ◽  
Bed Shear Stress ◽  
Breadth Ratio ◽  
Computational Fluid Dynamics Cfd ◽  
Simulated Flow

Research was undertaken in order to identify possible methodologies for the prediction of sedimentation in storage chambers based on computational fluid dynamics (CFD). The Fluent CFD software was used to establish a numerical model of the flow field, on which further analysis was undertaken. Sedimentation was estimated from the simulated flow fields by two different methods. The first approach used the simulation to predict the bed shear stress distribution, with deposition being assumed for areas where the bed shear stress fell below a critical value (τcd). The value of τcd had previously been determined in the laboratory. Efficiency was then calculated as a function of the proportion of the chamber bed for which deposition had been predicted. The second method used the particle tracking facility in Fluent and efficiency was calculated from the proportion of particles that remained within the chamber. The results from the two techniques for efficiency are compared to data collected in a laboratory chamber. Three further simulations were then undertaken in order to investigate the influence of length to breadth ratio on chamber performance. The methodology presented here could be applied to complex geometries and full scale installations.

Novel Magnetic Resonance Measurements of Fouling in Operating Spiral Wound Reverse Osmosis Membrane Modules

2021 ◽  
Vol 196 ◽  
pp. 117006 ◽  
Author(s):  
Nicholas W. Bristow ◽  
Sarah J. Vogt ◽  
Szilard S. Bucs ◽  
Johannes S. Vrouwenvelder ◽  
Michael L. Johns ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Reverse Osmosis ◽  
Reverse Osmosis Membrane ◽  
Membrane Modules ◽  
Spiral Wound
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