PIV-PLIF Experiment on Modification of Turbulent Scalar Diffusion Near the Wall by Uniform Blowing

2015 ◽  
Author(s):  
Hideaki Sugioka ◽  
Zaiguo Fu ◽  
Takahiro Tsukahara ◽  
Yasuo Kawaguchi
Keyword(s):  
Mass Transfer ◽  
Mass Transfer Rate ◽  
Porous Wall ◽  
Industrial Applications ◽  
Wall Turbulence ◽  
Small Scale ◽  
Turbulence Energy ◽  
Turbulent Schmidt Number ◽  
Heat Transfers ◽  
Scalar Diffusion

The transfer phenomena of wall turbulence are associated with the quasi ordered vortex structures, which are developed from small scale vortices near the wall. How to change the turbulent motion and turbulent transfer by modifying the condition of near wall is important for academic and industrial applications in the control of mass and heat transfers. In this study, we examined experimentally the effect on changing mass transfer in channel turbulence by uniform blowing from a porous wall. We used PIV/PLIF simultaneous measurement by mixing fluorescent dye into blown fluids to observe the spatial evolution of mass transfer in turbulence and analyzed flow fields from the view point of turbulence statistics. It was found that blowing enhanced fluctuation of disturbance and along with it, the coefficients of skin friction and mass transfer rate were increased. On the other hand, the isotropy of turbulence and turbulent Schmidt number were almost not changed. We concluded that there are universality in redistribution of turbulence energy and similar relationship between momentum and mass transfer.

scholarly journals Gas-solid and gas-liquid mass transfer: Effect of turbulent Schmidt number

2007 ◽  
Vol 13 (3) ◽  
pp. 167-168 ◽  
Author(s):  
Aleksandar Dudukovic ◽  
Rada Pjanovic
Keyword(s):  
Mass Transfer ◽  
Eddy Viscosity ◽  
Schmidt Number ◽  
Mass Transfer Rate ◽  
Transfer Effect ◽  
Transfer Coefficients ◽  
Mass Transfer Effect ◽  
Liquid Mass ◽  
Turbulent Schmidt Number ◽  
Liquid Mass Transfer

The scope of this paper is to explain effect of eddy viscosity and turbulent Schmidt number on mass transfer rate. New, theoretically based correlation for gas-liquid mass transfer coefficients are proposed.

Enhancement of Turbulent Shear Stress and Mass Transfer in Wall Turbulence Accompanied With Wall Blowing

2016 ◽  
Author(s):  
Yushi Okamura ◽  
Hideaki Sugioka ◽  
Yasuo Kawaguchi
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Spatial Distribution ◽  
Solid Wall ◽  
Structural Parameters ◽  
Wall Turbulence ◽  
Experimental Result ◽  
Turbulent Shear ◽  
Eddy Structure ◽  
Turbulent Schmidt Number

Spatial distribution of velocity and mass concentration fluctuation in turbulent channel flow with wall blowing were simultaneously measured by PIV/PLIF. The recorded pictures were analyzed to clarify the turbulent momentum and mass transfer from statistical view point and from spatial evolution of coherent eddy structure. Experimental result revealed that the Reynold shear stress and turbulent intensity are enhanced as the blowing rate increasing. On the other hand, structural parameters based on local turbulence such as turbulent Schmidt number and a degree of turbulent anisotropy is not affected by wall blowing. In comparison without wall blowing, we found that the turbulent eddy structure locates apart from the wall. Besides, energy spectrum and swirling strength is also enhanced by wall blowing. It is associated with increase of resistance by wall blowing. Generally in wall turbulence, fluctuation motions are restricted by the presence of solid wall. But for the blowing from the wall relaxes this restriction and Reynolds shear stress is enhanced, which leads to enhancement of turbulent mass flux. Moreover, from results of spatial distribution of instantaneous fields, wall-blowing helps development of hairpin vortexes. It is concluded that development of hairpins leads to enhancement of turbulent mass transfer.

scholarly journals Mass transfer effects in 2-D dual-permeability modeling of field preferential bromide leaching with drain effluent

2011 ◽  
Vol 8 (3) ◽  
pp. 5917-5967
Author(s):  
H. H. Gerke ◽  
J. Dusek ◽  
T. Vogel
Keyword(s):  
Mass Transfer ◽  
Preferential Flow ◽  
Mass Transfer Rate ◽  
Variable Mass ◽  
Chemical Properties ◽  
Small Scale ◽  
Transfer Coefficients ◽  
Permeability Model ◽  
Soil Matrix ◽  
Mass Transfer Coefficients

Abstract. Subsurface drained experimental fields are frequently used for studying preferential flow (PF) in structured soils. Considering two-dimensional (2-D) transport towards the drain, however, the relevance of mass transfer coefficients, apparently reflecting small-scale soil structural properties, for the water and solute balances of the entire drained field is largely unknown. This paper reviews and analyzes effects of mass transfer reductions on Br− leaching for a subsurface drained experimental field using a numerical 2-D dual-permeability model (2D-DPERM). The sensitivity of the "diffusive" mass transfer component on bromide (Br−) leaching patterns is discussed. Flow and transport is simulated in a 2-D vertical cross-section using parameters, boundary conditions (BC), and data of a Br− tracer irrigation experiment on a subsurface drained field (5000 m2 area) at Bokhorst (Germany), where soils have developed from glacial till sediments. The 2D-DPERM simulation scenarios assume realistic irrigation and rainfall rates, and Br-application in the soil matrix (SM) domain. The mass transfer reduction controls preferential tracer movement and can be related to physical and chemical properties at the interface between flow path and soil matrix in structured soil. A reduced solute mass transfer rate coefficient allows a better match of the Br− mass flow observed in the tile drain discharge. The results suggest that coefficients of water and solute transfer between PF and SM domains have a clear impact on Br− effluent from the drain. Amount and composition of the drain effluent is analyzed as a highly complex interrelation between temporally and spatially variable mass transfer in the 2-D vertical flow domain that depends on varying "advective" and "diffusive" transfer components, the spatial distribution of residual tracer concentrations, and the lateral flow fields in both domains from plots of the whole subsurface drained field. The local-scale soil structural effects (e.g., such as macropore wall coatings), here conceptualized as changes in mass transfer coefficients, can have a clear effect on leaching at the plot and field-scales.

Fabrication and Characterization of a Metal-Based Micro-Heat Exchanger by Electrodeposition Technique

2012 ◽  
Author(s):  
E. Ogbonnaya ◽  
L. Weiss
Keyword(s):  
Mass Transfer ◽  
Heat Exchanger ◽  
Transfer Rate ◽  
Thermal Power ◽  
Mass Transfer Rate ◽  
Working Fluid ◽  
Small Scale ◽  
Energy Scavenging ◽  
Nickel Surface ◽  
Micro Heat Exchanger

The investigation of a small-scale, MEMS-based heat exchanger is reported in this work. The Exchanger is based on capillary action and is designed for use in low-temperature thermal energy scavenging applications. The device is a microfabricated design, employing unique nickel channels for capillary effect. Fabrication of the nickel channels is based on processes that pattern and develop SU-8 negative photoresist on the substrate. Electroplating is then used to form metal channels between the bounding SU-8 structures. The removal of the SU-8 leaves only the metallic channels behind. Channels are fabricated to heights of 115 μm using these methods. The operation of this micro heat exchanger (MHE) is compared to other exchangers fabricated with SU-8 channels. Working fluid mass transfer rate from the heated MHE is utilized as a basic metric of operation. The mass transfer rate recorded from the nickel-based MHE is 2.51 mg/s. By contrast, an MHE fabricated with 150 μm tall SU-8 channels is shown to evaporate up to 3.01 mg/s. This translates into an effective thermal power consumption rate of 1.92 kW/m2 and 2.28 kW/m2 for the nickel and SU-8 based MHE respectively. Investigations of working fluid contact angle with the electroplated nickel surface are also presented. The surface is found to be a porous structure stemming from the electroplating process.

Free Convective Mass Transfer at Isosceles Triangular Surfaces of Varying Inclination

2003 ◽  
Vol 68 (11) ◽  
pp. 2080-2092 ◽  
Author(s):  
Martin Keppert ◽  
Josef Krýsa ◽  
Anthony A. Wragg
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Mass Transfer Process ◽  
Sulfate Solution ◽  
Convective Mass Transfer ◽  
Varying Length ◽  
Inclined Surface ◽  
Vertical Case ◽  
Limiting Diffusion Current

The limiting diffusion current technique was used for investigation of free convective mass transfer at down-pointing up-facing isosceles triangular surfaces of varying length and inclination. As the mass transfer process, copper deposition from acidified copper(II) sulfate solution was used. It was found that the mass transfer rate increases with inclination from the vertical to the horizontal position and decreases with length of inclined surface. Correlation equations for 7 angles from 0 to 90° were found. The exponent in the ShL-RaL correlation ranged from 0.247 for the vertical case, indicating laminar flow, to 0.32 for inclinations of 60 to 90°, indicating mixed or turbulent flow. The general correlation ShL = 0.358(RaL sin θ)0.30 for the RaL sin θ range from 7 × 106 to 2 × 1011 and inclination range from 15 to 90° was obtained.

Numerical Approaches for Modeling Gas–Solid Fluidized Bed Reactors: Comparison of Models and Application to Different Technical Problems

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Peter Ostermeier ◽  
Annelies Vandersickel ◽  
Stephan Gleis ◽  
Hartmut Spliethoff
Keyword(s):  
Calcium Carbonate ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Fluid Model ◽  
Industrial Applications ◽  
Small Scale ◽  
Fluidized Bed Reactors ◽  
Discrete Phase Model ◽  
Technical Problems ◽  
Numerical Approaches

Gas–solid fluidized bed reactors play an important role in many industrial applications. Nevertheless, there is a lack of knowledge of the processes occurring inside the bed, which impedes proper design and upscaling. In this work, numerical approaches in the Eulerian and the Lagrangian framework are compared and applied in order to investigate internal fluidized bed phenomena. The considered system uses steam/air/nitrogen as fluidization gas, entering the three-dimensional geometry through a Tuyere nozzle distributor, and calcium oxide/corundum/calcium carbonate as solid bed material. In the two-fluid model (TFM) and the multifluid model (MFM), both gas and powder are modeled as Eulerian phases. The size distribution of the particles is approximated by one or more granular phases with corresponding mean diameters and a sphericity factor accounting for their nonspherical shape. The solid–solid and fluid–solid interactions are considered by incorporating the kinetic theory of granular flow (KTGF) and a drag model, which is modified by the aforementioned sphericity factor. The dense discrete phase model (DDPM) can be interpreted as a hybrid model, where the interactions are also modeled using the KTGF; however, the particles are clustered to parcels and tracked in a Lagrangian way, resulting in a more accurate and computational affordable resolution of the size distribution. In the computational fluid dynamics–discrete element method (CFD–DEM) approach, particle collisions are calculated using the DEM. Thereby, more detailed interparticulate phenomena (e.g., cohesion) can be assessed. The three approaches (TFM, DDPM, CFD–DEM) are evaluated in terms of grid- and time-independency as well as computational demand. The TFM and CFD–DEM models show qualitative accordance and are therefore applied for further investigations. The MFM (as a variation of the TFM) is applied in order to simulate hydrodynamics and heat transfer to immersed objects in a small-scale experimental test rig because the MFM can handle the required small computational cells. Corundum is used as a nearly monodisperse powder, being more suitable for Eulerian models, and air is used as fluidization gas. Simulation results are compared to experimental data in order to validate the approach. The CFD–DEM model is applied in order to predict mixing behavior and cohesion effects of a polydisperse calcium carbonate powder in a larger scale energy storage reactor.

Numerical simulation and experimental investigation of multiphase mass transfer process for industrial applications in China

2019 ◽  
Vol 36 (1) ◽  
pp. 187-214
Author(s):  
Chao Yang ◽  
Guangsheng Luo ◽  
Xigang Yuan ◽  
Jie Chen ◽  
Yangcheng Lu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Transfer Process ◽  
Transport Phenomena ◽  
Measurement Techniques ◽  
Mass Transfer Process ◽  
Industrial Applications ◽  
Economic Benefits ◽  
Distillation Columns ◽  
Stirred Reactors

Abstract This paper presents a comprehensive review of the remarkable achievements by Chinese scientists and engineers who have contributed to the multiscale process design, with emphasis on the transport mechanisms in stirred reactors, extractors, and rectification columns. After a brief review of the classical theory of transport phenomena, this paper summarizes the domestic developments regarding the relevant experiments and numerical techniques for the interphase mass transfer on the drop/bubble scale and the micromixing in the single-phase or multiphase stirred tanks in China. To improve the design and scale-up of liquid-liquid extraction columns, new measurement techniques with the combination of both particle image velocimetry and computational fluid dynamics have been developed and advanced modeling methods have been used to determine the axial mixing and mass transfer performance in extraction columns. Detailed investigations on the mass transfer process in distillation columns are also summarized. The numerical and experimental approaches modeling transport phenomena at the vicinity of the vapor-liquid interface, the point efficiency for trays/packings regarding the mixing behavior of fluids, and the computational mass transfer approach for the simulation of distillation columns are thoroughly analyzed. Recent industrial applications of mathematical models, numerical simulation, and experimental methods for the design and analysis of multiphase stirred reactors/crystallizers, extractors, and distillation columns are seen to garnish economic benefits. The current problems and future prospects are pinpointed at last.

Distributed mass transfer rate for modelling the leaching of porous granular materials containing soluble pollutants

2000 ◽  
Vol 55 (7) ◽  
pp. 1257-1267 ◽  
Author(s):  
Tiruta-Barna Ligia ◽  
Barna Radu ◽  
Moszkowicz Pierre ◽  
Bae Hae-Ryong
Keyword(s):  
Mass Transfer ◽  
Granular Materials ◽  
Transfer Rate ◽  
Mass Transfer Rate
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