Steady-State and Dynamic Mass Transfer of Gases in Porous Materials

1997 ◽  
Vol 62 (7) ◽  
pp. 1043-1056 ◽  
Author(s):  
Axel Tuchlenski ◽  
Oliver Schramm ◽  
Andreas Seidel-Morgenstern
Keyword(s):  
Mass Transfer ◽  
Steady State ◽  
Binary Mixtures ◽  
Dusty Gas ◽  
Diffusion Cell ◽  
Transport Parameters ◽  
Dynamic Mass ◽  
Model Predictions ◽  
Dynamic Diffusion ◽  
Good Agreement

The diffusion of binary gas mixtures through a porous asymmetric tubular membrane has been studied experimentally. A modified Wicke-Kallenbach diffusion cell consisting of two gas compartments separated by the membrane was used. Steady-state experiments with pure gases and binary mixtures were carried out in order to determine the transport parameters of the membrane with respect to the dusty gas model. To verify these parameters, the dynamic transport of binary mixtures was examined applying the dynamic diffusion cell technique proposed by Novak et al. The measured transients were in relative good agreement with the model predictions.

Dynamic Gas Transport in Porous Bidispersed Alumina

1998 ◽  
Vol 63 (11) ◽  
pp. 1954-1962
Author(s):  
Vladimír Hejtmánek ◽  
Pavel Čapek ◽  
Olga Šolcová ◽  
Petr Schneider
Keyword(s):  
Optimization Algorithm ◽  
Inert Gases ◽  
Dusty Gas ◽  
Diffusion Cell ◽  
Transport Parameters ◽  
Transport Models ◽  
The Mean ◽  
Temporary Rise ◽  
Experimental Pressure ◽  
Good Agreement

A spontaneous temporary rise in the pressure gradient through countercurrent binary transport of inert gases in porous bidispersed alumina was observed in diffusion cell of the Wicke-Kallenbach type. Experimental pressure responses to gas step changes were detected and fitted to a set of partial differential equations. These were based on the transport models Mean Transport Pore Model (MTPM) and Dusty Gas Model (DGM). The dynamic set transport parameters 〈r〉, 〈r2〉 and ψ for both models were obtained using an optimization algorithm and discussed. It was found that the values of the transport radius 〈r〉 are in a good agreement with the mean radius obtained from the measurement of alumina texture.

scholarly journals Experimental results of wake steering using fixed angles

2021 ◽  
Author(s):  
Paul Fleming ◽  
Michael Sinner ◽  
Tom Young ◽  
Marine Lannic ◽  
Jennifer King ◽  
...  
Keyword(s):  
Steady State ◽  
Experimental Design ◽  
Wind Turbine ◽  
Wind Direction ◽  
Wind Farm ◽  
Engineering Model ◽  
Important Data ◽  
Model Predictions ◽  
Wake Model ◽  
Good Agreement

Abstract. In this article, the authors present a test of wake steering at a commercial wind farm. A single fixed yaw offset, rather than an optimized offset schedule, is alternately applied to an upstream wind turbine and the effect on downstream turbines is analyzed. This experimental design allows for comparison with engineering wake models independent of the controller's ability to track a varying offset and correctly measure wind direction. Additionally, by applying the same offset in beneficial and detrimental conditions, we are able to collect important data for assessing second-order wake model predictions. Results of the article from collected data show good agreement with the FLOw Redirection and Induction in Steady State (FLORIS) engineering model and offer support for the asymmetry of wake steering predicted by newer models, such as the Gauss-curl hybrid model.

Heat and mass transfer in wood composite panels during hot pressing: Part 4. Experimental investigation and model validation

Holzforschung ◽  
2007 ◽  
Vol 61 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Chunping Dai ◽  
Changming Yu ◽  
Changyan Xu ◽  
Guangbo He
Keyword(s):  
Mass Transfer ◽  
Experimental Investigation ◽  
Heat And Mass Transfer ◽  
Core Temperature ◽  
Hot Pressing ◽  
Gas Pressure ◽  
Wood Composite ◽  
The Core ◽  
Model Predictions ◽  
Good Agreement

Abstract The effects of panel density and strand size on the temperature and gas pressure inside strand mats during hot pressing has been experimentally investigated. The results show good agreement with model predictions. Strand dimensions have a strong effect on the core temperature and gas pressure when the mat/panel density is relatively high. At lower density, the temperature and gas pressure are controlled only by the panel density. Comparison between the model predictions and experimental results also reveals the need for further characterisation of the basic mat properties, especially conductivity and permeability.

scholarly journals Experimental results of wake steering using fixed angles

2021 ◽  
Vol 6 (6) ◽  
pp. 1521-1531
Author(s):  
Paul Fleming ◽  
Michael Sinner ◽  
Tom Young ◽  
Marine Lannic ◽  
Jennifer King ◽  
...  
Keyword(s):  
Steady State ◽  
Experimental Design ◽  
Wind Turbine ◽  
Wind Direction ◽  
Wind Farm ◽  
Engineering Model ◽  
Important Data ◽  
Model Predictions ◽  
Wake Model ◽  
Good Agreement

Abstract. In this article, the authors present a test of wake steering at a commercial wind farm. A single fixed yaw offset, rather than an optimized offset schedule, is alternately applied to an upstream wind turbine, and the effect on downstream turbines is analyzed. This experimental design allows for comparison with engineering wake models independent of the controller's ability to track a varying offset and correctly measure wind direction. Additionally, by applying the same offset in beneficial and detrimental conditions, we are able to collect important data for assessing second-order wake model predictions. Results of the article from collected data show good agreement with the FLOw Redirection and Induction in Steady State (FLORIS) engineering model and offer support for the asymmetry of wake steering predicted by newer models, such as the Gauss–curl hybrid model.

Cadmium salts transport through a nanofiltration membrane: experimental results and model predictions

1998 ◽  
Vol 38 (4-5) ◽  
pp. 529-535
Author(s):  
Y. Garba ◽  
S. Taha ◽  
N. Gondrexon ◽  
G. Dorange
Keyword(s):  
Transport Mechanism ◽  
Film Theory ◽  
Nanofiltration Membrane ◽  
Permeate Flux ◽  
Transport Parameters ◽  
Model Predictions ◽  
Experimental Values ◽  
Effective Transfer ◽  
Cadmium Salt ◽  
Good Agreement

This article discusses the transport mechanism of cadmium salts (CdCl2, Cd(NO3)2) through a nanofiltration membrane. A model based on the extended Nernst-Planck and the film theory equations is reported. This model is characterized by three transport parameters: the water permeability Lp, the ion transmittance Φ and the effective transfer coefficient Keff. The knowledge of the feed and permeate concentrations and the permeate flux enable the calculation of these parameters. The model was used to predict cadmium salt solution rejection by a NANOMAX 50 membrane. The experimental values and calculated predictions are in good agreement.

Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model

2003 ◽  
Vol 3 (1-2) ◽  
pp. 201-207
Author(s):  
H. Nagaoka ◽  
T. Nakano ◽  
D. Akimoto
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Turbulence Model ◽  
Uptake Rate ◽  
Oscillatory Flow ◽  
Substrate Uptake ◽  
Flow Conditions ◽  
Mass Transfer Mechanism ◽  
Substrate Uptake Rate ◽  
Good Agreement

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.

The effect of two-phase flow regime on hydrodynamics and mass transfer in a horizontal-tube gas-liquid reactor

1985 ◽  
Vol 50 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Andreas Zahn ◽  
Lothar Ebner ◽  
Kurt Winkler ◽  
Jan Kratochvíl ◽  
Jindřich Zahradník
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Flow Regime ◽  
Liquid Flow ◽  
Horizontal Tube ◽  
Liquid Holdup ◽  
Two Phase ◽  
Flow Rates ◽  
Type Relation ◽  
Good Agreement

The effect of two-phase flow regime on decisive hydrodynamic and mass transfer characteristics of horizontal-tube gas-liquid reactors (pressure drop, liquid holdup, kLaL) was determined in a cocurrent-flow experimental unit of the length 4.15 m and diameter 0.05 m with air-water system. An adjustable-height weir was installed in the separation chamber at the reactor outlet to simulate the effect of internal baffles on reactor hydrodynamics. Flow regime maps were developed in the whole range of experimental gas and liquid flow rates both for the weirless arrangement and for the weir height 0.05 m, the former being in good agreement with flow-pattern boundaries presented by Mandhane. In the whole range of experi-mental conditions pressure drop data could be well correlated as a function of gas and liquid flow rates by an empirical exponential-type relation with specific sets of coefficients obtained for individual flow regimes from experimental data. Good agreement was observed between values of pressure drop obtained for weirless arrangement and data calculated from the Lockhart-Martinelli correlation while the contribution of weir to the overall pressure drop was well described by a relation proposed for the pressure loss in closed-end tubes. In the region of negligible weir influence values of liquid holdup were again succesfully correlated by the Lockhart-Martinelli relation while the dependence of liquid holdup data on gas and liquid flow rates obtained under conditions of significant weir effect (i.e. at low flow rates of both phases) could be well described by an empirical exponential-type relation. Results of preliminary kLaL measurements confirmed the decisive effect of the rate of energy dissipation on the intensity of interfacial mass transfer in gas-liquid dispersions.

Nonlinear filter properties of the thick ascending limb

1997 ◽  
Vol 273 (4) ◽  
pp. F625-F634 ◽  
Author(s):  
H. E. Layton ◽  
E. Bruce Pitman ◽  
Leon C. Moore
Keyword(s):  
Steady State ◽  
Frequency Response ◽  
Transit Time ◽  
Concentration Profile ◽  
Tubuloglomerular Feedback ◽  
Thick Ascending Limb ◽  
Transport Parameters ◽  
Nodal Structure ◽  
Nacl Concentration ◽  
Fluid Transit Time

A mathematical model was used to investigate the filter properties of the thick ascending limb (TAL), that is, the response of TAL luminal NaCl concentration to oscillations in tubular fluid flow. For the special case of no transtubular NaCl backleak and for spatially homogeneous transport parameters, the model predicts that NaCl concentration in intratubular fluid at each location along the TAL depends only on the fluid transit time up the TAL to that location. This exact mathematical result has four important consequences: 1) when a sinusoidal component is added to steady-state TAL flow, the NaCl concentration at the macula densa (MD) undergoes oscillations that are bounded by a range interval envelope with magnitude that decreases as a function of oscillatory frequency; 2) the frequency response within the range envelope exhibits nodes at those frequencies where the oscillatory flow has a transit time to the MD that equals the steady-state fluid transit time (this nodal structure arises from the establishment of standing waves in luminal concentration, relative to the steady-state concentration profile, along the length of the TAL); 3) for any dynamically changing but positive TAL flow rate, the luminal TAL NaCl concentration profile along the TAL decreases monotonically as a function of TAL length; and 4) sinusoidal oscillations in TAL flow, except at nodal frequencies, result in nonsinusoidal oscillations in NaCl concentration at the MD. Numerical calculations that include NaCl backleak exhibit solutions with these same four properties. For parameters in the physiological range, the first few nodes in the frequency response curve are separated by antinodes of significant amplitude, and the nodes arise at frequencies well below the frequency of respiration in rat. Therefore, the nodal structure and nonsinusoidal oscillations should be detectable in experiments, and they may influence the dynamic behavior of the tubuloglomerular feedback system.

scholarly journals Steady-state organization of binary mixtures by active impurities

1998 ◽  
Vol 58 (3) ◽  
pp. 3547-3551 ◽  
Author(s):  
Mads C. Sabra ◽  
Henriette Gilhøj ◽  
Ole G. Mouritsen
Keyword(s):  
Steady State ◽  
Binary Mixtures ◽  
State Organization

An Experimental Study of Heat and Mass Transfer During Drying of Packed Beds

1992 ◽  
Vol 114 (3) ◽  
pp. 727-734 ◽  
Author(s):  
W. C. Lee ◽  
O. A. Plumb ◽  
L. Gong
Keyword(s):  
Mass Transfer ◽  
Experimental Study ◽  
Glass Beads ◽  
Drying Rate ◽  
Packed Beds ◽  
Transfer Coefficients ◽  
Model Predictions ◽  
Drying Models ◽  
Surface Saturation ◽  
Drying Conditions

An experimental study has been conducted to provide a data base for drying packed beds of granular, nonhygroscopic materials. Experimental results for drying rate, saturation distribution, temperature distribution, and surface saturation are reported for drying glass beads under carefully documented drying conditions. Capillary pressure for both imbibition and drainage was measured for the glass beads, whose size ranged from 65 μm to 450 μm. The drying results demonstrate that, contrary to available model predictions, porous materials do not necessarily exhibit saturation gradients that always increase with distance from the drying surface. Under certain conditions the capillary potential is sufficient to create an internal drying front. The measurements of surface saturation are the first to be reported. They are utilized to speculate on the reasons for the failure of drying models to compare well with experiment without adjusting the convective heat or mass transfer coefficients.

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