Flux measurement

Remick and Geankoplis made flux measurements for both species in the isobaric diffusion of nitrogen and helium through their tube bundle. Pressures spanned the interval from 0.444 nim, Hg to 300,2 ram Hg, which should cover the whole range between the limits of Knudsen streaming and bulk diffusion control. Then, since K and K, are known in this case, the form of the proposed flux relations could be tested immediately by plotting the left hand side of equation (10.15) against... 

They then compared measured and predicted fluxes for diffusion experiments in the mixture He-N. The tests covered a range of pressures and a variety of compositions at the pellet faces but, like the model itself, they were confined to binary mixtures and isobaric conditions. Feng and Stewart [49] compared their models with isobaric flux measurements in binary mixtures and with some non-isobaric measurements in mixtures of helium and nitrogen, using data from a variety of sources. Unfortunately the information on experimental conditions provided in their paper is very sparse, so it is difficult to assess how broadly based are the conclusions they reached about the relative merits oi their different models. 

In general, tests have tended to concentrate attention on the ability of a flux model to interpolate through the intermediate pressure range between Knudsen diffusion control and bulk diffusion control. What is also important, but seldom known at present, is whether a model predicts a composition dependence consistent with experiment for the matrix elements in equation (10.2). In multicomponent mixtures an enormous amount of experimental work would be needed to investigate this thoroughly, but it should be possible to supplement a systematic investigation of a flux model applied to binary systems with some limited experiments on particular multicomponent mixtures, as in the work of Hesse and Koder, and Remick and Geankoplia. Interpretation of such tests would be simplest and most direct if they were to be carried out with only small differences in composition between the two sides of the porous medium. Diffusion would then occur in a system of essentially uniform composition, so that flux measurements would provide values for the matrix elements in (10.2) at well-defined compositions. 

On the other hand, if the flux measurements were to be interpreted by... 

As In the case of the isobaric experiment, it would also be possible to interpret these flux measurements in terms of a Fick equation with an effective... 

Wicke-Kallenbach experiment would incorrectly predict the flux in the second experiment if used in a simple Fick equation of the form (10.31). However, if the isobaric flux measurements had been interpreted in terms of... 

Spunbonded fabrics are effective filters in that they are layered stmctures of relatively fine fibers, the three-dimensional stmcture of which creates a torturous path. Even relatively thin spunbonded fabrics (eg, 0.2—0.25 mm) present a significant challenge to the passage of soil fines and are suitable for use in some filtration appHcations. The porosity of geotextile fabrics is classified by means of several procedures such as flux (volume flow/area per time) and equivalent opening size (EOS), which is a measure of the apparent pore size of the openings in the fabric. The flux measures the porosity to Hquid water, and the EOS measures the porosity to soHd particles of a known diameter. Literature is available on limitations of particular styles of fabrics within an apphcation (63). 

F or NjO, estimates of soil emissions are perhaps slightly more straightforward, simply because so much more information on soil NjO emissions is available. For agricultural soils, estimates as a percentage of fertilizer input have been published " and, for the remaining land use classes listed in Table 5, mean annual emissions from a series of long-term flux measurements are available. The total annual soil NjO emissions for the ElK (27 kt N) are very similar to the annual soil NO emissions. Soils, however, have by far a greater impact on the... 

Berry, S., and Rnmberg, B., 1996. H" /ATP coupling ratio at the unmodulated CFiCFq-ATP synthase determined by proton flux measurements. 

Fig. 10-15 Organic carbon fluxes with depth in the water column normalized to mean annual primary production rates at the sites of sediment trap deployment. The undulating line indicates the base of the euphotic zone the horizontal error bars reflect variations in mean annual productivity as well as replicate flux measurements during the same season or over several seasons vertical error bars are depth ranges of several sediment trap deployments and uncertainities in the exact depth location. (Reproduced with permission from E. Suess (1980). Particulate organic carbon flux in the oceans - surface productivity and oxygen utilization, Nature 288 260-263, Macmillan Magazines.)...

Table 19-1 Radiatively important trace species in the atmosphere. Percent change in flux measured relative to the pre-industrial time...

The heat flux measured during the reaction was integrated. The heat of reaction at - 10°C has thus been calculated as 2.84 kcal/gr-mol "product BrCl". Since for each mole of BrCl 0.5 moles chlorine needed to be condensed and cooled from room temperature, releasing a heat of 2.54 kcal/gr-mol, the heat of reaction from liquid chlorine at the same temperature would be 0.3 kcal/gr-mol "product BrCl". For the degree of dissociation quoted above, i.e. 48 %, the heat of reaction in the liquid phase is obtained as 0.6 kcal/gr-mol, in conformance with the data in (ref. 2). 

Figure 5. Comparison between fluxes measured in shallow sediment traps and those calcnlated for the same depth and time from the " Th deficit in the overlying water colnmn. The data were compiled from many studies and the right-hand scale shows the factor of positive or negative offset between the two data sets. Significant differences are common and are linked to the varions assumptions and constraints of the two approaches for measnring POC finx. [Reprinted from Nature, Vol. 353, Buesseler, pp. 420-423, 1991, Macmillan Publishers Ltd.]...

The fluxes of POC determined by the " Th method applied to the world s oceans are summarized in Table 1. Where possible we have tabulated the ratio of Th-derived POC export to independent estimates of primary production. As noted above, this ratio, termed the 77i ratio (Buesseler 1998), is important in the euphotic zone carbon balance as it represents the leakage of POC out of the euphotic zone (The ThE ratio is so named to evoke the e ratio, which is defined as the ratio of POC flux measured with sediment traps to primary production). 

Benninger LK (1978) °Pb balance in Long Island Sound. Geochim Cosmochim Acta 42 1165-1174 Berelson WM, Buchholtz MR, Hammond DE, Santschi PH (1987) Radon fluxes measured with the MANOP bottom lander. Deep-Sea Res 34 1209-1228... 

Israel, S., J. F. Casterline, and B. Matzner, 1969, Critical Heat Flux Measurements in a 16-Rod Simulation of BWR Fuel Assembly, J. Heat Transfer 97 355, ASME, New York. (5)... 

Lienhard, J. H., V. K. Dhir, and D. M. Riherd, 1973c, Peak Pool Boiling Heat Flux Measurement on Finite Horizontal Flat Plates, Trans. ASME, J. Heat Transfer 95(4) 477-482. (2)... 

Matzner, B., J. E. Casterline, E. O. Moech, and G. A. Wilkhammer, Experimental Critical Heat Flux Measurement Applied to a Boiling Reactor Channel, ASME Paper 66-WA/HT-46, Winter Annual... 

Divide every scattering pattern and every background by the actual incident flux measured by the first ionization chamber, and divide it by the actual exposure time. 

The Experimental Determination of the Absorption Factor is based on two flux measurements by means of ionization chambers, one placed before (7i),... 

The thickness of the downflowing layers at the wall of the CFB is typically defined as the distance from the wall to the position of zero vertical solid flux. Measurements of the layer thickness were made on a 12 MW and 165 MW CFB boiler by Zhang, Johnsson and Leckner (1995). They found that the thickness increased for the larger bed. They related data from many different beds (Fig. 19), with the equivalent bed diameter, taken as the hydraulic diameter, using the following form... 

The objective of the present study is to develop a cross-flow filtration module operated under low transmembrane pressure drop that can result in high permeate flux, and also to demonstrate the efficient use of such a module to continuously separate wax from ultrafine iron catalyst particles from simulated FTS catalyst/ wax slurry products from an SBCR pilot plant unit. An important goal of this research was to monitor and record cross-flow flux measurements over a longterm time-on-stream (TOS) period (500+ h). Two types (active and passive) of permeate flux maintenance procedures were developed and tested during this study. Depending on the efficiency of different flux maintenance or filter media cleaning procedures employed over the long-term test to stabilize the flux over time, the most efficient procedure can be selected for further development and cost optimization. The effect of mono-olefins and aliphatic alcohols on permeate flux and on the efficiency of the filter membrane for catalyst/wax separation was also studied. 

Fig. 6 Cumulated proportion of the contributions of each part of the basin to the TDS flux measured in Tortosa. Note that data are not available for all the hydrological years. Years with data for all stations are highlighted in yellow...

Fig. 3.20. Idealized continuum and actual fluxes measured in 50-A-wide bands of A7 stars in the Hyades open cluster with Teff = 8000 K, plotted against inverse wavelength in turn-1. Horizontal lines above the spectrum show the locations of the Johnson U, B, V pass bands and the vertical boxes show schematically the corresponding properties of the Stromgren system with central wavelengths in A. (In that system, there are actually two H/3 pass bands, one narrow and one broad, so that comparison of the two gives a measure of the strength of the line.) Some prominent spectral features are marked.

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