Flux measurement conversion

The most important assumption that wiU be made in field use is that a measured efflux J corresponds to a steady state flux, J s- In many situations, corrosion activity will vary with time, and a spot flux measurement conversion should be viewed as yielding a minimum hydrogen activity at the entry face, irrespective of whether the flux is rising or faUing. Ahigh degree of confidence can obtained from low variance of efflux registered over time periods, as... 

For the sake of brevity only a few graphs on mass flux of conversion gas will be presented in this summary. The reader is referred to Paper IV for more detailed measurements of stoichiometry and air factors. 

Several studies have investigated empirically the flux of chemicals within snow or between snow and the atmosphere (Guimbaud et al., 2002 Albert and Shultz, 2002 Herbert et al., 2006). In particular, measured concentration gradients within the atmospheric boundary layer or within the snow pack have been used to calculate a chemical s flux into or out of the snow pack. This approach has resulted in miscellaneous parameterizations to calculate fluxes of, for example, carbonyl compounds and NO c species from the snow pack as a result of photochemical processes in snow (Domind and Shepson, 2002 Hutterli et al., 1999 Guimbaud et al., 2002 Grannas et al., 2002). However, flux measurements can only be used to derive kinetic transport parameters, such as diffusivities and mass transport coefficients, if the chemicals involved are reasonably persistent and do not undergo rapid conversions within the snow pack. For example, measurements of the flux of carbonyl compounds out of snow are more likely to reflect the kinetics of formation in the snow pack than the kinetics of snow-air gas exchange. As a result, there is a very limited number of experimental studies that provide quantitative information on the rate of chemical transport in snow. 

Radial density gradients in FCC and other large-diameter pneumatic transfer risers reflect gas—soHd maldistributions and reduce product yields. Cold-flow units are used to measure the transverse catalyst profiles as functions of gas velocity, catalyst flux, and inlet design. Impacts of measured flow distributions have been evaluated using a simple four lump kinetic model and assuming dispersed catalyst clusters where all the reactions are assumed to occur coupled with a continuous gas phase. A 3 wt % conversion advantage is determined for injection feed around the riser circumference as compared with an axial injection design (28). 

The lack of precise measurements of environmentally relevant chemical rate constants limits the number of quantitative evaluations of the importance of complex dynamics on uptake fluxes. Nonetheless, examples involving bicarbon-ate-CC>2 conversion [69,88] and trace metal complexation [8,46,325] have been examined theoretically in the literature. For example, comparison of the diffu-sional and reactional timescale allowed Riebesell and collaborators [69,88] to show that bicarbonate conversion to CO2 did not generally enhance the... 

The pot furnace was constructed so that the radiant heat flux, which would prevail at the top of the fuel bed in a traveling grate stoker or incinerator, could be simulated under batch conditions. The burning rates could be determined by measuring the weight loss of the fuel bed as a function of time. The pot was constructed in two sections (Figure 1)- the overbed section (combustion system) and the fuel bed section (conversion system). Secondary air (overfire air) was supplied at a number of... 

However, it is possible to directly or indirectly measure the mass flux (mass flow) of conversion gas. Several authors have measured the mass loss of the fuel bed as function of primary air velocities and biofuel [12,33,38,53] by means of a balance. Most of them have used the over-fired batch conversion concept. They utilise the relationship illustrated by Eq. 16 (formulised in amounts instead of flows) above and the assumption that no ash is entrained. As a consequence, the mass loss of the batch bed with time equals the conversion gas. In the simple three-step model [3], an assumption of steady state is made, which is not relevant for batch studies. If it is practically possible, the method of using a balance to measure the conversion gas rate is especially appropriate for transient processes, that is, batch processes. 

In this expression, x is the independent variable of measurement, whether it be wavelength, wave number, or other parameter. The quantity UM(x) is the flux, as measured by the spectrometer, after it has passed through the absorbing sample. The quantity BM(x) represents the flux that has passed over an identical path but in the absence of an absorbing sample. The term Dm(x) represents any additive offsets that might be introduced by stray flux, errors in electronic amplification and digital conversion, or other causes. We call the resulting measured transmittance TM(x). 

Negligible and medium interaction regimes. Experiments were carried out with an aqueous 2.0 M DIPA solution at 25 °C in a stirred-cell reactor (see ref. [1]) and a 0.010 m diameter wetted wall column (used only in negligible interaction regime, see ref. [4,5]). Gas and liquid were continuously fed to the reactors mass transfer rates were obtained from gas-phase analyses except for CO2 in the wetted wall column where due to low C02 gas-phase conversion, a liquid-phase analysis had to be used [5]. In the negligible interaction regime some 27 experiments were carried out in both reactors. The selectivity factors were calculated from the measured H2S and CO2 mole fluxes and are plotted versus k... 

Experimental measurements of absorption fluxes and colour development for the gas-liquid reaction between sulphur trioxide and dodecylbenzene have been carried out in a stirred cell absorber. A model with two parallel reaction paths representing sulphonation and discolouration has been applied to analyse the exothermic absorption accompanying conversions up to 70%. The results show that the two reactions have similar activation energies and that temperature increases greater than 100°C occur at the interface during absorption. The absorption enhancement factor exhibits a maximum value as liquid phase conversion proceeds. 

At present, we are not able to meet all the requirements for a proper quantification of the carbon content of P. pouchetii colonies. Neither can we assure that the vertical fluxes of P. pouchetii colonies are reliable, as fragmentation of colonies can overestimate the colony vertical flux in terms of number. Similarly, dissolution of colonies may lead to an underestimation of the colony number and size. Through tedious microscopical analysis we do, however, have reliable measurements of depth-dependent vertical fluxes of Phaeocystis spp. cells (Figs. 1, 2). To provide a preliminary determination of the potential contribution of Phaeocystis spp. carbon to the vertical POC export at 100 m, we select available carbon conversion rates for other Phaeocystis spp. species. 

The potential underestimation of Phaeocystis spp. carbon by only including cell carbon is thus not likely to be >40%. Based on measurements of vertical flux around 100 m depth from Antarctica, the coastal North Sea, North Norwegian fjords, the Barents Sea and the Arctic Ocean (Fig. 5), the average carbon contribution from Phaeocystis spp. to the POC flux will increase from 3% to <5% by including mucus carbon. Despite the lack of appropriate species-specific carbon conversion rates for all Phaeocystis species, the evidence clearly indicates that Phaeocystis spp. mucus, sinking as intact colonies with cells, is not significantly contributing to the total POC export. 

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