Volumetric flux measurement

Tabachow et al. (2002) conducted and compared the results of nitric oxide (NO) emissions measurements for both in situ field and laboratory experiments from unamended and municipal wastewater treatment plant biosolids-amended soil. Based on matching soil temperatures (within 5°C) and water filled pore space (WFPS) ( 5%), the ratio of volumetric soil water to total porosity of the soil, five of six scenarios showed no statistically significant difference in the NO flux measurements from the laboratory versus the field studies. 

Eor tubular membranes, the permeation flux measurements are generally carried out by a shell-and-tube arrangement as shown in Fig. 13.2 [7]. Since the membrane is plated on the outside of the porous substrate, the feed gas flows upward through the outside of the membrane (shell side), and the permeate gas is collected on the tube side. A purge gas can also be used on the tube side if desired. The upstream pressure is monitored by a capacitance pressure transducer and the permeate side pressure is kept atmospheric. The gas permeation rate (the volumetric flow rate) is measured in the permeate side at atmospheric pressure and room temperature. For mixture experiments, the permeate and retentate can be analyzed by an online gas chromatograph equipped with appropriate detectors, such as Thermal Conductivity Detector (TCD), Flame Ionization Detector (FID) or others, depending on the specific gas mixture... 

FIGURE 5.1 Experimental setup for water flux measurements on PEMs devised by Romero and Merida (2009). A PEM is mounted as a separator between a chamber with a stagnant fluid (liquid water to saturated vapor) and a flow chamber. Gas flows through the flow chamber at a steady volumetric flow rate, V. The partial pressure of water at the inlet, is held constant and the exhaust partial pressure, pout, is recorded over time. (Reprinted from 7. Memhr. ScL, 324, Monroe, C. et al. A vaporization-exchange model for water sorption and flux in Nafion, 1-6, Figures 1,2,3, Copyright (2008) Elsevier. With permission.)... 

The water flux into a cell, and hence the volume increase, is driven by the effective water potential difference between the inside and the outside of the plasmalemma. In calculating an effective water potential difference it is necessary to take account of the reflection coefficient, a, a measure of the degree of semipermeability of the membrane. The volumetric increase in cell size with attendant water influx can be described by ... 

Figure 14 Comparison of actual volumetric water contents (measured by time domain reflectom-etry) and calculated soil-water flux values (Penman equation) at four soil depths...

Optical probes were used to measure the bubble size, frequency and velocity within the dense bed. The bubble velocity for an actively bubbling bed was found to closely agree with the drift flux form proposed by Davidson and Harrison (1963). In contrast, the volumetric flow rate of the bubbles was found to be far less than that predicted by the two-phase hypothesis (Fig. 40). 

Conduction with Heat Source Application of the law of conservation of energy to a one-dimensional solid, with the heat flux given by (5-1) and volumetric source term S (W/m3), results in the following equations for steady-state conduction in a flat plate of thickness 2R (b = 1), a cylinder of diameter 2R (b = 2), and a sphere of diameter 2R (b = 3). The parameter b is a measure of the curvature. The thermal conductivity is constant, and there is convection at the surface, with heat-transfer coefficient h and fluid temperature I. ... 

This volumetric water flux density directed upward at the soil surface equals (1 x 10-8 m3 m-2 s 1)(l mol/18 x 10-6 m3), or 0.6 x 10-3 mol mT s-1 (= 0.6 mmol m-2 s-1). When discussing water vapor movement in the previous section, we indicated that Jm> emanating from a moist shaded soil is usually 0.2 to 1.0 mmol m-2 s-1, so our calculated flux density is consistent with the range of measured values. The calculation also indicates that a fairly large gradient in hydrostatic pressure can exist near the soil surface. 

Denitrification rates in the other two main ODZs, the ETNP and ETSP appear to be about 25 Tg a each Codispoti et al. (2002). In the ETNP denitrification was estimated by the geostrophic flux of nitrate deficit out of the ODZ area, with nitrate deficit determined from nutrient-density relationships (Codispoti, 1973 Codispoti and Richards, 1976). Volumetric estimates of denitrification rate based on ETS activity are in concert with this rate (Codispoti and Richards, 1973 Devol, 1975). The ETSP the denitrification rate is based on measurements of ETS activity (Codispoti and Packard, 1980). As with the Arabian Sea these estimates are again for canonical denitrification. It is likely that processes identified in the Arabian Sea are also occurring in the ETNP and ETSP. Thus, the rate of 25 Tg a might be raised to 50 Tg ar. Given a denitrification rate between 30 and 50 Tg a for each of the major ODZ s, global water-column denitrification would appear to between 90 and 150 Tg a. ... 

Measurement procedure A mixture of gases 1 and 2 flows through the bottom cell and another gas flows through the upper cell compartment (flow-rates of gases in both cells are 150 cm /min). Valves VI and V3 are closed and valve V2 opened at the same time. Movement of the soap film in the burette follows the net diffusion flux. The net volumetric diffusion flux, V, gradually decreased with the increase of the gas 3 concentration in the bottom cell compartment. Net volumetric diffusion flux is determined from the slope at zero time of the V(t) dependence. 

In all ultrafiltration systems reported in the literature, average volumetric flux rates at consecutively increasing lengths along the conduit are not measured. As a result it is not possi-... 

It was shown [3] how expansion measurements enable the permeability of the gels to be evaluated (Fig. 3). The increase in the volume inside the pores of a gel is due to the high thermal expansion coefficient of the liquid and the flux of liquid (time dependent), which is proportional to the pressure gradient, the liquid viscosity, and the gel permeability. The change in the volume of a liquid is related to the volumetric strain of the network. 

Few measurements rely on a single factor velocity, for example, is a product of time and distance—two factors. The volumetric flow rate through an orifice depends on the pressure drop, fluid density, and geometry, which adds up to three factors or more. Thermal conductivity, k, is the ratio of heat flux to temperature gradient— this measurement could have as many as six factors. All factors have an associated uncertainty that contributes to the overall uncertainty of the measurand. 

FIGURE 4.1 Schematic of flux. Imagine water flowing down this tube at a volumetric flow rate of 10 L/s. Dividing this flow rate by the cross-sectional area of the tube (A) gives the flux 7 of water moving down the tube. Fluxes of matter, especially for sohd species, are more commonly measured in molar rather than volumetric terms. In this example, then, the liters of water could be converted to moles. Do you know how ... 

In parallel, the group of Partridge at Oak Ridge National Laboratory developed an in situ capillary sampling technique to study species profiles in automotive catalytic converters. Their technique has meanwhile become commercially available. In this group, also the influence of the probe on the measured concentration profiles was studied for the case of catalytic CO oxidation (Sa et al., 2010). They found a negligible influence of the probe with the capillary in the comer of a channel and an increase of velocity for the channel with probe the volumetric flux was kept constant for all channels in the simulation. 

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