Area velocity

Free area velocity The velocity in a device where the flow is not influenced by... 

Pipe cross-sectional area Velocity, u Reynolds number... 

The ratio of the actual velocity to the speed of sound is called the Mach number M. Hence this equation expresses a relation between the cross-sectional area, velocity, and the local Mach number at any axial position in the nozzle, i.e.,... 

Figure 6 Companson of experimental and calculated effects of monolith length and area velocity AV = volumetnc flow rate/geometric surface area on NO conversion. Channel hydraulic diameter = 6 mm, a = 1 2, T = 380T. feed = 500 ppm NO, 500 ppm SO2. 2% v/v O2, 10% H2O + Nj. (From Ref 40 )...

Figure 7 Expenmental and calculated SO2 conversions over a commercial SCR monolith catalyst as a function of a = NH3/NO feed ratio and of the area velocity AV (From Ref 47 )...

Here, S is the specific surface area of the catalyst, a is the conversion and F is the gas flow. The term FjS is the area velocity. The rate constant depends on the type of catalyst material, the oxygen concentration, and the temperature. Additionally, it was found that the rate constant depends on the velocity in the channels, which implies that transport phenomena have an effect on the NO conversion. 

The aim of the present work was to study the activity of Pt/titania/sepiolite monolithic catalysts prepared with different kinds of titania, in the reduction of NOx with propylene under oxidising conditions. The influence of the source of titania, titania content, heat treatment, presence of water vapour in the gas exhaust and area velocity on the activity, and on the structure and properties of the catalysts were investigated. 

In order to evaluate the behaviour of the catalysts in conditions closer to those of real diesel exhaust, the linear, gas hourly and area velocities were increased, and water was added to the inlet gas mixture. Figure 7 shows the activity of the selected catalyst. A, in the absence and presence of 3 % water in the inlet gas mixture, at a GHSV of 11000 h and an area velocity of 13 Nmh. The area velocity increase from 6 to 13 Nmh (GHSV from 4400 to 11000 h ) induced a decrease in the NO conversion of ca. 15%. The presence of water vapour induced a 5% decrease in activity. This was higher than expected from the observations of Hamada [16], who reported that the NO reduction with propene in oxygen excess on Pt/Al203 was not affected by water. 

A 55% percent NO conversion was achieved at an area velocity of 6 Nmh" in the presence of 10% oxygen. However, this parameter showed to have a strong influence on the NO conversion, lowering it to 40% when approximately doubling the area velocity. The catalyst s activity was also slightly steam sensitive, falling by ca. 5% due to the presence of 3% water. 

Downcomer discharge area Velocity under downcomer... 

EFFECT OF CROSS-SECTIONAL AREA. The relation between the change in cross-sectional area, velocity, and Mach number is useful in correlating the various cases of noz2le flow. Substitution of p from Eq, (6.25) into fhe continuity equation... 

From these results it was clear that the incorporation of nickel was beneficial in both reactions. This increase was especially pronoimced in the reduction of nitric oxide where conversion values of 50% could be achieved working at an area velocity of 4.7 mli . 

The results obtained with SACuNi operating at 8 vol.% O2 improved when the active phases were introduced onto tiie monolith in the form of a washcoat SA(RCuNi). In Figure 5 the activity results obtained with this catalyst operating at two area velocities are presented. Of note were the NO conversions of greater tlian 75% at relatively low reaction temperatures (200-300°C). 

Adthough the operating temperature range was narrow and the area velocities low, this result may be considered as encouraging in offering... 

Activity tests - A detailed description of the two apparatuses has been reported elsewhere [7], Experiments were carried out in the presence of steam and SO2 at varying temperature in the range 300-390°C, that is under realistic conditions of power plant flue gas treatment. In DeNOx tests the feed stream consisted of 500 ppm NO, 550 ppm T 3, 500 ppm SO2, 10% by volume H2O and 2% by volume O2 in N2. The SO2 oxidation activity was measured in a dedicated apparatus wherein 1000 ppm SO2, 10% H2O, 2% O2 were fed in a N2 stream. Total flow rates were such that the resulting values of Area Velocity, AV (the ratio between the volumetric flow rate and the geometric surface of the monolith), equaled 33 or 10 mNTP/h (NTP = 273K and 1 atm). 

Show that for an axial dispersion flow system with variable density, area, velocity, and dispersion coefficients between two adjacent sections, equating total fluxes leads to the boundary condition ... 

First, we notice that the relations between the quantities dependent on s and t, as given in Eq. (1.26), are compatible with Eq. (1.25). This leads, see e.g. [3], directly to the renowned Einstein laws, the gravitational redshift and the gravitational time delay. Second, we observe that the area velocity multiplied by the mass is a constant of motion. In analogy with the special case [4], where... 

Using the area velocity D, see Eq. (1.16), which is a constant of motion, D = A in the classical case of the central force problem, one derives straightforwardly the following relations in standard polar coordinates r,

particle motion is in a plane perpendicular to the angular momentum vector L)... 

In order to obtain the resistance law to be applied to the vegetated area, velocity distribution is integrated from the bottom to the free surface as follows ... 

The area-velocity relation provides an important insight regarding the behavior of a quasi-ID compressible flow in a channel of varying cross sections. It states that for a subsonic flow (M < 1) to increase velocity, a decrease in cross-sectional area is required. This is an intuitive and familiar result similar to incompressible... 

An alternative and extremely useful form of the area-velocity relation Eq. 1 can be derived for... 

In equation 14, AV is the area velocity, that is the ratio of the volumetric flow rate to the overall geometric catalyst area, ocno, represents the fractional conversion of NO, and is given by ... 

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