Velocity efflux

Efflux velocity The discharge velocity of waste gases from the top of a stack. 

Chimney efflux velocity not less than 15 m/s at MCR Temperature of gases entering chimney not less than 120°C. 

There are two possible causes. The first could be incorrect control of water treatment and blowdown. This can result in excessive levels of suspended solids in the boiler water, organic matter in the boiler water or high alkalinity. The second can be mechanical. If the boiler is operated below its designed working pressure it will increase the efflux velocity of the steam leaving the water surface area to a point where it may lift the water surface and drop the water level. It is important therefore to give due consideration to the steam load required from the boiler. 

Several boilers discharging into a single-core chimney are to be avoided. At times of low load the efflux velocity will be very low, which, in turn, will allow the chimney to cool. This may then drop to dewpoint temperatures and, where sulfur is present in the fuel, acid will form. If the chimney is unprotected steel, it will suffer rapid corrosion. Even worse, as the boilers increase their load the efflux velocity will increase and start to discharge the acid droplets, which quickly fall out and cause damage to surrounding property. 

The method is designed to ensure the adequate dispersal of sulfur dioxide (and hence a different method is used for very low-sulfur fuels). It assumes certain efflux velocities, i.e. 

Note that the ground-level concentrations do not depend on the flue gas concentrations but rather on the amount of pollutant emitted. It is therefore not worth diluting the flue gases with fresh air (other than to raise the efflux velocity). 

The maximal efflux velocity (Vm) depended on the P-gp secretion transporter expression level. A baseline value was taken to be the expression level in ileum (Vmi). The value of maximal velocity in duodenum (Vmn) and jejunum (Vmj) was computed from the baseline value and a correction factor (Ej), based on... 

The purpose of this investigation is to find the flow features of the aforementioned jets from CFD simulations and establish their efficacy in predicting the mean flow field for which experimental results are available. For the plane and the three-dimensional wall jets, the simple point-source technique was also applied to predict the decay of the maximum velocity and the tracer concentration with the distance x. In the computations of the present study, GAMBIT ver 2.4 was used as the preprocessor and Fluent ver 6.3.26 as the processor and post processor. Based on the earlier experiences, the K-e realizable model was considered suitable for the computations. The efflux velocity was selected as 2.0 m/s and the slot height h = 0.01 m. The intensity of turbulence at the efflux section was considered as 1%. For finding the distribution of the tracers, the density of the particles was made equal to that of the ambient fluid. 

In some instances, ductwork will conduct noxious fumes directly to the treatment plant and in others, the extracted air can be discharged to atmosphere. In all cases, any appropriate legislation must be followed. For instance, the point of discharge will be stipulated (e.g. 3 m above the highest point on the roof, preferably at an efflux velocity of about lOm/s) and so on. 

A safe emission value would be 10 times this value, employing a good safety margin i.e. 0.25 X 10 = 250 ppm. The provisos for this would be that the emissions from the chimney must have a minimum efflux velocity for dry gases of 15 m s and for wet gases 8 m s with a chimney height that is about 2 A times the height of the factory. 

The effective chimney height,/f, is made up of two components. It is the sum of the actual chimney height and the plume rise, the latter being the additional height to which the plume centre-line ascends due to its buoyancy and efflux velocity. Examination of curves in which the maximum ground-level concentration is plotted as a function of H and atmospheric stability show that x is... 

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