Efficiency source distance

Control Room. The control room location can be critical to the efficient operation of a faciHty. One prime concern is to locate it the maximum distance from the most ha2ardous units. These units are usually the units where LPG or other flammables, eg, hydrocarbons that are heavier than air, can be released and accumulate at grade level. Deadly explosions can occur if a pump seal on a light-ends system fails and the heavier-than-air hydrocarbons coUect and are ignited by a flammable source. Also, the sulfur recovery unit area should be kept at a healthy distance away as an upset can cause deadly fumes to accumulate. 

Booths are partially enclosed workplaces with one or more open facefs) for access by workers. These openings at one or more sides of the enclosure function not only to capture air contaminants directly through their short-distance capture capability but also to cause an airflow in a certain direction (normally away from the worker/work process and into the enclosure). The capture efficiency could be increased by using an existing main flow direction (e.g., thermal flows caused by heat sources) to support the capture process. 

Simple exhaust hoods have a very short effective range and the hood must be placed very close to the contaminant source to be efficient, which may interfere with technological processes. This lack of direction of the flow may result in the use of excessive exhaust flow rates with large source-to-hood distances and this may result in a large amount of wasted energy. 

Exterior hoods intended to capture contaminants should be placed as close to contaminant sources as possible. In actual practice, however, the hoods can not always be placed close to the source due to circumstances such as working conditions. In such cases, to enhance the exhaust efficiency of exterior hoods, it is useful to use a low-momentum air supply directed toward the exhaust outlet. The supply airflow, which functions to transport contaminants emitted from sources located at a distance from the exhaust outlet,. should be relatively low with a uniform velocity but high enough so that it is not disturbed by the. surrounding air motions. The advantages of using low-momentum supply with exterior hoods are that (1) a lower supply airflow rate to the workspace is possible, (2) a lower exterior hood exhaust flow rate is possible, and (3) it is possible to supply clean air to the breathing zone of the worker. 

Most urban rail service is electric-powered and most urban bus service is diesel-powered, although diesel rail and electric bus operations do exist, as noted above. The efficiency and environmental impacts of electricity depend gi eatly on the source of electric power. Although electric vehicles produce no tailpipe emissions, generation of electricity can produce significant emissions that can travel long distances, Eor example, coal-powered electricity plants produce particulate emissions that travel halfway across North America, Urban buses also can be powered by a variety of alternative fuels. 

The advantages of microreactors, for example, well-defined control of the gas-liquid distributions, also hold for photocatalytic conversions. Furthermore, the distance between the light source and the catalyst is small, with the catalyst immobilized on the walls of the microchannels. It was demonstrated for the photodegradation of 4-chlorophenol in a microreactor that the reaction was truly kinetically controlled, and performed with high efficiency [32]. The latter was explained by the illuminated area, which exceeds conventional reactor types by a factor of 4-400, depending on the reactor type. Even further reduction of the distance between the light source and the catalytically active site might be possible by the use of electroluminescent materials [19]. The benefits of this concept have still to be proven. 

Exposure is minimized by choice of source, by duration of exposure, by distance from source (at 1 m the radiation level is reduced almost 10-fold), and by shielding. The greater the mass per unit area of shield material the greater the shielding efficiency. Whereas a- and fTparticles pose few problems (the former can be absorbed by, e.g., paper and the latter by 1 cm Perspex) y- and X-rays are not completely absorbed by shield material but attenuated exponentially such that radiation emerging from the shield is given by... 

Typical capture velocities are given in Table 11.9. Since velocity falls off rapidly with distance from the face of the hood, as shown in Figure 11.2, any source of dust should be within one hood diameter. Efficiency can be significantly improved by the use of flanges and by avoiding abrupt changes in direction of the ducting. 

Since the power of transmitted light drops off as the square of the distance from the light, for efficient reaction and energy usage the reactants must be as close as possible to the light source. This has practical implications for the design of industrial reactors. 

Some of the parameters that affect VCE behavior25 are quantity of material released, fraction of material vaporized, probability of ignition of the cloud, distance traveled by the cloud before ignition, time delay before ignition of cloud, probability of explosion rather than fire, existence of a threshold quantity of material, efficiency of explosion, and location of ignition source with respect to release. 

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