Stack design factor

The paper compares wet, dry and wet and dry cooling towers on the basis of their performance and costs. Design factors involving heat transfer characteristics wet bulb temperature effect, fans and stack, etc, are evaluated. 

The key factor in flare stack design is personnel escape time from the stack base at maximum discharge. Therefore, the selection of height and flare stack location should be made on the basis of safety for operating personnel as well as equipment. 

These factors are stack-design and application specific. 

Several different radial fuel cell stack designs have been developed. The primary reason to develop a radial system is to have the same form factor as a common battery. The radial design is typically fed fuel from an inner hollow core and air from the ambient around the unsealed cathode edges of the cell, as shown in Figure 6.48. An advantage of the radial design in this instance is that the diffusion path length is minimized. 

From the parameters in Equations (10-5) and (10-6), a new parameter may be derived, the so-called design factor, Df (kg/m ), which is simply the stack mass divided by the active area. This factor is useful in comparisons of various stack designs. A good fuel cell stack design, which means a stack... 

The following discussion clarifies the effect that topographic factors can have on the transport of pollutants and, consequently, on the design and especially the siting of the stack. 

Given the factors which influence the design of the stack, it is logical to proceed with the question of relating these factors to stack performance. It has already been proposed that a Gaussian distribution of pollutant... 

The principal factors which must be accounted for when designing a stack for air pollution control purposes are the dispersion and transport of the pollutants and the performance criteria against which the stack will be compared. These factors include (1) air quality standards, (2) meteorological conditions, and (3) topographical peculiarities. 

When stack gases are subjected to atmospheric diffusion and building turbulence is not a factor, gromid level concenlrations on the order of 0.001-1 % of the stack conccnuniion are possible for a properly designed stack. 

In summary, modern DAF units with only 3 min of retention time can treat water and wastewater at an overflow rate of 3.5 gpm/ft2 for a single unit, and up to 10.5 gpm/ft2 for triple stacked units. Of course, the actual retention time used for DAF design will be higher when an engineering safety factor is applied. Figure 27.1 shows a typical DAF clarifier that will be explained in detail later. 

The versatility and accuracy of the oxygen consumption method in heat release measurement was demonstrated. The critical measurements include flow rates and species concentrations. Some assumptions need to be invoked about (a) heat release per unit oxygen consumed and (b) chemical expansion factor, when flow rate into the system is not known. Errors in these assumptions are acceptable. As shown, the oxygen consumption method can be applied successfully in a fire endurance test to obtain heat release rates. Heat release rates can be useful for evaluating the performance of assemblies and can provide measures of heat contribution by the assemblies. The implementation of the heat release rate measurement in fire endurance testing depends on the design of the furnace. If the furnace has a stack or duct system in which gas flow and species concentrations can be measured, the calorimetry method is feasible. The information obtained can be useful in understanding the fire environment in which assemblies are tested. 

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