Blowing parameters

For a cone, v x 1,2 as for a flat plate, but is larger by the factor V3 for given values of x and /(0) (thus, the blowing parameter pwvwlpeue St0 remains unchanged). With this difference, the flat-plate results may be applied to a cone according to the equations above. 

Whereas there is no universally accepted specification for marketed natural gas, standards addressed in the United States are Hsted in Table 6 (8). In addition to these specifications, the combustion behavior of natural gases is frequently characteri2ed by several parameters that aid in assessing the influence of compositional variations on the performance of a gas burner or burner configuration. The parameters of flash-back and blow-off limits help to define the operational limits of a burner with respect to flow rates. The yeUow-tip index helps to define the conditions under which components of the natural gas do not undergo complete combustion, and the characteristic blue flame of natural gas burners begins to show yellow at the flame tip. These... 

The initial direction of transport of pollutants from their source is determined by the wind direction at the source. Air pollutant concentrations from point sources are probably more sensitive to wind direction than any other parameter. If the wind is blowing directly toward a receptor (a location receiving transported pollutants), a shift in direction of as little as 5° (the approximate accuracy of a wind direction measurement) causes concentrations at the receptor to drop about 10% under unstable conditions, about 50% under neutral conditions, and about 90% under stable conditions. The direction of plume transport is very important in source impact assessment where there are sensitive receptors or two or more sources and in trying to assess the performance of a model through comparison of measured air quality with model estimates. 

As an example of the use of the Gaussian plume equations using the Pasquill-Gifford dispersion parameters, assume that a source releases 0.37 g s of a pollutant at an effective height of 40 m into the atmosphere with the wind blowing at 2 m s . What is the approximate distance of the maximum concentration, and what is the concentration at this point if the atmosphere is appropriately represented by Pasquill stability class B ... 

Utility Baiances. The operating company should also require a balance for each plant utility. The most involved of the utility balances is usually the supply/demand steam tabulation showing all levels of steam and condensate and their interactions. The steam balance is almost always required at this stage for any required side studies. The steam balance influences many design parameters, such as boiler size and contingency, treated water makeup rates, blow -down disposal rates, chemicals usage, and surface condenser size. 

The value Pcr, critical pressure, is a fundamental parameter of the nature of gas-containing melt flows below this critical point, the flow becomes two-phase. This point was established by C. D. Han and C. A. Villamizer [8] by direct observations of the flow in a transparent channel. Data presented by these authors pertain to the case of incomplete decomposition of the blowing agent prior to its entrance into the channel. Obviously, Pcr depends on the amount of gas. 

As can be seen, the requirement for BD (in common with other control parameters) is fundamentally dependent on the level of MU required, reinforcing the need to establish some reasonably accurate assessment of water consumption. In practice, even with quite tight systems, some sludge does develop and a BD of 2 to 3 seconds duration is periodically required. It is preferable to blow the boiler down more frequently than to open up the BD valve for a longer time of, say, 8 to 10 seconds. 

The optimization of the moulding parameters can be difficult because of the delicate balance between the blowing agent decomposition and the part shaping. Part warpage and shrinkage are sometimes difficult to predict. 

Fig. 13.9 Computed blow-off parameter as a function of cross-flow velocity.

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