Dilution air

Donaldson and Snedickar (1971) studied jet impingement on flat plates as well as on convex- and concave-shaped objects. Base pressure changes were measured for all considered geometries and velocity measurements reported for the flat-plate geometry. The study indicated that wall jets are 

A good estimate of air entrainment flow in a spray can be obtained by examining in detail the momentum exchange between the spray and the surrounding air. We present a similar model to the one developed by Heske-stad et al. (1976). In deriving this simple model we assumed the following  

The forces acting on a single droplet include gravity, which acts vertically downward, and drag, which depends on the droplet shape and its relative velocity with respect to surrounding air. A force balance on a single droplet yields 

Ignoring the time dependence of droplet velocity, we can rewrite equation (4.21) as 

The increase in momentum flux in the air phase is attributed to the force exerted by the liquid droplets  

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In converter passes downstream of the first pass, exit temperatures are limited by thermodynamic equiUbrium to around 500°C or less. To obtain optimum conversion, the heats of reaction from succeeding converter passes are removed by superheaters or air dilution. The temperature rise of the process gas is almost direcdy proportional to the SO2 converted in each pass, even though SO2 and O2 concentrations can vary widely. 

The ammonia—air dilution system dilutes the vaporized ammonia by a factor of 20 to 25 with air for better admixing through the AIG and to prevent explosive ammonia—air mixtures. Once the catalyst volume is selected, the NO removal is set by the NH /NO mole ratio at the inlet of the SCR system (39). 

Air-dilute with necessary blowers, flow measurement, and control systems Use isokinetic sampling, refrigerated sample transport, and careful handling to minimize physical or chemical changes... 

For a high-production furnace the fume volume flow rate after air dilution to 130 °C will be considerably higher than for secondary fume control by enclosure. A separate primary fume capture system would be used for this case. 

Gombnstible concentration reduction can also be used to prevent deflagrations and detonations in process equipment and piping. The combustible concentration is reduced below the lower flammable limit (LFL) by means of ventilation (air dilution). 

This is also known as air dilution, and is a common procedure for gas-fired boilers. It is allowed for any very low-sulfur fuels (less than 0.04 per cent sulfur) or for fuels in the range 0.04-0.2 per cent S where the VLS fuels chimney heights calculation gives a lower value of U than the other fuels calculations. In these cases, the flue may terminate at the uncorrected height U so long as ... 

The best fit of velocity exponent n in Hp °c ug (Figure 4.3.11) for pure propane (n-butane) is n = 4.733 (3.638), corresponding to Sc = 1.37 (1.61) from n = (2Sc-l)/ (Sc -1), which agreed well with the suggested value of Sc = 1.376 (1.524). The experimental liftoff height data are shown in Figure 4.3.12 for various nozzle diameters and partial air dilutions to fuel [53]. It can be observed that the air dilution to fuel does not alter Ypst and S° sf The results substantiated the role of tri-brachial flames on flame stabilization in laminar jets. As mentioned previously. Equation 4.3.5 limits the maximum velocity Ug for Sc > 1, which corresponds to blowout condition. 

Thermal treatment of a material in a gas oxidizing atmosphere is the simplest concept. This can be done in air, air diluted in N2, dry air, or in ultrahigh purity O2. In the laboratory practice, calcination is done in flowthrough beds, aided by fluidization, or in static box furnaces. Important aspects are the bed geometry, the removal of the generated gases, and temperature gradients. 

Even more promising appears to be the selective reduction of TSNA by perforated cellulose acetate filter tips with higih air dilution. Although the smoker will compensate for the reduction in nicotine by smoking more intensely, it appears that the TSNA yield in smoke does, in this case, not increase to the level observed in smoke of an unperforated filter cigarette. 

If the contaminant cannot be placed in a hood and must be used in an open area or room, dilution ventilation is necessary. Unlike hood ventilation, where the airflow prevents worker exposure, dilution ventilation always exposes the worker but in amounts diluted by fresh air. Dilution ventilation always requires more airflow than local ventilation operating expenses can be substantial. 

Note that C02 acts as neither a simple asphyxiant (like N2) nor a chemical asphyxiant (like CO). The normal concentration of C02 in air is approximately 300 ppm (0.03 vol %). Table 23-19 (Air Products, Carbon Dioxide, Safetygram 18, 1998) illustrates that exposure to air diluted by 5 vol % C02 (yielding an oxygen concentration of 21 x 0.95, or approximately 20 vol %) prompts physiological effects that are more severe than those inferred from Table 23-18 for dilution by the same amount of nitrogen. 

Release momentum. For jet releases, the amount of air entrained in an unobstructed jet is proportional to the jet velocity. Depending on the orientation of the jet relative to nearby obstructions, the momentum of a jet can be dissipated without significant air entrainment. The degree of initial air entrainment can be an important determinant of the hazard extent, particularly for flammable hazards. It would be (possibly overly) conservative to assume the source momentum is dissipated without air dilution. Explosive releases are high-momentum, instantaneous releases. For explosive releases, a rough first approximation is to assume that the mass of contaminant in the explosion is mixed with 10 times that mass of air. 

Tobacco industry scientists studied filtration technology and indicated that then-results showed that this too can have a major influence on smoke pH and free-base nicotine (Chen 1976). They presented results indicating that carbon in filters can increase the pH of the smoke (Creighton 1988). By increasing air dilution of... 

Equation (4) states that, to quantify the combustion efficiency, the volume fractions of carbon monoxide and the total hydrocarbon (methane equivalents), the mass flow and the stoichiometry of conversion gas, and the volume flows of primary and secondary air need to be measured. The concept of combustion efficiency is a function of emissions, air dilution, and type of fuel. This concept can be applied to any type of continuous combustion system and any type of fuel. 

All these methods generally give (< 1 /xm) polydisperse aerosols of the solid particles and, unless rapid air dilution is provided, coagulation leads to large agglomerates of the small primary particles. 

The necessity for regeneration arises from the fact that catalyst activity declines with time on reaction, owing to small deposits of carbonaceous material and sulfur compounds on the catalyst. This deposit, of course, varies with feed stock, catalyst, and process conditions. The regeneration is carried out by oxidizing the deposits on the catalyst with a stream of air diluted to 2 to 3% oxygen with recycled flue gas. 

The reactor itself consists of a chamber that is thermally insulated from the surroundings. The reactants, which are a preheated mixture of fuel and air, dilute or concentrated, are injected through numerous radial nozzles and enter the reaction zone as small sonic jets. Because of the high-intensity turbulent mixing, temperature and concentrations can ideally be assumed to be homogeneously distributed. The rapid mixing thus results in sampled compositions that are purely kinetically controlled. The mixture of reactants and products exits through a number of radial ports. 

In unpublished experiments by the late P. Ya. Sadovnikov (Institute of Chemical Physics), the combustion velocities of explosive mixtures of carbon monoxide with air, diluted by the combustion products, were compared. The diluted mixtures were preheated so that their combustion temperatures did not differ from the combustion temperature of the undiluted mixture. These experiments confirmed with sufficient accuracy the relation required by the theory... 

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