Jet diameter

The principal parameters affecting the size of droplets produced by twin-fluid atomizers have also been discussed (34). These parameters include Hquid viscosity, surface tension, initial jet diameter (or film thickness), air density, relative velocity, and air—Hquid ratio. However, these parameters may have an insignificant effect on droplet size if atomization occurs very rapidly near the atomizer exit. 

Consider the case of the simple Bunsen burner. As the tube diameter decreases, at a critical flow velocity and at a Reynolds number of about 2000, flame height no longer depends on the jet diameter and the relationship between flame height and volumetric flow ceases to exist (2). Some of the characteristics of diffusion flames are illustrated in Eigure 5. 

X = distance from impeller source, not to exceed 100 jet diameters, ft... 

The pressure drop in the HAGO nozzle quickly reaches impractical values. There is always a combination of jet diameter and jet spacing that yields the same heat transfer coefficient as the spray, but at a much lower energy cost. 

Moissis and Berenson (1962) also derived the pool boiling CHF on horizontal surfaces by means of hydrodynamic transitions. Instead of taking 0 between values of f and d, they used the most unstable wavelength as proportional to the jet diameter, DJt... 

For true wall-jet behaviour rja should be >4. This means that the jet diameter should be decreased when the electrode diameter is decreased, which can cause pressure problems. 

Thus, the jet must have a smaller diameter than the tube in order for momentum to be conserved. This result is valid when the liquid s momentum is dominant. At very low Reynolds numbers, viscous stresses are dominant and the velocity profile starts to change even before the exit plane in this case the jet diameter is slightly larger than the tube diameter. 

Namely, the average droplet diameter D is roughly twice the liquid jet diameter d(). Another analysis based on the consideration of surface energy gave Xopt= Jtd0 8X ... 

The mechanism is essentially a combination of the deformation of a round liquid jet by aerodynamic forces and the instability of the deformed jet. The liquid jet is first accelerated rapidly in the high speed air stream (Fig. 3.3b). The jet diameter is thus significantly reduced as it interacts with the surrounding air stream. The direction of the thinning capillary liquid jet is influenced by the interaction between the liquid jet and the turbulent structures of the surrounding air stream. The formation of... 

Figure 24.3 shows typical single-sweep (raw data) measurements of spectral absorption coefficients obtained simultaneously by tuning two diode lasers independently at 10-kilohertz rates across H2O transitions near 1343 and 1392 nm over a 5-centimeter path through the combustion region x/d = 2) of the forced combustor (jet diameter d = 2.1 cm, 4> = 0.75). The product of the spectral absorption coefficient at frequency v ki, cm ) and path length L, cm) is given by ki,L = ln(/o//)j/, where / and Iq are the transmitted and... 

On the jet surface, waves are formed which grow rapidly at wave lengths of X>nd- (Jj—jet diameter). The fastest wave disturbance takes place at the optimum wave length of... 

Here, a is the jet diameter and k is a constant approximately equal to unity. If we rewrite the velocity components as... 

In the case of the wall-tube electrode, the electrode is smaller than the jet diameter. The original treatment was due to Frossling [47] who demonstrated that, close to the wall... 

JET. The diameters of most jets used today are roughly 0.5 mm. This is because of the type of flame used. In a diffusion flame, as opposed to a flame in which the oxidizer and fuel are premixed, the rate of diffusion of the two gases controls the rate of burning. The velocity of the gas flow out the jet must be set to match the rate of diffusion. If the jet diameter is a little different from 0.5 mm, the detector can be optimized at a proportionately different flow. Much beyond a factor of two differences in diameter leads to some other effects, such as thermal transfer or flow stability problems. 

In a study of the absorption of phosgene in water and aqueous sodium hydroxide [28], the inlet jet diameter was 0.63 mm and the jet length in the range 0.75-7 cm. Contact times were... 

Extrudate swelling refers to the phenomenon observed with polymer melts and solutions that, when extruded, emerge with cross-sectional dimensions appreciably larger than those of the flow conduit. The ratio of the final jet diameter to that of the capillary D/Dq, for Newtonian fluids varies only from 1.12 at low shear rates to 0.87 at high rates. Polymer... 

Impactor Jet Diameter cm No. Jet of Velocity Jets cm/sec d50 pm Final Stage Pressure Torr Flow Rate 1pm... 

Nozzle resonances technology.3 While forming a jet from a nozzle, this jet has a spontaneous tendency to break into droplets. By applying a vibration at a specific frequency (Figure 4b), uniform droplets are formed with a size approximately double the jet diameter. Several liters per hours can be reached for larger size droplets of 1 mm, but decreases proportionally to the droplet diameter. On the other hand, resonance is damped if the solution viscosity is too high. 

Figure 7.3 Impactor efficiency curves for rectangular and round impactors showing effects of jet-to-plate distances in Reynolds number Re and throat length T. W is impactor width or impactor jet diameter. (From Marple and WiUeke, 1979.) (a) Effect of jet-to-plate distance (Re = 3000). (6) Effect of jet Reynolds number (T/W = 1). (c) Effect of throat length (Re = 3000).

Example 7.4 A round jet impactor is operated such that the jet Reynolds number is 3000. Using Fig. 7.36, find the particle diameter (unit-density sphere) that will be collected with 50 percent efficiency if the jet diameter is 0.3 cm. 

The Andersen sampler is a six-stage circular jet impactor. Each stage has 400 jets of a certain diameter. For stage 3, the jet diameter is 0.028 in. For stage 4, the jet diameter is 0.021 in. Assuming a flow rate of 1 ft3/min and... 

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