Jet impactor

The extreme examples of such samplers are the single-jet impactors such as the Battelle of Florida State University, the LPI, or the DRUM, all of... 

JET IMPACTION. A rapidly moving particle, striking a suitably coated surface, will leave an impression whose size is a function of the original drop diameter. Pilcher (7S) illustrates the operation of the jet impactor. The higher the jet velocity, the smaller the particle size which will impinge. An instrument called the cascade impactor consists of a series of these slides. The jet velocity is increased from slide to slide thus, the cascade is useful in determining droplet size distributions. 

FIG. 14-110 Typical impingement separators, (a) Jet impactor. (b) Wave plate, (c) Staggered channels. (Blaw-Knox Food 6- Chemical Equipment, Inc.) (d) Vane-type mist extractor. (Maloney-Crawford Tank and Mfg. Co.) (e) Peerless line separator. (Peerless Mfg. Co.) (/) Strong separator. (Strong Carlisle and Hammond.) (g) Karbate line separator. (Union Catbide Corporation) (h) Type E horizontal separator. (Wright-Austin Co.) (0 PL separator. (Ingersoll Rand.) (/) Wire-mesh demister. (Otto H. York Co.)... 

Marple and Rubow (1986) state that the jet Reynolds number in an impactor can be expressed in terms of the air mass flow rate m. Show that for a round jet impactor Re = mW/p, and for a rectangular jet impactor Re = 2mW/p. Marple and Rubow point out that this is a useful form for the Reynolds number since m is constant for all stages of the impactor. 

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... 

Figure 6.9 Schematic diagram of jet impactor efficiency showing Stk corresponding to 50 impaction efficiency. For round jets, the lower tail of the cfticicncy curve may not exist (Miirpk and Liu, 1974),...

Macher J.M. (1989) Positive-hole correction of multiple-jet impactors for collecting viable microorganisms. Am. Ind. Hyg. Assoc. J., 50, 561-568. 

Several methods were used to characterize aerosol distributions within the exposure chambers. The principal method employed a rectangular jet impactor which was inserted through a port in the chamber and used to inertially classify particles larger than 0.3 urn in diameter. As an additional index, total sulfuric acid mass use per total mass flow was calculated to give an approximation of H SO, mass per volume. Since a substantial part of the aerosol distribution in this system was below inertial impaction limits, an electrical mobility size analyzer (Thermo-... 

Figure 5.11. The operation of a basic jet impactor involves fineparticles being thrown out of the aerosol stream by centrifugal force as the stream is turned away from the collecting slide.

The Centripeter impactor uses virtual collection surfaces [35]. The construction of this instrument is illustrated in Figure 5.15 [36]. In this device the aerosol stream is forced to turn sharply at the orifice entrance. The centrifugal action created by this sharp diversion is greater than that in a normal jet impactor of comparable orifice di-... 

A 400-jet impactor samples a bioaerosol at 28 L/min for 20 minutes. If 344 colonies are counted, what is the average airborne number concentration of viable particles. Assume no loss of viability during sampling. 

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