Spray factor

The results from FA for the other, smaller particle size fractions are qualitatively comparable the extracted factors have a similar pattern (Tab. 7-8 and 7-9). The dependence of the eigenvalues for the extracted factors on the particle diameter (Fig. 7-22) illustrates that the part of common variance described by the sea spray factor decreases with decreasing particle size and that the part of common variance described by the anthropogenic factor increases continuously with decreasing particle size. 

The scores of the sea spray factor (factor 2 in Fig. 7-23) have a maximum in a wind direction in the range of 30-70°. A plausible explanation is that the wind blowing from 30-70° is directed against the main direction of the sea waves and captures more sea spray than winds from other directions. 

Herrington PJ, EC Hislop, NM Western, KG Jones, BK Cooke, SE Woodley and AC Chappie, 1981. Spray factors and fungicidal control of apple powdery mildew. In ESE Southcombe (ed.), Application and Biology. Proceedings of a Symposium held at the University of Reading, Berkshire 7th-9th January 1985. British Crop Protection Council, BCPC Monograph No. 28, Croydon, UK, 1985, 289-298. 

As mentioned above, spray occurs under large vapor momentum (Mh<4) but small liquid gravitational force h. By considering density difference in vapor and liquid, the equation for spray factor describing the relative momentum was developed by Lockett (1986) as... 

IT = 1 for sieve trays and 2.5 for movable and fixed valve trays. The introduction of Kto the spray equation manifests that the valve tray has a better capability in suppressing entrainment than sieve trays. This is achieved by the mechanism of vapor entering the tray horizontally with valves, which reduces the entrainment significantly at low liquid loadings. According Lockett (1986) and Summers and Sloley (2007), spray factor 5p in equation (12.6) must be larger than 2.78 to avoid spray regime. 

Spray Flow Check The Summers and Sloley (2007) spray factor correlation in equation (12.6) is employed ... 

K = 2.5 is used for the valve tray in this case. The tray design point will be away from the spray regime as the spray factor is 2.88, which is larger than 2.78. 

Spray Limit Use spray factor = 2.78 and applying equation (12.6) yields... 

The spray mechanism can be best remembered by hjuyd, the momentum ratio of liquid and vapor. Spray factor is defined in equation (12.6) based on Lockett (1986) with the value of 2.78 as the spray limit. To avoid spray, one needs to increase weir loading, reducing vapor loading and/or hole diameter. 

Dimmick introduced the valuable concept of the spray factor to quantify the magnitude of the aerosol generated in one minute by a particular operation and the concept was developed in a further paper. The spray factor is defined as the number of viable organisms released into the air per minute divided by the number of viable microbes per millilitre of the material being handled. The factor has the units ml/min and derived units are given in Table 6.1. A major deficiency of the spray factor is that it gives no indication of the particle size of the aerosol generated. 

Cox gives an example of the use of the Spray Factor. Suppose a bacterial suspension at 4 X 10 bacteria per ml is to be sonicated for 5 minutes in a room of volume 6 X 10" litres, what concentration would be established in the room From Table 6.1 the spray factor is 1 X 10 . The source strength is 4 X 10 so that the number of bacteria generated per minute is 4 X 10 X 1 X 10 = 4 X 10 bacteria per minute. During 5 minutes sonication the total number of bacteria dispersed would be 5 X 4 X 10 = 2 X 10 bacteria. At equilibrium the aerial concentration would be... 

Table 6.1 Examples of spray factor during aerosol generation...

The ability of a specific component of a bio-reactor to generate an aerosol was evaluated by Cameron et al They operated a reactor inside a cabinet and then carried out operations such as taking a sample of the contents of the reactor and measured the aerosol which was created by the operation. Provided the operator technique was correct, no aerosol was generated but with poor technique it was possible to generate an aerosol with a peak concentration of 29 organisms per litre. Unfortunately the spray factor was not calculated. 

A simple example indicates that if a reactor with a spray factor of 0.005 and containing 10 cells suffered an accident on a night when the wind was... 

It is important to carry out risk assessments on bioprocesses in order to estimate the potential health risk to the exposed workers. The most effective method of assessing the aerosol risk created by a piece of bioprocessing equipment is the spray factor . This is a concept developed by Dimmick to relate the aerosol-producing capacity of a piece of... 

Dimmick introduced the concept of the spray factor to quantify the magnitude of the aerosols generated by laboratory operations and its significance is fully discussed in chapter 6 by Norris. Norris also emphasizes the importance of the size, shape and density of the particle in relation to the site of deposition in the body. Most aerosols generated by biotechnology operations consist of particles of a wide range of size and it is necessary to have an understanding of the particle size distribution before their hazardous effect can be fully appreciated. 

When the spray factor is multiplied by the number of bacteria or virus per milliliter of solution the expected number of airborne particles released by the operation can be calculated. 

SPRAY FACTOR Total AEROSOL output of a process per unit time in the particle size range of interest. 

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