Spray nozzle patterns

Evaluation of the spectral data showed that a component of the material being sprayed exhibited a significant absorption near 1480 nm (CH-bend fundamental combined with CH-stretch first overtone). This absorption was evident even after the spray had dried. Once this feature of the sprayed material was identified, it was a simple matter to apply peak area integration for the identified absorption across the entire image. The images shown on the left in the figure are maps of the peak area of the 1480 nm NIR absorption. 

These images, obtained in 10 min, led to a method for rapidly assessing the performance of spray delivery nozzles. Spatial distribution of spray, as well as some quantitative information about distribution uniformity, was quickly obtained. This test replaced a previous method where spray was deposited onto a 96-well plate (shown on the right half of the figure). The previous method required individual measurements at each of the 96 wells, took several hours to complete and resulted in much poorer spatial resolution. The NIR spectral imaging method provided a much quicker test. 

---

Another type of distributor, not shown in Fig. 14-64, is the spray nozzle. It is usually not recommended for hquid distribution for two reasons. First, except for small columns, it is difficult to obtain a uniform spray pattern for the packing. The fuU-cone nozzle type is usually used, with the need for a bank of nozzles in larger columns. When there is more than one nozzle, the problem of overlap or underlap arises. A second reason for not using spray nozzles is their tendency toward entrainment by the gas, especially the smaller droplets in the spray size distribution. However, some mass transfer in the spray can be expected. 

A friend developed a unique spray that holds very constant velocity and consistent spray pattern regardless of flow, thereby overcoming turndown problems in other spray nozzles. This is very useful in quench or desuperheating service. Figure 15-1 illustrates this unique spray. 

Sprinkler - Water deflector spray nozzle devices used to provide distribution of water at specific characteristic patterns and densities for purposes of cooling exposures, suppression of fires and vapor dispersions. 

The design of fixed water spray fire protection over pumps should provide one or more spray nozzles positioned so that all parts of all objects within the protection pattern are thoroughly wetted and enveloped by the spray. The recommended water spray densities based on the horizontal coverage area is a minimum of 0.5 gpm/ft (20 Ipm/m ) (API 2030). 

The EDV Wet Scrubbing System utilized proprietary nozzles to produce high-density water curtains through which the gas must pass. Each nozzle sprays water droplets that move in a cross-flow pattern relative to the flue gas. These cover the entire gas stream and uniformly flush the vessel s surfaces clean. The spray nozzles are nonclogging and are designed to handle highly concentrated slurries. 

Van Zele and Diener 1990 To investigate the effectiveness of water sprays in reducing hazards from HF releases. Many key variables were studied to enhance HF removal efficiency. Water-to-HF ratio is key. Upflow water sprays are more efficient than downflow sprays. Removal efficiency depends on spray nozzle configuration, nozzle size, spray pattern, spacing, etc. 

The differences in full- and hollow-cone spray patterns can be seen in Figure 4.5. In this figure the spray flux, gpm/ft2, is plotted versus the radial distance from the center line of the spray nozzle. For the hollow-cone spray there is very little water at the center of the spray. Instead, it is all at the outer edge. Conversely, for the full-cone spray, the water is fairly evenly distributed radially about the center line of the nozzle. 

Figure 4.5. Spray patterns for hollow- and full-cone spray nozzles. (BETE Fog Nozzle, Inc., 1994).

Spray nozzles are used for dust control, water aeration, dispersing a particular pattern of drops, coating, paintings, cleaning surfaces of tanks and vats, and numerous other applications. They develop a large interface between a gas and liquid, and can provide uniform round drops of liquid. Atomization occurs by a combination of gas and liquid pressure differences. The Figure below (courtesy of Misonix Inc.) compares the particle sizes from the ultrasonic nozzle with those from the conventional nozzle. 

The flooding (net fan) nozzle delivers a wide-angle net spray pattern. It operates at very low pressure and produces large spray droplets. Its pattern is fairly uniform across its width but not as even as the regular net fan nozzle pattern. If used for broadcast spraying, it should be overlapped to provide double coverage. It is frequently used for applying liquid fertilizers, fertilizer-... 

Liquid Fat Application to Mixed Feeds. The typical operation consists of a horizontal batch dry feed mixer, equipped with fat addition ports. Hot fat is added to the batch after the dry ingredients have been mixed to minimize segregation of ingredients into fat balls. Some operators spray the fat, and others prefer to let it mn into the mixer through small distributor fines or horizontal pipes with diagonal cuts. Much can be said in favor of the distributor line approach. Spray nozzles clog, even if equipped with screens. A spray fan pattern, that doesn t deposit fat on the sides of... 

In reality, few systems are Newtonian, and some of the other principal rheological profiles are also shown in Figure 5.1. In many cases a Newtonian behavior is not desirable for a formulated product. This can be illustrated by the case of a spray cleaner. A certain minimum viscosity is often required such that the material appears to be concentrated in the bottle. The visual appearance is referred to in this chapter as the apparent viscosity and is generally considered to correspond to a shear rate of the order of 10 sec-1 (reciprocal seconds). If the formulation is Newtonian, then the viscosity will remain the same even at the relatively high shear rates corresponding to spraying (Figure 5.2). This is not desirable, as the spray pattern obtained varies considerably with the viscosity of the fluid in the spray nozzle, and better atomization is observed when the viscosity is low. Consequently, an ideal profile for such a formulation is one in which the viscosity decreases as... 

Giles, D.K. and Comino, J.A. (1990) Droplet size and spray pattern characteristics of an electronic flow controller for spray nozzles. Journal of Agricultural Engineering Research, 47, 249-269. 

The spray nozzle is not widely used. If more than one nozzle is used, it is difficult to obtain a uniform spray pattern because of overlap and underlap of the patterns. Also, liquid entrainment from the sprays is a problem. Spray distributors are sometimes used in petroleum refinery vacuum columns. The full cone nozzle is normally used, singly or in banks. 

Sprays also may be used for liquid distribution. When more than one nozzle is needed, overlapping (or underlapping) of spray patterns is inevitable. Care must be taken to select a foil cone spray nozzle that does not have too fine a mean drop size (to prevent entrainment of liquid by the rising vapor) and which Has a good pattern of spray over the needed cross section. Nozzles are available for handling liquids containing suspended solids, and thus spray distribution is a possible solution lo tha need to distribute a dirty liquid. 

Fig. 7.22 Cross sections through two phase (pressurized gas assisted) spray nozzles, (a) Externai and (b) internai mix set-up (courtesy BETE Fog Nozzle, Greenfield, MA, USA) (c) photograph of an operating nozzle, cross section through the nozzle, and spray patterns that are obtainable with such nozzles (courtesy Spraying Systems Co., Wheaton, IL, USA).

---