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Understand the two most common spray nozzle . . , . , . . , designs, as well as their basic characteristics, in order to choose the best nozzle for your application.
(ProQuest: ... denotes formulae omitted.)
Spray nozzles disperse a liquid to form a spray. Choosing the optimal spray nozzle among the thousands that are available on the market is daunting - you must determine the spray characteristics that are required for your application and identify the nozzles that will produce those characteristics. Hydraulic nozzles (i.e., single-fluid) and air-atomized nozzles (i.e., two-fluid) account for 95% of all spray-producing devices used in the chemical process industries (CPI).
All spray nozzles require an energy input. The nozzle uses that energy to cause atomization, which is the process of liquid breakup to form a spray. The minimum required energy to form a spray is based on the surface energy of the new surface area generated by the nozzle. The surface energy depends on the liquid's surface tension and the diameter of the drops created:
...(1)
where Esur is the surface energy (J/kg), o is the surface tension (N/m), p, is the liquid density (kg/m3), and D is the drop diameter (m).
Smaller drops require a larger energy input (assuming the effectiveness of the input energy is constant). In all sprays, the energy input that is required for a nozzle is two to three orders of magnitude larger than the surface energy requirement. The bulk of the fluid energy input to the nozzle is output in the form of kinetic energy of the liquid drops.
Nozzle classifications
Over 150,000 combinations of nozzle designs and nozzle capacities are available; therefore, the best nozzle for an application is not simply a nozzle that works. Fortunately, spray nozzle manufacturers provide web-based tools to make the selection process easier. Understanding how nozzles are classified helps simplify and speed nozzle selection.
Energy input. Nozzles, or atomizers, can be classified based on energy input (Table 1 ). The two most common atomizers are single-fluid nozzles, which use liquid kinetic energy, and two-fluid nozzles, which use gas kinetic energy. Single-fluid nozzles are often a good choice because they are low cost, have a simple design, and provide robust operation and energy efficiency.
Spray pattern....