Full Cone Nozzles
In a full cone spray the droplets are distributed into a volume which is limited by a cone, having its origin point at the nozzle orifice. Such spray pattern is commonly used in a large variety of industrial processes, since it is the one which allows to distribute in an even way the water flow onto a surface: the full cone spray pattern is therefore useful, as a typical example, to evenly spray cooling liquid on a still surface. Another typical use is to distribute liquid droplets within a certain volume, like for example evenly distributing water droplets in he inside volume of a cooling tower.
Because of the wide number of processes performed by means of full cone nozzles the original shape has evolved into a range of specialised types, where the full cone spray pattern, or a pattern similar to a full cone one, is obtained by different techniques.
These nozzles use a specially shaped vane placed at the nozzle inlet, to give a rotational speed to the fluid flowing through the nozzle.
Because of the rotational speed of the fluid, water exiting the nozzle orifice is subjected to centrifugal force and opens up in the shape of a full cone.
The extent of the angle of the cone is a function of both exit speed (created from the inlet ressure) and the internal design of the nozzle. It can vary in practice from 15° to 120°.
These nozzles can be also produced as square full cone nozzles, where the square shape of the pyramidal spray is obtained by a special design of the outlet orifice.
Two important details have to be noted from the system designer when using these type of nozzles:
- the spray angle is measured on the side of the square section
- the square section of the spray rotates within the distance from the nozzle orifice to the target area.
This is not properly a full cone, but rather a continuous liquid curtain evolving with the shape of a spiral inside a conical volume. The disadvantage of a scarcely even distribution is compensated by an exceptionally good resistance to plugging, which makes this nozzle the best choice in those applications where safety or system reliability are the prime concern, e.g. fire fighting systems.
This spray pattern is used in two cases, that is:
- When a wide spray angle is to be reached with nozzles which inherently can only produce a narrow one, or in such cases where small size droplets and rather high capacities are required. Therefore several nozzles are grouped in a cluster with different spray directions: the resulting spray pattern occurs from the additional group of single nozzle sprays and the droplet size of the spray remains the same as one of single nozzle. It must be noted that a smaller nozzle will normally make smaller drops as compared to a larger size nozzle of the same type operating under the same conditions.
- When it is necessary to obtain a wide angle jet using nozzles which inherently deliver a limited angle spray. In the case of a wide angle air atomizer, for example, the droplet distribution is obviously not homogeneous and the result is rather a number of small angle sprays with different directions, but still the liquid is atomized towards all the parts of the volume to be treated.