LIQUID SPRAY AS A PROCESS

The process of spraying a liquid can be described as composed of two phases, namely:

1. Breaking up the liquid into separated droplets.

2. Directing liquid droplets onto a surface or an object, to achieve the desired result.
The above two phases are normally performed, by the types of nozzles being used in industrial processes, at the same time by means of different techniques which shall be illustrated below.

PURPOSES OF SPRAYING A LIQUID

Spraying a liquid through a spray nozzle can serve different purposes, among which the most important are the following:

1. Cooling - by means of heat transfer between the product itself and the liquid running on to its surface.

2. Washing - where the water directed onto the product removes dirt or undesired substances from the product surface.

3. Humidifying - a fine atomized liquid sprayed into a room or onto a surface.

4. Metering - controlling a set quantity of liquid in a given time.

5. Applying a product onto a surface, as in the case of spray painting or surface pre-treatment before painting.

6. Increasing the liquid surface to speed up heat transfer processes or chemical reactions.

It is self evident that the best results for every application are only obtained when the right choices in terms of nozzle type, flow value, spray angle and nozzle material are made.

QUALITY OF A SPRAY

A spray nozzle is a device that makes use of the pressure energy of a liquid to increase its speed through an orifice and break it into droplets.
Its performance can be identified and described precisely, so that the design engineer can specify exactly the spray nozzle required for a given process.

The relevant characteristics

1. The liquid flow delivered as a function of the nozzle feed pressure.

2. The opening angle of the produced spray.

3. The nozzle efficiency, as the ratio between the energy of the spray and the energy used by the nozzle.

4. The evenness of the flow distribution over the target.

5. The droplet size distribution of the spray