The Need of Drop Size Measurements in Spray Drying Nozzle

The heat transfer or say evaporative power, of any system is the direct function of the surface area when it exposed to the heating element. With spray drying, if the surface is large, the fluid sprayed dry quickly, with water from the fluid rapidly evaporating from the slurry.

A surface area of a fixed volume is opposite to the average size of the droplets which together make up the fluid. So the smaller the droplet size the larger the surface area. And hence, the spray drying system will have more drying power.

It, therefore, becomes crucial for the drying nozzles to be perfectly designed to form the very fine droplets. Break the fluid and create fine spray, nozzles need to work at very high pressure, using the internal energy of the slurry. So before making the use of nozzles, droplet size measuring test is a must.

Uniformity of Droplets

It is also crucial for the droplets formed to be fairly uniform in size. Nozzles that produce a broad spectrum of droplet sizes have no importance in spray drying applications, as larger droplets means liquid or water has not gone out from the slurry. And so drying is not so perfectly. Also smaller droplets remove the moisture but the remaining powder particle may be damaged by excessive heat.

So, it is important to design a nozzle that gives a high degree of regularity of droplet size. The relative span of particles is low and so the liquid dry quickly.

Measuring the Size of Droplets

A spray nozzle is designed in a way that it produces a range of droplet sizes that can often be summarized by a single number. And the single number that seems high appropriate for the use to compare the droplet spectrum of several sprays depends on the application.

So measuring droplet sizes or drop sizes of spray is very important. Doing this (measurement of the droplet spectra, produced by nozzles) was not that easy a few years go.

But it is not so. Thanks to several systems which are commercial available but these have generally been limited and confined to special laboratories. However, there are many that provide drop size measurement services in the USA for businesses.

Drop sizes can be measured in two ways: first, by spreading of droplet sizes within a spray. And second, by involving several methods used for actually analysing sprays. These methods will produce different results depending on the type of spray. Make sure that the same method is used when comparing the sprays produced by two different nozzles.

The drop size measurement is crucial, and this is what the performance of your nozzles and final results depend on.