Nozzle port size

Solution concentration (viscosity effects) Nozzle Port Size... 

Nozzle port size is selected to accomodate spray liquid viscosity and delivery rate and may influence droplet size because it affects the velocity of liquid at a given spray rate. At low atomizing air pressures and volumes, a low liquid velocity allows more complete atomization of liquid. Using a smaller nozzle port at the same spray rate generally results in a larger mean droplet size due to the higher liquid delivery velocity. At high atomization air pressures and volumes, this effect is minimized. 

Nozzle port size is also selected to accomodate desired spray rate and viscosity. The position of the nozzle is very significant. In top spray coating operations, the nozzle is positioned to spray liquid counter currently to the flow of product (see Figure 3). In the Wurster system, the nozzle sprays concurrently with the well organized flow of substrate (see Figure 4), and in the rotor technique, the nozzle sprays concurrently in the spiralling bed of product (see Figure 5). 

Figure 20 Droplet size as a function of 1.2mm and 3.0 mm nozzle ports spray rates of 1200 and 2500 mL/min using water.

This procedure is called reducing port size of the nozzle. It works fine, except that we have permanently derated the capacity of the turbine by 36 percent, and next month we might need this capacity. 

Low-viscose liquids can use small ports, and thicker solutions somewhat larger orifices to allow some back pressure to build in the spray nozzle. In this manner, if a port should become clogged, increasing the spray rate through the remaining ports, the total liquid line pressure will rise. An operator can intervene to correct the problem before the larger droplet size results in an increased granule size. 

These nozzles are available as a single-port or multi-port design. Generally, the single port nozzles are adequate up to 100 kg batch, but for larger size batches a multi-port nozzle such as either a three port (Fig. 10) or six port (Fig. 11) nozzle is required. When these nozzles are air atomized, the... 

The top spray system has been used to coat materials as small as 100 microns. Smaller substrates have been coated, but agglomeration is almost unavoidable due to nozzle limitations and the tackiness of most coating substances. Batch sizes range from a few hundred grams to approximately 1,500 kg. Typically, a single nozzle wand with up to six liquid delivery ports is used, but multiple nozzle systems have been applied. 

Level Control Filler. Plastic bottles can be manufactured clear thus for consumer appeal, they are filled to a level. This means the volume may vary but will appear to be equal due to the visually perceived common level in the containers. Flow is by gravity through a nozzle into a sealed container, whereas air equilibrates via a vent tube (Figure 8). When the rising liquid reaches the air vent port, flow stops. There is no overflow of product as in a pressure or pure vacuum filler. Aeration is at a minimum, perceived fill level is extremely accurate, and the filler is relatively simple and easy to maintain. Size consistency of the blow-molded container is critical to control, because this dictates the amount of product being sold. 

---