Air Atomizing Nozzles

Air atomizing nozzles use compressed air to shear liquid into a fine mist. Where a hydraulic nozzle relies on liquid pressure alone and bottoms out around 100 to 150 microns, air atomizing routinely reaches 10 to 50 microns, and does it at low liquid pressure, which matters when you are metering small volumes precisely.

The trade is air consumption. These nozzles cost compressed air to run, and air is the most expensive utility in most plants, so sizing them generously “to be safe” is expensive over a year.

Internal Mix Versus External Mix

Internal mix combines air and liquid inside the nozzle body before the exit orifice. It produces the finest droplets and the highest atomisation efficiency for a given air volume. The constraint is that liquid and air pressures interact, the liquid line sees back-pressure from the air, so you cannot run it with fluids that must not be pressurised or with anything prone to setting inside the body.

External mix keeps the streams separate until they meet outside the nozzle. Droplets are slightly coarser, but liquid and air flow can be adjusted independently, and it handles higher viscosity and mildly abrasive slurries far better. It is also the practical choice when the liquid supply is gravity-fed or pumped at very low pressure.

Adjustable variants add a needle or air cap adjustment so spray pattern and flow can be tuned in service without changing hardware, useful in coating duties where recipe changes are routine.

Droplet Size and What Drives It

Droplet size falls as the air-to-liquid mass ratio rises. In practice that means:

• More air at the same liquid flow gives finer droplets and higher air cost.
• Higher liquid flow at the same air gives coarser droplets.
• Higher liquid viscosity gives coarser droplets and needs more air to compensate.
• Surface tension matters, aqueous solutions with surfactant atomise finer than clean water at the same settings.

For humidification and gas cooling the fine end pays for itself, since small droplets evaporate before they wet surfaces. For coating, going too fine wastes material as overspray and airborne loss.

Range Walkthrough

The reference table above lists the range in one view; this section says when each model is the right answer.

AA-10I (internal mix): the fine end of the range. 0.5–6 L/h of liquid atomised to 10–25 µm on 3.5 Nm³/h of air at 2 bar. This is the model for coating, dosing and humidification where droplet size is the product and liquid volumes are small, the low-flow end of the range is where the smallest droplets live.

AA-20I (internal mix): the internal-mix workhorse. 2–30 L/h, 15–35 µm, 6.0 Nm³/h. For clean, low-viscosity liquids pumped at stable pressure: thin-film coating, glazing, fine humidification and spray-drying feed on clean solutions. The most common answer for single-point fine atomisation.

AA-40I (internal mix): high-flow internal mix. 10–120 L/h at 12 Nm³/h, 20–45 µm. For larger coverage areas or bigger liquid loads where fineness still matters, larger gas-cooling banks, bigger humidification cells, spray drying at higher throughput. The droplet band climbs with flow: expect 20 µm at the low end, 45 µm at the top.

AA-20E (external mix): mid-flow external mix. 2–40 L/h, 25–60 µm, 7.0 Nm³/h. Liquid and air trim independently and the liquid never enters a pressurised mixing chamber, so this is the model for viscous fluids, mildly abrasive slurries and gravity-fed or very low-pressure supply. If the fluid could clog an internal-mix body, this is the default.

AA-40E (external mix): the top of the liquid range. 15–200 L/h, 35–80 µm, 15–30 Nm³/h, for large pattern areas and heavy duties, dust suppression with wetting agent, high-volume coating, injection of viscous reagents. External mix costs roughly two to three times the air of internal mix per litre, which is the price of fluid tolerance at this scale.

AA-20A (adjustable external mix): 2–60 L/h, 25–70 µm, 5–12 Nm³/h. A needle and air-cap adjustment tune pattern and flow in service without changing hardware. The right answer when recipes change shift to shift, one body covers a family of coating or glazing duties. On a stable, never-changing line a fixed model repeats better.

AA-20P (pneumatic actuated): 2–40 L/h, 25–60 µm, 7.0 Nm³/h. The same mid external-mix duty with an air-actuated on/off cycle, so nozzles can be cycled from the control system without valves in the liquid line. Standard for intermittent lubrication, release-agent spraying and indexing coating lines.

AA-US (ultrasonic assisted): 1–20 L/h, 10–30 µm, 4.0 Nm³/h assist air. A piezo-driven surface forms the drops, giving the most uniform droplet in the range at the lowest flow. Electronics coating, pharmaceutical dosing and other duties where drop-to-drop repeatability matters more than throughput; multiple heads cover larger areas.

Application Matrix

Industry	Typical duty	Recommended model	Why
Coating & finishing	Thin-film coating, glazing	AA-20I / AA-20A	15–35 µm uniform film; adjustable trim for recipe changes
Humidification	Curing tunnels, textile conditioning	AA-10I / AA-20I	Fine droplets flash off in flight before wetting product
Gas cooling	Evaporative cooling of process gas	AA-20I / AA-40I	High-flow internal mix; droplets evaporate before contact
Dust suppression	Respirable dust capture with wetting agent	AA-20E / AA-40E	Handles dirty water and wetting agents; wide coverage
Pharma	Tablet coating, precise dosing	AA-US / AA-10I	Finest uniform droplets; 316L clean construction
Lubrication	Die and mould release agents	AA-20P	Pneumatic cycling without liquid-line valves
Chemical	Injection of viscous reagents	AA-20E / AA-40E	External mix tolerates viscosity and solids
Food & beverage	Spray-drying feed, drying tunnels	AA-20I / AA-40I	Droplet uniformity drives powder yield

Three-Step Selection

If the full checklist feels heavy, the decision collapses to three questions:

1. How much liquid per nozzle? Liquid flow in litres per hour sets the flow band: 0.5–6, 2–30, 2–40 or 15–200 L/h. Sizing to the actual flow matters because the droplet band climbs with flow: the low-flow end of any model is its fine end.
2. How fine must the droplets be? Sub-25 µm means internal mix, or ultrasonic if the flow is low and uniformity is critical. 25–60 µm is external-mix territory; 35–80 µm handles high flow with viscous or dirty fluid. The droplet target decides mix geometry before anything else.
3. What air do you have? Available Nm³/h at the working pressure, summed across every nozzle and derated for line losses. This confirms the model and sets the running cost: if the compressor cannot hold the volume, no model will hold its droplet spec.

Reference Specifications

Air consumption is quoted at the stated air pressure. Both air and liquid figures need checking against your compressor capacity before committing to a nozzle count.

Where These Nozzles Earn Their Keep

Humidification and evaporative gas cooling, where droplets must flash off in flight. Coating and lubrication, where film thickness is controlled by metering small liquid volumes. Dust suppression with wetting agent, where fine droplets capture respirable fractions that coarse sprays pass straight through. Spray drying and chemical injection, where droplet uniformity drives process yield.

How to Select an Air Atomizing Nozzle

• Target droplet size: this decides internal versus external mix before anything else.
• Liquid flow required per nozzle: and whether it must be metered precisely or just supplied.
• Available compressed air: volume at pressure, not just pressure. This is the constraint that most often forces a rethink.
• Fluid properties: viscosity, solids content and whether it can tolerate back-pressure.
• Whether flow must be adjustable in service: recipe changes push you towards adjustable types.
• Automation: pneumatically actuated versions allow on/off cycling without valves in the liquid line.

Frequently Asked Questions

How much compressed air will this cost me? Air consumption per nozzle multiplied by nozzle count multiplied by duty cycle. It is worth doing this arithmetic before selecting, since air cost over a year frequently exceeds the nozzle hardware cost several times over.

Can I use an air atomizing nozzle with a viscous fluid? Yes, external mix in particular. Heating the fluid to drop viscosity usually improves atomisation more than adding air pressure does.

Why is my spray suddenly coarser than it was? Most often falling air pressure under load, partial blockage of the air cap, or a change in liquid temperature. Check air pressure at the nozzle rather than at the compressor.

Do I need an air atomizing nozzle or will a misting nozzle do? If you can tolerate 100 micron droplets and have liquid pressure available, hydraulic misting is cheaper to run. Below roughly 50 microns, air atomising is the practical route.

Can I change droplet size without changing the nozzle? Yes, the air valve is the droplet knob. More air at the same liquid flow gives finer droplets, less air gives coarser ones. Adjustable models add needle and air-cap trim on top, and ultrasonic models hold their size by frequency rather than flow.

Do I need a pneumatic version to cycle the spray on and off? For intermittent coating or lubrication lines, the AA-20P cycles on an air signal from the control system without valves in the liquid line, which avoids the dribble and plugging that stop-start liquid valves cause.

How much air pressure should I run? Two bar at the nozzle is the rating for this range. Meter pressure at the cap, not the compressor, and remember consumption climbs with absolute pressure, so running 3 bar instead of 2 costs about 50 percent more air for a droplet gain you can barely measure.

Internal or external mix for my fluid? Thin and clean, internal mix, which gives the finest droplets for the least air. Viscous, loaded with solids, or gravity-fed, external mix, the only geometry that keeps running on those fluids.