Full Cone vs Hollow Cone Nozzles: Which Spray Pattern Fits Your Duty

The transfer point runs, the pump holds pressure, and the dust still rolls past the curtain. The wash crew swears the nozzles are new. They are. The spray is a solid disc of water, and the job needs a ring of fine mist, or the reverse. Full cone and hollow cone nozzles look identical from the fitting end. They are not interchangeable.

Every cone nozzle family ships with both patterns. Same body, same thread, same pressure, two completely different jobs. The question is not which nozzle is better. It is which pattern matches the physics of the duty. Is the target a volume to be wetted or a surface to be cooled? Must the droplets land, or must they evaporate?

This guide puts the full cone spray nozzle and the hollow cone spray nozzle head to head on the properties that decide duty fit. Those properties are coverage shape, droplet distribution, impact, evaporation behavior and clog resistance. Use it to shortlist before you open a catalog, so the pattern decision is made on purpose, not by habit.

What Each Pattern Does to the Liquid

Full cone spray nozzles in arrays need overlap planning the same way flat fans do: spacing at 40–60% of the coverage diameter keeps the ring-and-centre pattern uniform across the row.

The difference is where the liquid lands. A full cone nozzle lays spray across the entire circular footprint, all 360 degrees of it, from the centerline out to the edge. Stand under a full cone and the whole disc is wet, center included. A hollow cone nozzle throws liquid in a ring and leaves the center dry: an annulus of droplets with an air core in the middle.

Both are cone spray nozzles, but the cone is solid in one case and hollow in the other. The spray angle describes the cone; the words full and hollow describe what happens inside it.

The geometry comes from the internal structure. A full cone nozzle uses a vane core or a deflector. This slotted insert imparts swirl and breaks the stream into droplets that fill the whole cone. A hollow cone nozzle uses a swirl chamber with a tangential inlet that spins the liquid into a vortex. The vortex draws a central air core, and the liquid leaves as a thin annular sheet that breaks into droplets along the ring.

Same body size, same flow, same angle, different internals. That is the first lesson of this comparison: the pattern is written by the core, not by the nozzle size. Both patterns share the same angle bands. Full cone runs roughly 30 to 120 degrees and hollow cone 40 to 120 degrees, with specials outside those ranges. Angle is a separate choice from pattern.

The Droplet Distribution Profile

The distribution profile is where the two patterns part company most sharply. A full cone has its peak liquid density at the centerline, falling toward the edge. Vane design tunes the exact shape: some full cone nozzle spray patterns are engineered for even distribution across the disc, others are deliberately center-weighted. Either way the mass is biased toward the middle of the footprint.

A hollow cone is the opposite. The liquid mass concentrates at the outer ring and the center carries almost nothing. The hollow cone spray pattern peaks at the edge and drops to near zero at the axis.

That difference matters because droplets do the work where they are, not where you aim. A gas stream carries heat in its core, and a hollow cone misses the hottest part. A filter face needs even wetting, and a hollow cone double-wets the ring while starving the middle.

Droplet size follows the same split. At equal flow and pressure, a hollow cone typically atomizes finer than a full cone. More pressure energy goes into tangential swirl, less into axial velocity. Catalog values vary with flow and angle. As an order of magnitude at industrial pressures, full cone sprays run from about 200 to 800 µm SMD. Hollow cone runs from about 50 to 250 µm.

SMD is the Sauter mean diameter, the droplet size that best represents the surface area of the whole spray. Surface area is where the physics happens. Specific surface scales as 6 divided by diameter, so a 100 µm droplet carries ten times the specific surface of a 1000 µm droplet. Fine droplets evaporate faster, react faster and contact gas faster. Coarse droplets carry momentum and land.

Uniformity matters as much as the average size. A full cone profile can be tuned flat or center-weighted. Cooling duties usually want the flat version, so no hot spot survives at the rim. Data sheets often publish a uniformity value, commonly 80 to 90 percent for an even full cone; below that, the cone is center-weighted. For a hollow cone, the useful number is ring width relative to cone diameter, which tells you how thick the droplet curtain is.

Full Cone vs Hollow Cone at a Glance

Property	Full cone	Hollow cone
Coverage shape	Filled disc, all 360 degrees	Ring, center dry
Distribution peak	Centerline, falls to edge	Outer edge, near-empty axis
Droplet size at same flow and pressure	Coarser, roughly 200 to 800 µm SMD	Finer, roughly 50 to 250 µm SMD
Centerline impact	Higher	Lower
Evaporation speed per droplet	Slower	Faster
Typical angle band	30 to 120 degrees	40 to 120 degrees
Standard pressure window	1 to 7 bar	1 to 7 bar
Clog sensitivity	Set by vane slot width	Set by tangential inlet width
Classic duties	Cooling, rinsing, dust knockdown, deluge	Humidification, scrubbing, evaporative cooling

Keep this table when you spec. Each row is a different lens on the same fact. A full cone puts liquid where the target is. A hollow cone puts surface area where the gas is.

When the Duty Calls for a Full Cone

Cooling is the biggest full cone duty. A hot part, a packed bed or a gas stream loses heat by contact with liquid. The liquid must reach every part of the target. A full cone wets the whole cross-section, center included, so a round part cools evenly and a hot gas core is quenched rather than skin-cooled.

The heat math sets the water bill. Removing heat follows Q = m × cp × ΔT, so cooling 1 m³/h of water by 20 K needs about 23 kW: 0.28 kg/s × 4.18 kJ/kg·K × 20 K = 23.4 kW. A full cone that misses the center wastes part of that duty.

Washing and rinsing follow the same logic. A filter, a tank wall or a product surface gets a filled disc at moderate impact. The center bias helps, because residues usually concentrate mid-target, where the most liquid lands. That is why full cone nozzles dominate rinse headers and tank washing circuits.

Chemical dosing into a tank or basin is a quiet full cone job. The filled pattern disperses a dose across the liquid surface instead of dumping it at one point. The moderate impact folds the chemical in. Full cone nozzles appear in neutralization and pH trim loops where mixing quality, not atomization, is the goal.

Dust knockdown prefers full cone at most transfer and crushing points. The job is to place droplets in the path of airborne dust so particles collide and settle. Coarse droplets in the 100 to 300 µm range carry enough inertia to punch through the dust cloud and drag fines down. A fine mist under 50 µm follows the air currents and can carry dust away from the containment zone instead of settling it.

Fire deluge, foam breaking and general process wetting round out the full cone list. The requirement is the same everywhere: the entire footprint must be covered the moment the valve opens, with no dry center.

When the Duty Calls for a Hollow Cone

Humidification is the classic hollow cone duty. The goal is to add water to air, and every drop must evaporate before it lands. Evaporation time scales with the square of the diameter. A 500 µm drop takes roughly one hundred times longer to evaporate than a 50 µm drop in the same air. The hollow cone spray pattern concentrates the finest droplets at the ring, where they evaporate in seconds instead of falling out.

The psychrometric load is small but unforgiving. At 20 °C, saturated air holds about 14.7 g of water per kg of dry air. Raising a space from 40 to 90 percent relative humidity adds roughly 7 g per kg. Every gram must evaporate, and droplet size decides whether it does.

Gas scrubbing and absorption use hollow cone when the limiting step is gas-to-liquid contact. The ring of fine droplets presents a large surface area per liter, and the open center lets the gas stream sweep through the droplet curtain. Surface per liter scales as 6 divided by diameter, so halving the SMD doubles the contact area. That is the entire scrubber argument for a hollow cone. See the spiral full versus hollow guide for the tower-specific version of this argument.

Evaporative cooling of a gas stream is a hollow cone duty for the same reason. Fine peripheral droplets evaporate faster than heavy center droplets, so the ring extracts more cooling from the same water flow. The ceiling is set by latent heat: water absorbs 2260 kJ/kg when it evaporates, so 1 MW of evaporative cooling needs 0.44 kg/s of water, which is 26.5 L/min, assuming every drop evaporates. Coarse droplets that land un-evaporated simply waste that water.

Fine-atomization coating and odor control round out the list. Where surface area per liter does the work, the hollow cone wins; where liquid must land and stay, it loses.

The Engineering Decision: Flow, Pressure and Internals

Pattern choice is the first decision; sizing is the second. Three public relationships govern sizing, and none of them needs a catalog.

Flow scales with the square root of pressure: Q = K × √P, where K is the flow coefficient at 1 bar. Double the pressure and flow rises by only 41 percent, since the square root of 2 is 1.414. To double the flow of an existing nozzle you need four times the pressure. A 7 bar job and a 1 bar job usually need different nozzle sizes, not just different pressure settings.

Exit velocity follows Bernoulli: v = √(2P/ρ). Water at 7 bar exits at roughly 37 m/s; at 1 bar, about 14 m/s. Velocity sets impact. Stagnation pressure on a surface is 0.5 × ρ × v², so a full cone at 7 bar can land at roughly 0.7 MPa, enough to rinse but not to cut. Cutting force is a solid jet duty, not a cone duty.

Footprint grows with standoff: D = 2 × d × tan(θ/2), with d the distance to target and θ the spray angle. A 90 degree cone at 500 mm standoff covers a 1000 mm circle. At 1000 mm the same nozzle covers 2000 mm, and liquid per square meter drops to a quarter. Coverage claims without standoff are meaningless.

Worked example: a 1.5 m wide wash header uses 90 degree full cone nozzles at 300 mm standoff. Each disc is 600 mm, since D = 2 × 300 × tan 45°. Spacing the discs at 0.5 m gives about 17 percent overlap and needs four nozzles. At 8 L/min per nozzle that is 32 L/min, and the pump must hold the pressure the rating curve shows at that flow. Change any input and the header changes.

Internals set all three relationships. A full cone vane with more slots and finer pitch gives stronger swirl. The payoff is a more even disc and finer droplets, at the cost of pressure drop and clog resistance. A hollow cone swirl chamber with a tighter tangential inlet spins harder. It thins the annular sheet and atomizes finer, and it is the first part to clog on solids. Free passage is the number to check: it is the largest particle that passes the core. A common rule is to filter to one third of the free passage.

Overlap planning differs too. Two full cone discs blend into even coverage at 10 to 20 percent overlap. Two hollow cone rings need deliberate spacing. The wet annuli should just touch, or you get dry wedges between them and double-wet bands where they overlap. The full cone nozzle spray pattern tolerates sloppy spacing; the hollow cone spray pattern does not.

Common Mistakes That Cost Flow

Five mistakes show up again and again in plants that switch patterns.

Mistake one: buying a hollow cone for dust knockdown. Fine mist follows air, coarse droplets settle dust. Match the droplet to the particle.

Mistake two: assuming pressure fixes a pattern. A full cone below about 1 bar degrades toward hollow or irregular coverage. Pressure changes flow, never the pattern.

Mistake three: spacing hollow cone nozzles like full cone nozzles. Rings need deliberate spacing; the 10 to 20 percent overlap rule applies to discs only.

Mistake four: ignoring free passage in dirty water. A fine swirl chamber clogs in the first shift if the liquid carries sand. A spiral or a large-passage full cone is the fix.

Mistake five: reading impact from pressure alone. Impact comes from velocity and droplet mass, and a hollow cone throws both to the ring, leaving the axis nearly dry.

Spiral Nozzles: One Insert, Both Patterns

Many plants standardize on one body for both patterns: the spiral nozzle. A spiral full cone spray nozzle uses a one-piece helical insert. The insert breaks the flow into a filled cone with a large free passage, commonly 2.5 to 9 mm depending on size. That is why spiral full cone nozzles are the default in dirty water, slurry and high-solids cooling.

The same spiral body is offered with a hollow cut, so one spare part family covers both patterns. The free passage stays large either way. That is why scrubber and cooling specs often list a spiral body with a chosen pattern rather than two different nozzle families.

The trade-off is droplet uniformity. A spiral is a high-flow, coarse atomizer, not a precision fine-spray device. For dust knockdown, cooling and washing it is exactly right. For fine humidification, a swirl-chamber hollow cone or an air atomizer is the better tool.

For the full spiral story, see the spiral full versus hollow guide and the spiral product range. Note that pattern and family are orthogonal. A flat fan is a band, a full cone is a disc, a hollow cone is a ring, and a solid jet is a point. If your target is a wide flat surface, the band wins and the cone debate is moot. The flat fan versus full cone guide explains that fork. This guide assumes a round or volumetric target, which is where the two cones compete.

Full Cone vs Hollow Cone FAQ

Why does my full cone look hollow at low pressure? Every swirl-based cone needs a minimum pressure to fill. Below roughly 1 bar the swirl collapses, the air core widens, and the full cone degrades toward a hollow or irregular pattern. To keep the disc solid, run the pressure inside the rated window, typically 1 to 7 bar.

Which pattern clogs less? Neither pattern clogs on its own; free passage decides. A full cone vane with narrow slots and a hollow cone with a fine tangential inlet both clog on solids larger than their passage. For dirty water, choose a spiral or large-passage full cone, and filter to one third of the free passage.

Do I need higher pressure for a hollow cone? Usually not. A hollow cone atomizes partly through tangential swirl, and many models are rated from 1 bar up. Some full cone vanes need 1.5 to 2 bar to produce an even disc. Check the rating curve, not the family name.

Can I switch a full cone to hollow cone by changing pressure? No. Pressure changes flow, droplet size and footprint, but the internal core sets the pattern. A full cone stays a full cone from minimum to maximum pressure. Change the pattern by changing the core, the insert or the nozzle.

Which pattern gives the strongest cleaning impact? Full cone, at the centerline. The center bias concentrates liquid and velocity at the axis, where stagnation pressure can reach roughly 0.7 MPa at 7 bar. A hollow cone gives gentler, ring-shaped impact, which suits surfaces that must not be scoured.

What is the difference in cost? At equal size and material, the two patterns cost about the same, because the body is shared and only the core differs. The real cost is in flow: a pattern that misses the target wastes water, energy and treatment chemical for the life of the line.

Which is better for dust? For knockdown, full cone with 100 to 300 µm droplets. For a mist curtain on very fine dust, a hollow cone can work where air movement is controlled. Match the droplet to the dust: coarse droplets settle it, fine mist follows air.

Decision Table: Full Cone or Hollow Cone

Your duty	Pattern	Why
Cool a hot part or packed bed	Full cone	Center wetted, even heat removal
Quench a gas stream	Full cone	Hottest core gets liquid, not just the skin
Rinse a filter or tank wall	Full cone	Center bias cleans the middle
Knock down dust at transfer points	Full cone	100 to 300 µm droplets settle particles
Fire deluge or full-footprint cover	Full cone	Whole disc wetted on opening
Humidify a room or duct	Hollow cone	Fine ring droplets evaporate fast
Scrub or absorb a gas	Hollow cone	Maximum surface area per liter, open center
Evaporative cooling of a gas	Hollow cone	Fine droplets approach the latent-heat limit
Gentle wash of a delicate surface	Hollow cone	Lower centerline impact
Odor control with a fine mist	Hollow cone	Contact area per liter decides

When the duty is in the left column, the pattern is decided before you pick a size. Write the pattern into the spec, then size flow, angle and pressure from the physics above.

The Bottom Line

The full cone vs hollow cone nozzle decision is not a preference; it is a physics match. A full cone puts liquid where the target is: even, center-biased coverage for cooling, rinsing, dust knockdown and deluge. A hollow cone puts surface area where the gas is: fine ring droplets for humidification, scrubbing and evaporative cooling.

Start with the pattern, then the core, then the size. Check the free passage against your solids, run the pressure inside the rated window, and plan the overlap before the header is drilled. If the pattern is wrong, no pressure setting fixes it.

Need a second opinion on a specific duty? Send your flow, pressure, liquid and target geometry to the BoreJet team via the contact page, and get a pattern recommendation with the math shown. Browse the full cone range and the spiral range to see the hardware behind both patterns.

Related reading: PWM spray control with hollow cones for pulsing duties, and spiral spray patterns where one body offers both cones.