Hollow Cone Nozzle | Precision Casting & OEM Solutions

1. Introduction

Hollow cone nozzle is a highly specialized fluid-atomizing components that play an indispensable role in industries requiring fine atomization, high surface-to-volume ratios, and efficient gas–liquid contact.

Unlike full cone or flat fan designs, hollow cone nozzles generate an annular spray pattern with relatively small droplets concentrated along a circular band, leaving the central axis comparatively dry.

This makes them the preferred choice for humidification, evaporative cooling, scrubbing, pesticide spraying, and combustion processes.

2. What is a Hollow Cone Nozzle?

A hollow cone nozzle is a precision-engineered spray device designed to transform a liquid stream into a finely atomized, ring-shaped spray pattern.

Unlike full cone nozzles, which distribute droplets across the entire cone volume, hollow cone nozzle concentrate liquid droplets primarily along the peripheral annulus, leaving the center relatively dry.

This unique geometry makes them particularly effective in applications requiring fine atomization, rapid evaporation, and large gas–liquid interaction surfaces.

Working Principle

The fundamental operation of a hollow cone nozzle relies on the induction of liquid swirl:

• Swirl Induction: Fluid enters the nozzle body through one or more tangential channels, helical grooves, or a swirl insert.
• Vortex Formation: The fluid acquires angular momentum, forming a rapidly rotating liquid film inside the swirl chamber.
• Sheet Formation: As the liquid exits through a precisely machined orifice, it spreads outward due to centrifugal force, creating a thin annular liquid sheet.
• Atomization: This sheet breaks up under aerodynamic shear and surface tension instabilities, forming a ring of fine droplets in a conical pattern.

Defining Characteristics

• Spray Geometry: Conical with a hollow interior, typically with angles from 40° to 140°.
• Droplet Size: Fine atomization, often in the 10–200 μm range, depending on pressure and nozzle design.
• Distribution: Uniform droplet density along the cone perimeter, ideal for processes requiring even peripheral coverage.
• Hydrodynamics: High Weber numbers (We > 100) in operating ranges confirm droplet breakup is dominated by inertial forces rather than surface tension.

Why the “Hollow” Shape Matters

• Cooling & Humidification: Maximizes surface area for heat and mass transfer.
• Spray Drying & Combustion: Enhances evaporation rate due to smaller droplets.
• Scrubbing & Gas Treatment: Ensures high contact efficiency in absorptive systems.

3. Spray Physics & Performance Metrics

Key Metrics

• Spray Angle (40°–140°): Defines coverage width.
• Flow Rate (Q): Governed by orifice diameter and pressure differential (Q ∝ √ΔP).
• Droplet Size (D32, VMD): Typically 10–200 μm, crucial for evaporation and drift control.
• Distribution Uniformity: Determines how evenly liquid is deposited along the annular ring.
• Impact Force: Moderate compared to flat fans or full cones, making them suitable for cooling and humidification but not heavy-duty cleaning.

Fluid Dynamics Insight

At operating pressures above 5 bar, Reynolds numbers exceed 10⁴, ensuring turbulent conditions.

The Weber number (ratio of inertial to surface tension forces) often exceeds 100, confirming that aerodynamic forces dominate breakup, yielding fine, stable droplets.

4. Materials & Metallurgy Considerations

5. Types and Internal Geometries of Hollow Cone Nozzles

Hollow cone nozzle can be broadly categorized by how they generate the swirling flow that forms the annular spray.

The choice of internal geometry determines spray angle, droplet size, clog resistance, and overall performance.

Spiral Nozzles

• Design: Uses a continuous spiral cut or helical groove machined into the nozzle body.
  Liquid flows along the spiral path, breaking into fine streams at each edge, which collectively form a hollow cone spray. No dedicated swirl chamber is required, making the design simple yet highly effective.
• Features: Extremely wide spray angle (up to 180°); no internal swirl chamber.
• Advantages: Minimal clogging; handles dirty liquids and slurries well.
• Applications: Gas scrubbing, cooling towers, fire suppression, dust control.

Axial Swirl Nozzles

• Design: Incorporates a swirl chamber positioned directly behind the exit orifice.
  Liquid enters axially and is guided into rotation by spiral grooves or a swirl insert, creating a vortex before discharge.
  The chamber geometry (cylindrical or conical) controls spray uniformity and droplet size.
• Features: Well-defined, thin hollow cone spray with fine droplet size.
• Advantages: High uniformity, precise coverage; compact geometry.
• Applications: Chemical reactors, humidification, spray drying.

Tangential Entry Nozzles

• Design: Features one or more tangential inlet ports on the nozzle’s side, forcing fluid to spin rapidly inside a cylindrical swirl chamber.
  The resulting vortex exits through a round orifice, forming a hollow cone pattern. The size and number of tangential ports dictate flow stability and droplet distribution.
• Features: Strong vortex with high shear, producing narrow droplet distribution.
• Advantages: Very stable spray pattern; effective with low to medium viscosity liquids.
• Applications: Gas cooling, pesticide spraying, surface coating.

Vane-Type (Insert) Nozzles

• Design: Employs a removable internal vane insert positioned before the nozzle orifice. The vane has multiple angled slots or blades that impart controlled swirl motion to the liquid.
  Vane geometry (slot width, angle, count) directly influences spray angle and droplet size, and inserts can be swapped to customize performance.
• Features: Adjustable droplet size by vane geometry; orifice easily replaceable.
• Advantages: Serviceable design; tailored performance; easier maintenance.
• Applications: Food processing, flue gas desulfurization (FGD), precision cooling.

Multi-Orifice Hollow Cone Nozzles

• Design: Consists of several small orifices arranged circumferentially around the nozzle face.
  Each orifice emits a fine jet that forms part of the overall hollow cone spray, combining into a uniform annular pattern.
  The design allows scaling of flow capacity by simply adjusting orifice number and size.

  

• Features: High flow rates with distributed droplet streams.
• Advantages: Good redundancy; continues functioning even if one orifice clogs.
• Applications: High-capacity cooling, large-scale irrigation, fire suppression.

6. Manufacturing Methods and Quality Controls of Hollow Cone Nozzles

Manufacturing Methods

Precision Casting

• Process: Uses investment casting (lost wax) or precision sand casting. A wax model of the nozzle is made, coated with ceramic slurry, then melted out to form a mold cavity.
  Molten alloy (e.g., stainless steel, Hastelloy, or ceramics) is poured in, solidified, and finished by machining or grinding.
• Advantages: Capable of producing intricate internal swirl chambers and large, one-piece designs; excellent for high-temperature or corrosive environments.
• Applications: Power generation scrubbers, chemical reactors, and large-scale cooling towers.

CNC Machining

• Process: Begins with solid bar stock or forged blanks. Multi-axis CNC turning and milling machines cut precise geometries, including the orifice, vane slots, and swirl chamber.
  Final polishing and honing remove burrs and ensure tight tolerances (±0.01 mm).
• Advantages: High dimensional accuracy, excellent repeatability, and flexibility for low- to medium-volume production.
• Applications: Pharmaceutical spray drying, food sanitation nozzles, gas turbine cooling.

Powder Metallurgy & Sintering

• Process: Fine powders of metals (stainless steel, tungsten carbide) or ceramics (alumina, zirconia) are pressed into a die under high pressure (200–800 MPa), then sintered at 1,000–1,500°C.
  Secondary finishing like grinding or laser drilling creates the orifice.
• Advantages: Produces extremely hard, wear-resistant materials; allows close control of porosity and microstructure.
• Applications: Abrasive slurry spraying, coal-fired boiler desulfurization, mining and cement industries.

Injection Molding (Polymers & Composites)

• Process: Thermoplastics (e.g., PP, PVDF, nylon) or engineered composites are melted and injected into steel molds at high pressure.
  Cooling solidifies the part, which may require deflashing or surface treatment. Glass or carbon fiber reinforcements can be added for strength.
• Advantages: Low-cost, scalable mass production; lightweight and corrosion-resistant; wide range of shapes achievable.
• Applications: Agricultural spraying, disposable chemical handling nozzles, water treatment dosing.

Additive Manufacturing (3D Printing)

• Process: Layer-by-layer fabrication using Selective Laser Melting (SLM) for metals or binder jetting/stereolithography for ceramics/polymers.
  Allows fabrication of complex lattice-like swirl chambers and non-linear flow paths that enhance atomization. Post-processing (heat treatment, polishing) improves durability and finish.
• Advantages: Enables designs impossible with traditional machining; rapid prototyping; small-batch customization.
• Applications: Aerospace cooling channels, pharmaceutical atomizers, R&D of novel spray geometries.

Surface Finishing & Heat Treatment

• Process: After forming, nozzles undergo finishing such as polishing, honing, or lapping for smooth internal surfaces.
  Heat treatments (carburizing, nitriding, or quenching & tempering) enhance hardness.
  Coatings such as PTFE, ceramic, or hard chrome are applied to reduce friction and improve chemical/abrasion resistance.
• Advantages: Extends service life, reduces clogging risk, and enhances performance consistency.
• Applications: Chemical processing plants, fire suppression systems, marine environments.

Quality Assurance

• Dimensional Inspection (CMM, optical metrology).
• Spray Pattern Testing (collection grids, photographic mapping).
• Droplet Size Characterization (Laser Diffraction, PDPA).
• Material Certification (MTCs, corrosion/erosion testing).

7. Advantages & Limitations of Hollow Cone Nozzles

Key Advantages

• Perimeter Coverage: Annular spray reduces fluid use and avoids oversaturation.
• Versatile: Works with low-viscosity liquids to moderate slurries; pressure range 1–100 bar.
• Clog & Erosion Resistant: Larger orifices and swirl vanes prevent blockage.
• Low Surface Impact: Gentle on delicate surfaces while ensuring coverage.
• Energy Efficient: Requires less pumping power than full cone or solid stream for similar coverage.

Critical Limitations

• Central Dead Zone: Non-wetted center unsuitable for full-area coverage.
• Pressure Sensitivity: Spray angle and droplet size change with pressure fluctuations.
• Lower Impact: Not ideal for abrasive cleaning or heavy-duty applications.
• High-Viscosity Limitation: Fluids >5,000 cP need higher pressure or heated nozzles.
• Maintenance Needed: Swirl vanes can accumulate deposits; periodic cleaning required.

8. Industrial Applications of Hollow Cone Nozzle

A Hollow cone nozzle is widely used where perimeter coverage, uniform wetting, and controlled droplet size are critical. Key applications include:

Agriculture & Horticulture

• Even pesticide, herbicide, and fertilizer distribution around plants.
• Reduces chemical usage by 10–20% compared to flat fan nozzles.

Cooling & Humidification

• Cooling towers, HVAC humidifiers, and greenhouse misting systems.
• Ensures uniform coverage without over-saturating surfaces.

Fire Protection & Suppression

• Ring-shaped spray covers sensitive equipment and perimeter areas.
• Compatible with NFPA-approved sprinkler systems.

Industrial Cleaning

• Light washing or rinsing of delicate equipment and conveyors.
• Reduces impact damage compared with full cone or solid stream sprays.

Dust Suppression & Material Handling

• Mining, cement, and bulk material facilities to control airborne dust.
• Efficient perimeter wetting prevents particle escape.

Chemical & Process Industries

• Spray reactors, gas scrubbing, and chemical dosing.
• Provides uniform annular coverage, minimizing dead zones.

9. Comparison with Competing Nozzle Types

Summary:

• Hollow cone nozzles excel in perimeter coverage and low-impact applications.
• Full cone nozzles are best for uniform, filled-area sprays.
• Flat fan nozzles are ideal for linear surface coverage.
• Solid stream nozzles provide high-force cleaning or cutting, but limited area coverage.

10. Conclusion

Hollow cone nozzles are precision tools that redefine efficiency in gas-liquid interactions, cooling, and precision dosing.

Their annular spray pattern—engineered via vortex fluid dynamics—delivers unmatched surface area and contact efficiency, making them indispensable in industries from power generation to pharmaceuticals.

As industries prioritize sustainability and smart operations, the hollow cone nozzle will continue to evolve—integrating IoT sensors, 3D-printed customization, and eco-friendly materials.

For engineers and buyers, success lies in understanding the technical nuances of design, material selection, and maintenance—aligning nozzle specs with application needs to optimize performance and lifecycle cost.

FAQs

What material should I use for a hollow cone nozzle in 98% sulfuric acid?

PTFE or Hastelloy C276. PTFE resists 98% sulfuric acid up to 260°C with a service life of 3–4 years.

Hastelloy C276 is preferred for high-pressure applications (≥50 bar) due to its superior strength (tensile strength = 724 MPa). Brass or 316L will corrode within 3–6 months.

Can hollow cone nozzles handle high-viscosity fluids (e.g., motor oil, 3,000 cP)?

Yes, with modifications:

(1) Use a swirl vane nozzle with a 2–3 mm orifice (larger orifices reduce clogging);

(2) Heat the fluid to 60°C (reduces viscosity to ~1,000 cP);

(3) Increase pressure to 20–30 bar (vs. 10 bar for water) to maintain Dv50 = 80–100 μm.

How often should I clean hollow cone nozzles used in wastewater treatment (5% solids)?

Weekly. Wastewater solids (5%) clog orifices faster than clean fluids.

Clean by soaking in a 5% citric acid solution (30 minutes) and brushing with a soft nylon brush. Install a 10 μm inline filter to extend cleaning intervals to biweekly.

What is the typical service life of a hollow cone nozzle in gas scrubbing?

2–3 years for 316L nozzles, 4–5 years for Hastelloy or ceramic nozzles.

Factors reducing life:

(1) Chemical abrasion (e.g., scrubbing SO₂ with caustic soda);

(2) Particulate wear (e.g., fly ash in power plant exhaust);

(3) Poor maintenance (infrequent cleaning). Extend life by using ceramic nozzles and cleaning monthly.