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Cyclone Calculator

Effective turns equals pi over h times 2 cylinder length plus cone length

Solution

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Effective Turns

Calculates the number of effective turns the gas makes inside the cyclone based on inlet height, cylinder length, and cone length.

N = π/h × (2L_cyl + L_cone)

Cut Diameter

Determines the particle size at which the cyclone achieves 50% collection efficiency.

d_cut = √(9μ_g W / 2πN v_i (ρ_p − ρ_g))

Radial Velocity

Describes how fast particles migrate outward due to centrifugal force.

v_r = (ρ_p − ρ_a) r ω² d² / 18μ

Pressure Drop

Quantifies the energy cost of operating the cyclone.

P_drop = 3950 K Q² P ρ_g / T

Separation Factor

Compares radial velocity to settling velocity. A factor greater than 1 indicates effective separation.

S = v_r / v_s

How It Works

A cyclone separator spins dirty gas at high speed so that centrifugal force pushes heavier particles outward against the wall while clean gas exits through a central vortex. Five core equations govern cyclone design: effective turns, cut diameter, radial velocity, pressure drop, and separation factor.

Example Problem

A cyclone has an inlet height of 0.5 m, cylinder length of 1.5 m, and cone length of 2.5 m. How many effective turns does the gas make?

  1. N = π / h × (2L_cyl + L_cone)
  2. N = 3.1416 / 0.5 × (2 × 1.5 + 2.5) = 6.283 × 5.5
  3. N ≈ 34.6 turns

Key Concepts

Cyclone separators exploit centrifugal force to remove particles from a gas stream. Dirty gas enters tangentially, creating a vortex that pushes heavier particles outward against the wall while clean gas exits through a central tube. Performance depends on five interrelated parameters: the number of effective turns the gas makes, the cut diameter (particle size at 50% efficiency), radial migration velocity, pressure drop, and separation factor.

Applications

  • Industrial air pollution control: removing dust and particulates from factory exhaust streams
  • Woodworking shops: separating sawdust and chips from air before it reaches the dust collector bag
  • Grain handling: removing chaff, dust, and lightweight debris from grain in agricultural processing
  • Cement and mining: pre-cleaning kiln exhaust and crusher dust before baghouse or ESP treatment
  • Oil and gas: separating sand and liquid droplets from natural gas in production facilities

Common Mistakes

  • Expecting high efficiency on fine particles — standard cyclones struggle below 5 µm; PM2.5 requires high-efficiency designs or downstream filters
  • Ignoring the pressure drop trade-off — higher inlet velocity improves efficiency but increases fan power consumption and operating cost
  • Using air-density values for process gases — gas density and viscosity vary with temperature and composition, significantly affecting cut diameter
  • Oversizing the cyclone — too large a diameter reduces centrifugal force and degrades collection efficiency

Frequently Asked Questions

What is the cut diameter of a cyclone separator?

The cut diameter is the particle size at which the cyclone achieves 50% collection efficiency. Particles larger than the cut diameter are mostly captured; smaller ones pass through. Typical cyclones have cut diameters of 5–25 μm.

How does inlet velocity affect cyclone performance?

Higher inlet velocity increases centrifugal force and improves collection efficiency, but also raises the pressure drop and energy cost. Typical inlet velocities range from 15 to 25 m/s for standard designs.

Can cyclones remove PM2.5 particles?

Standard cyclones are not efficient at removing particles below about 5 μm. For PM2.5 removal, you need high-efficiency cyclones, multi-cyclone arrangements, or downstream devices like electrostatic precipitators or baghouses.

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