Heat Exchanger Tube Natural Frequency & Baffle Span Calculator

Determine fundamental natural frequency (fn) of heat exchanger tubes accounting for tube metal, inside fluid, and hydrodynamic virtual added mass.

Tube Span & Material Properties

Unsupported Span Length L (mm):

Support End Conditions:

Tube Outer Dia d_o (mm):

Wall Thickness t (mm): 16 BWG = 1.65 mm

Tube Metal E (GPa): Stainless ~ 195 | Carbon Steel ~ 205 | Titanium ~ 110

Tube Metal Density (kg/m³):

Tube-Side Fluid Density (kg/m³):

Shell-Side Fluid Density (kg/m³):

Natural Frequency & Structural Rigidity

Fundamental Frequency (f_n):

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Effective Total Mass (m_e):

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Added Hydrodynamic Mass:

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Flexural Rigidity (E·I):

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TEMA Span Rigidity Guidance:

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Frequently Asked Questions

What is hydrodynamic virtual added mass?

When a tube vibrates transversely in a dense fluid, it must displace the surrounding fluid back and forth. This inertial resistance acts as an extra virtual mass, reducing the tube’s natural frequency by 20% to 50% compared to vibration in air.

How does baffle spacing influence tube natural frequency?

Because natural frequency is inversely proportional to span length squared (fn ∝ 1/L²), reducing the unsupported baffle span by 30% nearly doubles the tube’s fundamental natural frequency (1 / 0.7² ≈ 2.04).

Why is the first span at the tubesheet stiffer than intermediate spans?

The tube-to-tubesheet joint is tightly expanded or welded, creating a fixed (clamped) end condition with a higher coefficient Cn ≈ 15.4 compared to loose clearance baffle holes (Cn ≈ 9.87).