What is a heat exchanger fouling factor?

The fouling factor (Rf) represents the thermal resistance introduced by deposits (scaling, corrosion, biological growth) on heat transfer surfaces over time. It reduces the overall heat transfer coefficient (U).

How does water velocity affect fouling?

Higher water velocities (typically > 0.9 m/s or 3 ft/s) tend to reduce fouling by increasing shear stress at the wall, which inhibits deposit formation and improves the cleanliness factor.

Heat Exchanger Water Fouling Factors

Reference fouling resistance for process water selection in heat exchanger design

When sizing a shell and tube heat exchanger or a plate heat exchanger, it is critical to account for the buildup of material on the tube surface. This thermal resistance is called the Fouling Factor (\(R_f\)).

⚠️ ENGINEERING NOTICE & EDUCATIONAL DISCLAIMER: This interactive calculator is provided exclusively for preliminary estimation and educational purposes. It is not intended for detailed design or equipment procurement without certified vendor rating.

SI Metric US Customary

Water Type:

Heating Medium Temperature: °C

Water Temperature: °C

Water Velocity: m/s

Fouling Resistance (\(R_f\)): 0.0001763 m².K/W

Industrial Rules of Thumb & Safety Limits

Velocity Limit: Aim for velocities between 0.9 m/s and 2.4 m/s. Velocities below 0.9 m/s significantly increase deposition (fouling).
Temperature Threshold: For water with mineral content, fouling rates increase exponentially above 50°C (122°F) due to inverse solubility of salts like Calcium Carbonate.
Overall U-Value Impact: In cooling water applications, the fouling factor often accounts for 10% to 30% of the total thermal resistance.
Pressure Drop: Designing for high velocity reduces fouling but increases pumping costs as \(\Delta P \propto v^2\).

The overall heat transfer coefficient (\(U\)) including fouling is calculated as:

\[ U_{dirty} = \frac{1}{\frac{1}{U_{clean}} + R_f} \]

Where:

\(U_{dirty}\) = Fouled heat transfer coefficient
\(U_{clean}\) = Clean (design) heat transfer coefficient
\(R_f\) = Fouling resistance factor

Detailed Fouling Resistance Data Table

Please find below the reference values used in the calculator. Note: Data is for preliminary estimation only.

Fouling Factor: Water (SI Units)

Water Type	Heating ≤115.5°C Water ≤51.6°C Vel ≤0.9m/s	Heating ≤115.5°C Water ≤51.6°C Vel >0.9m/s	Heating >115.5°C Water >51.6°C Vel ≤0.9m/s	Heating ≤115.5°C Water >51.6°C Vel >0.9m/s
Units	(m².K/W)
Boiler Blowdown	0.0003526	0.0003526	0.0003526	0.0003526
Brackish Water	0.0003526	0.0001763	0.0005289	0.0003526
Condensate	8.815E-05	8.815E-05	8.815E-05	8.815E-05
Cooling Tower (Treated)	0.0001763	0.0001763	0.0003526	0.0003526
River Water (Avg)	0.0005289	0.0003526	0.0007052	0.0005289
Sea Water	8.815E-05	8.815E-05	0.0001763	0.0001763