Heat Exchanger Fouling Factors

Fouling factors references for oil, gas and other process fluids (heat exchanger sizing)

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Fouling is the accumulation of undesired material on heat transfer surfaces. In heat exchanger design, this is accounted for using a Fouling Factor ($R_f$), which reduces the overall heat transfer coefficient ($U$).

The relationship between the clean and dirty heat transfer coefficients is given by:

\[ \frac{1}{U_{dirty}} = \frac{1}{U_{clean}} + R_{fi} + R_{fo} \]

Where:

$U_{dirty}$: Overall heat transfer coefficient with fouling
$U_{clean}$: Overall heat transfer coefficient of the clean exchanger
$R_{fi}$: Fouling resistance on the inside surface
$R_{fo}$: Fouling resistance on the outside surface

⚠️ 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.

Interactive Fouling & Sizing Estimator

Clean U-Value ($U_{clean}$) W/m²·K

Heat Duty ($Q$) kW

LMTD ($\Delta T_{lm}$) K or °C

Inner Fouling $R_{fi}$ m²·K/W

Outer Fouling $R_{fo}$ m²·K/W

Dirty U-Value ($U_{dirty}$):-

Clean Area Required ($A_{clean}$):-

Dirty Area Required ($A_{dirty}$):-

Area Margin Required:-

Engineering Rules of Thumb: Fouling

Design Margin: Typically, an area margin of 10-25% is added to account for fouling in standard process applications.
Velocity Control: Increasing tube-side velocity (target 1.0 - 2.0 m/s for liquids) reduces fouling but increases pressure drop and erosion risk.
Temperature Effects: High wall temperatures can significantly accelerate chemical reaction fouling or scaling.
Critical Design Limit: If Fouling Resistance ($R_{fi} + R_{fo}$) exceeds 50% of the total thermal resistance ($1/U_{clean}$), the design is highly sensitive to small changes in fouling; consider oversized nozzles for easier cleaning.

1. Data table of fouling resistances of some processing fluids

Please find below a table of fluids found in process industries and the fouling resistance it is expected they can generate in heat exchangers.

Warning 1 : values were not verified individually
Warning 2 : These data are for preliminary reference. Actual fouling depends on temperature, turbulence, and fluid purity.

Fouling factor : Oils

Fluid	Description	$R_f$ (h·ft²·F/Btu)	$R_f$ (m²·K/W)
Fuel Oil #2	Fouling factor of Fuel Oil #2	0.002	0.0003526
Fuel Oil #6	Fouling factor of Fuel Oil #6	0.005	0.0008815
Transformer Oil	Fouling factor of Transformer Oil	0.001	0.0001763
Engine Lube Oil	Fouling factor of Engine Lube Oil	0.001	0.0001763
Quench oil	Fouling factor of Quench oil	0.004	0.0007052

Fouling factors : gases and vapors

Fluid	Description	$R_f$ (h·ft²·F/Btu)	$R_f$ (m²·K/W)
Acid gas	Fouling factor of Acid gas	0.002	0.0003526
Ammonia vapor	Fouling factor of Ammonia vapor	0.001	0.0001763
Chlorine Vapor	Fouling factor of Chlorine Vapor	0.002	0.0003526
CO2 vapor	Fouling factor of CO2 vapor	0.001	0.0001763
Coal flue gas	Fouling factor of Coal flue gas	0.01	0.001763
Compressed Air	Fouling factor of Compressed Air	0.001	0.0001763
Hydrogen	Fouling factor of Hydrogen	0.0005	8.815E-05
Natural Gas	Fouling factor of Natural Gas	0.001	0.0001763
Steam (non-oil)	Fouling factor of Steam (non-oil)	0.0005	8.815E-05

Fouling factors : liquids

Fluid	Description	$R_f$ (h·ft²·F/Btu)	$R_f$ (m²·K/W)
Ammonia Liquid	Fouling factor of Ammonia Liquid	0.001	0.0001763
Asphalt / Residuum	Vacuum tower bottom	0.01	0.001763
Ethylene Glycol	Ethylene Glycol Solutions	0.002	0.0003526
Gasoline	Fouling factor of Gasoline	0.002	0.0003526
Kerosene	Fouling factor of Kerosene	0.0025	0.00044075
Methanol Solutions	Fouling factor of Methanol solutions	0.002	0.0003526