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Heat Transfer

Fouling Factor Selector

Fouling deposits on heat exchanger surfaces add thermal resistance, reducing the effective overall heat transfer coefficient (U-value). This calculator helps you select typical fouling resistance values by fluid category and estimate the fouled U-value from a known clean U-value. The result shows how much additional heat transfer area may be needed to compensate for fouling. All values are generic preliminary defaults — project standards, vendor data, and client specifications always override these.

TypeInteractive calculator — separate from unit conversions

Calculator

W/(m²·K)
m²·K/W
m²·K/W
Hot-side Rf0.000176 m²·K/W
Cold-side Rf0.000176 m²·K/W
Total fouling resistance0.000352 m²·K/W
Clean U-value600 W/(m²·K)
Fouled U-value495.376 W/(m²·K)
Fouling penalty17.4373 %
At these assumptions, fouling reduces the overall heat-transfer coefficient by about 17.4373%, meaning a larger heat-transfer area may be required for the same duty and temperature driving force. Use the fouled U-value in the Heat Exchanger Area Calculator to estimate the required area.

Preliminary estimate only. Generic typical values are shown as editable defaults. Project standards, vendor data, and client specifications override these values. Not a TEMA, API, or AS compliance calculator. Confirm with detailed thermal design and qualified engineering review before use.

Formulas

Fouled U-value
1/U_fouled = 1/U_clean + Rf_hot + Rf_cold
Total fouling resistance
Rf_total = Rf_hot + Rf_cold
Fouling penalty
penalty % = (1 − U_fouled / U_clean) × 100

Diagram

tube wallRf_hotRf_coldHotCold1/U_fouled = 1/U_clean + Rf_hot + Rf_coldFouling resistance on heat transfer surfacespenalty % = (1 − U_fouled / U_clean) × 100

Worked example

A heat exchanger has U_clean = 600 W/(m²·K). Hot side: cooling water (Rf = 0.0002 m²·K/W). Cold side: light hydrocarbon (Rf = 0.0002 m²·K/W). What is the fouled U-value?

  1. 011/U_fouled = 1/U_clean + Rf_hot + Rf_cold
  2. 021/U_fouled = 1/600 + 0.0002 + 0.0002
  3. 031/U_fouled = 0.001667 + 0.0004 = 0.002067
  4. 04U_fouled = 1 / 0.002067 ≈ 483.87 W/(m²·K)
  5. 05Fouling penalty = (1 − 483.87/600) × 100 ≈ 19.35%
Result

U_fouled ≈ 483.87 W/(m²·K). Fouling reduces the overall heat transfer coefficient by about 19.4%, meaning a correspondingly larger heat transfer area may be required.

FAQ

Are these fouling values from TEMA or API standards?
The default values shown are generic typical ranges for preliminary estimation. They are not presented as TEMA, API, or any other standard. Always confirm fouling resistances against project standards, vendor data, or client specifications.
What is the difference between clean and fouled U-value?
Clean U-value assumes no deposit on either heat transfer surface. Fouled U-value accounts for the additional thermal resistance of fouling deposits on one or both sides. Heat exchangers should always be sized using the fouled U-value.
Can I enter my own fouling resistance values?
Yes. The selector provides defaults, but you can enter any value manually. Use project-specific data when available.
Does this replace a thermal design rating?
No. This is a preliminary estimation tool. Detailed thermal design requires a full rating (e.g., using HTRI, HTFS, or equivalent thermal design software) with actual geometry, fluid properties, and operating conditions.

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