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Plant Engineering Calculator

Updated Sep 17, 2026

Heat Exchanger Fouling Resistance Calculator — Clean vs Dirty U-Value

Calculate added thermal fouling resistance and UA degradation from clean and dirty overall heat-transfer coefficients.

Live calculationWorking shownPrivate in browser

Inputs

Results

Added fouling resistance 0.000417 m²-K/W
U degradation 25.0 %
Clean UA 80.0 kW/K
Dirty UA 60.0 kW/K
UA loss 20.0 kW/K
More actions

Shared links reopen these inputs. Recent and saved calculations stay in this browser unless you clear site data.

Formula

Rf=1/Udirty−1/Uclean.

Your calculation, step by step

These steps use the values currently entered above so the result can be checked independently.

  1. 1.Dirty resistance = 1/600.0; clean resistance = 1/800.0.
  2. 2.Added fouling resistance = 1/Udirty − 1/Uclean = 0.000417 m²-K/W.
  3. 3.UA loss = (800.0 − 600.0) × 100.0 ÷ 1000 = 20.0 kW/K.

How to use this calculator

  1. Enter measured or design values using the units shown beside each field.
  2. Review the live results and the substituted calculation steps before using the estimate.
  3. Check the assumptions below, then continue to a related calculator when the next engineering decision needs another model.

Worked example

A clean U of 800 and dirty U of 600 W/m²-K implies added resistance of about 0.000417 m²-K/W.

Assumptions and limits

  • U-values must use the same area basis and units.
  • This is an observed overall resistance change, not a diagnosis of which side is fouled.

How to interpret the result

Treat the primary result as an engineering screening value, then use the secondary outputs to understand scale, energy or operating impact. Confirm site measurements, equipment limits and applicable standards before making a design or control change.

Questions engineers ask

How is heat-exchanger fouling resistance calculated from U-values?

When clean and dirty overall U-values use the same area basis and units, the added observed resistance is 1/Udirty minus 1/Uclean.

What does a rising fouling resistance indicate?

It indicates deterioration in overall heat-transfer performance relative to the clean reference. It does not by itself identify whether deposits, scaling or another resistance changed on the hot or cold side.

Can I compare U-values based on different heat-transfer areas?

No. Overall coefficients must use the same reference-area basis before their reciprocal resistances are subtracted.

Continue the calculation

Use the next calculator in the same engineering workflow instead of restarting from search.

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Methodology. MAXScanner shows the governing formula, entered values and calculation outputs so the estimate is auditable. The calculator is a screening aid; assumptions and equipment-specific limits remain part of the engineering review.