Heat exchanger fouling and cleaning
Actual U and fouling resistance from a field test — and how much duty, money and time the fouling is costing you.
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Heat Exchanger Excel kit — coming soon
Shell-and-tube performance and fouling trends, cleaning-schedule payback, plate exchangers and condensers — with print-ready reports, any units and visible formulas.
How this calculator works
From your test readings, the calculator works out the duty, the corrected mean temperature difference and the actual overall coefficient: U = duty ÷ (area × F × LMTD). The fouling resistance is the difference between the actual and the clean resistance: Rf = 1/Unow − 1/Uclean.
To see what fouling costs, the exchanger is re-rated by the effectiveness-NTU method at the clean U with the same flows and inlet temperatures. The difference in duty is the heat lost to fouling. Valued at your fuel or steam price, it gives a yearly cost and the number of days a cleaning takes to pay back.
The example uses the same heat-recovery exchanger as the LMTD calculator, 80 m², clean U 600 W/m²·K. The test gives U = 408 W/m²·K (68 % of clean) and Rf = 0.00078 m²·K/W — more than twice the 0.00035 allowed in design. A clean exchanger would recover about 350 kW more, worth about USD 89,000 a year at USD 30/MWh, so a USD 6,000 cleaning pays back in under a month.
Limits: fouling assumed to be the only change since the clean U; constant specific heats, no phase change. References: Perry's Chemical Engineers' Handbook §11; Kern, Process Heat Transfer; Heat Exchanger Design Handbook; TEMA Standards (fouling resistances).