EngineerHub.orgWhat this tool does
Enter a clean overall heat-transfer coefficient and either a current fouling resistance or a measured dirty U-value. The tool estimates present duty loss, expected post-cleaning recovery, annual lost value, cleaning payback and net benefit.
Inputs
Cleaning economics
Fouled U-value: 1/Udirty = 1/Uclean + Rf
Duty: Q = U A ΔTlm,eff
Residual fouling after cleaning: Rf,after = Rf,current(1 − ηclean)
Gross recovered value: Crecovered = (Qafter − Qdirty) t cenergy
Total cleaning cost: Cclean,total = Cdirect + tdown cdown
- Area, flow regime and effective LMTD are treated as constant between states.
- Additional pumping cost from fouling-induced pressure drop is not included.
- Cleaning effectiveness is applied to thermal fouling resistance, not pressure drop.
- Economic value should be marginal and defensible; do not use gross product selling price without process justification.
Results
Thermal resistance and cleaning effect
Fouling adds thermal resistance between the process fluids. Cleaning removes part of that resistance, increasing U and restoring duty.
What to do with the result
Compare like-for-like flow rates, inlet temperatures and control-valve positions. A low apparent U-value can be caused by maldistribution, bypassing, air binding or bad instruments rather than fouling.
Thermal fouling and hydraulic restriction often develop together. A rising pressure drop can increase pumping cost and may justify cleaning earlier than the thermal calculation alone.
Confirm compatibility of chemical cleaning, CIP, hydrojetting or mechanical cleaning with plates, tubes, gaskets, metallurgy and deposits.
Record pre- and post-cleaning temperatures, flows, pressure drop and calculated U-value. Use the recovered performance to improve the next cleaning decision.
Limitations and model basis
The model is strongest when comparing the same exchanger at similar operating conditions. If flow, phase change, bypassing, LMTD correction factor or available utility temperature changes materially, use a full rating calculation.
- US NRC Heat Transfer handbook — overall heat-transfer coefficient, fouling factors and heat exchangers.
- Spirax Sarco heat-transfer principles — U as the reciprocal of total thermal resistance.
- Alfa Laval plate heat exchanger calculation method — fouling factor, clean U-value and design margin.
- Use equipment-vendor procedures and site maintenance rules for cleaning selection and execution.