MAXScanner engineering calculator
LMTD Calculator — Counterflow & Parallel Heat Exchanger
Calculate terminal temperature differences and log mean temperature difference for counterflow or parallel-flow heat exchangers.
Last updated: September 17, 2026
Results
Temperature differences must stay positive; check for temperature cross
Formula, example and assumptions
LMTD=(ΔT1−ΔT2)/ln(ΔT1/ΔT2).
Counterflow 150→80 °C hot and 30→90 °C cold gives ΔT1=60 K, ΔT2=50 K and LMTD≈54.85 K.
- No temperature cross is permitted in this simple sensible-heat model.
- For multipass or crossflow equipment apply an appropriate correction factor F.
Frequently asked questions
What does this LMTD Calculator solve?
Calculate terminal temperature differences and log mean temperature difference for counterflow or parallel-flow heat exchangers.
Which units should I use?
Use the SI units shown beside each input. The results also expose practical converted outputs where useful.
Can I use this for final equipment selection?
Use it for transparent engineering estimates and cross-checks. Confirm fluid properties, manufacturer curves and applicable design codes before final selection.