LMTD Calculator
Calculate ΔTlm for heat exchanger analysis.
How to Use This Calculator
Enter hot and cold stream inlet/outlet temperatures. Works for both parallel and counterflow; LMTD uses temperature differences only.
Formula
ΔTlm = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂)
ΔT₁ = |Thi − Tco|, ΔT₂ = |Tho − Tci|
Example: Thi=80°C, Tho=60°C, Tci=20°C, Tco=40°C → ΔT₁=40, ΔT₂=40 → ΔTlm=40°C
About LMTD Calculator
The log mean temperature difference is used to compute the driving force for heat exchange across a heat exchanger.
Common Applications
- Design: Determine required surface area.
- Performance: Evaluate exchanger effectiveness.
- Troubleshooting: Identify fouling or imbalance.
Frequently Asked Questions
Does flow arrangement matter?
LMTD formula applies regardless, but ΔT values differ between parallel and counterflow.
What if ΔT₁ = ΔT₂?
Then LMTD equals that common ΔT value because ln(1)=0 and the limit is ΔT.