Calculate the effective temperature difference in heat exchangers.
Flow Temperatures
°C
°C
°C
°C
LMTD Results
Enter temperatures to calculate LMTD. Ensure all ΔT values are positive.
About this calculator
Quick Reference
ΔT₁ (Counter)T_h1 - T_c2
ΔT₂ (Counter)T_h2 - T_c1
ΔT₁ (Parallel)T_h1 - T_c1
ΔT₂ (Parallel)T_h2 - T_c2
Overview
In heat exchanger design, the temperature of fluids changes as they flow through the equipment. LMTD is the appropriate average temperature difference to use when calculating heat transfer rate (Q = U * A * LMTD).
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Pro Tips
Counter-current flow is generally more efficient and results in a higher LMTD than co-current flow.
LMTD = (ΔT1 - ΔT2) / ln(ΔT1 / ΔT2).
If ΔT1 = ΔT2, then LMTD = ΔT1 (arithmetic mean is used).
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Fun Facts
"Wait, did you know that in a counter-flow heat exchanger, the cold fluid can actually reach a higher temperature than the hot fluid's exit temperature? This is impossible in a co-flow design!"
"The 'logarithmic' part of the name comes from the fact that the temperature change along the exchanger follows an exponential curve."
"Most industrial heat exchangers (like those in power plants or car radiators) are designed for counter-current flow whenever possible to maximize efficiency."
