Heat Exchanger Log Mean Temperature Calculator
Calculate log mean temperature difference and ideal duty or exchange area for entered parallel/counterflow end temperatures.
YOUR CALCULATION
Result
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Calculation steps
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How to calculate
Pair stream temperatures at the two physical ends. Both differences must be positive. Use their logarithmic mean, including the equal-difference limit, then duty=U×area×mean difference.
LMTD=(ΔT1−ΔT2)/ln(ΔT1/ΔT2); Q=UA×LMTD
Worked example
Counterflow hot temperatures 100→60°C and cold temperatures 20→50°C give end differences 50 K and 40 K; LMTD is about 44.8142 K. U=500 W/(m²·K) and A=2 m² give 44.8142 kW.
Assumptions and input details
Ideal constant U, no external heat loss, no axial conduction and no multi-pass/crossflow correction. Hot outlet cannot exceed hot inlet, and cold outlet cannot be below cold inlet. Positive end differences allow appropriate counterflow temperature crossover. Stream capacity/flow consistency is not independently established by the entered temperatures.
References: MIT: counterflow heat exchangers and logarithmic mean
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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