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Log Mean Temperature Difference Calculator — result sheet
Calculate the logarithmic mean temperature difference between two streams in a counterflow or parallel-flow heat-exchanger setup.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: ΔT₁ = Th,in − Tc,out; ΔT₂ = Th,out − Tc,in; LMTD = (ΔT₂−ΔT₁)/ln(ΔT₂/ΔT₁), with the equal-difference limit LMTD = ΔT₁.
The logarithmic mean temperature difference compresses the changing temperature driving force along an idealized heat exchanger into one representative difference.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Hot-stream inlet temperature — temperature units; minimum -1000000; maximum 1000000
- Hot-stream outlet temperature — temperature units; minimum -1000000; maximum 1000000
- Cold-stream inlet temperature — temperature units; minimum -1000000; maximum 1000000
- Cold-stream outlet temperature — temperature units; minimum -1000000; maximum 1000000
Worked example
| Input | Value |
|---|---|
| Hot-stream inlet temperature | 500 |
| Hot-stream outlet temperature | 400 |
| Cold-stream inlet temperature | 120 |
| Cold-stream outlet temperature | 310 |
The end differences are 190 and 280, giving an LMTD of about 232 temperature units.
Assumptions and limits
- Hot-stream temperatures exceed the corresponding cold-stream temperatures at both ends.
- All four temperatures use one consistent scale where differences are meaningful, such as Celsius or Fahrenheit differences.
- The result is a temperature-difference input to a heat-exchanger balance, not a complete exchanger design or performance guarantee.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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