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Heat Exchanger (LMTD / ε-NTU) Calculator

Size the area (LMTD) or rate an existing unit (ε-NTU) for counter-current, co-current and shell & tube exchangers.

Thermal · Heat Transfer
Version1.0.0MethodLMTD

Streams flow in opposite directions — the most thermally efficient arrangement (F = 1).

1

Input Parameters

Calculation Mode

Terminal Temperatures

°C
°C
°C
°C

Duty & Coefficient

kW
W/m²K
m²K/W

optional — 0 for clean

%

over-surface allowance

2

Results

Ready to compute?

Enter your parameters and press Calculate Area

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Reference Codes & Standards

  • TEMA (10th Ed.)

    Standards of the Tubular Exchanger Manufacturers Association

    Mechanical design & nomenclature for shell-and-tube exchangers.

  • ASME BPVC VIII-1

    Boiler & Pressure Vessel Code, Section VIII, Division 1

    Pressure-part design of exchanger shells, channels & tubesheets.

  • Bowman, Mueller & Nagle (1940)

    Mean Temperature Difference in Design — Trans. ASME 62

    Analytical LMTD correction factor F for 1 shell / 2N tube passes.

Further Reading

  • Kern, D. Q. (1950). Process Heat Transfer. McGraw-Hill — LMTD sizing method.
  • VDI Heat Atlas (2010), 2nd Ed. — thermal design data & correlations.
  • Incropera & DeWitt, Fundamentals of Heat and Mass Transfer — ε-NTU / LMTD.

Engineering Tips

Sizing (LMTD) finds the area when all four terminal temperatures and the duty are known. Rating (ε-NTU) finds the duty & outlet temperatures for an existing area.

  • Counter-current gives the largest LMTD for the same duty — smallest area.
  • Co-current can never raise the cold outlet above the hot outlet.
  • F factor corrects multi-pass shell & tube units. Keep F ≥ 0.75 — add shell passes if it drops.
  • Add a fouling resistance and a design margin for a realistic service area.

Full formulas with substituted values appear in the Calculation Breakdown.