Heat Exchanger Sizing Calculator
Size a counterflow heat exchanger using the LMTD method. Calculate heat duty, log mean temperature difference, and required surface area.
Inputs
°F
°F
°F
°F
GPM
BTU/lb·°F
BTU/hr·ft²·°F
Results
Heat Duty
3,998,400 BTU/hr
Required Surface Area
340.4 ft²
LMTD78.3 °F
Effectiveness57.1%
Mass Flow Rate49,980 lb/hr
How to Use This Calculator
- Enter the Hot Fluid Inlet and Outlet temperatures in °F to define the hot-side duty.
- Enter the Cold Fluid Inlet and Outlet temperatures in °F — verify the cold outlet is lower than the hot inlet for a valid counterflow arrangement.
- Enter the Hot Side Flow Rate in GPM and the Specific Heat of the fluid (water = 1.0 BTU/lb·°F).
- Set the Overall U-Value in BTU/hr·ft²·°F: water-to-water ≈ 150–300, steam-to-water ≈ 200–500.
- Review the Heat Duty in BTU/hr and the LMTD in °F — the LMTD drives the required surface area.
- Use the Required Surface Area in ft² to select or specify a heat exchanger model from vendor catalogs.
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