Plan exchanger surface area from real process data. Choose counterflow or parallel flow configurations easily. Estimate tubes, plates, and duty with confidence today quickly.
| Case | Arrangement | Th,in → Th,out | Tc,in → Tc,out | ṁh, ṁc | U(clean) | F | Area (m²) |
|---|---|---|---|---|---|---|---|
| A | Counterflow | 120 → 80 °C | 25 → 60 °C | 2.2, 3.0 kg/s | 650 W/m²·K | 1.0 | ≈ 9.6 |
| B | Parallel | 150 → 95 °C | 35 → 80 °C | 1.6, 2.4 kg/s | 550 W/m²·K | 0.9 | ≈ 12.9 |
| C | Counterflow | 90 → 65 °C | 20 → 55 °C | 1.0, 1.2 kg/s | 700 W/m²·K | 1.0 | ≈ 4.3 |
Heat duty (single-phase):
Q = ṁ · cp · (Tin − Tout)
Terminal temperature differences:
Log-mean temperature difference:
LMTD = (ΔT₁ − ΔT₂) / ln(ΔT₁ / ΔT₂)
Area by LMTD method:
A = Q / (U · F · LMTD)
Fouling-adjusted U:
Ueff = 1 / (1/Uclean + Rf)
NTU–Effectiveness method (optional):
The calculator estimates NTU from effectiveness ε and capacity ratio Cr, then uses UA = NTU · Cmin and A = UA / Ueff.
Heat exchanger sizing translates process targets into a realistic heat transfer surface area. In early design, undersizing risks missed outlet temperatures, while oversizing increases capital cost and can worsen controllability. This calculator focuses on single-phase duties and two workhorse approaches: the LMTD method for known outlet temperatures and the NTU-effectiveness method for performance targets.
The most influential inputs are inlet/outlet temperatures, mass flow rates, and specific heats. For sensible heating or cooling, the duty is computed from Q = ṁ·cp·ΔT. A good practice is to confirm the hot-side and cold-side duties agree within about 5–10%. Larger mismatches often indicate incorrect flow rates, unit errors, or an unmodeled phase change.
LMTD reflects the temperature driving force across the exchanger. Counterflow typically produces a higher LMTD than parallel flow, especially when outlet temperatures approach each other. Small terminal differences create a large required area, so even a 2–3 K approach change can materially shift size. The calculator checks that both terminal differences are positive before reporting results.
The overall heat transfer coefficient bundles convection, conduction, and fouling into one parameter. Typical clean U values can vary widely: liquids with good turbulence may exceed 500 W/m²·K, while viscous oils may fall below 200 W/m²·K. Plate exchangers often achieve higher U than shell-and-tube for comparable services because of enhanced turbulence.
Fouling progressively adds thermal resistance. The calculator applies Ueff = 1/(1/Uclean + Rf) to reduce performance. Even a modest Rf = 0.0002 m²·K/W can lower U by 10–15% for many services. Always align Rf with your fluid, material, and cleaning strategy.
When outlet temperatures are not fixed, designers often specify an effectiveness target. Effectiveness compares actual heat transfer to the maximum possible based on Cmin. Using ε and the capacity ratio Cr, the calculator estimates NTU and then UA, converting to area with Ueff. This is useful for screening alternatives rapidly.
Area alone is not the full design. Tube count, tube length, and bundle diameter influence velocity, pressure drop, vibration risk, and fouling tendency. Plate count affects port velocities and gasket limits. The geometry block provides preliminary counts to support early feasibility, but final selection should include allowable pressure drop, materials, and mechanical codes.
Common preliminary practices include a surface area margin of 10–25% to cover uncertainty in U, fouling, and operating variability. Recheck results at expected minimum and maximum flow rates. Use the CSV export for quick design tables and the PDF export for review packages, then refine inputs as test data becomes available.
1) Which sizing method should I choose?
Use LMTD when both outlet temperatures are known. Use NTU-effectiveness when you have an effectiveness target or when outlet temperatures will be determined by exchanger performance.
2) Why do hot and cold duties sometimes differ?
Differences usually come from unit mistakes, inaccurate cp values, or temperature entries. Large differences can also signal a phase change or heat loss to surroundings that the simple energy balance does not include.
3) What does the correction factor F represent?
F adjusts LMTD for non-ideal flow patterns such as multipass or crossflow arrangements. If you do not have a detailed configuration, start with F near 1 and reduce it as layout complexity increases.
4) How should I pick U(clean)?
Use historical plant data, vendor guidance, or typical ranges for similar fluids and geometries. For early estimates, bracket U with low and high values and compare required areas to understand sensitivity.
5) How does fouling resistance affect sizing?
Fouling adds thermal resistance and lowers Ueff. A lower Ueff increases required area directly. Include Rf that matches your service and maintenance plan to avoid undersizing after run time.
6) Are the tube and plate counts final designs?
No. They are preliminary counts based on heat transfer area only. Final design must check pressure drop, velocities, mechanical limits, and detailed heat transfer correlations for the chosen exchanger model.
7) Can I use this for condensation or boiling?
This version targets single-phase sensible heat. Phase change services need latent heat duties and different correlations for U and temperature profiles. You can still use it for rough screening if you convert phase change to an equivalent duty carefully.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.