The overall heat transfer coefficient U combines shell-side film resistance, tube-side film resistance, wall conduction, and fouling on both surfaces. ChemCalc implements Q = U·A·ΔTlm area estimation with a built-in U-value reference table for common shell-and-tube services, alongside the full ε-NTU method for rating and sizing.
Overall U Formula
| Term | Meaning | Typical unit |
|---|
| 1/ho | Shell-side (outside) film resistance | m²·K/W |
| Rfo | Shell-side fouling resistance | m²·K/W |
| t/k | Tube wall conduction (t = wall thickness, k = thermal conductivity) | m²·K/W |
| Rfi | Tube-side fouling resistance | m²·K/W |
| 1/hi | Tube-side (inside) film resistance | m²·K/W |
| U = 1 / (sum above) | Overall coefficient | W/(m²·K) |
Typical U Values by Service (Shell-and-Tube, TEMA)
| Service | U [W/(m²·K)] |
|---|
| Water–water | 800–1500 |
| Light organic–water | 300–700 |
| Heavy organic–water | 100–300 |
| Gas–water (10 bar) | 50–200 |
| Condensing steam–water | 1000–4000 |
| Boiling liquid–steam | 500–2500 |
| Gas–gas (high pressure) | 20–100 |
Fouling Resistance Reference (TEMA R-2007)
| Fluid | Rf [m²·K/W × 10⁻⁴] |
|---|
| River water (below 52 °C) | 3.5 |
| Sea water (below 43 °C) | 1.0 |
| Treated cooling water | 1.7 |
| Light hydrocarbon liquids | 1.7 |
| Heavy fuel oil | 8.8 |
| Steam (non-oil-bearing) | 0.9 |
ChemCalc Heat Exchanger Modules
ε-NTU — 5 flow arrangements
LMTD (counter / parallel)
Q = U·A·ΔTlm area estimator
Built-in U reference by service pair
ε-NTU vs LMTD — Which to Use
| Method | Use when |
|---|
| ε-NTU | Outlet temperatures unknown (rating / sizing); need effectiveness ε = Q/Qmax |
| LMTD | All four terminal temperatures known; checking an existing exchanger against duty |
| Q = U·A·ΔTlm | Quick area estimate from duty and assumed U; preliminary design |
Related Calculators
← Back to ChemCalc — 44 engineering modules