Overall Heat Transfer Calculator — Formula
## Overall Heat Transfer Coefficient
The overall heat transfer coefficient U combines all thermal resistances (convection on both sides, wall conduction, fouling) into a single parameter for heat exchanger design.
### Formula
**Q = U × A × LMTD**, therefore **U = Q / (A × LMTD)**
Typical U values: water-water: 800-1500 W/(m²·K), gas-gas: 10-40, condensing steam-water: 1000-4000. Low U indicates fouling or poor heat transfer conditions.
The overall heat transfer coefficient U combines all thermal resistances (convection on both sides, wall conduction, fouling) into a single parameter for heat exchanger design.
### Formula
**Q = U × A × LMTD**, therefore **U = Q / (A × LMTD)**
Typical U values: water-water: 800-1500 W/(m²·K), gas-gas: 10-40, condensing steam-water: 1000-4000. Low U indicates fouling or poor heat transfer conditions.
Esempio Risolto
A heat exchanger transfers 500 kW with 20 m² area and 50°C LMTD.
- U = 500 × 1000 / (20 × 50)
- U = 500000 / 1000 = 500 W/(m²·K)
- In imperial: 500 × 0.176 = 88.1 BTU/(h·ft²·°F)