ft²/h
square foot per hour
Diffusivityexact by definition
The square foot per hour is exactly 0.09290304/3600 m²/s, that is 2.58064 × 10⁻⁵ m²/s. It is the customary unit for thermal diffusivity in United States heat transfer handbooks, where it pairs with conductivity in Btu/(h·ft·°F) and specific heat in Btu/(lb·°F). The factor is exact by definition.
Watch out: Air's thermal diffusivity is about 0.85 ft²/h and water's about 0.0055 ft²/h, so values in this unit cluster near 1 for gases and near 0.01 for liquids. That makes it easy to lose a factor of ten when transcribing.
| 1 ft²/h | 25.8064 mm²/s |
Solvers that use diffusivity