Typical Overall Heat Transfer Coefficients U
| Fluid combination | U, W/(m²·K) | U, Btu/(h·ft²·°F) (calculated) |
|---|
Representative ranges from Incropera Table 11.2 [1]; fouling, velocity and geometry move the real value across the range and beyond. US values are calculated with 1 Btu/(h·ft²·°F) = 5.678263 W/(m²·K) [2], here and in the tables below.
Typical Convection Heat Transfer Coefficients h
| Process | h, W/(m²·K) | h, Btu/(h·ft²·°F) (calculated) |
|---|
Ranges from Incropera Table 1.1 [1].
Representative Fouling Factors R″f
| Fluid | R″f, m²·K/W | R″f, h·ft²·°F/Btu (calculated) |
|---|
From Incropera Table 11.1 [1]: the deposit’s thermal resistance per unit area of the fouled surface, added in series with the clean-surface resistances when finding U.
Thermal Conductivity k at 300 K (27 °C)
| Material | k, W/(m·K) | k, Btu/(h·ft·°F) (calculated) | k, Btu·in/(h·ft²·°F) (calculated) |
|---|
From Incropera Tables A.1 and A.3 [1]; k changes with temperature, and for insulation and masonry with density and moisture. US columns use 1 Btu/(h·ft·°F) = 1.730735 W/(m·K) = 12 Btu·in/(h·ft²·°F) [2].
Emissivity ε near 300 K
| Surface | ε |
|---|
Total emissivity from Incropera Table A.11 [1], as a range where the table gives one. Surface finish and oxidation change ε strongly.