Convective Heat Rate
输入表面传热系数、面积与温差，求对流换热功率。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Newton law of cooling | q = hA(T_s − T_∞) | Newton 1701 |
| Convection coefficient | h from Nusselt number | Convection theory |
| Nusselt number | Nu = hL/k | Dimensionless groups |
| Typical h | Air natural 5–25; water forced 500–10 000 W/(m²·K) | Heat transfer handbook |
| Heat flux | q'' = h·ΔT | Heat transfer |
| Validity | h roughly constant for modest ΔT | Analysis assumption |
Typical convective heat-transfer coefficients and their sources (h comes from empirical correlations, it is not a material constant)
| Situation | Coefficient h | Unit | Source |
|---|---|---|---|
| Natural convection, air | 2 – 25 | W·m⁻²·K⁻¹ | ASHRAE Fundamentals / heat-transfer handbook range |
| Forced convection, air | 10 – 500 | W·m⁻²·K⁻¹ | ASHRAE Fundamentals (the page default h = 10 is at the low end) |
| Forced convection, water | 500 – 10 000 | W·m⁻²·K⁻¹ | Common heat-transfer handbook range |
| Boiling water / condensing steam | 2 500 – 100 000 | W·m⁻²·K⁻¹ | Common heat-transfer handbook range |
Note: in Newton's law of cooling Q̇ = hA·ΔT, h must be obtained from a Nusselt-number correlation Nu = f(Re, Pr) for the specific geometry and flow regime; tabulated values serve only as estimates.