Heat Transfer
Comprehensive guide to heat transfer principles, equations, and applications.
Conduction Heat Transfer
Conduction is the transfer of heat through a material without the movement of the material itself. The rate of heat transfer by conduction is given by Fourier's Law:
q = -k * A * (dT/dx)
Where:
- q = heat transfer rate (W)
- k = thermal conductivity of the material (W/(m·K))
- A = cross-sectional area (m²)
- dT/dx = temperature gradient (K/m)
Convection Heat Transfer
Convection is the transfer of heat by the movement of fluids. The rate of heat transfer by convection is given by Newton's Law of Cooling:
q = h * A * (Ts - T∞)
Where:
- q = heat transfer rate (W)
- h = convective heat transfer coefficient (W/(m²·K))
- A = surface area (m²)
- Ts = surface temperature (K)
- T∞ = fluid temperature (K)
Radiation Heat Transfer
Radiation is the transfer of heat by electromagnetic waves. The rate of heat transfer by radiation is given by the Stefan-Boltzmann Law:
q = ε * σ * A * (T₁⁴ - T₂⁴)
Where:
- q = heat transfer rate (W)
- ε = emissivity (dimensionless)
- σ = Stefan-Boltzmann constant (5.67 × 10⁻⁸ W/(m²·K⁴))
- A = surface area (m²)
- T₁ = temperature of the radiating surface (K)
- T₂ = temperature of the surroundings (K)