Thermal Conductivity Conversion Guide
Thermal conductivity (k or λ) measures a material's ability to conduct heat. It appears in Fourier's law: q = -k × (dT/dx), where q is heat flux. The SI unit is W/(m·K).
Key conversions: 1 W/(m·K) = 0.5778 BTU/(h·ft·°F), 1 BTU/(h·ft·°F) = 1.7307 W/(m·K). Reference values: copper = 401 W/(m·K), steel = 50 W/(m·K), concrete ≈ 1.4 W/(m·K), fiberglass insulation ≈ 0.04 W/(m·K), air = 0.026 W/(m·K).
Thermal conductivity is critical for building insulation design, heat exchanger sizing, electronic thermal management, and refractory lining selection. HVAC engineers use R-values (resistance = thickness/k) and U-values (1/total R) for wall and roof assemblies.
Key pitfalls: confusing k-value, R-value, and U-value (high k = good conductor, high R = good insulator). R-value units differ between US (ft²·°F·h/BTU) and SI (m²·K/W) by a factor of 5.678. US R-19 insulation is only R-3.35 in SI units.