Heat Transfer Calculator
Calculate heat transfer rate (W) and heat flux (W/m²) for conduction, convection, and radiation. Includes composite wall R-value, U-value, and thermal resistance for up to 3 layers.
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°C
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Heat Transfer Rate (W)
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Heat Flux (W/m²) —
Thermal Resistance (K/W) —
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W/m·K
m²
°C
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Heat Rate Q (W)
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Heat Flux (W/m²) —
Thermal Resistance (K/W) —
Professional Full parameters & maximum detail ▾
W/m·K
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W/m·K
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W/m·K
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°C
Composite Wall Resistance
R Layer 1 (K/W) —
R Layer 2 (K/W) —
R Layer 3 (K/W) —
Total R (K/W) —
Overall Heat Transfer
U-value (W/m²·K) —
Heat Transfer Rate (W) —
How to Use This Calculator
- Select heat transfer mode (conduction, convection, or radiation).
- Enter the relevant parameters.
- Results show heat rate in Watts, heat flux, and thermal resistance.
- Use the Professional tab for composite wall analysis with R-value and U-value.
Formula
Conduction: Q = k·A·ΔT/L
Convection: Q = h·A·ΔT
Radiation: Q = ε·σ·A·(T₁⁴ − T₂⁴), σ = 5.67×10⁻⁸ W/m²·K⁴
Example
Example (Conduction): Steel plate, k=50 W/m·K, A=1 m², ΔT=50°C, L=0.01 m. Q = 50×1×50÷0.01 = 250,000 W.
Frequently Asked Questions
- Conduction is heat transfer through a solid material. Convection is heat transfer between a surface and a fluid in motion. Radiation is energy transfer through electromagnetic waves — no medium required.
- Fourier's Law: Q = k × A × ΔT ÷ L, where Q = heat rate (W), k = thermal conductivity (W/m·K), A = area (m²), ΔT = temperature difference (°C), L = thickness (m).
- Newton's Law of Cooling for convection: Q = h × A × ΔT, where h = convection coefficient (W/m²·K), A = surface area, ΔT = temperature difference between surface and fluid.
- R-value is thermal resistance (K/W) — higher R = better insulation. U-value = 1/R = overall heat transfer coefficient (W/m²·K). Lower U-value = better insulation.
- Common k values (W/m·K): Steel 50, Aluminum 205, Copper 385, Concrete 1.4, Glass 1.0, Brick 0.7, Wood 0.17, Fiberglass insulation 0.04, Air 0.026.