Heat Transfer Calculator
Calculate heat transfer rates for conduction, convection, and radiation. Analyze thermal resistance, heat exchangers, and thermal system performance.
Heat Transfer Calculator
Comprehensive thermal calculations for conduction, convection, radiation, and heat exchangers
Heat Transfer Calculation
Conduction Parameters:
Calculation Result
280.000
W
Conduction
Formula Used:
Q = k × A × ΔT / L
Three Modes of Heat Transfer
Conduction
Heat transfer through a solid material. k = thermal conductivity (W/m·K), A = cross-sectional area (m²), ΔT = temperature difference, L = thickness. Higher k = better heat conductor. Copper (400 W/m·K) conducts heat ~1,000× better than wood.
Applications:
• Heat sink design
• Building insulation
• Pipe heat loss
• Electronic cooling
Convection (Newton's Law of Cooling)
Heat transfer between a surface and a fluid. h = convective heat transfer coefficient (W/m²·K), Ts = surface temperature, T∞ = fluid temperature. Natural convection: h ≈ 5-25 W/m²·K. Forced convection: h ≈ 25-250 W/m²·K.
Applications:
• HVAC systems
• Engine cooling
• Heat exchangers
• Electronic cooling fans
Radiation (Stefan-Boltzmann)
Heat transfer via electromagnetic waves — no medium required. ε = emissivity (0-1), σ = Stefan-Boltzmann constant (5.67×10⁻⁸ W/m²·K⁴), T = absolute temperature (K). Dominant at high temperatures — furnaces, boilers, solar collectors.
Applications:
• Solar energy systems
• Furnace design
• Spacecraft thermal control
• Building energy modeling
Frequently Asked Questions
What is thermal conductivity and which materials have the highest values?
Thermal conductivity (k) measures how well a material conducts heat in W/m·K. Highest conductors: diamond (~2,000), silver (429), copper (401), aluminum (237), steel (15-50). Insulators: fiberglass (0.04), air (0.024), aerogel (0.015). This determines whether a material should be used to conduct or block heat.
What is the R-value in building insulation?
R-value is thermal resistance = L / (k × A), measuring how well insulation resists heat flow. Higher R-value = better insulation. US homes typically need R-38 to R-60 in attics. R-value is additive — R-19 batt + R-19 batt = R-38 total. SI equivalent is RSI (1 RSI = 5.678 R-value).
What is the LMTD method for heat exchanger design?
LMTD (Log Mean Temperature Difference) is used to calculate heat transfer in exchangers where fluid temperatures change continuously. Q = U × A × LMTD, where U is the overall heat transfer coefficient. LMTD = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂). Counter-flow exchangers are more efficient than parallel-flow because they maintain larger temperature differentials.
How is heat transfer relevant to electronics thermal management?
Electronic components generate heat that must be removed to prevent failure. Typical approaches: thermal interface materials (TIM) to reduce contact resistance, heat sinks (finned aluminum) to maximize convection area, fans for forced convection, heat pipes for spreading heat, and liquid cooling for high-power devices. Maximum junction temperature for most semiconductors is 85-150°C.