Heat Transfer Calculator
Our thermodynamics & heat calculator computes heat transfer accurately. Enter measurements for results with formulas and error analysis.
Formula
Q = kAΔT/L (conduction) | Q = hAΔT (convection) | Q = εσA(T₁⁴-T₂⁴) (radiation)
Heat conduction rate depends on thermal conductivity, area, temperature difference, and thickness (Fourier's Law). Convection depends on the heat transfer coefficient. Radiation follows the Stefan-Boltzmann law with the fourth power of absolute temperature.
Worked Examples
Example 1: Wall Insulation Heat Loss
Problem: Calculate heat loss through a 150mm fiberglass-insulated wall (k = 0.04 W/m·K), area = 20m², with 20°C inside and -10°C outside.
Solution: k = 0.04 W/(m·K), A = 20 m², ΔT = 30°C, L = 0.15m\nQ = kA(ΔT)/L = 0.04 × 20 × 30 / 0.15 = 160W\nThermal Resistance = L/(kA) = 0.15/(0.04×20) = 0.1875 °C/W\nR-value = L/k = 0.15/0.04 = 3.75 m²·K/W\nHeat Flux = 160/20 = 8 W/m²
Result: Q = 160W | R_th = 0.1875 °C/W | R-value = 3.75
Example 2: Cooling Electronics with Forced Convection
Problem: A 50W processor has a heatsink with 0.02m² surface area. Air is forced over it with h = 150 W/(m²·K). What is the temperature rise?
Solution: Q = hA(ΔT), so ΔT = Q/(hA)\nΔT = 50 / (150 × 0.02) = 16.7°C\nIf ambient = 25°C, heatsink temp = 41.7°C\nThermal Resistance = 1/(hA) = 1/(150×0.02) = 0.333 °C/W
Result: ΔT = 16.7°C | T_surface = 41.7°C | R_th = 0.333 °C/W
Frequently Asked Questions
What are the three modes of heat transfer?
Heat transfers through three fundamental mechanisms: (1) Conduction — heat flows through a solid material or between materials in direct contact, driven by a temperature gradient. Rate depends on thermal conductivity, area, temperature difference, and material thickness. (2) Convection — heat transfer between a surface and a moving fluid (liquid or gas). Can be natural (driven by buoyancy) or forced (driven by fans/pumps). Rate depends on the convection coefficient, area, and temperature difference. (3) Radiation — heat transfer via electromagnetic waves (infrared). Does not require a medium and can occur through vacuum. Rate depends on emissivity, temperature, and area.
What is the convection heat transfer coefficient?
The convection heat transfer coefficient (h) quantifies how effectively heat transfers between a surface and a fluid. It depends on fluid properties, flow velocity, geometry, and whether convection is natural or forced. Typical values: Natural convection in air = 5-25 W/(m²·K). Forced convection in air = 25-250 W/(m²·K). Natural convection in water = 100-900 W/(m²·K). Forced convection in water = 250-12,000 W/(m²·K). Boiling water = 3,000-100,000 W/(m²·K). The coefficient is often determined empirically using dimensionless correlations involving Nusselt, Reynolds, and Prandtl numbers.
What formula does Heat Transfer Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.
Is Heat Transfer Calculator free to use?
Yes, completely free with no sign-up required. All calculators on NovaCalculator are free to use without registration, subscription, or payment.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
Can I use the results for professional or academic purposes?
You may use the results for reference and educational purposes. For professional reports, academic papers, or critical decisions, we recommend verifying outputs against peer-reviewed sources or consulting a qualified expert in the relevant field.