Productive ToolboxHeat Transfer Calculator
Calculate heat transfer rate instantly using conduction, convection, or radiation formulas. Supports SI and imperial units with real-time results and formula breakdowns.
Heat Transfer Calculator
Select a heat transfer mode — conduction, convection, or radiation — enter your values, and get instant results with formula breakdowns and unit conversions.
Transfer Mode
Heat Transfer Rate
Settings & Actions
Conduction Inputs
Material Preset
Copper: 401 · Aluminum: 205 · Steel: 50
Press Esc to reset
What is a Heat Transfer Calculator?
A Heat Transfer Calculator is an engineering tool that computes the rate of thermal energy transfer between systems or surfaces. Heat transfer occurs through three fundamental mechanisms: conduction, convection, and radiation — each governed by a distinct physical law.
This calculator supports all three modes. For conduction, it applies Fourier's Law (Q = kAΔT/L). For convection, it uses Newton's Law of Cooling (Q = hAΔT). For radiation, it applies the Stefan-Boltzmann Law (Q = εσA(T₁⁴ − T₂⁴)).
Results are displayed in Watts (W), kilowatts (kW), BTU/hr, and kcal/hr simultaneously, supporting both SI and imperial unit systems for global engineering use.
How to Use the Heat Transfer Calculator
Step-by-Step Guide
- 1Select the transfer mode: Conduction, Convection, or Radiation
- 2Enter the required inputs for the selected mode
- 3Choose your preferred unit system (SI or Imperial)
- 4For conduction, use material presets to auto-fill conductivity
- 5View the heat transfer rate instantly in all units
- 6Save results to history or export as a TXT report
Key Features
- ✓Real-time calculation as you type
- ✓Three heat transfer modes in one tool
- ✓Material presets for conduction (Copper, Aluminum, Steel, etc.)
- ✓Scenario presets for convection (Natural Air, Forced Air, Water)
- ✓Emissivity slider for radiation inputs
- ✓Automatic temperature unit conversion to Kelvin
- ✓Multi-unit output: W, kW, BTU/hr, kcal/hr
- ✓Calculation history with localStorage persistence
- ✓Export results as a TXT file
Heat Transfer Formulas Explained
🔥 Conduction
Heat flows through a solid material. Higher conductivity (k) and larger area increase heat flow; greater thickness reduces it.
💨 Convection
Heat transfers between a surface and a moving fluid. The coefficient h depends on fluid type and flow conditions.
☀️ Radiation
Heat transfers via electromagnetic waves. Requires absolute temperatures in Kelvin. σ = 5.67×10⁻⁸ W/m²·K⁴.
Example Calculations
| Mode | Inputs | Result |
|---|---|---|
| Conduction | k=205 W/m·K, A=2 m², ΔT=40°C, L=0.1 m | 164,000 W |
| Conduction | k=50 W/m·K (Steel), A=1 m², ΔT=100°C, L=0.05 m | 100,000 W |
| Convection | h=25 W/m²·K, A=5 m², ΔT=20°C | 2,500 W |
| Convection | h=500 W/m²·K (Water), A=0.5 m², ΔT=15°C | 3,750 W |
| Radiation | ε=0.9, A=3 m², T₁=400 K, T₂=300 K | ≈2,237 W |
| Radiation | ε=1.0, A=1 m², T₁=1000 K, T₂=300 K | ≈55,960 W |
Thermal Conductivity Reference
| Material | k (W/m·K) | Category |
|---|---|---|
| Copper | 401 | Metal |
| Aluminum | 205 | Metal |
| Steel | 50 | Metal |
| Glass | 1.05 | Non-metal |
| Concrete | 1.7 | Building material |
| Wood | 0.15 | Building material |
| Fiberglass | 0.04 | Insulation |
| Air | 0.026 | Gas |
Real-World Applications
Building Insulation
Calculate heat loss through walls, roofs, and windows to optimize insulation thickness and energy efficiency.
HVAC Systems
Size heating and cooling equipment by calculating convective heat transfer between air and surfaces.
Electronics Cooling
Design heatsinks and cooling systems for CPUs, power electronics, and LED lighting.
Industrial Furnaces
Radiation dominates at high temperatures. Calculate heat output from furnace walls and heating elements.
Material Science
Compare thermal conductivity of materials to select the best option for heat exchangers or insulation.
Engineering Education
Verify textbook problems and explore how changing parameters affects heat transfer rates.
Frequently Asked Questions
What is heat transfer?
Heat transfer is the movement of thermal energy from a hotter region to a cooler one. It occurs through three mechanisms: conduction (through solids), convection (through fluids), and radiation (through electromagnetic waves).
What is the Stefan-Boltzmann constant?
The Stefan-Boltzmann constant (σ) equals 5.67×10⁻⁸ W/m²·K⁴. It appears in the radiation formula and relates the heat radiated by a blackbody to the fourth power of its absolute temperature.
Why must radiation temperatures be in Kelvin?
The Stefan-Boltzmann Law uses absolute temperatures raised to the fourth power. Celsius and Fahrenheit scales have arbitrary zero points, so they cannot be used directly. The calculator automatically converts °C and °F to Kelvin.
What is emissivity?
Emissivity (ε) is a dimensionless value between 0 and 1 that describes how efficiently a surface emits thermal radiation compared to a perfect blackbody (ε = 1). Polished metals have low emissivity (~0.05), while painted surfaces and most non-metals have high emissivity (~0.9).
What is the difference between conduction and convection?
Conduction transfers heat through direct molecular contact within a solid material. Convection transfers heat between a solid surface and a moving fluid (liquid or gas). Convection is generally faster than conduction in fluids because fluid motion carries heat away.
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