Heat Transfer Coefficient Calculator
Calculate overall heat transfer coefficient and thermal resistance for multi-layer structures
Heat Transfer Coefficient Calculator
Material Layers
Layer 1
Calculation Results
Mode: Conduction Only
Contact Area: 0 m²
Active Layers: 1
Formula Used
1/U = (1/A) × Σ(Li/ki)
Where U = Heat Transfer Coefficient, A = Area, L = Thickness, k = Thermal Conductivity
Example: Double-Glazed Window
Problem Setup
Structure: Double-glazed window
Layer 1: Glass (2 mm thick, k = 0.78 W/(m·K))
Layer 2: Air gap (5 mm thick, k = 0.026 W/(m·K))
Layer 3: Glass (2 mm thick, k = 0.78 W/(m·K))
Area: 1.2 m²
Convection: hi = 10 W/(m²·K), ho = 40 W/(m²·K)
Solution
R = (1/A) × [1/hi + L₁/k₁ + L₂/k₂ + L₃/k₃ + 1/ho]
R = (1/1.2) × [1/10 + 0.002/0.78 + 0.005/0.026 + 0.002/0.78 + 1/40]
R = 0.833 × [0.1 + 0.00256 + 0.192 + 0.00256 + 0.025]
R = 0.269 K/W, U = 3.72 W/(m²·K)
Common Material Properties
Thermal Conductivity [W/(m·K)]
• Concrete: 1.7
• Brick: 0.72
• Glass: 0.78
• Steel: 50
• Aluminum: 237
• Copper: 401
• Wood (Oak): 0.17
• Insulation (Fiberglass): 0.04
• Air Gap: 0.026
• Plaster: 0.48
Typical Convection Coefficients
h [W/(m²·K)]
• Still air: 5-10
• Moving air (wind): 10-100
• Water (natural): 100-1000
• Water (forced): 1000-15000
• Steam condensing: 5000-25000
• Boiling water: 2500-100000
Heat Transfer Tips
Lower U-value means better insulation
Add insulation layers to reduce heat transfer
Air gaps provide excellent insulation
Consider both conduction and convection
Thermal resistance adds in series
Understanding Heat Transfer Coefficient
What is Heat Transfer Coefficient?
The heat transfer coefficient (U-value) measures how well a structure conducts heat. It represents the rate of heat transfer through a unit area per unit temperature difference. Lower values indicate better insulation properties.
Key Concepts
- •Thermal resistance opposes heat flow
- •Resistances add in series for multiple layers
- •Convection occurs at fluid-solid interfaces
- •U-value is the reciprocal of total thermal resistance
Calculation Methods
Conduction Only
R = Σ(L/k)/A
Sum of layer resistances
With Convection
R = [1/hi + Σ(L/k) + 1/ho]/A
Includes surface convection
Heat Transfer Coefficient
U = 1/R
Reciprocal of thermal resistance
Applications
Building Design
Wall insulation, window design, energy efficiency
Heat Exchangers
Thermal analysis, performance optimization
Industrial Processes
Equipment design, energy conservation