Thermal Conductivity Calculator
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The thermal conductivity calculator allows you to calculateheat flux (q),thermal conductivity coefficient (λ),temperature difference (ΔT) orlayer thickness (Δx) based on Fourier's law. The tool supports SI and technical units and enables fast thermal simulations for metals, insulation and fluids. Perfect for engineering calculations, teaching and insulation quality control.
Theoretical foundations
Fourier's law
q = -λ · (ΔT / Δx)
- q– heat flux [W/m²]
- λ– thermal conductivity coefficient [W/(m·K)]
- ΔT– temperature difference between surfaces [K]
- Δx– material layer thickness [m]
In practice, the negative sign indicates the direction of heat flow (from the warmer to the cooler layer). The calculator operates in absolute values, taking positiveΔTas the temperature difference in the direction of flow.
Calculation modes
Select the quantity you want to calculate:
- q– calculate heat flux with known λ, ΔT and Δx
- λ– calculate thermal conductivity with known q, ΔT and Δx
- ΔT– calculate temperature difference with known q, λ and Δx
- Δx– calculate the layer thickness with known q, λ and ΔT
Each mode allows you to set the units for temperature, power and length as well as the precision of the result.
Units and conversions
| Size | Symbol | Units | Default |
|---|---|---|---|
| Heat flux | q | W/m², kW/m² | W/m² |
| Thermal conductivity | λ | W/(m K) | W/(m K) |
| Temperature difference | ΔT | K, °C | K |
| Material thickness | Δx | m, mm | m |
Thermal conductivity coefficient values λ
| Material | λ [W/(m K)] | Characteristics |
|---|---|---|
| Silver | 429 | The best natural heat conductor |
| Copper | 398 | Very good conductivity, typical of installation |
| Aluminum | 237 | Light, good conductor |
| Steel | 50 | Moderate conductor |
| Concrete | 1.7 | High thermal mass, moderate conductivity |
| Water | 0.6 | Liquid conductor in convection processes |
| Glass | 1.05 | Insulator for most applications |
| Styrofoam | 0.036 | Very good insulator |
| Air | 0.025 | The most common insulator in structures |
Calculation examples
Example 1 - calculation of heat flux
- λ = 0.04 W/(m·K)
- ΔT = 30 K
- Δx = 0.15 m
q= 0.04 × (30 / 0.15) = 8 W/m². This is the heat flux through a 15 cm layer of Styrofoam at a difference of 30°C.
Example 2 - calculation of λ
- q = 50 W/m²
- Δx = 0.02 m
- ΔT = 5 K
λ= (q · Δx) / ΔT = (50 × 0.02) / 5 = 0.2 W/(m · K). Typical for engineering plastics.
Example 3 - calculation of ΔT
- λ = 0.5 W/(m · K)
- q = 25 W/m²
- Δx = 0.1 m
ΔT= (q · Δx) / λ = (25 · 0.1) / 0.5 = 5 K. This means a difference of 5°C between layers of 10 cm of material.
Example 4 - layer thickness
- λ = 0.037 W/(m · K)
- q = 10 W/m²
- ΔT = 25 K
Δx= (λ · ΔT) / q = (0.037 × 25) / 10 = 0.0925 m = 9.25 cm. Insulation of this thickness will provide a given temperature drop.
Practical applications
- Design of insulation for buildings, pipes and tanks.
- Analysis of heat losses through partitions and walls.
- Assessment of thermal efficiency of composite materials.
- Laboratory tests on the thermal conductivity of samples.
- Thermal modeling in industrial and HVAC processes.
Most common errors and notes
- ΔT should be used in Kelvin (the difference in °C is equivalent).
- Note the thickness in mm - convert to meters before calculation.
- Do not use the formula for materials with convection (e.g. moving fluids).
- The flux q applies to a unit area. For the total power, multiply by the area A.
- The value of λ depends on the temperature, humidity and structure of the material.
FAQ
Does the calculator take convection into account?
No. The calculations concern only thermal conductivity in the steady state.
How to convert mm to m units?
Divide the value in millimeters by 1000. Example: 50 mm = 0.05 m.
Is the temperature difference in °C and K the same?
Yes. ΔT in Kelvin numerically corresponds to ΔT in degrees Celsius.
What materials are the best insulators?
Styrofoam, mineral wool, polyurethane and air. They have λ below 0.05 W/(m·K).
How to increase thermal conductivity?
Use metals, increase material density or lower contact resistance between layers.
Summary
The thermal conductivity calculator is based on the simple but fundamental Fourier's law. It allows you to verify insulation losses and efficiency, select material thicknesses and analyze the thermal properties of solids. Thanks to the support of various units and flexible calculation modes, it is an indispensable tool in construction, thermal and materials engineering.