Thermal Conductivity Calculation Formula

Thermal Conductivity Equation:

\[ k = \frac{Q \times L}{A \times \Delta T \times t} \]

Heat (Q):

Length (L):

Area (A):

m²

Temperature Difference (ΔT):

°C

Time (t):

Thermal Conductivity (k):

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1. What is Thermal Conductivity?

Thermal conductivity (k) is a measure of a material's ability to conduct heat. It appears in Fourier's law of heat conduction and is defined as the quantity of heat (Q) transmitted through a unit thickness (L) in a direction normal to a surface of unit area (A) due to a unit temperature gradient (ΔT) under steady state conditions.

2. How Does the Calculator Work?

The calculator uses the thermal conductivity equation:

\[ k = \frac{Q \times L}{A \times \Delta T \times t} \]

Where:

\( k \) — Thermal conductivity (W/m·K)
\( Q \) — Heat transferred (J)
\( L \) — Length of material (m)
\( A \) — Cross-sectional area (m²)
\( \Delta T \) — Temperature difference (°C)
\( t \) — Time (s)

Explanation: The equation calculates how much heat is transferred through a material of given dimensions under a specific temperature gradient over time.

3. Importance of Thermal Conductivity

Details: Thermal conductivity is crucial in material science, building insulation, heat exchanger design, and many engineering applications where heat transfer needs to be controlled or optimized.

4. Using the Calculator

Tips: Enter all values in the correct units. Ensure all values are positive numbers. The calculator will compute the thermal conductivity in watts per meter-kelvin (W/m·K).

5. Frequently Asked Questions (FAQ)

Q1: What are typical thermal conductivity values?
A: Metals have high k (e.g., copper ~400 W/m·K), while insulators have low k (e.g., air ~0.024 W/m·K).

Q2: How does temperature affect thermal conductivity?
A: For metals, k decreases with temperature; for gases and insulators, k generally increases with temperature.

Q3: What's the difference between thermal conductivity and thermal resistance?
A: Thermal resistance is the reciprocal of thermal conductivity and includes thickness (R = L/k).

Q4: Can this calculator be used for composite materials?
A: No, this calculates k for homogeneous materials. Composites require more complex calculations.

Q5: What are common measurement methods for thermal conductivity?
A: Common methods include guarded hot plate, heat flow meter, and laser flash techniques.