Comparing Thermal Conductivity Methods


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Methods for Measuring Thermal Conductivity: Steady-State vs Transient Methods


Steady-state methods apply a heat source continually to sample material. They are considered the traditional standard in some applications, such as the Guarded Hot Plate method for building materials. Measurement accuracy often requires large samples, exacting sample preparation to conform to ISO standards, and long test times. This destructive method does not work for liquids or high thermal conductivity materials and required specially machined sample slabs.

Steady-state methods for measuring thermal conductivity include:

  • Guarded Hot Plate (ASTM C177)
  • Heat Flow Meter (ASTM C518)
  • Guarded-Comparative–Longitudinal Heat Flow Meter (ASTM E1225)
  • Comparative-axial-heat-flow (cut-bar) Method

Transient methods apply the heat source periodically or in a pulse, which dramatically reduces test times (minutes versus hours). Transient methods have surpassed steady-state methods over the past three decades due to their flexibility in terms of short test times, accuracy, and smaller sample size.

There are four common transient methods for measuring thermal conductivity:

  • Modified Transient Plane Source (MTPS): (ASTM D7984)
  • Transient Plane Source (TPS): (ISO 22007-2 and GB/T 32064)
  • Transient Line Source (TLS): (ASTM D5334 and D5930)
  • Laser Flash Diffusivity: (ASTM E1461) 

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Comparing Thermal Conductivity Methods

Compare Method

Modified Transient Plane Source

Transient Line Source

Transient Plane Source

Guarded Hot Plate / Heat Flow Meter

Laser Flash Diffusivity


Sample Preparation None Required None Required Some Extensive Extensive
Testing Time Seconds Minutes Minutes Hours Hours
Training Time Minimal Minimal Significant Moderate Moderate
Non-Destructive Yes Yes No No No
Method Development
ASTM/ISO Standards ASTM D7984, WK50791, WK43689 ASTM D5334, D5930, IEEE442


GB/T 32064

ASTM C518, C177 ASTM E1461, E2585


k-Range (W/mK) 0 – 500 0.1 – 6 0.005 – 2000 (requires Cρ) 0 – 2 0 – 500 (requires density & Cρ)


Minimum 0 – 500 80 ml Two Identical Samples 6” x 6” (150 x 150mm) 0.5” diameter (12.4mm) 0.004” thick (1mm)
Maximum Unlimited (17mm) Unlimited Two Identical Samples Unlimited 24” x 24” (600 x 600mm) 0.5” diameter (12.4mm) 0.004” thick (1mm)
Material Testing Capability Solids, Liquids, Powders, Pastes Granular Materials, Powders, Slurries, Gels, and Pastes Solids Solids Solids
Isotropic & Anisotropic Materials Yes No Yes (Requires Cρ and Density) No Yes
Heterogeneous Materials Yes No Yes No No
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