How to Measure Thermal Conductivity: Method Selection Guide 2nd Edition

How to Measure Thermal Conductivity: Method Selection Guide 2nd Edition

Steady-State Methods for Measuring Thermal Conductivity

Steady-state methods apply a heat source continuously to a sample. They are considered the traditional standard in some applications, such as the Guarded Hot Plate method for building materials. While these methods can be highly accurate, they often often requires large samples, exacting preparation to conform to ISO standards, and long test times. These constraints make steady-state methods challenging to apply against liquids, high-thermal conductivity materials, or smaller samples, such as films or slab-like materials.

Common steady-state methods 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 for Measuring Thermal Conductivity

Transient methods apply the heat source momentarily  and monitors the temperature progression through time, which dramatically reduces test cycle times (minutes versus hours). Over the past three decades, transient methods have been the preferred approach versus steady-state for many researchers due to their speed, flexibility, and smaller sample requirements.

The 2nd Edition highlights the following core transient methods:

• 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)
• Transient Hot Wire (THW): (ISO 22007-4)

Additional Methods Covered in the 2nd Edition (Educational Overview)

To provide a complete picture of the thermal conductivity testing landscape, the guide also includes educational overviews of other methods not part of Trident, such as:

• Single-Sided TPS
• Laser Flash Diffusivity (LFA): (ASTM E1461)
• Frequency-Domain Thermoreflectance / Time-Domain Thermoreflectane (FDTR/TDTR)
• 3-omega