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)
Get the Method Selection Guide for Measuring Thermal Conductivity
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 |
|---|---|---|---|---|---|
SPEED & FLEXIBILITY |
|||||
| 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 |
ISO-22007-2, GB/T 32064 |
ASTM C518, C177 | ASTM E1461, E2585 |
RANGE |
|||||
| k-Range (W/mK) | 0 – 500 | 0.1 – 6 | 0 – 100 (100 – 500 requires Cρ) | 0 – 2 | 0 – 500 (requires density & Cρ) |
SAMPLE CONFIGURATION |
|||||
| 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, Liquid | Solids | Solids |
| Isotropic & Anisotropic Materials | Yes | No | Yes (Requires Cρ and Density) | No | Yes |
| Heterogeneous Materials | Yes | No | Yes | No | No |
| PRICING | $$-$$$ | $ | $$$ | $$$ | $$$$ |
