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Thermal Conductivity of Solids
There are a number of accurate methods for measuring the thermal conductivity of solids. For highest accuracy, absolute methods are preferred as they offer the least uncertainty in the measurement. In selecting an appropriate method, there are a number of other considerations, such as thermal conductivity range, surface, sample size, and temperature.
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Transient Plane Source
The Transient Plane Source is one of the most versatile methods of measuring thermal conductivity. As the method is absolute, the contact resistance between sensor and sample is able to be removed and the true value tested. With this capability materials of varying surface finish are able to be tested. There are a number of sensor sizes to accommodate different sizes samples. The method also has the ability to measure anisotropic materials.
Materials | Solids, Liquids, Paste and Powder |
Thermal Conductivity Range | 0.005 to 1800 W/m•K |
Directional Measurement | Bulk, Through-thickness and In-plane |
Temperature Range | -160°C to 1000°C |
Accuracy, Repeatability | 5%, 2% |
Standard | ISO/DIS 22007-2.2 |
Thermtest Heat Flow Meter
The Heat Flow Meter is universally used for the thermal conductivity measurement of foams and heterogeneous materials. The strength lies in the ability to test large samples, which is critical for the measurement of non-homogenous samples.
Materials | Solids and Loose Materials |
Thermal Conductivity Range | 0.001 to 0.5 W/m•K |
Directional Measurement | Bulk |
Temperature Range | -20°C to 75°C |
Accuracy, Repeatability | 3%, 1% |
Standard | ASTM C518 |
Thermtest Transient Line Source
The portable TLS is simple to use and convenient for testing of soft or drillable materials.
Materials | Soil and Soft Materials |
Thermal Conductivity Range | 0.1 to 5 W/m•K |
Directional Measurement | Bulk |
Temperature Range | -50°C to 100°C |
Accuracy, Repeatability | 5%, 2% |
Standard | ASTM D5334 |
Thermtest Transient Hot Wire Solids
The Transient Hot Wire for solids is especially designed for testing very small insulative samples. The wire can also be integrated into cast-able materials like aerogel for intimate contact.
Materials | Solids |
Thermal Conductivity Range | 0.01 to 0.2 W/m•K |
Directional Measurement | Bulk |
Temperature Range | Room temperature |
Accuracy, Repeatability | 5%, 2% |
Standard | NA |
Laser Flash Apparatus
The laser flash method is a popular testing method for a board range of materials. Thermal Diffusivity is the output, with known specific heat, thermal conductivity can be calculated. The LFA performs best on materials with a thermal conductivity over ~ 0.2 W/m•K and offers an excellent temperature range.
Materials | Solids |
Thermal Conductivity Range | 0.1 to 2000 W/m•K |
Directional Measurement | Through-thickness |
Temperature Range | -160°C to 1600°C |
Accuracy, Repeatability | 5%, 2% |
Standard | ASTM E1461 |
Guarded Hot Plate
The measuring tools allow the determination of the thermal conductivity and the thermal resistance of homogenous plates and inhomogeneous test specimens, if the samples are plane and plate-shaped.
Materials | Solids |
Thermal Conductivity Range | 0.005 to 2 W/m•K |
Directional Measurement | Through-thickness |
Temperature Range | -160°C to 100°C |
Accuracy, Repeatability | 2%, 0.5% |
Standard | ASTM C177 |
Guarded Heat Flow Meter
The guarded heat flow meter is ideally suited for materials from plastics to metals up to 40 W/m•K. The minimum sample size is 2 inch diameter.
Materials | Solids & Pastes |
Thermal Conductivity Range | 0.1 to 40 W/m•K |
Directional Measurement | Through-thickness |
Temperature Range | -20°C to 300°C |
Accuracy, Repeatability | 5%, 2% |
Standard | ASTM E1530 |
Guarded Heat Flow Meter – Gasket Materials
This is the only standard method specifically designed for testing thermal conductivity of gasket materials.
Materials | Solids |
Thermal Conductivity Range | 0.1 to 1 W/m•K |
Directional Measurement | Through-thickness |
Temperature Range | -10°C to 80°C |
Accuracy, Repeatability | 3%, 1% |
Standard | ASTM F433 |
Guarded Comparative Longitudinal Heat Flow Meter
Has wide temperature range for testing metals and ceramics.
Materials | Solids |
Thermal Conductivity Range | 0.2 to 200 W/m•K |
Directional Measurement | Bulk |
Temperature Range | up to 1000°C |
Accuracy, Repeatability | 5%, 2% |
Standard | ASTM E1225-13 |
Physical Properties Measurement System
Specially designed for testing to -270°C.
Materials | Solids |
Thermal Conductivity Range | 0.1 to 20 W/m•K |
Directional Measurement | Through-thickness and In-plane |
Temperature Range | -270°C to 100°C |
Accuracy, Repeatability | 5%, 2% |
Standard | NA |