Tackle a Vast Range of Applications

This application note presents the development and application of our innovative Hot Cell® sensors. These have been tailored for testing batteries of all modern types: cylindrical-cell; button-cell; pouch-cell; and prismatic-cell.

Modern batteries (Li-ion) have drastically different thermal ­conductivity in different directions. Using a Hot Disk instrument makes it easy and accurate to ­measure these properties, in one single transient.

The Hot Disk® method is commonly used for measuring anisotropic materials, which has different thermal properties in the in-plane (radial) and through-plane (normal) directions. These are materials with plane fillers or stacks of sheets, or laminates; most batteries are a good example of such composites, where it is crucial to understand the thermal transport in-plane and through-plane to avoid overheating and hence ignition. It is straightforward to use Hot Disk® sensors and the Hot Disk® Anisotropic module to test this type of sample.

One of the few drawbacks of thermoplastics is their limited thermal conductivity, which can be an issue in some applications, where this is necessary for thermo-management of components like electronics. The aim of this work was to improve the thermal conductivity of selected plastics with the addition of particles and assess these changes in thermal conductivity with the Hot Disk TPS 2200.

In this work, the thermal conductivity values of construction materials including 3D printed samples for different directions are measured using a Hot Disk TPS 2200 (Hot Disk AB, Sweden) device. The obtained thermal properties are directly utilized to evaluate the material performance for heat flow as well as insulation and can also be utilized for numerical analysis as an input parameter. Following are some examples of the application of the Hot Disk device for building materials.

Testing the intrinsic thermal conductivity of liquids can be a challenge compared to testing solids. The reason for this is that convective heat transfer in the fluid during the measurement. However, the Hot Disk method can be utilized to test liquid samples with relative ease. The keys to success are small volumes, closed sample cells and short measurement times.

In this example, a commercial silicone oil has been tested to demonstrate the robustness of Hot Disk results when measuring on liquids.

Two figures of merit are commonly used to describe how “good” an analysis technique is. One is Accuracy, telling how correct the measurement is, the other is Precision, telling how well a result is repeated using the same instrument. This application note deals with the accuracy of thermal conductivity measurements, utilizing water to exemplify how the quality of a Hot Disk measurement can be assured.

Testing high-conducting graphite with the Hot Disk method is gives fast and accurate results.

For testing low-viscosity liquids (eg. Toluene and H₂O), short measurement times are required to avoid convective heat transfer.

Thermal Conductivity Measurements on powders depend on applied particle-particle pressure as well as interstitial gas pressure. Here we show how these factors affect the measurement results.

Thermal contact resistance is always present in the interface between two solid surfaces. In this example, we look at contact resistance between layers in a stack of copper sheets and its impact on the apparent thermal conductivity across the layers.

Testing small thermoelectric samples is easy with the Hot Disk technique. In this example two sets of hot-pressed Bi₂Te₃, p- and n-type, with diameter 12 mm and thickness 3.5 mm where analysed.