Hot Disk® Instruments is proud to introduce two new Hot Disk® sensors with diameters of 120 and 180 mm. Developed for measurements over larger sample areas and volumes, the sensors extend thermal property characterization to materials with coarse particles and structural features, including gravel, expanded clay aggregate, lightweight concrete, and asphalt.
In heterogeneous materials, a smaller sensor may sample too few particles, pores, inclusions or local features to represent the material as a whole. By including more of the material structure in each measurement, the new large-diameter sensors can reduce sensitivity to sensor position and provide a more representative value for the effective bulk properties.
The 180 mm sensor provides a sensor-to-sample contact area of 254 cm². In a double-sided configuration, using the maximum targeted probing depth, it can probe sample volumes of up to 55 litres. This expands the range of particle sizes, structural features and sample volumes that can be investigated with the Hot Disk® technique.
Measurements presented in our new Application Note confirmed the performance of the 120 mm sensor against established smaller Hot Disk® sensors across materials spanning more than three orders of magnitude in thermal conductivity. Further measurements using the 120 and 180 mm sensors demonstrated their practical value for porous bulk and granular materials. In lightweight concrete, the thermal conductivity values obtained with the two sensors differed by only 0.22%. For expanded clay pellets, the larger measurement region of the 180 mm sensor provided a more representative estimate of bulk thermal conductivity by sampling more particles and interparticle voids.
Read the full Application Note: Large Diameter Hot Disk® Sensors Enabling Thermal Conductivity Measurements of Aggregates and Particulates