In liquids, convective heat transfer has to be avoided to be able to test the conductive heat transfer and thermal conductivity. With the Hot Disk method this is achieved by using short measurement times and small sample volumes in minimal contact with the surroundings. The close proximity of the chamber walls and the negligibel evaporation eliminates natural convection. The short measurement times makes it possible to collect measurement data before the heating of the sensor generates convection.

 

Onset of convection due to sensor heating occurs after 0.5 – 1 seconds for low viscosity liquids. For best possible results, Hot Disk sensors 7577 and 5465 are recommended, along with either the TPS 2500 S or TPS 3500 system. Further improvement is achieved by locking the specific heat of the sample, which stabilizes the result when the Total-to-Characteristic-time is low.