The thermal conductivity of roller bearings is a relevant property for applications in optical instruments or aerospace technology (i.e. reaction flywheels), especially due to the fact that waste heat cannot be cooled through convection in the vacuum of space. Another application that has gained importance in recent years are flywheel energy storage systems (FESS), which can be used as uninterruptible power supplies (UPS) for critical loads, for load averaging in hybrid vehicles or even to store energy from renewable, volatile sources.
However, the steady state temperature level of the FESS strongly depends on the thermal conductivity of the bearing, but not data is scarce and the relevant values could not be found in literature. In order to generate reliable input data for numerical thermal models, a test rig to investigate the relevant properties of roller bearings was designed. Thermal conductivity, torque/heat loss etc. can be determined depending on a variety of operating conditions such as axial pre-stress, ambient pressure, speed, lubrication, mass imbalance and so on.