Static Ball Bearing Thermal Conductance in Air and Vacuum: Review and Correlation

A literature review of static ball bearing thermal conductance in both air and vacuum was performed, with an emphasis on understanding the conductance that would be expected across ball bearings of various sizes. Although a large number of variables can affect bearing thermal conductance, the review and survey of 353 data points from previous studies indicates that a reasonable relationship between the bearing size and thermal conductance exists. Correlations of bearing conductance as a function of the bearing outside diameter were developed for dry, marginally lubricated, and flooded bearings in vacuum. The correlation for dry bearings is a less accurate, but more convenient, order-of-magnitude estimate than the analytical expressions widely available in the literature for dry bearings. However, the marginally lubricated and flooded correlations have R-squared values of 0.87 and 0.89, and 95% of the data points for these bearings fall within 50% of the value given by the proposed correlations. This work is of practical use to engineers who seek to estimate the static bearing thermal conductance in vacuum and atmospheric environments.