Heat transfer measurements in rotating-disc systems Part 2: The rotating cavity with a radial outflow of cooling air

Abstract

A comparison between theorerical and experimental results is presented for the flow and heat transfer in a rotating cavity with a radial outflow of cooling air for a range of rotational Reynolds numbers up to Re φ = 3.3 × 10 6 and dimensionless flow rates up to C w = 14,000. Flow visualization confirmed that the flow structure comprises a source region, Ekman layers, a sink layer, and an interior core of rotating fluid, and measured values of the size of the source region are in good agreement with a simple theoretical model. Except at high flow rates and low rotational speeds, where the source region fills the entire cavity, the agreement between the measured and theoretically determined local Nusselt numbers is mainly good. A maximum value of Nusselt number occurs at the approximate edge of the source region, and Nu increases with increasing C w and Re φ. The radial distribution of temperature has a significant effect on the Nusselt numbers, particularly in the Ekman-layer region, and under some conditions negative values of Nu have been predicted and measured.