In some cases, the mass flow rate needed to prevent ingress through rim seals in turbine is smaller than that entrained by a free disk. In order to obtain the heat transfer features of the rotor-stator system at such a small mass flow rate, a combined computational and theoretical study has been carried out. It is found that the average Nusselt number (Nuav) on the rotor drops approximately linearly down to zero with decreasing turbulent flow parameter (λt) when λt is smaller than λt,c (λt,c < λt,fd), while Nuav almost keeps constant when λt is larger than λt,c. A correlation between Nuav and λt has been developed, which is expected to be useful in determining disk temperatures in the preliminary design of an internal air cooling system. The Eckert number, which can express the relationship between heat generated by windage and heat conducted through disk, turns out to be an important nondimensional number in describing the heat transfer features of such rotor-stator systems. Moreover, the effect of rotational speed on heat transfer when λt,c<λt<λt,fd has been studied, further identifying the significance of the Eckert number.

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