Discussion: “Internal Bearing Chamber Wall Heat Transfer as a Function of Operating Conditions and Chamber Geometry” [ASME J. Eng. Gas Turbines Power, 122, No. 2, pp. 314–320]¹

The subject under investigation is very important to the gas turbine industry, and the derivation of a correlation for the oil chamber wall heat transfer coefficient is long past overdue. The complexity, however, is that the correlation needs to represent the two-phase flow regime (liquid oil + air) along the chamber wall which changes with engine operating conditions. Therefore, the proposed correlation in this paper requires further validation in order to delineate the effect of two-phase flow regime. Would the authors comment on why the definition of the Reynolds number (Eq. (12)) is not based on local tangential velocity $ns×rs$ but rather a pseudo tangential velocity based on circumference $ns×2πrs.$ Also, if the chamber circumference is $U=πDh,$ why are the Reynolds numbers of Eqs. (15) and (16) written without the π?