The importance of thermal entrance effects in gas-cooled beam windows for radioisotope production targets

The applicability of the Dittus-Boelter and other duct equations in estimating convection heat-transfer coefficients for beam windows used in radioisotope production targetry was investigated. Calculated predictions were compared with experimental measurements for fully-developed flow of helium in a round-duct geometry. It was found that calculations by means of the duct equations are unrealistic unless thermal entrance effects are taken into account.