Convective Heat Transfer Correlatons for use with Helium at High Heat Fluxes. Dragon Project Report

A survey has been carried out which covers a total of sixteen heat transfer correlations ranging from the classical Dittus-Boelter relationship. to the formula recommended by M. F. Taylor in 1965. The correlations obtained by Dalle Donne and Bowditch working in the Dragon Project are included. Each formula is applied to the determination of wall temperature in three practical cases comprising an experimental fuel irradiation facility and two sets of reactor operating conditions, one corresponding to the Dragon Experimental Reactor while the other is related to a core design study for a 1,250 MW(th) power reactor. Four correlations were selected for application to a wider range of hypothetical channels in connection with the same design study. Where practical measurements are available the appropriate comparisons are made. A brief reference is made to the applicability of results obtained on circular channels to those of other shapes. The predicted temperatures vary considerably. The differences emphasise the importance of ascertaining the range of validity of a correlation as defined by the conditions covered by the supporting experiments. Equally important is the use of appropriate values for the physical properties of helium. Some of the correlations are particularly sensitive to these and other uncertainties. The decision as to the best formula to apply to a given problem must rest on the above considerations and on the strength of its experimental support. (author)