New correlations for mixed turbulent natural and forced convection heat transfer in vertical tubes

This work deals with mixed natural and forced turbulent convection hear transfer in vertical tubes. It summarizes the experimental results available in literature for both aiding and opposing flow conditions and presents own experimental results that concentrated on the influence of length-to-diameter ratio and of heal and mass flux directions on heat transfer in vertical tubes. Finally, it presents two new empirical correlations that represent experimental results better than all existing correlations in literature, since they take into account the laminarization of turbulent flow that occurs during aiding mixed convection. They predict experimental results from literature and from this work with an accuracy of better than +/-20%. (C) 1997 Elsevier Science Ltd.