Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.
Void fraction correlations for various pipe inclioations, both theoretical and empirical, that are widely available in the literature, are compared with experimental data from various sources with different experimental facilities. The discussion here consists of results from collaborated studies on void fraction, which led to the recommendation of a general correlation for various pipe inclinations and working two-phase fluids, and the recommendation of a correlation specifically for upward vertical pipes. The work demonstrated that more accurate predictions can be obtained by giving attention to specific ranges of void fraction in upward vertical pipes. An ongoing study on void fraction in horizontal pipes has led to several correlations, which compared satisfactorily with the experimental data, and the best correlation has yet to be identified. Flow pattern maps of different pipe inclioations that are available in the literature are compared and discussed.