Analytical pressure drop correlation for adiabatic vertical two-phase flow

A new correlation for two-phase wall friction is proposed derived from analytical considerations and based upon an annular flow model. In spite of this basis in annular flow the correlation is consistent for all flow patterns in vertical two-phase flow.The correlation yields a smooth transition from two-phase flow to single-phase liquid flow, mainly because it incorporates the friction factor of the Moody diagram [1] for single-phase flow.The correlation is checked against 236 measurements from various sources and has turned out to be most favourable in comparison with the correlations of Dukler (case 2) [2] and Lockhart-Martinelli [3]. The standard deviation of these 236 measurements is 27.8%, with 68% having a relative error of less than 28.2%.