Date of Award
Master of Science (MS)
Simultaneous flow of gas and liquid, generally termed two-phase flow, is often encountered in the chemical, pharmaceutical, and petroleum industries. Annular flow, in which the gas phase flows through the channel center and the liquid moves up along the wall, is a common flow pattern in two-phase flow and occurs when the gas velocity is very high. The gas phase also carries liquid droplets as an entrained phase.
Estimation of pressure drop across a flow channel is often required for analysis and design of the system. Frictional pressure gradient is the major contributor to total pressure gradient during annular two-phase flow, often accounting for more than 90% of the total pressure drop. However, the chaotic nature of this flow regime causes difficulty in predicting the friction factor needed to calculate the frictional pressure gradient.
Three correlations are available to estimate friction factor during annular two-phase flow. These are the Wallis correlation, the Whalley-Hewitt correlation, and the Henstock- Hanratty correlation. This study has found that there large errors in pressure gradient calculations when using the correlations as compared with experimentally measured pressure gradient. The predicted gradients, obtained using the three correlations, were compared with several sets of experimental data. The results show that the Whalley- Hewitt correlation provides the best agreement,but the predictions vary by about 30% from pressure gradients measured experimentally. The Wallis and Henstock-Hanratty correlations are about 40% and 100% in error, respectively. Modification of the Whalley- Hewitt correlation was considered, and the relationships between the flow parameters and the estimation errors were examined. However, the variation between the predicted and the experimental pressure gradient appear to be random and unbiased, and the correlation was not modified.
Si, Danping, "Void Fraction and Pressure Drop in Annular Two-Phase Flow" (1994). Theses and Dissertations. 3844.