Understanding Separated Flow Model-5 — Lesson 7

This lesson covers the concept of the separated flow model in fluid dynamics. It delves into the estimation of the frictional pressure gradient and the void fraction from the separated flow model. The lesson explains the empirical approach to developing the model, which assumes that the two phases are flowing at different velocities. It also discusses the basic assumptions of the simplified one-dimensional approach. The lesson further explores the correlations for finding out the frictional pressure gradient and the void fraction. It also explains the concept of two-phase multipliers and the correlations developed by Lockhart and Martinelli. The lesson concludes with the analytical expression of the graphical correlation and its accuracy.

Video Highlights

00:16 - Introduction to the separated flow model and the estimation of the frictional pressure gradient and void fraction from the model
06:19 - Explanation of the assumptions made for the derivation of phi L square and phi g square from the basic single-phase hydrodynamics
33:37 - Discussion on the analytical expression of the graphical correlation between phi L square and phi g square
42:40 - Explanation of the force balance on the combined phase and the gas phase in the annular flow pattern
45:26 - Discussion on the assumptions made for the analysis of the annular flow pattern and the derivation of phi L square

Key Takeaways

- The separated flow model in fluid dynamics is used to estimate the frictional pressure gradient and the void fraction.
- The empirical approach to developing the model assumes that the two phases are flowing at different velocities.
- The basic assumptions of the simplified one-dimensional approach are crucial in understanding the model.
- The correlations for finding out the frictional pressure gradient and the void fraction are based on no phase change, no acceleration, and negligible body force.
- The concept of two-phase multipliers is essential in understanding the flow of liquid and gas in the pipe.
- The correlations developed by Lockhart and Martinelli are widely used in this field.
- The analytical expression of the graphical correlation is used to determine the accuracy of the model.