Understanding Choking Condition in Two Phases — Lesson 5

This lesson covers the derivation of the condition of chocking constrained with two phases separately and the change of phase. The instructor explains the momentum equation for phase two and phase one, and how to derive the condition of compound chocking. The lesson also discusses the condition of chocking in the presence and absence of flashing. The instructor then presents a problem based on the flow of an air-water mixture through a nozzle, demonstrating how to solve it under two extreme conditions: when the two phases are intimately mixed and when they flow in separate layers.

Video Highlights

3:22 - 3:59 - Discussion on the denominator part of the equation and its relation to the Mach number
5:09 - 5:33 - Mixture momentum equation and its relation to the condition of choking
7:28 - 7:52 - Derivation of the Mach number from the two fluid model
17:19 - 17:33 - Assumptions made in deriving the condition of choking
26:10 - 26:28 - Derivation of the condition of choking considering two phases separately with change of phase
32:5 - 32:17 - Equation of continuity and its role in deriving the condition of choking
45:20 - 45:54 - Explanation of the final expression for the condition of choking for phase 2
47:13 - 47:20 - Derivation of an identical equation for phase 1

Key Takeaways

- The condition of chocking can be derived by considering two phases separately and the change of phase.
- The momentum equation for phase two and phase one can be written and simplified to derive the condition of compound chocking.
- The condition of chocking varies in the presence and absence of flashing.
- In real-world problems, it's essential to consider the flow pattern and how the two phases are mixed together.
- Two extreme conditions can be considered when solving problems: when the two phases are intimately mixed (homogeneous flow) and when they flow in separate layers (separated flow).