Hello,
For simplicity, let's assume we have two relief valves connected to a main header that discharges to atmosphere. Each device has been sized with the Omega method and stagnation conditions have been determined. Both relief conditions are two-phase flow and their relief is the result of a shared fire-case condition.
I'm somewhat confused on how to approach this problem in general and the resources that I have read have only added to that confusion. In:
Leung, J.C., (1996) Easily size relief devices and piping for two-phase flow. CEP, 92 (12), 28-50
Leung suggests starting from the last piping segment for relief headers, but doesn't provide a clear description of how to determine Omega of the two-phase flow mixture in this segment. This leads me to two basic (possibly ignorant) questions:
- If the stagnation conditions for each valve have a different Omega value, how can a combined Omega of the two streams be determined.
- If the quality or void fraction of a stream is known (estimated) at the relief valve, the quality will change throughout the system as the stream isenthalpically expands, right? I don't see this taken into account in the Omega method and I'm not sure how to re-calculate Omega for each segment of pipe.
My apologies if some of these questions are rudimentary. I'm still learning.
Edited by seetheforest, 19 November 2013 - 09:24 AM.