Oil- gas separator Boundary Conditions!!!

juliom · April 6, 2011, 08:39

Hey guys, I have been working in a oil- gas separator on CFX. The most difficult part has been the correct selection of the boundaries conditions.
The inlet condition is the less difficult since I have the flow rates in that point, the hardest part are the oil outlet and the gas outlet, because I do not have the mass flow in each outlet, Therefore I have thought about to select an outlet with a estimated pressure, the problem is that the outlet pressure is not know!!!
WHAT SHOULD I USE!!! have someone worked with this kind of problem????

cactilio86 · April 12, 2011, 03:43

Julio,

The performance of the oil separator is mainly determined by the pressure at the outlets. You can imagine that if you have lower pressure at the overflow, more gas will go out; if not, you will be pushing the flow out the underflow (lower liquid hold-up).

So in my view ... what is the point of the CFD model if you have such an uncertainty in the BC's ? Try to find that information or in the worst case, depending on what you want to study, check if using 2 or 3 different values for the pressure at the outlet changes your conclusions dramatically.

Regards

April 6, 2011, 08:39	Oil- gas separator Boundary Conditions!!!	#1
juliom Senior Member Julio Mendez Join Date: Apr 2009 Location: Fairburn, GA. USA Posts: 290 Rep Power: 18	Hey guys, I have been working in a oil- gas separator on CFX. The most difficult part has been the correct selection of the boundaries conditions. The inlet condition is the less difficult since I have the flow rates in that point, the hardest part are the oil outlet and the gas outlet, because I do not have the mass flow in each outlet, Therefore I have thought about to select an outlet with a estimated pressure, the problem is that the outlet pressure is not know!!! WHAT SHOULD I USE!!! have someone worked with this kind of problem????

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April 12, 2011, 03:43		#2
cactilio86 New Member Join Date: Mar 2009 Posts: 11 Rep Power: 17	Julio, The performance of the oil separator is mainly determined by the pressure at the outlets. You can imagine that if you have lower pressure at the overflow, more gas will go out; if not, you will be pushing the flow out the underflow (lower liquid hold-up). So in my view ... what is the point of the CFD model if you have such an uncertainty in the BC's ? Try to find that information or in the worst case, depending on what you want to study, check if using 2 or 3 different values for the pressure at the outlet changes your conclusions dramatically. Regards