please review the solidworks KB and also this forum, this has been discussed mutliple times. outlet volume flow rates are not recommended by the developers. the recommended setup is flow rate in and pressure opening at the outlet. while you don't know the outlet pressure, pressure is just a place holder so the important thing will be that the inlet pressure will be calculated and you will know what the delta P is across teh component.
the main reason that outlet volume flow rate is not recommended is that would mean that you're forcing a uniform flow rate at the outlet which is unlikely realistic. if you NEED to do this, then you need to put the outlet a LONG ways away from your pump so the BC doesn't affect your analysis.
Ah that makes sense. I think I read about it a long time ago but had already forgotten. I will stick with the inlet flow then since extending the outlet channel 150 times longer than the diameter of the outlet made no difference.
Thank you for the reply.