1. The problem statement, all variables and given/known data Well I was given an assignment to find ways to solve the the problem of how to mix the 2 streams in the digram together at the lowest cost possible. The pressures of the 2 streams that are being mixed together are 10 bar and 30 bar The fear is that instead of combining into 1 stream, the flow from the 30 bar will flow into the 10bar stream and damage the pump [PLAIN]http://img94.imageshack.us/img94/1051/drawing1x.jpg [Broken] 2. Relevant equations 3. The attempt at a solution The only way i can think of so far is to just add in a tank at the intersection where the 2 streams meet to store both streams before i pump them out as 1 combined stream. But however i don't think it is very cost effective. So i stuck to as how i can continue.