Hey everyone, sorry I posted this in two different forums. I think this forum was more applicable so I wanted to move it. I have a fluid system of water coming from a pressure source. Then there is a converging nozzle, which I have calculated the resistance coefficient using Crane's Manual and it has an outlet to the atmosphere. I have tried to simplify the system. The full system is a pressure source, converging nozzle which has outlet into original diameter at converging nozzle inlet followed by hose to outlet to atmosphere. (this is like a fire hose system - slightly different for my actual application) The pressure of the pressure source is my independent variable, I am doing a sweep in excel. So if it helps for simplicity, you can assume the pressure is 100 psi. How do I calculate the flow rate (in GPM)? Do I need to take away the outlet of the system? Currently I am thinking using: hL = [k(v)^2]/(2g) ΔP = (ρ*hL)/144 then what for q?? Or I am thinking q = K*A*(2*144*g*ΔP/ρ) but then what is ΔP?? is it the pressure drop across the converging nozzle or is it the pressure drop from the inlet to outlet at atmospheric?