Ok, so I'm a third year ChemEng but ever since first year when this was taught to me I have never been able to understand it.
So imagine a horizontal pipe of which is a constant diameter. The pipe will have a given pressure at the beginning of the pipe and also a given flowrate. Given that the pipe has constant diameter this in turn must mean that the velocity is the same at all points within the pipe (continuity equation). Obviously, there will be pressure losses as the water flows through the pipe as a result of the shear from the walls. This is where my issue comes in. If the pressure is lost the further along the pipe you go, will this not cause the pressure to eventually reach 0? How is this possible? The water can't stop flowing as the volumetric flowrate must be equal at all points? It's baffled me since the day I learnt it.
Please don't think I'm stupid, promise I'm not. I've just never got this concept in Chem Eng for whatever the reason. Danke.