Example A: Pressure loss in complex systems

Energy loss because of pressure drop are really important in the industry. We are going to take a look at these pressure losses in complex systems. We have a straight pipe with diameter and at both ends a different pressure, and . Describe how you can calculate the pressure drop in the way you learned before.

But, we need a new method if we want to calculate the pressure loss over a bend. What is this method?

And, what if we want to calculate the total pressure loss of a whole system existing of a straigt pipe, followed by a bend, a straight pipe, a bend, a straight pipe, a valve and a straight pipe (so 7 parts)? How do we do this?