Where i work has a chilled water loop to every building for the ac system. A rooftop unit has not been performing as it should so we are investigating into the possible causes. Right now i am trying to come up with the different variables that accompany the givens. I know the pipe is 2.5", the flow rate must have been measured at some point because one of the drawings says 53 GPM, and the length of the pipe is approximately 135'. Now is there any way to determine the pressure in the pipe with these givens. And also, would the length of the pipe effect the velocity or is that just based off the flow rate and diameter?
You can determine the pressure drop through that length of pipe, but that's about it. The length of pipe affects the velocity indirectly. As the length of pipe affects the pressure drop, it in turn affects the flow rate, which in turn determines (along with pipe diameter) the flow velocity.
Yep, pipe friction and losses due to viscous forces within the liquid itself (turbulence and all that), chiefly.