in a open loop system that circulates water to process then back to tower. should the supply and return piping be the same size or should reurn be a larger size.
In a cooling water supply/recirculation system, the supply and return headers are normally of equal size and run together. However, based on engineering and space convenience, supplies are taken off to the various consumers along the supply line. One shouldn't overlook the fact that the available delta P (the difference in pressure between both headers) decreases as one goes further along the supply points. Design must ensure that preferential supply be given to critical or "sensible" water users. A common guideline is, say, delta P = 20 psi. If this is reduced to 16 psi, this means a reduction of about 11% in water supply capacity. All these remembering that for turbulent flow the pressure drop per unit length of pipe is assumed proportional to q2/d5, where q is flow rate, and d is pipe diameter. For these reasons, it may be needed to resize sections of one or both headers.
