Performing a cooling water system calculate in Excel. The system is being pressure balanced using butterfly valves. I have always heard that in real life it is incredibly difficult to actually balance a cooling water system this way. I am wondering if the calculations that I am performing would actually give me something that sort of resembles the actual system. Say I put in the pipe length, size, fittings, flows that I want to go through and use the butterfly valves to take the excess pressure drop I need to balance everything, would the flow rates that I have specified resemble what would happen out in the field?
Regarding the method of calculating the hydraulic network, I have actually programmed the Hardy-Cross method, which is a "beginner's" method, not too accurate because of the restrictive assumptions.  This can be implemented in Excel (very tedious even for small problems; besides the spreadsheet would be a unique solution to a given network - therefore of no generic value).  There are, needless to say, much better commercial programs available at modest cost.

Your real problem, of course, will be finding a proper way to characterize the hydraulic resistance of partially open butterfly valves.  The pressure drop changes dramatically over just a few additional degrees of opening when you are in the effective regulation range for this type of valve.  Unless you spend umpteen hours "fine-tuning" the parameters, I wouldn't be too optimistic about the results, as far as matching field results, even if you have programmed correctly.

MORE NEWS