Looking for a formula to calculate pressure

[fmtdesign]

I design plastic injection molds and they require cooling channels. I have been working on better understanding the performance of these systems. I have developed some spread sheets to calculate the amount of flow required in GPM to get turbulent flow but I am having difficulty in how to figure out what pressure is required to drive the system.

Example might be I want 5GPM to flow through a .500 Diam line. What pressure is required? I know there is alot going on in a system with pressure loss and all but I need to be able to give my customer some kind of idea as to the pressures required.

Thanks

 

[pmover]

it seems that if you know the piping layout or geometry of cooling channels, you should be able to generate a system resistance curve; thus generate an equation of resistance with flow as the independent variable and pressure as dependent variable. then the pressure required would simply be a function of flow, provided other fluid properties remain relatively constant.

there are two good reference books that seasoned engineers use to determine system resistant - Cameron hydraulic Data and Crane Technical Paper No. 410. Both are avaliable via internet and are not free.

good luck!
-pmover