Has anyone tried head on their reservoir?
 

Having worked with very high pressure systems, we always had a nitrogen head on the system to pressurize it and force the air out. Has anyone tried this? Maybe with a CO2 cartridge or a drop or two of LN2?

Obviously, I'm a newbie.

How bout 3 1/2" bay reservoirs? Or do I need to stay late at work this week?

Is there a reason you think this is necassary/could be usefull in a PC water cooling loop?

I think he's referring to getitng out all the air, but a res gets it all out anyway.

Besides any added pressure ina bay-res would likely blow it up.

More pressure = more chance of leaks = no thanks. ;)

Actually, the most common reason I know of for doing this is to avoid cavitation. Nitrogen gets used when the fluid may be harmed by oxidation.

All the pressure does is artificially raise the static pressure in the system. Since cavitation results from too low a static pressure, it is an effective means to prevent it.

In water cooling systems, you can get the same effect with a vented reservoir that keeps the water surface well above the pump intake.

Why I asked ....
 

I'm new and was looking at some of the pumps listed on the "What's your pump?" question, and calculated that with 0.5" hose and a 1200 lph flow, the velocity in the system was over 8 m/sec. Thats plenty to start to get cavitation and that's one of the small pumps listed on that page. I figured you'd have to run a pressurized system to actually get the rated flows mentioned. Am I just looking at the problem wrong?

20LPM will not be found in any system that I know of. Rerun your calculations with "real" numbers, such as 6LPM, most likely, or maybe a questionable 12LPM (High powered pump, single pass heater core, and a Maze 4)

Then why?
 

If 6 lpm is closer to reality then why buy a pump listed at over 1000 GPH? What's the physics?

The physics is that 1000 gph is with no head loss (i.e. just open flow), a real system has anything from about 2 to 6 feet of head loss, which puts most of these "1000 gph" pumps down at nearer to 100 gph. ;)

The head loss varies based upon the flow rate, BTW. I would search for Cathar's pump comparison that shows the pressure drop of a WW at various flow rates as well.