Help Calculating time to recharge air tanks

[nuclearnerd]

Thanks for the responses so far.

Originally Posted by Pratik341

Using the function that Excel generated, the integral from 0-120 yields 88.332 seconds for a full charge from 0-120 psi.

...I'm not sure you can just take the integral of that curve. The integral of flow(P) dP would give you something with units of volume/time*pressure (not just time). We would need a function for pressure(volume) for the units to come out right, which is what I was grabbing at (probably wrongly) with the ideal gas law

Originally Posted by MrRoboSteve

I don't think you're accounting for the lower flow rate at higher pressures. If you plot how long it takes to make each 10psi increment you'll find that the higher ones take a lot longer.

I only showed the step from 60 to 70 psig. You would need to repeat the next step with the viaair flowrate at 70 psig and so forth for every increment up to 120 psig (where the flowrate is .34 cfm). In fact, the time to fill each increment of pressure goes *down* in my calculation because the pressure increases faster (for a given volume) than the flowrate decreases.

Originally Posted by MrBasse

I would go through and check all the math, but I learned a long time ago that with air storage it is faster and easier to just plumb it up and try it with a stopwatch to get an accurate measurement of time.

Yeah, when it comes down to it, that's what we'll have to do. I would prefer to have a theoretical grasp of it though, so we could make intelligent choices during the design stage about how many tanks to buy, or how often we can actuate our cylinders.

It's been my experience with FRC robotics, that if you need to worry about the refill rate of the storage tanks with this much detail, then you're probably using pneumatics for something that would be better handled with a more powerful motor, like a CIM.

But it should work! (sigh).