Just in case you ever feel like doing a little pressure drop testing...I was doing two curves today and figured hey...why not share my redneck setup..
So, might as well share a little DIY on creating pressure drop curves. It's pretty easy really, and you don't need much more than the following:
- Variable pump or valve: Valve should be free flowing like a globe valve or gate valve, pump could be a D5 variable. You could also run off of tap water pressure, but if you have any variability in your source pressure, your flow rate will change, so preferrably use a pump. I experimented with this and I'm pretty sure there is too much variability in pressure..better use a pump if you want something very accurate.
- Tubing for water columns: Any size will do, just need two colums of water. It doesn't matter if the tubing bends a bit at the base, and it doesn't matter if you have a high/low inlet or outlet. They will change the pressure, but the difference between will be the same regardless. The key to pressure drop is you want to measure the "ELEVATION DIFFERENCE".
- T-fitting: You need two 5/8" T fittings. you could use 1/2", but the pressure drop includes everthing between the two fitting centers, so minimze the tubing and 5/8" fitting will be less restrictive. I found that 5/8" T fittings and 1' of tubing is such a small amount of restriction you can ignore it. If you're anal enough you could create an equation for that then subtract it from your test run but I think most people ignore this small amount.
- Measuring Bucket: Any old trash can or 5 gallon bucket will do, preferably something clear you can easily see water level within, or you can attach a barb like I have and graduate the tubing for more precise reading.
- Stop Watch: Just need something that can click On and Off at least to the nearest second.
This is actually a fairly accurate test method for creating these curves. I feel comfortable that I can measure the pressure drop column of water to within 1/4" which is equivalent to .009 PSI (.1% (try to find a guage with PSI graduations to the nearest hundredth. And flow rate (if your source is constant) is at worst within 1 second of time, at 3 GPM that's 1/60th or 1.6%, if you wanted better than that...get a bigger bucket!
Anyhow, this is the basic setup:
This is one of two test series I ran today, this one being about 10' of 3/8" ID tubing:
And this is what pressure drop looks like at very very low flow rate (this happens to be one of my 1/2" test)
Yes... I prefer to setup my laboratory lounging in the shade outside
It's an interesting test and teaches you alot about pressure drop and those curves. If you decide to try it let me know, I can help through the excel graphing part too!