Bubble formation pressure of water
Bubble formation pressure of water
(OP)
I am running several pumps in parallel that are pumping water. A major concern for our application is that bubbles will form because the bubbles will cause our accuracy to be destroyed. I have found a little information on the bubble point of liquids but I am not familiar with the topic of bubble point. I was wondering if anyone could let me know the pressure at which bubbles form in water at a temperature slightly higher than room temperature. Any help will be greatly appreciated.





RE: Bubble formation pressure of water
other way of forming bubbles i can think of would be gas leaving solution. for this to happen, temperature had to be higher before your pumps (which is not really the most probable thing to happen...).
give a little more info in line with my comments above, then i'd be able to help further.
hth,
chris
RE: Bubble formation pressure of water
BobPE
RE: Bubble formation pressure of water
Thanks guys
RE: Bubble formation pressure of water
in other words, the pressure at suction side of your pump is low enough for the liquid to boil at the working temperature. this means, your npsh required is higher than your npsh available.
as your process liquid is water, you can get the neccessary information from steam tables. a freeware calculator is available here:
http://www.atkinsopht.com/eng/asmetabl.htm
hth,
chris
RE: Bubble formation pressure of water
You will have to know the disolved gas makeup of the stream and detrmine the partial pressures of these gasses. You will discover the limiting gas pressure from your analysis and this will become your minimum pressure on the suction side. The next thing to cause bubbles will be the liquid constituants of the stream...but this wont be a concern since you would have already generated bubbles from off gassing....
BobPE
RE: Bubble formation pressure of water
RE: Bubble formation pressure of water
may i do some dancing for guessing right? ;)
RE: Bubble formation pressure of water
RE: Bubble formation pressure of water
Best Regards
Morten
RE: Bubble formation pressure of water
What is required is to look at the NPSH, or the required net pressure at impeller to avoid cavitation. this pressure is pump and system specific. NPSH increases with flow and pump impeller speed. Also some manufacturers allow some cavitation.
Your pump manufacturer should be able to tell you what the NPSH is for your particular conditions.
Also thanks guys (all of you!) Thanks to your postings i found a site distributing software for calculating vapour pressures. I have joined and will be participating in forums!
Wotuwish
RE: Bubble formation pressure of water
I would say one thing, pump manufacturers do not allow cavitation, engineers allow cavitation...If the manufacturer tells you that, then their pump is junk and you should find another....They go throug great pains to hide and alter their curves so that we engineers have no clue what they are selling us, but we can figure out what they are doing....and when you get to the bottom of their curves, they tell a far different story sometimes....not that said, not all pump manufacturers are like this...it takes years of experience to figure out who sells the junk....
BobPE
RE: Bubble formation pressure of water
Thanks. However I have seen some literature (it could be from a manufacturer!) that new coatings have been invented that can resist the pressure of the bursting gas bubbles! You are right however, it is better to ensure that the available NPSH exceeds required NPSH by a good 0.5 m at least