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Bubbles in vertical pipeline

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Old   March 8, 2007, 05:32
Default Bubbles in vertical pipeline
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Hello All,

I have a tank of five compartments filled with petroleum based liquids (different in different compartments). There is a measuring system to measure the amount of liquid being drawn out at a customer location which is a turbine meter. The whole process starts in several stages, that means different types of valves are in different places before and after this turbine meter. When all the valves are close, there is air in this measuring system (turbine meter, all valves and the entire piping). I open one valve at the time and wait till that much piping is filled with liquid and then the next valve and so on. In the crucial (not the important valve in this system but my area of interest at the moment) valve, When I open it, the liquid flows downward and the air which is in the bottom pipeline goes inside the valve and finally back in to my tank. I fixed a valve somewhere away and tilted my pipeline by a certain angle to hinder (I know I cannot fully hinder this but atleast minimize it) this bubbles going back into my tank. Success but not full. I still have bubbles (which are in the pipeline) going into my tank as the air is replaced by liquid in this pipeline.

So, I put some piece of metal to open the valve (it is a pneumatic valve) not full but only a bit in order to avoid this bubbles to go through it but from somewhere else. Full success. When the valve open full, valve disc moves somewhat 40 mm away, this is full open. I have bubbles every where. With my metal piece, I made this opening as small as 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4mm. Till 0.8 mm I didnt get the bubbles in this valve but from 1mm onwards the same story. But, no problem as this is what I wanted to know and I got the answer. (I wanted to know the time taken to fill my pipe system with this small opening and how big is it in comparison to when the valve is full open)

My questions is, what makes this bubbles not to go through this small opening(0.2 till 0.8 mm) but when it is more than 1 mm? What is the influencing parameters here, I dont think static pressure of the height of liquid, because it is then same even when my valve is fully open. My colleague says, it is due to adhesion (i cannot accept it though my knowledge of adhesion is just in textbook level, I have never come across adhesion between gas(air in liquid medium) and solid(valve wall), or may be it is and i am wrong). But I think it is something else.

The bubbles are much (maybe of the order of couple of cms in diameter) bigger than the opening (the opening is a circumference of a cylinder type opening in my valve). One more info, it is a vertical pipeline. That means when I open a valve, the liquid in the above zone comes down and the air from the bottom zone goes up but there is a bypass in this stage where I am trying to take the air out from it and not through the valve from where I have the liquid coming. Experts please comment.

Thanks in advance

Have a good day.

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Old   March 9, 2007, 14:11
Default Re: Bubbles in vertical pipeline
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I'm no expert in the field. There is a book called "Acoustic bubble " which I came across once.The contents of the book and the bibliography might contain something of interest to you.
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