Pressuredrop duo to water freezing
Pressuredrop duo to water freezing
(OP)
Hi,
I am working on a problem where I am tasked to calculate how much the pressure in a pipe will increase by when a portion of the water is turned to ice
For this example I am using a pipe with an 3Inch OD and the pipe has a length of 1 meter. The iceplug is placed within the pipe in the center and has a length of 3 x OD. The initial condition inside the pipe is that it is filled up with water, the pressure is around 2 bar.
I could use some tips on what formulas that could be used to solve this problem, so that I can further evaluate different pipes with different sizes, and be sure that the length of the pipe is long enough to prevent a large pressure drop.
Any help is much appreciated.
Best regards,
Arve
I am working on a problem where I am tasked to calculate how much the pressure in a pipe will increase by when a portion of the water is turned to ice
For this example I am using a pipe with an 3Inch OD and the pipe has a length of 1 meter. The iceplug is placed within the pipe in the center and has a length of 3 x OD. The initial condition inside the pipe is that it is filled up with water, the pressure is around 2 bar.
I could use some tips on what formulas that could be used to solve this problem, so that I can further evaluate different pipes with different sizes, and be sure that the length of the pipe is long enough to prevent a large pressure drop.
Any help is much appreciated.
Best regards,
Arve
RE: Pressuredrop duo to water freezing
your title says Pressure drop when freezing, but the body of the post says pressure increase, but then keeps talking about a pressure drop???
Ice is less dense than water by about 9% or to put it another way, for the same mass of water it increases in volume by 9%.
So if you start with a closed volume at 2 bar and then freeze part of it the pressure will increase by quite a lot as the ice starts to form.
Define your question better please.
Is this homework?
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RE: Pressuredrop duo to water freezing
Sorry, pressureDROP is the wrong term, I guess pressure-buildup could be better?
This is not homework no. We are looking into how short a pipe could be when we freeze a portion of it, without risking the safety of anyone involved due to high pressure.
I will try to put it in a simpler question:
How do I calculate the new pressure within a pipe, when a small portion/volume of the initial water turns to ice.
RE: Pressuredrop duo to water freezing
The bulk modulus gives pressure volume relations.
Free water will expand 10% in volume when changing phase to ice.
Expansion pressure is balanced with hoop stress of the pipe that is restraining the ice from expanding radially.
If the ice plug begins freezing from each end, it will expand longitudinally until enough length is developed to restrict further longitudinal expansion, at which time radial expansion will begin. If that happens, your pipe will most assuredly burst, as it will not be able to increase its volume by 10% without tearing apart.
The key to the solving the problem is finding out the bonding strength of the ice to pipe wall and that I do not know. Due to the high number of pipe bursts from frozen water pipes every winter, I'd guess it is extremely high.
RE: Pressuredrop duo to water freezing
https://www.ridgid.com/us/en/sf2500-superfreeze
Johnny Pellin
RE: Pressuredrop duo to water freezing
--- Best regards, Morten Andersen
RE: Pressuredrop duo to water freezing
RE: Pressuredrop duo to water freezing
Also if the freezing starts at one small location and then spreads the stress isn't bad.
When you trap of volume of water and freeze it then you burst pipes.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
RE: Pressuredrop duo to water freezing
Freeze plugs do work on pipelines and don't burst the line, but then the pipe material is very strong. However it is the radial force which stops the plug from moving and seals the pipe.
In a simple sense start with your fixed volume of water then make up a spread sheet where the volume of water increases. As it increase the pressure will rise due to the increase in diameter of the pipe and the compression of the water. The amount of change will be whatever length of ice plug you choose divided by the total volume and then multiplied by 9%.
Try looking at this FAQ which you might be able to adapt. Just ignore the initial bit about thermal and input the changes into the change of volume part
https://www.eng-tips.com/faqs.cfm?fid=1339
Usually the way around it is to induce a small air pocket, much like you get when you put a bottle of beer in the freezer and then forget about it. Sometimes the bottle breaks, sometimes it just compresses the gas at the top of the bottle, sometimes it blows the top off.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressuredrop duo to water freezing
Watch this demonstration by Richard Trethewey:
Link
The pressure increases very quickly as shown in the video.
RE: Pressuredrop duo to water freezing
LittleInch, I tried to work with the equation you presented, but does this not apply for temperature change as the complete volume changes temperature? You said I could ignore the thermal part, but I struggle to use this formula.
I tried however to focus on the fixed volume (Script of attempt below), and tried to but together a script in matlab where the input is ID, OD and length of the pipe.
I read that it takes 220 bar to compress 1% of the total volume of water. So what I did is I calculated the volume added from the 9% extra (VolumeIceCube*0.09) when the water turns to ice. I then calculated the actual required volume it has to compress by dividing the change in volume by the total volume (VolumeRequiredCompression). I used the relationship and timed it with the 220 bar and ended up with a pressure of 59.4 bar. If I reduce the length of the pipe from 1000mm to 100mm the required pressure goes up to 594 bar.
I expect that there are flaws that I struggle to see here.. Any tips?
SCRIPT:
{
OD = 76.2
ID = 75
L = 1000
r = ID/2
A = pi * r^2
InitialWaterVolume = A * L
VolumeIceCube = A * 30
VolumeAddedFromIceCube = VolumeIceCube * 0.09
deltaV = VolumeAddedFromIceCube
VolumeRequiredCompression = deltaV / InitialWaterVolume * 100
PressureRequiredToCompress = 220/1 * VolumeRequiredCompression = 59.4 BAR
}
Best regards,
Arve
RE: Pressuredrop duo to water freezing
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressuredrop duo to water freezing
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pressuredrop duo to water freezing
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressuredrop duo to water freezing
this is too thin and your ice plug will almost certainly break the pipe.
I don't think even my copper pipe is that thin and it's like 15mm OD.
So this will fail.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressuredrop duo to water freezing
RE: Pressuredrop duo to water freezing
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressuredrop duo to water freezing
For example, if you freeze a vertical pipe that is open at the top, from the bottom, there will be no pressure increase when it is fully frozen. However, if it freezes at the top first, the trapped water below will burst the pipe as it freezes. In a cold environment there is a natural tendency for water to freeze from the top down, because the density of water is at a maximum at 4C.
If ice expanded after freezer it would slough off of surfaces due to this expansion. But we know that ice adheres to most surfaces very tightly. It is this adhesion that keeps ice plugs in place.
RE: Pressuredrop duo to water freezing
Here are some pictures of frozen piping. The client insisted on keeping this outside piping on standby until the last minute with winter rapidly approaching. In addition to your scenario, there may be instances when the entire pipe freezes causing expansion. I had a project some years ago when the equipment was not operating (and blocked in) and a very quickly moving severe freeze occurred. As you can see from the pictures, the entire pipe froze which split almost the entire PVC pipe. The third picture shows the entire pipe split and fell off leaving an ice core.