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Ice Formation On a Cryogenic Service Line

02/04/2013 5:37 AM

We know that ice is a good cold insulation on a continuos service line once the ice is formed on the surface since it hinder further heat gain to occur.

My question is that, how much thick ice is required to to prevent a -50 deg C service line at 95% humidity?

What is the impact of dew point/humidity/vapor pressure on the ice formed above the uninsulated cryogenic line?

It is very clear that at less humidity, less ice is formed and at high humidiy ice formed is more. Expecting yours' technical expertise on this issue.

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Guru
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#1

Re: Ice formation on a cryogenic service line

02/04/2013 6:33 AM

The impact is that, without proper insulation on the cryogenic line, the facility is wasting money. Call it 1kW per ice ball?

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Guru

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#2

Re: Ice formation on a cryogenic service line

02/04/2013 6:58 AM

There is a flaw in your judgement. Thickness is NOT function of humidity but how fast the thickness will be reached is.

Ice is forming as far as the surface temperature is under 0°C. Thickness depends on the internal temperature, on the existing insulation and on the outside temperature. Convection conditions are also determinant.

On outlet pipes the ice layer is conical since internal fluid will warm up and the pipe wall is also conducting heat from the environment.

All those aspects determine layer thickness and mow fast it grows. As you see it is a complex phenomenon.

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#3
In reply to #2

Re: Ice formation on a cryogenic service line

02/04/2013 7:11 AM

Are you saying there is no relation between the thickness of ice formed and the relative humidity?

Then why there is an increase in thickness of ice formed if it is high humid?

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Guru
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#4
In reply to #3

Re: Ice formation on a cryogenic service line

02/04/2013 7:22 AM

<...saying...>

What the ice ball is saying is that the line's insulation is woefully inadequate at that place. Get it fixed.

<unsubscribes>

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#5
In reply to #4

Re: Ice formation on a cryogenic service line

02/04/2013 7:28 AM

I understand it Mr PWSlack.

But I just need the technical clarification as I posted at the top.

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Guru
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#6
In reply to #5

Re: Ice formation on a cryogenic service line

02/04/2013 8:20 AM

Providing there is any humidity in the air, ice will continue to form until evaporation / sublimation is equal to condensation. Density of air does have a factor on evaporation, the higher density or higher air pressure on the surface of the liquid will cause evaporation to occur slower and allow more ice to accumulate.

If you have a wet ice ball then as the water evaporates it is absorbing heat from the air. Somone will correct me if I am wrong, but I believe your heat loss would be the same ice ball or not.

As advised above you would be better off using an insulated pipe with an insulation value that is known. The best way of insulating a cryogenic fluid is with a vacuum, but there are many other methods of keeping the heat out. You should contact a few suppliers and send pictures or descirbe your installation so they can provide you with the best solution.

Drew k

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Guru
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#7
In reply to #6

Re: Ice formation on a cryogenic service line

02/04/2013 8:38 AM

Yes, the key point is that ice will form until the condensation/sublimation-evaporation (or melting) point is reached. That point is reached quickly with dry air, so the ice is thin; in humid air that point takes longer to achieve so the ice layer is thick.

In either case, there are products available to insulate lines like this to minimize heat gain and help maintain efficiency of the system. -- Not to mention to minimize the mess that is created due to melting ice and (perhaps) corrosion due to the water.

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#8
In reply to #3

Re: Ice formation on a cryogenic service line

02/04/2013 10:48 AM

Dear Mr. Jithin,

The thickness alone is not the criterion for Insulation. There are atleast 6 factors govern the HEAT TRANSFER mechanism. One among the factors is THICKNESS which may constitute 7% to 11% role in the Total Heat Transfer Mechanism. Ice thickness will depend upon several factors which are subject to more variations and it is NOT worth to take that amount of risk.

Further the self weight of ice over the pipe/conduit is to be accounted in supporting the pipe/conduit, which will add to the cost. If by chance ice is melting the total cryogenic effect will be reduced or lost - which will be much more costlier than the one time Insulation Cost.

DHAYANANDHAN.S

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#10
In reply to #8

Re: Ice formation on a cryogenic service line

02/04/2013 12:01 PM

Sir, I know that thickness is not only the parameter deciding the insulation. I need these values for a root cause analysis. I am from Kerala.

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#15
In reply to #2

Re: Ice formation on a cryogenic service line

02/06/2013 4:30 PM

I think he means that a high water content influences the rate at which ice forms. The thickness is determined by the amount of water present and available for making ice. It is important to take the available water into consideration but it is also important to consider the time factor. Another thing that could be important is other factors like air flow and the drying effect it has on the humidity. A dynamic system is harder to predict unless the variables can be kept tightly controlled.

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Guru

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#9

Re: Ice Formation On a Cryogenic Service Line

02/04/2013 11:46 AM

Get some of this: WRAP-ON FOAM PIPE INSULATION - Amazon.com

Install it per this: How to Insulate Pipes : How-To : DIY Network

Don't over analyze the apparent problem.

Fix the real problem.

Your pipes are not properly insulated.

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#11

Re: Ice Formation On a Cryogenic Service Line

02/05/2013 1:26 PM

Dear Jithin ,

Apart from Foam tapes, you can also use PUF Spray cans to insulate the pipe.

we have them as one of our product offerings @ www.superweld.in

regards

Sanjay Bahl, Delhi

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#12
In reply to #11

Re: Ice Formation On a Cryogenic Service Line

02/05/2013 10:56 PM

I am interested in PIR spray than PUF spray. Have you got that one? It would be good if you can send me the details.

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#13
In reply to #12

Re: Ice Formation On a Cryogenic Service Line

02/05/2013 11:43 PM

sent you details

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#14

Re: Ice Formation On a Cryogenic Service Line

02/06/2013 12:27 PM

Have you guys hear of Cabot's AEROGEL Insulation , Claims to be the best insulating material in the world , can any one guide more on Aerogel and its application in this case.

Regards

Sanjay

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#16
In reply to #14

Re: Ice Formation On a Cryogenic Service Line

02/06/2013 10:58 PM

I have exposure with Aerogel products, but not cabot's, its Aspen Aerogel. We can say it as solid smoke. And probably it is one of the nick names of aerogel products. Application of cryogel is a possibility in these types of applications.

Jithin K Narayanan

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dhayanandhan (1); Drew K (1); Goewin Rose (1); Jithin (5); lyn (1); nick name (1); PWSlack (2); sanjayb (3); Usbport (1)

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