Does someone can tell me what's the latent heat of the propylene glycol for various concentrations.
I need to know that to use it as an ice (glicol) bank storage. Any of you guys have done or see it this before?
Tanks in advance.
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Does someone can tell me what's the latent heat of the propylene glycol for various concentrations.
I need to know that to use it as an ice (glicol) bank storage. Any of you guys have done or see it this before?
Tanks in advance.
I would need about 11.000 kWh of frozen propylene glycol at -12ºC on a ice glycol storage tank. The point is to cool glycol from -5ºC to -9ºC.Quote:
Originally Posted by Sandro Baptista
I'm afraid about the stratification of the brine (separation on its main components » ice water and liquid glycol). I'm afraid about the behaviour of the heat exchanger.
Does someone can help me?
In Coolpack software you could find required data.
I hope this will help.
Thanks guys but I couldn't find the answers I ask.
see encosed file
Quote:
Originally Posted by sevilou
It's not the specific heat that I need. Thanks anyway.
How serous is your request, & how urgent?Quote:
Originally Posted by Sandro Baptista
I'm happy to run off a simulation for you, where this will be predicted via a Process-Modelling package I use in-house.
914(kJ/kg)
See enclosed
I think that's impossible. That is more than for pure water (333 kJ/kg).Quote:
Originally Posted by sevilou
This is specific heat (for sensible heat calculation)...it's not what I want. Thanks anyway.Quote:
Originally Posted by sevilou
B”H
Hello Sandro,
Are you creating slurry ice using the mixture of water and glycol? When you create ice crystals it will be pure water. Glycol will not freeze up unit the temperature will reach eutectic. So you should use in your calculation latent heat of water 144Btu/lb. What type of heat exchanger do you use for the process? It has to be scrape surface type heat exchanger so you will continuously remove ice crystals from the surface.
The purpose is cool the propylen glycol from -5ºC to -9ºC using a tank, like a normal ice storage tank.Quote:
Originally Posted by michaelm
I would use a concentration of about 28% so I have the guarantee that the glycol would freeze about -12ºC. The ice water that would result around the tubes would be about -12ºC. Of course that during the the ice construction the glycol concentration on the system would increase resulting in a continuous lower initial freezing point. Having in account all internal volume of the system I estimate an increase up to 40%. This also requires lower evaporating temperatures but despite that I think there is no problem.
What do you think on that? If you don't understand parts of my english tell me that I will try to explain better.
B”H
If I understood you correctly that you are trying to build ice on the coils. Why you do not use standard system like Calmac from US.
Sandro. Hi.
From past experience I did not try to build ice on coils in tank, reason being that viscosity changes of glycol increased pumping drawn Kw, plus the volume in tank was primary consideration, as in the colder the volume the more thermal storage.
At the mix ratio you are quoting, the pump drawn power will increase nominally 15%, check mix by volume with a hydrometor at the design temp., if using in food processing consider mono-propylene [ food grade ] and add the colouring dye to identify leaks quickly.
To stop stratifying consider agitated pump flow or an agitator sturring things up bottom to top.
When the ice is been constructed around the tubes you still have only ice...the pure glicol will be separated from the water.Quote:
Originally Posted by Magoo
Sandro,
you missed my point, I do not want to form ice on tubes, I would go for a stronger mix to avoid icing on coils for previous stated reasons. I would mix at a ratio of 30% by volume of mono/glycol for a base mix temperature of -5.0'C this will give a safety margin and limit pumping overloads. Because at that mix ratio I have a controlled specific weight and density.
An additional thought:
Ice is an excellent insulator. This would mess up the local heat-transfer coefficient to the coil.
Another good reason to follow Magoo's advice of not building an ice layer on the tubes.
Thanks desA. for your support, glycol is a funny stuff under zero, can burn pumps and act like glue if not applied correctly.
Guys,
But I want to have a latent thermal storage so I have do construct ice on the coils, like a conventional ice tank.
OK.
use the latent heat for water, because that is all that is going to build ice on your coil.
Then let us know the specific density of solution ( with hydrometer ).
I think this is important.Quote:
Originally Posted by Magoo
The coil icing would then act as a separator, with the solution remaining becoming stronger in glycol % as the water component moves out of solution. He should look at the range as the ice builds up, until the end point, where the glycol % in the final remaining mix is at its maximum.
On the other side, once the heat has been recovered & all the ice returned to solution, the system has to re-mix the glycol & water properly.
An interesting, moving target. :)
That point you have mentioned I also had think it when I create this thread (see my firsts emails). That's why I want to heard about your positive and negative experiences.Quote:
Originally Posted by desA
Hi Des A.
Agree totally, as varying solution mixes do effect system loses and pump drawn power. As you earlier mentioned the ice will act as insulator as well. The idea of glycol storage tanks is to maximize thermal storage and reduce peak demands etc,.
You need an ice battery. This is a large tank containg plastic balls filled with a phase change solution. The correct concentration of glycol is then circulated around the balls to store or recover energy. See the web site for Cristopia.
While on this subject would anyone know where I can get Propylene Glycol? It used to be available at walmart but no one seems to carry it any more...Tried all the auto stores? I have a large chiller and the propylene glycol is used to maintain lube for the pumps and provide about 70° constant solution to an exchanger. It's in a piece of equipment that's really hard for me to shut down and go through a through purge process right at this time and using different additives. I know I have to bite the bullet soon but need some for now to hold me over. All I've heard is that's it's too expensive to manuf. What happen to 'Low Tox"? I thought we were trying to protect the enviorment? I don't want to take this thread off track, thought it might be the place to ask though. Thanks!
:off topic:With the power of Google I found this for youQuote:
Originally Posted by Robearbam
http://www.allanchem.com/cosm.html