Water brine solution for freezing purpuses 1

[Salah 1]

Dear members:
I have an idea of using water brine solution for freezing plastic water bottles,how practical such design?
I think about using same idea of vapor compression refrigration unit but the evaporator (will not be an insulated room with crazy fans running inside, with the importance of insulation and long time to get the job done) ..
instead it will be insulated water brine solution basin with evaporator coils running inside in the upper side :
The coold energy can be stored for long time .
Water specific heat is much higher than air ,which means that even with some air leaking into the basin it would not effect the process as in the case in walk-in freezer.
Thermal conductivity of water is much better than air which might make shorter time to get job done. ..
I know that some corrosion issues might make this unpractical...
But anyway, how such design is practical?
Thank you.

 

[LittleInch]

Freezing plastic bottles full of what? Water?

Why??

Just stick them in a freezer.

I can't follow what your trying to do and why this would be a good idea.

 

[Salah 1]

Thank you for your reply, I am trying to do same thing as ice block machine which as I guess works well using water brine solution.....
I was looking for something more releated to heat transfer, thermodynamics basics.
Thank you anyway..

 

[EdStainless]

In the food processing industry, they often chill product using water.
As long as you pump pure water vigorously it will stay as slush a few degrees below freezing.
They us this bath to get products nearly frozen quickly and then they put them into freezers to let them finish freezing.

 

[LittleInch]

Thank you for your reply, I am trying to do same thing as ice block machine which as I guess works well using water brine solution.....
I was looking for something more releated to heat transfer, thermodynamics basics.
Thank you anyway..

Well give us some data to work with then.

This https://www.engineeringtoolbox.com/sodium-chloride-water-d_1187.html gives you an idea of the freezing point of brine. You probably don't want to be within 5C of this.

Seawater is 3.5%. So to get anything decent you're looking at 15% by mass. If that gets aerated and warm that's a very corrosive fluid so you need high cost materials to avoid corrosion.

At the end of the day is all about heat transfer and heat transfer rate.

Very cold blown air can chill things very fast. So yes the heat transfer is better with water and the is a larger heat capacity of water but if you're cooling water then some of that advantage goes away.

You asked a very vague question which tends to get very vague answers.

 

[Salah 1]

Thank you for the reply :
As I understand the water brine solution in the case of an ice block machine should be made with 23% NaCl by mass or volume?
The brine temp should go down to minus 10-15 celsius...
that is why I asked if such system can be used for freezing purposes instead of using walk- in freezer..
To give you more info I could (during the day)get water temp drop of 12 using evaporative cooling with water final temp of 12 celsius simply by putting a water bowl in the surface with wind air passing through...
And during the night I could start at 8 pm with that water bowl at 12 celsius and make it even colder using night sky radiative cooling with final water temp about +3 celsius in the morning at 5:30 am..
Now with such water I could safe some time and energy to run either water brine brine freezer or normal vapour comp freezer by precooling the material required to be freezen befor ...
the limiting stage might be the one with phase chane which consumes most of the energy but anyway ....

 

[georgeverghese]

So you want to freeze water in PET bottles ?
If this water is meant for human consumption, you could use food grade PPEG-water solution also as the chilling medium. And chill the PPEG in a countercurrent PHE with anhydrous ammonia or CO2 compression cycle

 

[Salah 1]

Well give us some data to work with then.

This https://www.engineeringtoolbox.com/sodium-chloride-water-d_1187.html gives you an idea of the freezing point of brine. You probably don't want to be within 5C of this.

Seawater is 3.5%. So to get anything decent you're looking at 15% by mass. If that gets aerated and warm that's a very corrosive fluid so you need high cost materials to avoid corrosion.

At the end of the day is all about heat transfer and heat transfer rate.

Very cold blown air can chill things very fast. So yes the heat transfer is better with water and the is a larger heat capacity of water but if you're cooling water then some of that advantage goes away.

You asked a very vague question which tends to get very vague answers.

It is me and to make my Q clear and specific:
why the ice blocks are not made samply by using walk-in freezers ???
Why does it have to be using brine solution

 

[dvd]

There are always a few challenges. How will you monitor and maintain the salinity? What is the temperature of the chiller and will you freeze the saline solution on the walls of that heat exchanger? The chart below provides some idea of your possible salinity range. I like the glycol suggestion above. Attached is some reference material.

 

[georgeverghese]

From the tables on freeze point for PPEG solutions ( see link @dvd posted), looks like 40% PPEG should do for this application to avoid the risk of solute dropping out of solution on the hat exchanger surfaces of the PPEG - refrigerant HX.

Cooling the plastic water bottles against a liquid coolant on the outside will give you much better heat transfer coeff than against a vapor phase coolant - this is because the Prandtl number for most liquids is much more than for vapors.

 

[Salah 1]

There are always a few challenges. How will you monitor and maintain the salinity? What is the temperature of the chiller and will you freeze the saline solution on the walls of that heat exchanger? The chart below provides some idea of your possible salinity range. I like the glycol suggestion above. Attached is some reference material.

View attachment 2803

I was thinking

There are always a few challenges. How will you monitor and maintain the salinity? What is the temperature of the chiller and will you freeze the saline solution on the walls of that heat exchanger? The chart below provides some idea of your possible salinity range. I like the glycol suggestion above. Attached is some reference material.

View attachment 2803

I was thinking about the same system that is used for making ice blocks ( as i understand such system uses water brine solution )..
Such brine solution have freezing temp far below zero Celsius ( -21 C).
Now if we can arrange the evaporator of basic Vapor compression refrigeration system to pass through the brine solution ( with or without aggregation) and keep the brine solution temp between negative (10-15) C we can get the job done just the same way the ice blocks are made...
The brine solution will be fixed in an insulated basin and the refrigeration HTF will be circulated passing through the evaporator which is nothing but piping going back and forth in the upper part of the brine basin...and get back to the compressor to repeat the cycle...
I know that some corrosion issues might come across in such system but the heat transfer is too much better than using air to transfer the heat.......
Thank you...