Help with eutectic solution please

[bront]

hi all,

i am giving my boats freezer system an overhaul. it consisted of 2 systems, the first had a car airconditioning compressor driven by the generator with 2 cold plates in series. this was in the boat when i purchased it. it worked pretty well and the second a 220vt AC compressor with a flat plate evaporator which has corroded and leaks.

i have managed to score a 2nd hand plate that has 2 coils in it and want to connect the AC system to one coil and the other to the aircond comp which will then connect to one of the old plates in series. the plates are stainless with copper piping.

the new plate is from a fridge system so will have the wrong solution in it. the old one although it worked ok i would like to get the right solution in it as well.

so my guestion is, does anyone know what eutectic solution would be the right one? i would like to have a temp of -15c in the box or lower if possible.

any help would be greatly appreciated

thanks
bront

[The Viking]

Hmm,
There is more to it than that, much more.
It will all depend on expansion devices, oil and then temperature.

Your best option would be to find a local refrigeration guy that could help you.

[bront]

i have the refridgeration guy but he doesn't know about eutectic solutions.

i seached this site after i raised my question and it would appear that this subject has been touched on before. Peter 1 sugests water and salt but i am concerned about electrolysis.

[Peter_1]

We're making these ourselves since more then 15 years and never had problems with it.

[nike123]

Check this (http://www.glacierbay.com/Eutectic.asp)article!

[Chef]

The best solution to form a eutectic plate liquid is ethylene glycol (EG) or normal antifreeze and it is normally green in colour. This comes in virtually neat or diluted with a little water depending on the manufacturer.

About 30% is the limit of the EG to water and will give you a plate temp of about -20C. If you try to put say 40% into the water then you start to run out of water and hence ice and hence your store of cold so dont push it too hard.

If you have some digital kitchen scales you can assess the % you have by weight but be accurate.

Freezing point data and Specific Gravity
10% is -3C
20% is -8C
30% is -16C with an SG of 1.048 at room temp
40% is -25C with an SG of 1.06 at room temp
Neat EG is 1.13 SG at room temp so you find out if its pure or not before mixing.

Note the specific heat capacity drops to 0.89 KJ/KgdegC at 30% and down to 0.84 at 40%.

Warning
If you freeze then partially defrost and freeze etc many times you will find the water will cluster in an ice block with a lower content of EG whilst the solution elsewhere becomes a higher % and will not freeze so you loose performance, ie the solutions seperate. It appears your freezer is not holing over so well, 10 to 20 cycles is enough for this to happen so every 4 or 5 cycles let it fully melt and get the box temp up to say -5 then suck it down again this will remix your solution.

Also you will need some small peices of pipe insulation dotted about inside the plate to stop the freezing solution from crushing your copper pipes. Usually occurs when you seperate the solutions and build up an ice plug. Its more common than you think.

Good Luck

Chef

[bront]

thanks guys

it looks like the simplest way is an antifreeze solution, not a eutectic one.

has anyone used the solution (tss-8)from glacier bay that nike123 suggests, it is their own promotional article so not sure how true it is.

good info, thanks chef, i see you are also on the water.

bront

[Peter_1]

But you're a pilot on a boat, some sort of flying boat or sailing airplane :p

[bront]

but i could be a boat pilot, however i am a helicopter pilot taking a year or so off.

[Peter_1]

Wow, am I jealous man! Look once to my my profile.
What's the type of your helicopter if I may ask?

[bront]

wow, nice cv, small world. for the last few years i have been mainly doing aerial filming, commercials and movies. normally i fly eurocopter 350's (squirel) but also quite a bit of bell jet and longranger. did a bit of fire fighting in a huey last summer, now thats good fun. all this in south africa but spend half the year on my boat cruising, :D last 3 years in the carribean but about to head off for the pacific hence the year or so off or till the money runs out:rolleyes:. in st. croix, us virgins at the moment. what are you flying peter? are you looking to change jobs?

[bront]

out of interest just spoke to glacier bay and they don't make their plates anymore. they don't want to give away their secret recipe either.

[Peter_1]

To be honest, I'm becoming to old for this.
If I was sure that I could get a job, I should not hesitate one minute.

There is also another RE member -James- who followed almost exactly the same route as I did.
He had his own refrigeration company in the UK and emigrated to Australia a year ago .

If you can't start at the age 30 to 35, then you're to old.
I already spend a small fortune on my ATPL and from my prom, only 3 are flying now.
My Belgium flying partner in the US is now flying since some months (got his license in 2000) with a Citation for business flights.

Did my ATPL training mainly in Belgium, multi-engine (Seneca) in La Verne (nearby Los Angeles), flew 100 hours in 5 weeks or so, flew from San Francisco to Key West (Florida) via Las Vegas, Mojave, Grand Canyon, New Orleans, back to the state Oregon (Eureka, Arcata, and another small airfield I don't remember right now), Denver, back to La Verne.

My ultimate dream always was flying Helicopter but doing this professionally in Belgium is almost impossible.
One of my instructors was a former military helicopter SAR pilot (Westland Seaking, Alouette, also Eurocopter, ..) and he flew also some years on small jets.

An uncle of mine flew also helicopter in the army (Sikorsky) and when retired at 45 years, he then flew to control pipelines and electricity cables.

Still giving lessons now in Aerodynamics for the PPL.

[bront]

never too old, you have just got to want it enough. you still have 20 years. there is a shortage of experienced pilots, you just have to get that first job. the pay will be bad though but then you just have to look at that as another investment. good luck.

bront

[bront]

peter 1, everything i read says that a salt and water mix will cause problems in a stainless tank with copper pipes. are you doing something special to stop the electrolysis? i imagine that you make sure that there isn't any air in them but anything else. is this a better mix than glycol?

thanks bront

[Chef]

Hi bront

The salt and water combination is very corrosive and will eat away your pipes near the joints very quickly (a few years or less) but the ethylene glycol solution is inert.

Our first set of freezer plates had salt in them and they died so we had to re-pipe them and then switched to EG, been runnng for 15 years with perfect internals. Every season we drain the fluid and check its weight and is has not changed in colour or composition in that time.

The salad chiller also runs EG but with a 10% mixture to get a cabinet temp of +5C and is not sealed tight so even a small amount condensate could enter over a period of time but that one is now 12 years old and looks like new inside. (It has a flanged and sealed front plate and a drain hole).

Probably your best peice of equipmen would be an internal/external temperature gauge - a cheap household item is all that is required. With at least 50% full of stuff and teh unit has stabalised after a couple of days.
Slip the external probe onto the freezeer plate and when the system is runnng record the temp every 1/2 hour and plot it. You will see a drop in temp - then a flat spot and a drop again. The flat spot is where the ice is melting at its depressed temp (caused by the EG) to provide the cold. This will tell you 2 things.
First the "ice temp" of your solution so ou can then add a little more EG if you need it.
Second and more usefull is how long the freezer stays at this 'flat spot'. If it is say 6 hours then you need to run it 2 times a day but if its is say 12 to 15 hours then one run a day is fine.

The out come of the 'flat spot' time gives you a handle on how much cold is lost through the freezer walls and its easy to calculate the cold storage of your plates and the losses.

Then you get to see if your insulation is enough or if you have enough plates in the system for it to perform.

Our test was depressing and so we had to add an extra 2" of foam and a second plate. Now it holds for 24 hours on a 2 hour run.

So you and Peter_1 are both pilots, interesting as that makes 3 of us in this thread. :D

Regards Chef

[bront]

thanks chef.

yeah, looks like eg or pg is the way to go. cant find pg on this island so far though. my plan is that one of the 2 plates in the freezer has 2 coils, one of which will be hooked to a 220v ac comp. which will hopefully keep the freezer nice and cold for longer and then maybe i only need to run the gen with mechanical comp. on the 2 plates every 2 days or so. was getting away with 1 hr in the morning and 1/2 hr evening with just the mechanical system but that was with taking cold air from the freezer to cool the fridge. now the freezer is completely seperate so that should make a huge difference anyway.

i'm guessing your a charter skipper but what are you flying. skipper on a stink pot with helicopter would be first prize.

bront

[Peter_1]

peter 1, everything i read says that a salt and water mix will cause problems in a stainless tank with copper pipes. are you doing something special to stop the electrolysis? i imagine that you make sure that there isn't any air in them but anything else. is this a better mix than glycol?

thanks bront

We have now plates which are more than 15 years old with salt and never had problems with it.
When filling the plates, we put some spanners on the plate to make it hollow. So it can expand afterwards.
We fill them completely full and then screw the stop on on it.
Why we're using salt? Make once a mix in the same recipient with the same eutectic point and place it in the freezer.
Then place i beside each other and watch the melting process from both. The salt last very longer.
Don't forget we have to use foodgrade stuff in case of leaking. We used some time in the past Antifrogen http://www.antifrogen.de/businesses/antifrogen/internet.nsf/vwWebPagesByID/AECE0AC6004F0B41C125693D00332F1B
Our experience was that the solution solidifies very difficult, which is in my opinion the intention of an Antifreeze, protecting the circuit . You can describe it as some sort of sticky syrup, some sort of colored ice slurry http://cache.daylife.com/imageserve/06ZRfk4aGk1Il/340x.jpg

Besides this, you then have for each type you fly a type rating and a two-yearly type rating exam?

[bront]

confusing stuff. completely opposite views which appear to be honest opinions based on first hand experience. what to do?

peter i have australian and south african atpl with 13 types but we never have to renew the types. an australian lic is valid forever as long as you have a valid medical and 2 year check ride. south africa as long as i renew within 5 years with medical and 3 year check ride i am good.

bront

[Chef]

Hey Peter what are your plates made of? Sounds like they may be Stainless Steel?

My old plate that caused the problem was cast Aluminium and that is not so tolerant to salt!

I like the second coil set with shore power to maintain the cold, saves running the genset every day. Sounds like your system is similar to ours, or was, because we had the little thermoflaps that bled cold from the freezer to the fridge and it just killed the system, now it has a seperate plate for the fridge and is way better.

Its not a stinky with a helio, its sail and the flying is just for fun, fixed wing, UK and South African licenses.

Chef

[bront]

ok, aluminium plate would certainly be a prob. saw a photo of peter's plates on a different thread and they were stainless i think. is your fridge plate connected in series to your freezer plates chef?

yeah, i have high hopes for the new setup. at the moment i have too much electricity (rare on a boat) so hopefully i can use that to drive the ac freezer between genny runs. aiming to run the gen every second day for an hour or so.

were are you sailing?

bront

[Chef]

There are 2 freezer plates, then a fridge plate and then a salad chiller plate in series. The freezer is a top loader so OK but the fridge is a front loader and dumps its cold every time you open the door, even with a little plastic damn we have to be careful.

Not sure how you have too much electricity:eek:

At the moment Malaysia, Thailand and Indonesia.

Chef

[bront]

my freezer is also a top loader and the fridge front loader. everyone is concerned about the cold falling out of a front loader but the air entering contains very little in the way of BTU's. according to an article from glacier bay a cubic foot of air at 100 f only has 18 BTU which takes a few seconds of compressor run time to remove and sitting your food stuff on the bench whilst finding stuff at the bottom in a top loader actually adds more heat. makes sense to me.

too much electricity as i have solar panels and wind gen but have to run the gen to drive the mechanical comp. so make even more electricity which i dont use.

nice area i believe, hope to be there in a few years.

bront

[bront]

hi guys

i am going with propylene glycol, does anyone know the specific gravity for a 30 and 40% mix?

thanks

bront

[nike123]

hi guys

i am going with propylene glycol, does anyone know the specific gravity for a 30 and 40% mix?

thanks

bront


At what temperature?

[bront]

25 C outside air temp i guess nike 123

bront

[Chef]

30% is -15C and 40% is -23C based on an SG for 30% of 1026 and for 40% of 1034 (these SG's at 15C so you have to correct for 25C)

Chef

[Chef]

Because PG has an expansion coeff 3 times that of water the correction must be for each % concentration.
For 30% the SG at 25C is 1022.6 and at 40% the SG comes to 1030.2
Chef

[nike123]

25 C outside air temp i guess nike 123

bront

I mean at what temperature of solution you want specific gravity (density)?

*****************************************************
Fluid = Propylene Glycol
X [vol %] = 30,00
T [°C] = 25,00
Density [kg/m^3] = 1025,29
Specific heat [kJ/(kg K)] = 3,867
Conductivity [W/(m K)] = 0,449
Dynamic viscocity [10^-5 Pa·s] = 257,147
Kinematic viscocity [cSt] = 2,508
Freeze point [°C] = -13,10
*****************************************************
Fluid = Propylene Glycol
X [vol %] = 40,00
T [°C] = 25,00
Density [kg/m^3] = 1032,75
Specific heat [kJ/(kg K)] = 3,721
Conductivity [W/(m K)] = 0,405
Dynamic viscocity [10^-5 Pa·s] = 372,845
Kinematic viscocity [cSt] = 3,610
Freeze point [°C] = -21,51

[bront]

thanks nike123, aiming for a box temp of 10f, -12c so solution temp of 0f or -18c i presume.

bront

[bront]

i found a graph on the net that had specific gravity at 15c of 1.04@ 30% and 1.055@ 40%. is there such a difference between 15c and 25c?

bront

[Peter_1]

...aiming for a box temp of 10f, -12c so solution temp of 0f or -18c i presume
I should take at least a DT of 8KC and even better 10K. Depends how well it's isolated.

[nike123]

thanks nike123, aiming for a box temp of 10f, -12c so solution temp of 0f or -18c i presume.

bront


Software (Coolpack) (http://www.google.com/url?sa=t&ct=res&cd=2&url=http%3A%2F%2Fwww.et.web.mek.dtu.dk%2FCoolpack%2FUK%2Fdownload.html&ei=voWtSO-9BYzO0QXo2fjsDA&usg=AFQjCNHgCNrH_6wJf25Djd5mX1w-vXdHbg&sig2=zav_fVBBuiuAF-wec8jyBQ) doesn't allow me to go below -15°C for 30% or -18°C for 40% mixture. So I cant help you with that in these situations.
Check for your self. Module for solutions has name "Heat transfer fluid calculator".

[bront]

thanks nike, good site.

not sure what you mean peter. what is DT?

the numbers i found above are incorrect, obviously i cant read graphs properly!

[Twinwheeler]

i have the refridgeration guy but he doesn't know about eutectic solutions.

i seached this site after i raised my question and it would appear that this subject has been touched on before. Peter 1 sugests water and salt but i am concerned about electrolysis.
I would use ethylene glycol as the temperature depressant and this should be mixed in a ratio to produce an ice crystalisation point around the required -15 C.
Glycol supplier will have data on mixing ratios to achieve this temperature.
The latent heat extracted from this temperature and beyond represents the stored negative energy you are looking for.
Electrolysis will not be a problem in this instance.
Hope this helps.

[Magoo]

Hi Bront.
Have you considered using car anti-freeze. Necessary for all modern cars with aluminium heads and radiators. It is based on EG with anti corrossion properties. Use it neat, you wont need alot.
magoo