Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 22-02-2015, 10:09   #1
Long Range Cruiser
 
MarkJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2007
Location: Australian living on "Sea Life" currently in England.
Boat: Beneteau 393 "Sea Life"
Posts: 12,828
Images: 25
The science of Freezing. Do Freez Paks work??

Now I have a full electrical system upgrade I can have a freezer on 24 hours per day! Yipppppeeeeee!

ICE CREAM!!

But I am trying to be economical with power.

I have put in the freezer some Freez Paks an "ice substitute" that I think contains Sodium polyacrylate

The idea is you freeze them then put them in your picnic basket etc. but I have some in the freezer with the idea that they freeze and then buffer the temperature increase therefore requiring less electricity to operate the freezer.

I did do thermodynamics sometime in the dim distant past ummmmm but my memory....

Is it better to use a Freez Pak or just reduce the excess space with water and foam?
Attached Images
 
__________________

__________________
Notes on a Circumnavigation.
OurLifeAtSea.com

Somalia Pirates and our Convoy
MarkJ is offline   Reply With Quote
Old 22-02-2015, 10:26   #2
Senior Cruiser
 
atoll's Avatar

Cruisers Forum Supporter

Join Date: Mar 2010
Location: gettin naughty on the beach in cornwall
Boat: 63 custom alloy sloop,macwester26,prout snowgoose 37 elite catamaran!
Posts: 9,312
Images: 75
Re: The science of Freezing. Do Freez Paks work??

works like a eutectic holding plate,glycol freezes at about -8 celecius depending on the solution.

water freezes at 0deg celcius,so glycol better
__________________

__________________
my catamaran building project updates http://www.cruisersforum.com/forums/...36#post2502136
atoll is offline   Reply With Quote
Old 22-02-2015, 10:29   #3
Registered User
 
toddedger's Avatar

Join Date: Mar 2012
Location: Michigan
Boat: Morgan 27
Posts: 264
Re: The science of Freezing. Do Freez Paks work??

They are going to act like a holding plate. So they will take energy to cool and hold it for a while. Somewhere I heard an idea of using packing peanuts in plastic bags to fill in any dead space between food. I haven't tried it yet, but plan on giving ita try.
__________________
toddedger is offline   Reply With Quote
Old 22-02-2015, 10:40   #4
Don't ask if you can't handle it
 
sailorboy1's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: On the boat somewhere
Boat: Hunter 410
Posts: 12,319
Re: The science of Freezing. Do Freez Paks work??

Personally all I feel they do is increase the cycle times. So it takes longer for the system to drop the temperature down, and longer for it to heat back up. But that is a plus if you are making more power than you can store.
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is offline   Reply With Quote
Old 22-02-2015, 10:47   #5
Senior Cruiser
 
senormechanico's Avatar

Cruisers Forum Supporter

Join Date: Aug 2003
Boat: Dragonfly 1000 trimaran
Posts: 5,832
Re: The science of Freezing. Do Freez Paks work??

http://www.amazon.com/Arctic-Ice-Tun...rds=arctic+ice

These work great !
Way more efficient than those "blue ice" blocks.
__________________
Memento,homo, quia pulvis es, et in pulverem reverteris.
senormechanico is online now   Reply With Quote
Old 22-02-2015, 11:02   #6
Registered User

Join Date: Oct 2007
Location: Winters cruising; summers Chesapeake Bay
Boat: Catana 471
Posts: 1,239
Re: The science of Freezing. Do Freez Paks work??

They will work no better than putting already frozen food into your freezer, unless they are somehow colder. If you have excess space after loading your already frozen food, yes, adding any extra mass that is already frozen will save you some power. But the key is not expecting your freezer to freeze anything from ambient temperature.

Dave
__________________
2Hulls is offline   Reply With Quote
Old 22-02-2015, 11:24   #7
Marine Service Provider

Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,940
Re: The science of Freezing. Do Freez Paks work??

There are really two answers here.

The first is once a freezer achieves a steady state (doors closed, and all items at the same temprature) it takes exactly the same amount of energy to maintain a given temp regardless of how full it is. Because the amount of energy needed is dependent on the insulation not the thermal mass.

However there are a few real work caviats.

First is that a full cold box will coast longer between when the compressor needs to turn on. Because the thermal mass takes longer to heat up. But it also takes longer to cool back down again.

Second. By replacing the air inside the box with stuff you decrease the amount of warm moist air exchanged every time you open the box. This will decrease energy consumed.

Third: when you add new, warm items to the freezer the temprature won't spike as high, since the thermal mass acts to absorb heat.

Fourth: froze bottles of water are great to have independent of the energy used just to carry with you on the dink. But don't use those cold packs, they just take up space. At least water bottles can be drunk, and achieve the same effect.
__________________
Greg

- If animals weren't meant to be eaten then they wouldn't be made of food.
Stumble is offline   Reply With Quote
Old 22-02-2015, 13:45   #8
Senior Cruiser
 
senormechanico's Avatar

Cruisers Forum Supporter

Join Date: Aug 2003
Boat: Dragonfly 1000 trimaran
Posts: 5,832
Re: The science of Freezing. Do Freez Paks work??

The cold packs I listed freeze @ +5 degrees f.
They are a true eutectic.
In other words, they phase change over a very narrow range.
This keeps the average temperature in the insulated space much closer than food.
Water phase changes (freezes/thaws at 32f, and the food around it will follow at roughly the same temp.
I'd rather keep my food frozen until I use it.
__________________
Memento,homo, quia pulvis es, et in pulverem reverteris.
senormechanico is online now   Reply With Quote
Old 22-02-2015, 14:28   #9
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Re: The science of Freezing. Do Freez Paks work??

Quote:
Originally Posted by Stumble View Post
. . . Second. By replacing the air inside the box with stuff you decrease the amount of warm moist air exchanged every time you open the box. This will decrease energy consumed. . . .

Not enough to be worth the trouble.

Air has a specific heat of about 1006 J/Kg Degree C, compared to 4200 for water. , and air has a density nearly a thousand times less than water. So a complete change of the air inside an empty marine fridge, say 0.1 cubic meters, will require less energy to cool down than a teaspoon of water. Actually, a teaspoon of water, 6cc, can hold about 25 times as much heat energy as 0.1 cubic meters of air. A whole empty fridge full of air holds about the same amount of heat energy as 4 drops of water, in fact.

If this were not so, then front-opening fridges would be disastrously inefficient. In fact, they are not -- as long as they have decent gaskets.

So forget about stuffing anything in your fridge or freezer to reduce the air inside -- waste of time.
__________________
Dockhead is offline   Reply With Quote
Old 22-02-2015, 14:36   #10
Long Range Cruiser
 
MarkJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2007
Location: Australian living on "Sea Life" currently in England.
Boat: Beneteau 393 "Sea Life"
Posts: 12,828
Images: 25
Re: The science of Freezing. Do Freez Paks work??

Quote:
Originally Posted by Dockhead View Post
So forget about stuffing anything in your fridge or freezer to reduce the air inside -- waste of time.
Blocks of foam would be good, though, wouldnt they? Reduces space and only the surface of the foam cools as its insulates itself.
__________________
Notes on a Circumnavigation.
OurLifeAtSea.com

Somalia Pirates and our Convoy
MarkJ is offline   Reply With Quote
Old 22-02-2015, 14:36   #11
Registered User

Join Date: Oct 2007
Location: Winters cruising; summers Chesapeake Bay
Boat: Catana 471
Posts: 1,239
Re: The science of Freezing. Do Freez Paks work??

Quote:
Originally Posted by senormechanico View Post
This keeps the average temperature in the insulated space much closer than food.
What does that mean? You mean colder than food?

The only way they would be a benefit is if their mass is higher than an equal volume of food AND they are colder than the frozen food already in the freezer when you add them. In that case, you will save power until the temperature equalizes within the freezer. After that, very little benefit as stumble described, above.

Dave
__________________
2Hulls is offline   Reply With Quote
Old 22-02-2015, 14:48   #12
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Re: The science of Freezing. Do Freez Paks work??

Quote:
Originally Posted by MarkJ View Post
Blocks of foam would be good, though, wouldnt they? Reduces space and only the surface of the foam cools as its insulates itself.
It does not reduce the cooling power required, and it interferes with air circulation around your food, which is the only way it gets cooled down. Don't overcomplicate a simple thing. Just put your food in the fridge (or freezer) and don't worry about it.
__________________
Dockhead is offline   Reply With Quote
Old 23-02-2015, 10:03   #13
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 6,063
Re: The science of Freezing. Do Freez Paks work??

Quote:
Originally Posted by toddedger View Post
They are going to act like a holding plate. So they will take energy to cool and hold it for a while. Somewhere I heard an idea of using packing peanuts in plastic bags to fill in any dead space between food. I haven't tried it yet, but plan on giving ita try.
It sounds as possibly the peanut idea may be self defeating if it causes more open time to find the specific food you are looking for?

Possibly you are more organized than me.
__________________
Cadence is offline   Reply With Quote
Old 23-02-2015, 10:17   #14
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Re: The science of Freezing. Do Freez Paks work??

Quote:
Originally Posted by Cadence View Post
It sounds as possibly the peanut idea may be self defeating if it causes more open time to find the specific food you are looking for?

Possibly you are more organized than me.
Not only that, but they may prevent the food from freezing in the first place by keeping the heat in and preventing circulation.

This is not a good idea.
__________________
Dockhead is offline   Reply With Quote
Old 23-02-2015, 10:24   #15
Registered User

Join Date: Jan 2015
Posts: 134
Re: The science of Freezing. Do Freez Paks work??

Thermal storage is a good idear in combination with solar power.
Since cold space is limited I prefer beer,fruit juice and water for thermal storage
__________________

__________________
Now or Never
warrior 90 is offline   Reply With Quote
Reply

Tags
enc

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
CruisAir System Freezing Up on Heat Cycle Big Moe Plumbing Systems and Fixtures 8 07-05-2015 07:04
Freezing Canuck - Had Enough . . . Heading South ! eliems Meets & Greets 24 11-01-2011 12:26
GPS Freezing Sakura Marine Electronics 3 03-08-2010 11:41
New Member Freezing in Florida gardnsailor Meets & Greets 16 31-03-2010 08:04



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 21:24.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.