Dry ice lifespan

[IslandInfedel]

Hey all

So I was thinking, I have limited LG rigid solar and a small battleborn bank, all good equipment, but space is a premium, thinking of a small theoretical 1wk passage in cloudy conditions, running nav/com autopilot and plotters, LED lights, one of my larger draw items is my fridge, in this low light situation where priority needs to be autopilot and nav systems, could I turn off my fridge and load with dry ice (it has a bottom throughhull drain) and make the passage on dry ice to avoid spinning up compressors?

[mlydon]

Yes you can. Many use some dry ice in combination with regular, as dry ice tends to freeze everything....

[S/V Illusion]

Dry ice sublimates in an ice chest generally at a rate of 5 to 10 pounds/24 hours. This is true almost regardless of temperature.

Although not a perfect direct extrapolation, for 7 days, you might need a bigger refrigerator. Stated differently, you need a Plan B.

[IslandInfedel]

Originally Posted by mlydon

Yes you can. Many use some dry ice in combination with regular, as dry ice tends to freeze everything....

Do you think a 5lb dry ice brick would do 1wk in a top load cooler?

[IslandInfedel]

Originally Posted by S/V Illusion

Dry ice sublimates in an ice chest generally at a rate of 5 to 10 pounds/24 hours. This is true almost regardless of temperature.

Although not a perfect direct extrapolation, for 7 days, you might need a bigger refrigerator. Stated differently, you need a Plan B.

So 35-70lbs of dry ice or run the fridge...

Any other recommendations?

[Jammer]

The obvious choice is to quit running the fridge.


Eat foods that don't require refrigeration. There are many, and it's pretty easy to make it for a week. I've done it a number of times.

[S/V Illusion]

Originally Posted by IslandInfedel

So 35-70lbs of dry ice or run the fridge...

Any other recommendations?

Yes. You are trying to substitute dry ice to serve the purpose of what a larger battery capacity gets by running the refrigeration.

Understand the sublimation rate will continue regardless of how much you run your refrigerator. Even run normally, the temp difference between it and dry ice is so large that running the refrigerator would be useless. The dry ice will be gone and you are still left with the basic problem of battery capacity.

Plus, to state the obvious, 70 pounds of dry ice means you have little/no room for food, much of it burned by close proximity to the ice.

[IslandInfedel]

Originally Posted by S/V Illusion

Yes. You are trying to substitute dry ice to serve the purpose of what a larger battery capacity gets by running the refrigeration.

Understand the sublimation rate will continue regardless of how much you run your refrigerator. Even run normally, the temp difference between it and dry ice is so large that running the refrigerator would be useless. The dry ice will be gone and you are still left with the basic problem of battery capacity.

Plus, to state the obvious, 70 pounds of dry ice means you have little/no room for food, much of it burned by close proximity to the ice.

I get the sublimation thing, just didn’t know the numbers

Yeah keeping a small foot print on this boat has been a bit of a issue outside of sunshine.

So best bet I load dry ice and I run the fridge for 1 or 2 days less, hmmmm

[Jim Cate]

Not quite sure what you mean by "(it has a bottom throughhull drain)" but I'd be a bit concerned about releasing that quantity of CO2 inside the boat. Even if the drain remains clear, it isn't absolutely certain that the gas will be exhausted into the sea, and a big buildup of CO2 below decks is a dangerous thing.

Not a good idea safety wise IMO.

Jim

[a64pilot]

I’m sure he’s talking about a regular ice box that has a drain to let the water out as the ice melts, often into the bilge.

How long the dry ice will last is directly proportional to the insulation, if there were such a a thing as perfect insulation and the container was sealed, it would last forever. In order to sublimate it has to pick up heat, the more heat, the faster is sublimates.

That’s never going to happen in an ice box of course, to start with you can’t let food fold get that cold.

CO2 will kill you in high enough concentrations, and you won’t know it either. If you know a rebreather diver talk to them about CO2 safety wise.

Just run your motor like everyone else and motor sail for awhile to charge batteries, it’s just a few gallons at most of Diesel.

[IslandInfedel]

Ships ice box, now modified to a fridge/freezer with a drain in the bottom with goes to overboard, not the bilge

[Island Time O25]

What is the cubic feet capacity of your fridge?

Years ago when I was stocking up for one of my first week long trips I was at the ice supply place asking for X number of 10lbs bags of ice. The owner asked what was the ice for. After I told him he recommended getting 1/2 of the lbs but in blocks. Said, pound for pound, ice blocks will last twice as long as cubed ice.

I used this piece of wisdom ever since and now just freeze 1gal or 2.5gal jugs of water. The longer they sit in the freezer the better. Same idea for block vs. pieces works for dry ice.

Another trick I learned from an old salt is to cover the fridge top hatch with heavy folded blanket, preferably wool or felt. You can hear the difference in less frequent pump cycling.

Also unless you decide to go with dry ice, plug that drain hole and just have a grate at the bottom to have food above the pooled water. That water is still cold and dumping it into the drain and at the same time allowing warm air to enter is not conducive to keeping the fridge cold. May be open the drain hose from the bilge end periodically just to keep the water level in the fridge from ruining the food.

Still another idea is to have a block of dry ice in the thick styrofoam container with thick lid top. The type in which Omaha steaks are packed for delivery. Hopefully with little or any space for air inside. Then duct tape around the lid seam and use it from the middle of the trip. Theoretically, if you make it really air tight you should have the same amount of dry ice a few days later.

[HobieDog]

I’ve had 10 lbs of dry ice keep steaks frozen for a weeklong canoe trip. This was in a cheapo cooler. Layer as follows: Dry ice on bottom, cardboard, steaks, Ice, other cold foodstuff.

And, you won’t kill yourself with the amount of c02 released slowly over the week (8.3 cubic feet per lb). Leave a port open at night if you’re worried about it (and you shouldn’t be)

[HobieDog]

Originally Posted by S/V Illusion

Yes. You are trying to substitute dry ice to serve the purpose of what a larger battery capacity gets by running the refrigeration.

Understand the sublimation rate will continue regardless of how much you run your refrigerator. Even run normally, the temp difference between it and dry ice is so large that running the refrigerator would be useless. The dry ice will be gone and you are still left with the basic problem of battery capacity.

Plus, to state the obvious, 70 pounds of dry ice means you have little/no room for food, much of it burned by close proximity to the ice.

I'm sorry, but you must have no experience with dry ice other than what you found on a quick google search. 70lbs!?!? Sure, if he wants to keep ice cream frozen the entire trip, I guess so.

15 lbs used appropriately in a cooler along with regular ice will absolutely meet his needs. This has been discussed ad nauseam on this and other forums.

I suggest block ice for the supplemental ice, but made at home in the 2.5 gallon containers. The dry ice will deep freeze everything near it, and so by the time the dry ice is gone you're left with deeply frozen meats and ice.

There is a learning curve to using it. Many people will keep things they don't want frozen too close to the dry ice (drinks) and make a mess when everything freezes solid. If you decide to use dry ice (and I'd recommend it based on what you want to accomplish), practice before your trip. The other advice about keeping the dry ice airtight in a styrofoam cooler sounds interesting and like it may work too, but I have no experience doing that. I may try that this weekend to see what is left after a few days.

[S/V Illusion]

Originally Posted by HobieDog

I'm sorry, but you must have no experience with dry ice ...


... but I have no experience doing that. I may try that this weekend to see what is left after a few days.

Why accuse me of that just before saying you have no experience?

I was trying to help - not sure what you are trying to do.

Regardless, I speak from my background as a chemical engineer who worked as a consultant in the food packing industry for a while so your premise is monumentally flawed. Have a nice day.