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      A Few Simple Rules   05/22/2017

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Poda

Electricity Free Refrigeration

29 posts in this topic

As the water evaporates through the surface of the outer pot, it draws heat from the inner one, keeping up to 12kg food fresh for as long as three to four weeks without using a single watt of electricity

 

This would not have a hope in hell of cooling anything off even 1 degree in Maryland. Evaporates implies the air could possibly hold more water.

 

http://www.bensdiscountsupply.com/propane-refrigerator.aspx ;)

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When cruising (and racing in the olden days) we used to take plastic milk crates and sew up a thick burlap cover for them. About once ever two hours someone would toss the burlap cover over the side tied by one corner to a bit of line. Once it was nice and wet, they'd haul it up and put it over the plastic crate again. The salt water evaporated, making things a lot cooler and the salt water dripped on the veggies and eggs in the crate. It turns out that most of what causes rot in veggies doesn't seem to like salt water much, so things like lettuce, cabbage, squashes, eggs, etc... lasted a LOT longer than when we kept them in the "normal" refrigerator.

 

I measured the temp once in the S. Pac. and with an air temp outside the box of 84 deg. the temp inside the box was 70. Not perfect, but a big improvement over what the temp was down below and not in the fridge.

 

After than I built a mini-tarp of shiny silver plastic to reflect the sun off the burlap. That lowered the inside temp to 65 deg.

 

BV

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Hey Pods, glad to see you still around!

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Good stuff BV - gonna have to play around and see what I can come up with to improve efficiency..

 

Ajax - Yeah, been busy.. But things have settled a bit, and I'm chomping at the bit to get back into a boat. I'm a year or two out of being able to afford one again, but OPBs are filling the gap in the meantime :) Good to be back - I've missed this place

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So, what's the news on the Farr 27? (tigerregis). Couldn't log on, had to start over. Hence, piztov.

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Hey Regis - It's gone on to another member here at SA. Currently boatless, but still able to get out once in a while on the other 727 at the club.

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Those things work by a combination of evaporative cooling and huge thermal mass. That's more or less how we get permanent ice caves at latitudes where the textbooks say it's impossible. Presents certain difficulties on a boat though.

Anyway, technically propane-powered fridges are electricity-free.

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Alot of people here use evap air conditioners here because its so dry. They work exceptionally well here but as the humidity rises the performance nose dives to nothing.

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Alot of people here use evap air conditioners here because its so dry. They work exceptionally well here but as the humidity rises the performance nose dives to nothing.

 

Here, those are referred to as "Swamp Coolers". They work great in the desert. Not many deserts at sea.

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Those things work by a combination of evaporative cooling and huge thermal mass. That's more or less how we get permanent ice caves at latitudes where the textbooks say it's impossible. Presents certain difficulties on a boat though.

Anyway, technically propane-powered fridges are electricity-free.

 

My parents have one of those on their motor sailer. Open flame... not sure I'd put one on my sailboat, although it seems to work well for them.

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Those things work by a combination of evaporative cooling and huge thermal mass. That's more or less how we get permanent ice caves at latitudes where the textbooks say it's impossible. Presents certain difficulties on a boat though.

Anyway, technically propane-powered fridges are electricity-free.

 

My parents have one of those on their motor sailer. Open flame... not sure I'd put one on my sailboat, although it seems to work well for them.

Chartered a catamaran with one once. It worked well, but blew hot air on the helmsman's feet. Unacceptable. .

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Those things work by a combination of evaporative cooling and huge thermal mass. That's more or less how we get permanent ice caves at latitudes where the textbooks say it's impossible. Presents certain difficulties on a boat though.

Anyway, technically propane-powered fridges are electricity-free.

 

My parents have one of those on their motor sailer. Open flame... not sure I'd put one on my sailboat, although it seems to work well for them.

Chartered a catamaran with one once. It worked well, but blew hot air on the helmsman's feet. Unacceptable. .

 

Apart from the risk they dont like being tilted when running. Blocks up the heat exchanger thingy.

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I wonder if this concept could be adapted for use on a boat.. no shortage of water on long passages, and without electrical drain. Could be a cool (pun intended) way to keep the brewskies cold. I may have to tinker with this once I get a boat back.

 

http://gizmodo.com/5935104/how-to-make-an-electricity+free-refrigerator

Welcome back Poda.

 

I did accualy try a form of this on my boat: Basicly a plastic bucket full of bilge temp beer filled with sea water at about the same temp And then a towl draped over the bucket with the middle allowed to sit in the water in the bucket. The idea was that the evaparating water would cool the water in the bucket and the beer.

End result was "No, I still don't like warm beer"

The main problem I had was that for the bucket to be in the wind at anchor it also had to be in the sun, I was fighting a losing battle.

I think more forward planning on my part may have given me cooler beer, You usually start thinking about beer in the hottest part of the day. That is possably not the best time to be cooling beer by nature's means.

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Apart from the risk they dont like being tilted when running. Blocks up the heat exchanger thingy.

 

This. And, like any refrigeration that relies on heat exchange (incl. Peltier junctions), their efficiency drops off spectacularly as ambient temperature rises. No place to dump the heat you've stripped out of the cooler box: Tropics got plenty, thnx. ;) Same thing happens with compressor-powered systems, of course. But THEY use mechanical power to generate a much bigger absorption capacity. You're not mucking around in the region of +/- 10F passive cooling. As long as you have the amps and a big-ass motor, you can ignore the ambient.

 

Should be noted (tho I've never seen it discussed) that compressor-driven fridges also don't like being tilted or gyrated about. Creates an unbalanced condition inside the compressor. Hard on seals & bearings.

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I wonder if this concept could be adapted for use on a boat.. no shortage of water on long passages, and without electrical drain. Could be a cool (pun intended) way to keep the brewskies cold. I may have to tinker with this once I get a boat back.

 

http://gizmodo.com/5...ee-refrigerator

Welcome back Poda.

 

I did accualy try a form of this on my boat: Basicly a plastic bucket full of bilge temp beer filled with sea water at about the same temp And then a towl draped over the bucket with the middle allowed to sit in the water in the bucket. The idea was that the evaparating water would cool the water in the bucket and the beer.

End result was "No, I still don't like warm beer"

The main problem I had was that for the bucket to be in the wind at anchor it also had to be in the sun, I was fighting a losing battle.

I think more forward planning on my part may have given me cooler beer, You usually start thinking about beer in the hottest part of the day. That is possably not the best time to be cooling beer by nature's means.

 

Get net. Put beer in net with a weight. Tie rope to net. lower beer filled net over the side. Sink beer filled net to cooler water. Wait. Pull beer filled net out of water. Extract beer. Open beer. Enjoy! Well it works in the Northwest anyway.

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I wonder if this concept could be adapted for use on a boat.. no shortage of water on long passages, and without electrical drain. Could be a cool (pun intended) way to keep the brewskies cold. I may have to tinker with this once I get a boat back.

 

http://gizmodo.com/5...ee-refrigerator

Welcome back Poda.

 

I did accualy try a form of this on my boat: Basicly a plastic bucket full of bilge temp beer filled with sea water at about the same temp And then a towl draped over the bucket with the middle allowed to sit in the water in the bucket. The idea was that the evaparating water would cool the water in the bucket and the beer.

End result was "No, I still don't like warm beer"

The main problem I had was that for the bucket to be in the wind at anchor it also had to be in the sun, I was fighting a losing battle.

I think more forward planning on my part may have given me cooler beer, You usually start thinking about beer in the hottest part of the day. That is possably not the best time to be cooling beer by nature's means.

 

Get net. Put beer in net with a weight. Tie rope to net. lower beer filled net over the side. Sink beer filled net to cooler water. Wait. Pull beer filled net out of water. Extract beer. Open beer. Enjoy! Well it works in the Northwest anyway.

Yep, that would work here too. I just wanted to try this method, and I didn't have a net or weight on board at the time.

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I wonder if this concept could be adapted for use on a boat.. no shortage of water on long passages, and without electrical drain. Could be a cool (pun intended) way to keep the brewskies cold. I may have to tinker with this once I get a boat back.

 

http://gizmodo.com/5...ee-refrigerator

Welcome back Poda.

 

I did accualy try a form of this on my boat: Basicly a plastic bucket full of bilge temp beer filled with sea water at about the same temp And then a towl draped over the bucket with the middle allowed to sit in the water in the bucket. The idea was that the evaparating water would cool the water in the bucket and the beer.

End result was "No, I still don't like warm beer"

The main problem I had was that for the bucket to be in the wind at anchor it also had to be in the sun, I was fighting a losing battle.

I think more forward planning on my part may have given me cooler beer, You usually start thinking about beer in the hottest part of the day. That is possably not the best time to be cooling beer by nature's means.

 

Get net. Put beer in net with a weight. Tie rope to net. lower beer filled net over the side. Sink beer filled net to cooler water. Wait. Pull beer filled net out of water. Extract beer. Open beer. Enjoy! Well it works in the Northwest anyway.

 

My grandfather and I used to do this to cool beer back when I used to sail with him.. Somehow, once I turned 14-ish, we'd "forget" to put the pop in too. Oh well, can't have your grandson thirsty or drinking warm pop.. ;) Works well in the Atlantic off the coast of Brittany too.

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Apart from the risk they dont like being tilted when running. Blocks up the heat exchanger thingy.

 

This. And, like any refrigeration that relies on heat exchange (incl. Peltier junctions), their efficiency drops off spectacularly as ambient temperature rises.

...

 

Yah, pretty much all refrigeration relies on heat exchange ;-)

 

You'll see pretty spectacular efficiency differences when using a keel cooler for dumping the heat - although the water temperature may not be any cooler than the air, the heat transfer coefficient is dramatically better (on the order of 50-100x).

 

And no warm breeze blowing on your ankles in the galley...

 

Mike

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Apart from the risk they dont like being tilted when running. Blocks up the heat exchanger thingy.

 

This. And, like any refrigeration that relies on heat exchange (incl. Peltier junctions), their efficiency drops off spectacularly as ambient temperature rises.

...

 

Yah, pretty much all refrigeration relies on heat exchange ;-)

 

You'll see pretty spectacular efficiency differences when using a keel cooler for dumping the heat - although the water temperature may not be any cooler than the air, the heat transfer coefficient is dramatically better (on the order of 50-100x).

 

And no warm breeze blowing on your ankles in the galley...

 

Mike

 

Except icebox cooling -- or at least, with ice all end-user heat exchange takes place inside the cold box.;) You are right about using water for the heat sink. Much better transfer rate for a given gradient. Even better if the water is moving some. At the cost (there's always a cost) of greater complexity.

 

How far down the keel is the typical cooler located? Might not matter in Tonga, but in temperate areas in summer, the water 5' deep is a whole lot colder than the surface layer.

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I wonder if this concept could be adapted for use on a boat.. no shortage of water on long passages, and without electrical drain. Could be a cool (pun intended) way to keep the brewskies cold. I may have to tinker with this once I get a boat back.

 

http://gizmodo.com/5...ee-refrigerator

Welcome back Poda.

 

I did accualy try a form of this on my boat: Basicly a plastic bucket full of bilge temp beer filled with sea water at about the same temp And then a towl draped over the bucket with the middle allowed to sit in the water in the bucket. The idea was that the evaparating water would cool the water in the bucket and the beer.

End result was "No, I still don't like warm beer"

The main problem I had was that for the bucket to be in the wind at anchor it also had to be in the sun, I was fighting a losing battle.

I think more forward planning on my part may have given me cooler beer, You usually start thinking about beer in the hottest part of the day. That is possably not the best time to be cooling beer by nature's means.

 

Get net. Put beer in net with a weight. Tie rope to net. lower beer filled net over the side. Sink beer filled net to cooler water. Wait. Pull beer filled net out of water. Extract beer. Open beer. Enjoy! Well it works in the Northwest anyway.

 

My grandfather and I used to do this to cool beer back when I used to sail with him.. Somehow, once I turned 14-ish, we'd "forget" to put the pop in too. Oh well, can't have your grandson thirsty or drinking warm pop.. ;) Works well in the Atlantic off the coast of Brittany too.

 

You guys are making me jealous. That method here isn't very good in summer. We had several inches of cold rain earlier this week so the water temp went down a little. All the way down to 83 degrees F. :angry:

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Evidently people do sail with propane fridges e.g.

"On Naga, our refrigerator, inconveniently located in the sail locker far away from the rest of the galley, is powered by propane, and a tiny pilot light magically keeps the 2' cubic space cold enough to keep the butter from melting." from http://www.trimaran-naga.com/truth.htm

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They will work if you heal, just not if you heal the same for hours. An RV fridge works fine when you are driving, even on a windy road. It is technically feasible to make an absorption refer that would easily accommodate 30 degrees of continuous heel. It is simply a matter of arranging the coils to provide more than 30 degrees downslope as they are gravity drained. A good RV fridge works just fine at 105 deg ambient, if combined with a keel cooler (that would require a little ingenuity) or water cooling (that would require a little electricity) and a sealed combustion chamber it would make a great boat fridge. Just not enough volume in sales to justify it I guess.

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Apart from the risk they dont like being tilted when running. Blocks up the heat exchanger thingy.

 

This. And, like any refrigeration that relies on heat exchange (incl. Peltier junctions), their efficiency drops off spectacularly as ambient temperature rises.

...

 

 

 

Yah, pretty much all refrigeration relies on heat exchange ;-)

 

You'll see pretty spectacular efficiency differences when using a keel cooler for dumping the heat - although the water temperature may not be any cooler than the air, the heat transfer coefficient is dramatically better (on the order of 50-100x).

 

And no warm breeze blowing on your ankles in the galley...

 

Mike

 

Except icebox cooling -- or at least, with ice all end-user heat exchange takes place inside the cold box.;)/> You are right about using water for the heat sink. Much better transfer rate for a given gradient. Even better if the water is moving some. At the cost (there's always a cost) of greater complexity.

 

How far down the keel is the typical cooler located? Might not matter in Tonga, but in temperate areas in summer, the water 5' deep is a whole lot colder than the surface layer.

 

Wonder how you would go using the keel bolts on an external keel.

A fair bit of thermal mass there, bolts are also a decent size, and the rate of heat generated is pretty low.

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So, we have an 8000 lb lead keel on a 12" stub, around 10x1" keel bolts.

The stub usually has some rainwater in it, comes down the mast or from the shower.

What about circulating the water in the stub through the compressor heat exchanger, maybe put some heat sinks onto the keel bolts,

Hey presto, a keel cooler

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Cast a few loops of cooling pipe in the lead of the keel. Always wanted to try that.

 

-jim lee

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