MacGregorSailors.com

BOAT wrote: The ballast tank by volume could never be effected by even several pounds of warm food - so I think it actually WOULD work as a better location for a cooler.

It's not a matter of the ballast tank water temp being affected by warm food,...the premise was to utilize the ballast tank water temperature to cool the food or at least to slow the melting of the ice. The ice in a properly insulated cooler would last longer than ice in a pan on a 60-65° surface (then consider the ambient air temp of the cabin).

Keeping food relatively cool in a 'proper' bilge of a sailboat is nothing new, I just don't see it being accomplished in a Mac.

Google search 'zeer', or 'pot-in-pot refrigeration'. I've been planning to do experiments with this kind cooling system when summer rolls around.

BOAT wrote:I dunno - I can tell you the key to discovering good mods is to let your brain go crazy - you really need to be a little bit nuts to engineer good mods - by letting your brain go wild you come up with all kinds of idea that don't work but those same ideas that don't work point you in new directions that DO work.

Excellent .... Isn't this a main reason we own Macs

Does any one have any experience with water cooled heat-sinks? ....Tom you mentioned "cold plate" but not sure if thats the same thing?

Sumner... I appreciate your advice on this (about choosing compressor type) and I know your right but I'd still like to try the cheap option 1st

Al the best.
Neo

Cold plate refers to the evaporator half of a split system retrofit for ice boxes.

https://www.westmarine.com/buy/waeco-ad ... ecordNum=7

The one in the link is a box and is like the one I had in my last boat but they also make flat plate styles. They're only one half of the system as you also need the condenser half (which has the compressor).

The Fridge in the original post is a sterling compressor, it works differently than a standard compressor.

Looks interesting - from wikepedia

The Free Piston Stirling Cooler (FPSC) is a completely sealed heat transfer system that has only two moving parts (a piston and a displacer), and which can use helium as the working fluid. The piston is typically driven by an oscillating magnetic field that is the source of the power needed to drive the refrigeration cycle. The magnetic drive allows the piston to be driven without requiring any seals, gaskets, O-rings, or other compromises to the hermetically sealed system.[29] Claimed advantages for the system include improved efficiency and cooling capacity, lighter weight, smaller size and better controllability.[30]

For several years starting around 2004, the Coleman Company sold a version of the Twinbird "SC-C925 Portable Freezer Cooler 25L" under its own brand name,[34][35] but it has since discontinued offering the product. The portable cooler can be operated more than a day, maintaining sub-freezing temperatures while powered by an automotive battery.[36] This cooler is still being manufactured, with Global Cooling now coordinating distribution to North America and Europe.[37] Other variants offered by Twinbird include a portable deep freezer (to −80 °C), collapsible coolers, and a model for transporting blood and vaccine.[38]


Looks identical to the 25L coleman



https://www.amazon.com/o/ASIN/B000A1FCI ... oltools-20

you guys are making my head hurt.

I think the warming effects of the summer sun shining on a fridge (even with a cover on) can be greatly underestimated (especially with powerful resource hungry cooling units inside). I also think that the cooling effects of placing something next to a cool surface (floor to ballast tank, in a locker) can be easily underestimated too.

For my application I am really not looking to get/build a full blown refrigerator. I only need to keep a few small things cool and none of that will be meat, fish, dairy or canned drink products. A small 20 Liter conpartment kept down to a temperature somewhere between 35°F (1.6° C) and 40°F (4.4° C) should be fine.
The ballast tank (and water) seems to be an great resource for dissipating a lot of heat. If I could just tap into that in a safe, effective and electrically efficient way?

If I have to make major electrical upgrades (expensive solar, chargers, batteries, fat wires etc.) then I'd rather just make a cooling enclosure to throw off the stern and drag behind the boat

I hear you Neo et al .. seems lie ther ehsoud be a clever solution , but there isn't .. The only , .. quick, reasonable mod I can think of is to add some water cooling to a thero electric unit. I think "sailing uma" has a commercial unit that works this way , . but these are expensive. I think if you were to add a small tank of water to the hot side, you could have the cooler work more effectively , as it could disapte more heat, faster, and also achive lower temperature, as the water temp is usually lower then the ambient temperature ( at least during the day) . I don't think it would bother me too much to dump water in to the ballast value, or sink, and replace 2 times a day. if you could attach a tank somehow, you would save the power draw of the exterior fan, not sure how much that is worth.

one thing that is present in my mind is taht you can't have both air , and water cooling because the "air cooling" section with necessarily start to warn the water with the air. So if you want "both" you would have to have a way to disable the air when water is present, . even if just with a switch.


And of course, all fridges can benefit from more insulation.

Thanks kevinnem.

Maybe it's just my part of the Globe but water, away from the beaches, always seems quite cold (compared to the air temperature) Summer/Winter, day or night

You could look at computer CPU coolers, they have been doing water cooled gaming computers for a few years now due to the massive heat they generate, you could cook a chicken with the hot air the fan pushes out if you put it behind my gaming laptop for any period of time when she is running at full boost.

Im not 100% sure but if you have water cooling you would need to have a pump to pump the water around, so you replace the inefficiency of a fan with the greater electrical efficiency of a pump, im sure if there was a simple and economical way to use liquid cooling the big brands of thermoelectrics (Waco) would be using it as it would make the coolers more effective at doing their job.

If you want to have a play, just pick up a old computer off the "hard waste" on the side of the road and strip the heat sink off it, drill some holes for copper tubing and give it a go

Assume that the average daytime air temperature on the water is 85°F, and for the sake of round numbers, that the shaded inside cabin air temp is 75°F. The ocean water temp is 60° in Maine / 55° California. The in-water hull temp is same as the water, ballast water temp is (for discussion) same as ocean water. The cabinside of the fiberglass surface that separates the cabin air from the ballast water is, lets say, closer to ballast temp.

How does an insulated cooler or non insulated container that is in contact with the 55-60° fiberglass surface create/maintain an internal temp of 35-40° just by virtue of surface contact?

K9Kampers wrote:How does an insulated cooler or non insulated container that is in contact with the 55-60° fiberglass surface create/maintain an internal temp of 35-40° just by virtue of surface contact?

Not sure if you are asking or debating?
My goal it to use the the 55-60° water in the ballast tank to cool the Thermoelectric Cells Heatsink.... not the cooler enclosure itself .... And also keep the cooler enclosure next to the 55-60° ballast tank (and away from the sun) so it may benefit from the cooler thermal conductivity.

Surely the water temperature is higher than 60 degrees (15.5 c) even down here in Victoria the water temperature its much higher. Port Phillip bay is 73f (23c) and Bass Strait is 67f (19.5c), up there on the central coast NSW its pushing 79f (26c).

By the time that water sits in the tank and is heated by air from the cabin it will be close to 85f (29.5c)

Given that the huge amount of heat produced by the thermoelectric coolers, it wont take long to heat the water in the tank, which will also raise the cabin temperature causing the cooler to have to work harder and produce more heat, that will heat the water more and further increase the cabin temp, so the cooler has to work still harder.

As you can see its just a vicious loop that you cant win, the body of water just isnt big enough or cold enough

What you need is a proper heat exchanger with a fan to cool the water before it re-enters the tank

What you need is a proper heat exchanger with a fan to cool the water before it re-enters the tank

No what you need is proper marine refrigeration that uses a water cooled condenser, the water is pumped in and then overboard using the whole ocean as your heat sink Problem is they are very expensive and for our little boats a self contained compressor fridge is a far more viable and cost benefit option.

e.g.
http://www.ozefridge.com.au/?page_id=20

kadet wrote: No what you need is proper marine refrigeration that uses a water cooled condenser

Water cooled condensers are most efficient.

This is the norm for marine Air Conditioners. Our old marina was chock full of powerboats and at night all you heard was the water splashing out of all the A/C cooling units. Every one of them.
A friend had his A/C stop working. When they took it apart they found all kinds of jellyfish and junk sucked up and clogging it up.




--Russ

Ditto on the Engel for me. I have had one for the last 2 years. Quiet, efficient and will cool to -5 F. Pricey but worth it to me.