Water Cooled Fridges ?

[onionbargee]

Why are we not using water cooled fridges ?

"What is a keel cooler?

On large commercial & fishing boats, the cooling water from engines, generators, etc., is often circulated through pipes that are mounted on the underside of the boat, below the waterline. This gives a very efficient method of cooling without having to pump raw water into the boat & then discharge it. We have borrowed the term "keel cooler" to describe a unique fitting that is installed through the bottom of the boat, below the waterline, with the boat out of the water.

How does the Frigoboat keel cooler work?

The keel cooler condenser fitting has two copper tubes projecting from it, & these are connected together through a cupro-nickel loop that is cast into the sintered bronze. Through the action of the compressor, the hot, high pressure refrigerant gas is circulated through the keel cooler where it is cooled & condensed into a cool, high pressure liquid that is then fed to the evaporator (the part that is in the insulated box). Here it is subjected to a large pressure drop & evaporates (boils) at a very low temperature before being fed back to the compressor as a cool, low-pressure gas.

Why is it more efficient than other systems?

In small, 12v dc refrigeration systems, the most popular method of cooling & condensing the refrigerant gas is with an air cooled condenser coil, usually with a fan forcing air over it. This is also common in domestic refrigerators, & the efficiency depends on the temperature of the cooling air. The system is essentially removing heat from the insulated box & giving it up to the cooling air, & if an air cooled condenser is installed in an enclosed space, the air will be re-circulating & getting hotter & hotter, making the system less & less efficient.

A water cooled condenser is generally regarded as being at least 20% more efficient than an air cooled equivalent, & so, as a boat is usually sitting in water, it would make sense to substitute a water cooled heat exchanger for the air cooled version mentioned above. All that is then needed is a pumping system to bring water into the boat, through the condenser coil, & then overboard. This will result in a far more efficient system, but it has drawbacks, the most significant & obvious being the 1 amp (typical at 12v dc) current draw of the pump. Pump failure, clogged strainers, noise & inconvenience are some other negative factors of a pump-fed, water cooled system, so if we replace it with a keel cooler we now have the most efficient system of all, together with minimum current draw (compressor only), almost silent operation, unequaled reliability, & mechanical simplicity.

[Kwacker]

 

Why are we not using water cooled fridges ?

"What is a keel cooler?

On large commercial & fishing boats, the cooling water from engines, generators, etc., is often circulated through pipes that are mounted on the underside of the boat, below the waterline. This gives a very efficient method of cooling without having to pump raw water into the boat & then discharge it. We have borrowed the term "keel cooler" to describe a unique fitting that is installed through the bottom of the boat, below the waterline, with the boat out of the water.

How does the Frigoboat keel cooler work?

The keel cooler condenser fitting has two copper tubes projecting from it, & these are connected together through a cupro-nickel loop that is cast into the sintered bronze. Through the action of the compressor, the hot, high pressure refrigerant gas is circulated through the keel cooler where it is cooled & condensed into a cool, high pressure liquid that is then fed to the evaporator (the part that is in the insulated box). Here it is subjected to a large pressure drop & evaporates (boils) at a very low temperature before being fed back to the compressor as a cool, low-pressure gas.

Why is it more efficient than other systems?

In small, 12v dc refrigeration systems, the most popular method of cooling & condensing the refrigerant gas is with an air cooled condenser coil, usually with a fan forcing air over it. This is also common in domestic refrigerators, & the efficiency depends on the temperature of the cooling air. The system is essentially removing heat from the insulated box & giving it up to the cooling air, & if an air cooled condenser is installed in an enclosed space, the air will be re-circulating & getting hotter & hotter, making the system less & less efficient.

A water cooled condenser is generally regarded as being at least 20% more efficient than an air cooled equivalent, & so, as a boat is usually sitting in water, it would make sense to substitute a water cooled heat exchanger for the air cooled version mentioned above. All that is then needed is a pumping system to bring water into the boat, through the condenser coil, & then overboard. This will result in a far more efficient system, but it has drawbacks, the most significant & obvious being the 1 amp (typical at 12v dc) current draw of the pump. Pump failure, clogged strainers, noise & inconvenience are some other negative factors of a pump-fed, water cooled system, so if we replace it with a keel cooler we now have the most efficient system of all, together with minimum current draw (compressor only), almost silent operation, unequaled reliability, & mechanical simplicity.

 

 

The idea of using a small computer fan to blow cold air up from the bilge over the existing air-cooled condenser gets my vote.

[ditchcrawler]

 

The idea of using a small computer fan to blow cold air up from the bilge over the existing air-cooled condenser gets my vote.

You can buy water cooled condensers refrigeration units from Waeco

http://www.waeco.com/blaetterkatalog/More_comfort_on_board_2013_en/blaetterkatalog/index.html?lang=en_GB

[Bod]

I think the answer is..... Cost!

 

Bod

[by'eck]

American sailboat owners love water cooled fridge systems, probably because many spend their time cruising the Bahamas and Caribbean. The extra water pump and maintenance of inlet filters seemed to cause some unreliability though.

 

I managed with a couple of fan assisted air cooled ones without issue in the same environment, although I admit the area they vented to sometimes got quite warm.

[BEngo]

Why are we not using water cooled fridges ?

 

[<SNIP>

Because when the BCN shopping trolley/oil drum/nicked car reef rips the designed for salty water with no lumps keel cooler off you don't have a fridge. Just lots of bubbles in the cut.

 

Because if you put the keel cooler on the swim to avoid most of the cr@p it makes for a very long inefficient refrigerant circuit and needs a lot of refrigerant.

 

Because every installation in a canal boat would be different so they'd need to be installed and gassed-up by a professional.(Expense, boat builders not familiar so more expense.) Yots which are often built on a production line can have a 'standardised' set-up which can be installed by the builder. If it isn't standard then at least the builder understands the basics.

 

Yes they are more efficient- but what actual increase in the Coefficient of Performance would be achieved? A keel cooler is a lot more expensive than a fan driven by the existing terminal on the common Danfoss 12/24 V electronic unit.

 

I'm not sure whether a near freezing cut might not provide too much cooling in a unit designed for summer water temps- I guess that would depend on the exact set-up, but might involve more complication.

 

I think the 'Is my skin tank big enough for my fridge/freezer' thread could be quite interesting, but I'm not expecting to see one any time soon.

 

 

N

[onionbargee]

Because when the BCN shopping trolley/oil drum/nicked car reef rips the designed for salty water with no lumps keel cooler off you don't have a fridge. Just lots of bubbles in the cut.

 

Because if you put the keel cooler on the swim to avoid most of the cr@p it makes for a very long inefficient refrigerant circuit and needs a lot of refrigerant.

 

Because every installation in a canal boat would be different so they'd need to be installed and gassed-up by a professional.(Expense, boat builders not familiar so more expense.) Yots which are often built on a production line can have a 'standardised' set-up which can be installed by the builder. If it isn't standard then at least the builder understands the basics.

 

Yes they are more efficient- but what actual increase in the Coefficient of Performance would be achieved? A keel cooler is a lot more expensive than a fan driven by the existing terminal on the common Danfoss 12/24 V electronic unit.

 

I'm not sure whether a near freezing cut might not provide too much cooling in a unit designed for summer water temps- I guess that would depend on the exact set-up, but might involve more complication.

 

I think the 'Is my skin tank big enough for my fridge/freezer' thread could be quite interesting, but I'm not expecting to see one any time soon.

 

 

N

you would not have an external keel cooler on a Narrowboat, it would be internal, or recessed.

 

The heatsink can be under the fridge on the bare bottom plate.

 

the units are supplied fully gassed with leakproof connectors.

 

Fan uses power, heatsink / cooler does not.

 

 

 

I have thought about it.

[ditchcrawler]

you would not have an external keel cooler on a Narrowboat, it would be internal, or recessed.

 

The heatsink can be under the fridge on the bare bottom plate.

 

the units are supplied fully gassed with leakproof connectors.

 

Fan uses power, heatsink / cooler does not.

 

 

 

I have thought about it.

I "think" Waeco bring the water to the refrigeration plant for cooling via a sea cock. If I remember correctly they use to have a motion driven pump to push the water round which works on the lumpy stuff so now power required for cooling water circulation.

[by'eck]

I "think" Waeco bring the water to the refrigeration plant for cooling via a sea cock. If I remember correctly they use to have a motion driven pump to push the water round which works on the lumpy stuff so now power required for cooling water circulation.

 

That's correct although it was Isotherm that offered this means of cooling via their complex through-hull fitting replacing the sink drain one, which had to exit below the water line. Just the motion of waste water moving gently up and down through the fitting gave a self pumping action to conduct the heat to water.

 

 

Apparently the fridge would still work with the boat on the hard (whilst laid up) but with much less efficiency since only conduction to air allowed dissipation of heat.

[Ex- Member]

I have an idea for cooling a fridge just by using the air temp outside. When external air reaches fridge temperature it seems daft to continue powering your fridge when there's masses of cold air sitting a few feet away.

 

My plan is to use one inch hose to convey cold air into the fridge through a skin fitting, the hose will have a filter to stop ingress of insects. A mini fan built in to the hose line will draw the cold air in to fridge. A slightly smaller outlet at the top of the fridge would dispel warmer air at the top of the fridge simply through convection.

 

With some clever electronics and a thermostat, when outside air becomes warmer than fridge air temp requirement, the hose system shuts down and the general fridge operation cuts in . There would have been a lot of days last winter where the fridge could have been switched off. The running of a small fan would be a fraction of the energy used to cool the fridge normally.

 

I'm looking out for a smaller 1/2 sized fridge to do an experiment with in the back cabin. I see no reason why it wouldn't work.

 

I like the keel cooler idea though, I reckon you could do fridge and air con on a large wide beam base plate.

[Captain Zim]

There are a few good ways to cool the fridge mentioned above. The other thing to do to double the effect would be to redesign the fridge structure. A thicker insulation and top opening door (difficult on a boat, I know) would make a huge difference. Using all these techniques I think it's possible to run a fridge really efficiently. I'm redesigning my galley and I'm seriously thinking of doing all this since the fridge is what kills batteries.

[onionbargee]

I clad my gas fridge in insulation board and it immediatly went into north pole mode, i had to turn it down to it's lowest setting. just shows you how poor the standard cabinets are.

[MtB]

 

Why are we not using water cooled fridges ?

 

Because air cooled fridges work perfectly well.

 

MtB