Getting rid of fridge heat

[whiteoaks7]

Reading Rosssavage's post about aircon reminded me of one of my future jobs - getting rid of the fridge heat. The problem is an obvious one (one of those lovely positive feedback loops) the fridge on my Moody dumps all it's heat into the saloon which is where the fridge is installed anyway. Come the summer (did I miss it?) the fridge works hardest and the saloon gets hot because of the waste heat from the fridge and the fridge works harder and we all get hotter. The best solution is to dump the heat into the sea but (a) I can't face any more plumbing, and (b) I don;t want to spend the money. The alternative is to conduct the heat from the fridge via an insulated duct to deck level and then out through a vent . . . Has anyone tried anything like this before and with what results?

btw - there's no reason in principle why rosssavage's idea would not work but as someone said the answer's in the detailed calcs - one very open rule of thumb is for every Watt of heat you want to move you need to feed the unit another Watt to move it. You then have 2W of energy to get rid of (please - I know this is very rough)

 

[Andrew_Fanner]

Gas or electric fridge? The Shoreline ones have terminals for a heat dissipation fan thta uses very little power and it should be possible to duct this out of the saloon.

 

[asj1]

My unit is has a fan driving the air over the radiator? and tehn into the cockpit locker, seems to work OK.

Regards

 

[Talbot]

A bit of heat ducting (either eberspacher or B&Q plastic rectangular vent trunk)
Plus
A computer fan used to suck the waster heat and dump through the trunking.

 

[William_H]

Yes a computer fan comes in many sizes will move air for you and may improve the cooling of the cabin.

I have often wondered how good the fibreglass hull would be at dissipating heat. No where near as good as aluminium or even steel but I wonder if a large area were given over to a water jacket (even the fressh water tank that is in contact with the hull would move a lot of heat out into the sea.
Soi my brain storm is a piece of heavy aluminium plate clamped tightly around the pipe going into the condenser but after the compressor for a lenght of perhaps 6 inches then bent down to press against the hull with close contact and as large area as possible. using (electronic) heat transfer paste.
Would it get too hot for the fibreglass? Probably not. Would it shift much heat from the pipe into the fibreglass? ..maybe...

Comments please.(not that i am planning it, just dreaming my boat is too small for a fridge. olewill

 

[ccscott49]

Ducting with a solar powered fan, the deck type, will do nicely, wired to suck not blow, ducting made to fit over solar vent, neatened up of course, seen it done was very effective and best at the hottest (sunniest) times of the day.

 

[Ruffles]

The instructions for my Isotherm compressor recommend placing it near the hull below the waterline. The idea being I imagine that in warm weather the water will be cooler than the air.

See http://www.isotherm.com/econtent/3065

 

[steve_cronin]

I used an alternative remedy

I reversed the fan on the condenser matrix so that it sucks relatively cool air from the bilges and blows it out through one half of the double grill on the compressor compartment door. To the back of the other I've fitted an identical fan which blows saloon air directly onto the compressor motor. They are both switched by the fridge thermostat.

The result is that the air evacuated into the saloon is now far cooler than it was originally, the compressor motor stays cool to the touch now and the fridge uses significantly less current.

if only I could get the evaporator (Fan assisted THIS one

to not frost up every three days and thereby stifle airflow leading to rising temperatures. However, I'm getting quite swift at defrosting it with a hair dryer - about 4 minutes now!

I suppose this set-up is actually using the whole of the bilge surface area as a heat exchanger.

Steve cronin

 

[LadyInBed]

I have just finished fitting a new (home made) fridge. I put the compressor in an adjacent locker, below waterline, blowing the heat along the line of the hull. I also keep the mooring lines in that locker, so it will help to dry them out /forums/images/graemlins/wink.gif

 

[jollyjacktar]

I once owned a fibre glass yacht which was permanently moored year round. On one trip I temporarily stored some victuals in the bilge including potatoes and onions, as this was always dry and solved a storage problem at the time. However one onion escaped and the next summer when doing the same storage thing. I discovered my wayward onion. It was still fresh and showed no sign of decay. I cooked and ate it and suffered no ill affects. So who needs a fridge when nature has povided the solution.

 

[tangofour]

[ QUOTE ]
I discovered my wayward onion. It was still fresh and showed no sign of decay. I cooked and ate it and suffered no ill affects. So who needs a fridge when nature has povided the solution.

[/ QUOTE ]

Much as I like biltong I somehow think storing the steaks in the bilge is going to put off the patrons somewhat /forums/images/graemlins/smile.gif /forums/images/graemlins/ooo.gif

 

[whiteoaks7]

First - thanks to everyone for some useful comments.
Second - WilliamH - I did some quick calcs on the GRP as a heat transfer proposition. Thermal conductivity for GRP varies between K= 0.3 and 0.16 W/m^2/degC (taking figs from the internet and without knowing the composition). So if I remember the formula we get 40W needing only about 1 m^2 to reduce the temperature from 25C to 8C (UK water) or 2 m^2 for 18C water. These are rough calcs but well worth following up - thanks for the idea.