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View Full Version : Hi all & not sure if this is even the right forum



Tango
04-12-2006, 02:45 AM
hi all & as I've out lined above, am not sure if this is the right forum for the HELP I'm looking for, but here goes any way.
Am toying with the idea of using a 'radiator' on the back of a domestic refrigerator charged with oil as a means of a solar collector/heat transfer rather than solar tubes to heat water. Was thinking of setting up a test rig with a refrigerator radiator to trap the radiant energy & another radiator or copper tubing in a insulated barrel to transfer the radiant energy to the water with a couple of pumps to circuclate the oil & water.
Any ideas, suggestions etc: would be most welcome.
i have no engineering knowledge what so ever :confused: but believe the idea has merit.

Brian_UK
04-12-2006, 07:45 PM
Hi Tango and welcome.

Yes it might work but you need to be aware that if you take away too much heat from the domestic condenser then the fridge might stop working. This is assuming that you make direct contact with the pipework.

If you are just working on radiant heat then I suppose an insulated box might help but make sure that the domestic condenser doesn't overheat.

Also considering the low running times of a domestic fridge I doubt if there is going to be much heat to recover over a 24 hour period.

Tango
04-12-2006, 09:05 PM
Hi Brian UK,
thanks! Some how I have not explained my idea very well. :(
You know on the back of a domestic refrigerator there is a 'heat exchange', I really dont know its proper name.
My intent is to use this radiator/heat exchange, filled with oil & completely divorced from a refrigerator, as a means of catching the Sun's energy & by means of a pump driving the hot oil into another radiator/heat exchange which would be immersed in a suitable insulated container of water, which inturn would be connected to another pump, connected to the house hot water system.
???, what do you think would be the best means of transfering the heat from the HOT OIL circuit to the HOT WATER circuit? any ideas, a Copper distilation type spirals, or a small heat exchange unit?
Please! I'm open to any input.

Thanks once again.

Ciao!

Brian_UK
05-12-2006, 12:02 AM
Probably start off with a coil inside a water container to see how it goes.

If using the condenser (Fridge radiator) be aware that the inside diameter of the tubing will be quite small and the oil will need to be a very low viscosity to flow through the pipe.

I have a feeling that yur pumping costs may outweigh the heating costs saved......

Tango
05-12-2006, 01:06 AM
Thanks,
what are your thoughts on a truck radiator for example? with ref: to the size of the tubing of fridge condensor.
From a stand point of heat transfer medium in the condensor/radiator, I've chosen oil because of its high temp: ie: 380C as apposed to water or glycol.

Thanks once again for sharing your oppinions & knowledge.

Ciao.

taz24
06-12-2006, 01:31 PM
Thanks,
what are your thoughts on a truck radiator for example? with ref: to the size of the tubing of fridge condensor.
From a stand point of heat transfer medium in the condensor/radiator, I've chosen oil because of its high temp: ie: 380C as apposed to water or glycol.

Thanks once again for sharing your oppinions & knowledge.

Ciao.


A domestic wall heating radiator painted black will be better.

Cheers taz.

Electrocoolman
06-12-2006, 02:32 PM
The commercially made units that I've seen on my holidays appear to have a large storage header tank mounted above the solar collector. This would suggest that they use a 'gravity flow' operation using reasonably sized tubing. They would obviously not require a pump to circulate the water through the heat exchangers. Mains water probably feeds into the header tank which serves as the main storage vessel as well.
Don't forget 'sanitary' hot water should be 65degC min for health reasons, so you may need to boost hot water to this temperature. Solar collection is better used to pre-heat water (greater temperature difference) in UK but in Portugal my guess is that the Sun delivers higher w/sq m.
Things to consider are do you get freezing conditions in the winter? This would effect your choice of 'operating fluid'....I don't see where you are going with 380degC!
Obviously the higher the temperature differences, the better the heat transfer capabilities.
Agree with previous posts that the condenser from the back of a fridge is not the most suitable unit..a c.heating radiator painted black does work....I've seen them used for swimming pools! (don't think they last due to corrosion).
I've toyed with the idea of making a collector up using copper tubing either in a bent continuous length, but maybe also along the lines of a larger top and bottom header with multiple vertical risers. Pump operation should be temperature controlled to cut running costs and to prevent 'reverse' heat flow from storage to solar collector.