Fridge Covers, they ARE arse about
Submitted: Thursday, Mar 19, 2009 at 21:11
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My fridge has been sitting outside for the last 5 days and is exposed to sun.
I've always reckoned the shiny/foil side should be on the outside to reflect the heat. The other theory is that that foil inside reflects the cold.
BOLLOCKS.
When my fridge has been in the sun, I have reached in under the cover and the lid of the fridge is hot.
Sure, at night the foil on the inside may help keep it cold, but it is durfing the heat of the day that the fridge works hardest.
Jim.
Reply By: Robin Miller - Thursday, Mar 19, 2009 at 22:05
Thursday, Mar 19, 2009 at 22:05
Hi Jim
It makes little difference particularly as the cover gets older
and there is a specific saftey reason for the dull surface being on the outside.
That reason is that it doesn't cause a dangerous reflection into
drivers eyes.
For the same reason building sisalation is now dull on the outside(and also builders can get sunburn from it).
As for the heat reflection , it also works on heat being emitted from a surface,including the inside surface.
The emission is proportional to the smoothness of the surface and over time an outside surface gets roughened up causing a loss of efficentcy.
The fact that the air is hot between the inner layers is not ideal but its also not as bad as it seems because the warm air has little thermal mass as doesn't pass the heat thru readily.
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Reply By: Member - Matt M (ACT) - Thursday, Mar 19, 2009 at 22:07
Thursday, Mar 19, 2009 at 22:07
Jim,
I agree with you, never been able to work that one out myself. Its like roof insulation, shiny side up - reflects the heat away, dark side down - absorbs heat form the roof space.
Foil doesn't keep it colder at night, it still reflects any trapped heat back to the fridge and stops it escaping for longer. Same way a space blanket works.
Maybe its just a fashion thing.
Matt.
AnswerID:
355025
Reply By: Member - Mfewster(SA) - Thursday, Mar 19, 2009 at 22:22
Thursday, Mar 19, 2009 at 22:22
The silver side can't "block cold in". Heat always moves from hot to cold, so therefore the shiny side should be out, but as heat is simply energy and their are different types, silver is only effective in reflecting some types of heat ie, sunrays. As far as I can see, silver side only doing its thing if the fridge and cover are in direct sunlight. In the back of a covered vehicle where the heat is coming from air temp, the silver will heat up as much as any other material. What matters then is the insulating factor of the layers, that is, the rate at which heat can through the layers. If it is hotter outside the fridge than in, heat will continue to move through the layers (including the fridge case) until the temp inside of the fridge balances with the temp outside. The thicker and higher insulation factor of the layers, the slower heat can move through to do its balancing trick. The fridge motor removes heat from inside the fridge and dumps it into the air outside the fridge.
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355030
Reply By: Totaltip - Thursday, Mar 19, 2009 at 23:21
Thursday, Mar 19, 2009 at 23:21
Hello Jim and the
Forum,
I use a refridgerated Transit van for work, drive long distance with fridge on 2-3 degrees. The rear fridge section is fully insulated, and in my opinion
well insulated, it has to be.
When I stop, the outside of the vehicle (the fridge part) is cool to touch, sides, roof, doors, all cool, even on a very hot day like 40 degrees.
So if we consider this to be a big car fridge, then if a cover was put on it, the cover would have the reflective silver stuff on the inside to reflect to coolness back in, and that is probably why our car fridges have it on the inside. Keeping coolness in rather than the ambient temperature out.
The idea of covering with a reflective windscreen cover works too because it does minimise the ambient heat entering the cabinet, as does
parking it in the shade, covering with a blanket, or operating it at night or overcast days, it does make a difference.
My point is maybe the covers are designed to keep coolness in rather than heat out.
Remember the heat from within the cabinet is taken out by the system and pumped out into the car via the vent in the compressor containment. If your car is not able to let this heat out it is then adding to the ambient temperature around the fridge.
Cheers
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355048
Follow Up By: ross - Thursday, Mar 19, 2009 at 23:37
Thursday, Mar 19, 2009 at 23:37
"the cover would have the reflective silver stuff on the inside to reflect to coolness back in'
You can reflect coolness ! LOL
I dont think even the Fonz could do that.
I think the foil maybe a moisture/air barrier like they wrap people in to keep them warm after exposure.
I think the foil also has perforations ,possible to allow some breathing between inner and outer
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Reply By: Member - Mike DID - Friday, Mar 20, 2009 at 21:27
Friday, Mar 20, 2009 at 21:27
If you have an object hotter than its surroundings and you want it to cool down, paint it black, it radiates heat better than silver does.
If you have an object cooler than its surroundings and you want to keep it cool, paint it silver, it will reflect the surrounding heat away.
This only applies to air interfaces because its about radiation. Two surfaces in contact with each other are controlled by conduction, not radiation.
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