Heat transfer through radiator reflector foils with data!

smjpl

Hi all,

We got these rad reflector foils to improve your heating bills in our shop today. Trying to figure out if there any good.

As a really quick test to see if they do anything, i stuck one to the kettle and measured the temp difference with a thermal imaging camera. (pics attached)

They seem to do something as they lowered surface temp by around 32C which was a 40% decreased compared to the kettle wall.

Anyone know how I can come up with an Rvalue (m^2K/W) from this or any relevant way to show that they have some insulating properties. My problem is that the foil has virtually no thickness so I can't do a one dimensional analysis and I don't know of any zero dimensional analysis. I do know that it can have an r value though because air is given an rvalue and there is no dependence on the thickness for it.

Any help is much appreciated.


I will do it over a range temps if there isn't too much work in it as generally your walls aren't at 80C.

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mfb

That foil gives results not far away from a perfect black body with perfect heat conduction inside. Thermal radiation is proportional to T^4, and if you calculate the average T^4 between heat source and cold environment you end up with a value close to the temperature of your foil. It is a bit better, indicating reflection of parts of the radiation.
The isolation quality will depend on the absolute temperature itself, but if you know the environment of the foil, you could use this blackbody radiation to get a value of m^2K/W.