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Q & A: Are infrared heating pads a scam?

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Most recent answer: 11/03/2014
Is there still radiant heat transfer between two objects of different temperatures if I bring the objects into physical contact? I.E. is the transfer just conduction now or conduction plus radiation? (Are these infrared heating pads on the market now just a scam because their heat is conductive not infrared?)
- Al (age 60)

Nice question.

Putting the objects in close proximity shouldn't shut down radiative heat transfer, although often simple conduction becomes more important.

I looked up the infrared absorption spectra of different types of tissue, given in this paper: . It does look like there are some frequency windows for which the infrared can penetrate several cm before being absorbed by the tissue. 

Unfortunately, I don't really know how well those pads do at blocking short-range conduction and enhancing the deeper infrared heating. Nor do I know whether that's even a good thing to do. You could test how well it works using a chunk of meat and a meat thermometer inserted from the side opposite the pad. You could compare heating at various depths from the surface with similar measurements taken with a warm piece of metal rather than a fancy pad. Unfortunately, if it turns out the pads don't work I don't know how you could get your money back.

Mike W. 

posted without vetting until Lee returns from the Serengeti 

(published on 11/03/2014)

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