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I have a problem. I am suspecting heating mat I got is not working. It is barely warm to the touch, to the point I wonder if I'm imagining it. It's parameters are 230V, 16W, 26.5 x 28 cm. It's flat and supposed to have similar heating on both sides. Manufacturer declares almost all heat it gives is conductive. Ambient is 20 degree Celsius.

I can't find an equation to find out what expected temperature should be. I found equations for a wire, not for a pad.

Note, I will check it with ohmmeter when I'll get my electrical toolbox back. Or when I'll buy a new one. But the temperature calculation seems like a problem interesting enough in its own right.

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  • \$\begingroup\$ Anyone care to explain why it was perceived as unfocused? I believe I provided very specific description of the situation and precise question. \$\endgroup\$
    – Mołot
    Commented Feb 21, 2022 at 10:57
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    \$\begingroup\$ Test it again sitting on a folded blanket with another folded blanket on top of it. \$\endgroup\$
    – user16324
    Commented Feb 21, 2022 at 11:22
  • \$\begingroup\$ I think you've misunderstood how these heat pads are supposed to be used. If you just sit it out on a surface in the open air then you shouldn't expect it to get very warm at all - the majority of its heating energy is just being dissipated into the air. If you rather wrap it inside some blankets or even just put it into a small enclosed space you'll see its effects much more noticeably. Put it on your chair and sit on it for 10 minutes - you'll soon notice its heating effect. \$\endgroup\$
    – brhans
    Commented Feb 21, 2022 at 14:09

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16 W for that area is not a lot and there's a reason for that. If you were to have it in between bed sheets or under a blanket it wouldn't be able to dissipate the heat as easily and temperatures would easily rise to uncomfortable level. Surely there is thermal protection, but it's set to prevent fire, not to set it to comfortable setting. So usually the specification for usage would be to provide "some" extra warmth and if you need to heat a space you need another kind of a device.

Thermal radiation power rises to the 4th power of temperature so the smaller the temperature and if the material is placed in contact with the object to be heated, then it's clear that most of heat trasnfer would be through conductive heat transfer, even if the thermal contact of a heating mat is not spectacular.

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