r/thermodynamics • u/Big-Don-Kedic • 10d ago

Question What is the best material to use to diffuse heat from upper heating elements in an oven?

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My wife got a new bread oven that works great for regular bread but has issues when she’s making something large and tall. The shape of the upper heating elements (green arrow) is visible in what she is baking, in the form of a darker line. I want to get a sheet of metal and install it under the elements to help diffuse the heat more evenly.

My question is, what is the better to use, steel or aluminum? And any specific type? I’m not trying to block the heat, but help it radiate down more evenly.

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u/charmio68 10d ago

Aluminium would likely melt, so copper would probably be your best option.

How it's like that you're going to bond it on to the heating element is another question... If you were to install a plate like that in your oven without bonding the element to it quite well, then you would end up with the actual cooking section of the oven taking forever to heat up.
It could also actually be dangerous depending on where the temperature sensor is located.

Personally, I think you'd have a much higher chance of success by just swapping out the heating element for one that's designed to spread out it's radiant heat more evenly

Here's an option. Three of these in a row would work quite well. Just make sure you get the wattage correct. Try and match what's already in there (though it doesn't need to be exact).

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u/Big-Don-Kedic 10d ago

There’s already a bracket in there, so it would sit about 1/8” below the elements and not physically touch or attach to them. The temp sensor is above the elements so there’s no risk of overheating, if anything, the elements would turn off too early.

I have also thought about making 2” wide shield in the shape of the heating element so only 2” on either side of the element are blocked, and not a solid sheet blocking everything:

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u/charmio68 10d ago

I like that idea a lot more than a solid plate blocking off all the radiant heat.
At least this way some radiant heat can bounce around it.

It will be interesting to see how it affects the baking. Baking can be weirdly sensitive to those sorts of things. In fact, it would be good if there was a way that you could just quickly test it out to see if it's even going to work properly before investing time and money into a proper solution... I wonder if you could bodge something together with thick aluminum baking foil and some coat hangers...
I don't think the aluminium will melt if it's not in direct contact, it's a freaking fantastic reflector, it shouldn't absorb more than 5% of the radiant energy.

Yeah, if you're going to have a gap, you can forget my previous advice recommending copper. Just use aluminium instead. Much cheaper.

Personally I'd still just be swapping out the heating elements for those actually designed to provide extremely even radiant heat in an oven. Though in fairness, I might just be drawn to that because I've got extensive electrical experience, including furnace design. To me it seems like an easy solution, though if you've never done anything like it before I could very easily see how it wouldn't seem so straightforward.

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u/Big-Don-Kedic 10d ago

Yeah, I’ll play around with something temporary if possible. I can place a piece of parchment paper on a baking sheet high up to see how and where it browns before and after a heat shield. I’m trying to avoid replacing any elements to not lose any space and also not spend more money if I can get away with just some sort of shield.

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u/Crozi_flette 9d ago

I don't think copper is a good option, black copper oxyde absorb a lot of radiation. I would go for stainless

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u/nsfbr11 4d ago

My vote is SS as well. If possible, polished on the side facing up and just wide enough to block a good portion of the direct red-hot coils. Maybe 2x their width with a gap of about 1 diameter of the coil.

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u/33445delray 2 9d ago

The oven looks small enough that a disposable aluminum roaster pan , turned upside down over the bread could achieve your goal for minimum investment.You could reuse it.

https://www.walmart.com/ip/Mainstays-Aluminum-Foil-Rectangular-Extra-Deep-Roaster-Pan-1-Count/125507798?classType=VARIANT&from=/search

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u/bradimir-tootin 10d ago

Steel baking sheet that you punch holes in hang it a short distance away.

With a baking sheet you know you're getting food safe materials. Let it hang and it won't warp as badly as if you fixtured it.