Glass in Ovens

Is the air sealed into the gap ...?

If so wouldn't it be better to have ventilation holes top and bottom to allow the air to heat and by convection remove the heat in the gap?

John.

Not sealed, the problem comes from radiation I think we need low-emissitivity glasses but I don't know suppliers

helium sealed into the gap will help. In a large gap like that you may also be able to have a partial vacuum as well as a helium filled gap. In addition IR reflective coating on the inside of both panes will also help.

Can you examine a sample of their product for evidence of a sealed cavity and/or IR reflective coating.

It would be virtually impossible to keep helium sealed in a low tech application as an oven due to its ability to pass through the smallest of gaps, also it is a good transmitter of heat differentials.

yes, indeed, helium has high thermal conductivity. No good. Helium can be sealed OK in glass etc.

Heat transfer is by

Radiation --> Very slow process

Conduction --> very fast is it is conductor and slow but will conduct based on delta T

Covection --> slow but reseanable

To make heat work before it get out Is this not a good idea to use vacuum pannel

Use glass which is lower in alkali ions which provide ionic conductivity

If you use Vacuum slab type modules it will work if not than you need custom glass which does not conduct heat. Custom glass is actually glass ceramic and there are composition which you can touch opposite side of 1000c heat and will not feel

Masyood

Heat transfer by radiation is a very slow process eh?

As radiation travels at the speed of light I would suggest its one of the very fastest ways to transmit heat!!

As has been said (I think) the glass would need to be coated in an infrared reflecting substance to reflect heat radiation back into the oven.

John.

Radiation should not be a factor as the glass should pass most thru it. If the glass is not sealed then to which atmosphere is the air between the to open to. If to the oven chamber then heat could be entering there. Should be open to the outside.

Hi Ozzb and Electroman,

unfortunately radiation is not passed but absorbed as most of the radiation is in the infrared where the glass is not transparent.

So Electroman is right with demanding for a good thermal reflector, transparent only in the visible.

What can be used for this purpose?

RHABE

Yes, in fact the question is "IS there any layer that can be fitted on glass to reflect IR?" or "Does anybody knows special glass with IR reflection and enduring 300ºC?"