How much more energy does it take to melt circular glass that is half the size?

[rdolin]

I would like to figure out if I take a circular piece of glass that is about 1/8 inch in diameter and crush it to 1/16 of an inch in diameter will I be able to use less energy to melt the same weight of material?

 

[0xDEADBEEF]

No, the energy required is the same. But since most of the energy of the flame is blown into the air that doesn't really matter. So you might melt the glas faster if it is not as thick. In a well insulated furnace for example the thickness should not really matter.

 

[jagedlion]

I would go one step further and say that it may require more energy to melt, depending on what you mean by crush.

If your glass has a volume and you compress it to a smaller volume, then the glass transition and melting temperature will actually increase. Conceptually, you can just think of how liquid glass has a larger volume than solid glass.
If then you compressed more, you would need a higher temperature to melt.

Another way to look at is is that glass flows when the molecules making it up can move freely past each other. By compressing the glass, you are actually limiting the ability of the molecules to move. Thus sufficient compression will keep it glass when it might normally melt.

This can become pretty important with glassy polymers. I've included an example for polyethylene. You can see that under higher pressures the glass transition temperature (the point where the volume starts increasing rapidly) increases. The melting point (the next time the graph slope changes) is also increased.If instead of compress, you simply meant reform it into a new shape, then DEADBEEF is correct. It will melt faster (heat does not conduct through glass well, so a larger surface area will absorb heat much more rapidly) but the total energy required under ideal circumstances remains the same.

 

[rdolin]

To deadbeef response:would the melting time of the glass be considered critical. I believe if there is an increase in residence time I would be able to use less energy. Let me know if this assumption is correct and if there is a way to calculate the savings. The typical residence time in the furnace is 24 hours.

To jagedlion response: The glass would not be compressed, it would be simply shatered or broken into smaller pieces with the same density.

Thank you for your response