Moly cooling

[Rollin Karg]

A friend sent me a schematic of a European built Moly furnace. At that time we were changing a pot and doing some upgrades on one of our furnaces. I noticed that the cooling tubes on the schematic seemed to be metal and quite a lot larger than what we do here. It made for a nice uncluttered look.

It made me start thinking about this area and I decided to build a plenum with some 2" flexible tailpipe attached to it. This would allow us to aim the air flow at the element tops. I gathered up some parts and formulated a plan.Then I had to leave town.

When I got back my plans had been modified and my guys had come with a new and I think better approach. We installed one of these a few months ago and it seems to be working well. We did the second one last week and that's what these photos are about. Still a work in progress but I like how it's going.
The blower is from Grainger and costs I think $112. It puts out 463 CFM. If you stand at the edge of the furnace and look at the elements you can feel a nice little breeze on your face.

[Steve Stadelman]

That is a really nice way to do that Rollin.

[Rollin Karg]

Thanks boss !!

[Larry Cazes]

Nice manifold, Rollin. Very clean design.

[Charles Friedman]

Paint it all gray. It will help it disappear.
That seams like a bit too large of a blower.
But, if it works? it works.

[Rollin Karg]

Originally Posted by Charles Friedman

That seams like a bit too large of a blower.

Yeah ,probably. I just took a guess at the size to start and at $112 I can't see I would saving much to downsize. I do think some reflective paint would be a good idea.

[Eben Horton]

looks really nice, but is that actually cooling the top of your furnace along with the elements?

[Kenny Pieper]

Rollin I am curious. Have you found that Steve's way with the two washers welded to a tube that blows the air just on the top shaft of the element to be inadequate?

[Rollin Karg]

Eben, the way it's setup, all the air is directed at the top of the elements and I can't see it having much impact on the overall temp of the furnace. The European unit had the airflow coming down from the top and I think that might have a small impact.

Kenny, I'm getting more air where I want it and I don't have hoses to deal with, so this what I like about it. The other way works, but I think this is a little better. We're using four furnaces right now and that's a lot of hoses. Plus with this system the top of the element is a little less cluttered. I don't see this an earth shaking improvment, but I think it's a little better.

looks like it should be a lot easier to change out a broken element. :crossing fingers:

plastic hoses melt, sheet metal usually doesnt.

i like it

[Steve Stadelman]

I think that this is a really good way to do this, i started using hoses because I got it out of the kanthal super handbook. There are lots of ways to skin a cat and keeping the transition from the strap to the heater is what is important.

[Pete VanderLaan]

It does look good. I would again stress that cooling the leads at your transformer is a place where you can prevent a lot of serious damage. I have a blower running there whenever I go to High Fire.

[Jon Myers]

That looks good Rollin, how much insulation do you run on the top of your furnace?

How much insulation do you run on the sides?

In my opinion, as a guy who used to insulate his SiC furnace with 18 '' of fiber all 'round, the Stadelmelter is under insulated.

I think a combination of Steve's ideas and the Electroglass furnace, is where the furture of the electric furnace is going.

An ovel crucible is easier to gather from and the glass sits closer to the elements.

The door mounted from below as in Electroglass leaves more room to insulate the sides.

A thermal engineer I know told me that heat flows like water going down a stream. If it hits a rock, it flows around it.If heat hits a barrier, (insulation) it will flow to and through the area of lesser insulation.

So if you have 10'' on top and 2'' on the sides, guess where the heat is going to go...

[Eben Horton]

if you have 18 inches of fiber, your actually paying to heat up the last 9 to 8 inches of insulation when you turn your furnace up due to conduction.

[Scott Novota]

Eben,


Are you saying that anything out more than 9 inches of fiber? IE> after 9 inches of fiber it does you no good.


Am I reading this right?


Scott.
.

[Eben Horton]

Originally Posted by Scott Novota

Eben,


Are you saying that anything out more than 9 inches of fiber? IE> after 9 inches of fiber it does you no good.


Am I reading this right?


Scott.
.

I believe so. especially when you turn up to charge. the outer layers will draw heat out from the core due to conduction.

This is why most furnaces have 8 inches of fiber and not 15

[Jeff Thompson]

If you increase the insulation from from 8" to 15", you've increased the surface area of the exterior of the furnace so much that like Eben says, it's conducting the heat away from the furnace. Under or over insulated in no good, it's the Goldie-locks syndrome.

[Larry Cazes]

Originally Posted by Eben Horton

if you have 18 inches of fiber, your actually paying to heat up the last 9 to 8 inches of insulation when you turn your furnace up due to conduction.

Eben, I agree in concept. How have you determined that 8" is optimum? Theoretical data or just by experience?

[Paul Hayworth]

http://www.gsl.cz/en/products/pot-furnaces.html

[Eben Horton]

Originally Posted by Larry Cazes

Eben, I agree in concept. How have you determined that 8" is optimum? Theoretical data or just by experience?

I am not sure- its sort of the industry standard in glass furnaces- Hub, wetdog, etc....

[Pete VanderLaan]

I recommend 8 inches as well and I documented the diminishing returns on insulating about ten years ago. I set a furnace at a floating temp with fixed settings. I kept adding insulation and the temps kept going up with the fuel input constant. After eight inches, it stopped changing. It didn't drop after 12 inches, it just didn't change at all.

Enough?

[Eben Horton]

Originally Posted by Pete VanderLaan

I recommend 8 inches as well and I documented the diminishing returns on insulating about ten years ago. I set a furnace at a floating temp with fixed settings. I kept adding insulation and the temps kept going up with the fuel input constant. After eight inches, it stopped changing. It didn't drop after 12 inches, it just didn't change at all.

Enough?

And.. if you stuck a thermocouple in the insulation at 8 inches, you would see that the tempature of the insulation would in increase dramaticly as you added more and more. So, when you are idling at 2000° and turn the furnace up to charge, you would have to heat up all of that hot insulation..

[Edward Skeels]

Originally Posted by Eben Horton

And.. if you stuck a thermocouple in the insulation at 8 inches, you would see that the tempature of the insulation would in increase dramaticly as you added more and more. So, when you are idling at 2000° and turn the furnace up to charge, you would have to heat up all of that hot insulation..

No. Wrong.

[Eben Horton]

no. right.