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Rollin Karg 08-03-2010 11:16 AM

Moly cooling
 
5 Attachment(s)
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 08-03-2010 11:33 AM

That is a really nice way to do that Rollin.

Rollin Karg 08-03-2010 12:14 PM

Thanks boss !!

Larry Cazes 08-03-2010 12:48 PM

Nice manifold, Rollin. Very clean design.

Charles Friedman 08-03-2010 02:10 PM

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 08-03-2010 02:48 PM

Quote:

Originally Posted by Charles Friedman (Post 89940)
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 08-03-2010 04:23 PM

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

Kenny Pieper 08-03-2010 05:35 PM

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 08-03-2010 06:15 PM

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.

Scott Garrelts 08-03-2010 10:16 PM

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 08-04-2010 12:00 AM

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 08-04-2010 06:17 AM

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 08-04-2010 02:37 PM

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

Lawrence Ruskin 08-04-2010 03:33 PM

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 08-04-2010 03:44 PM

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 08-04-2010 04:41 PM

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 08-04-2010 04:55 PM

Quote:

Originally Posted by Scott Novota (Post 89965)
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 08-04-2010 05:53 PM

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 08-04-2010 06:22 PM

Quote:

Originally Posted by Eben Horton (Post 89964)
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 08-04-2010 06:22 PM

steel flex piping for cold air
 
http://www.gsl.cz/en/products/pot-furnaces.html

Eben Horton 08-04-2010 06:42 PM

Quote:

Originally Posted by Larry Cazes (Post 89969)
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 08-04-2010 07:11 PM

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 08-04-2010 08:05 PM

Quote:

Originally Posted by Pete VanderLaan (Post 89972)
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 08-04-2010 08:18 PM

Quote:

Originally Posted by Eben Horton (Post 89973)
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 08-04-2010 08:32 PM

no. right.


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