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snwcmpr
11/27/2019 11:44 AM
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Sivetz 14Kw 12 pounds
seedlings
Video shows repairs on a 14Kw Electric Sivetz heat element. Kinda boring. It's for us geeky homeroasters.

Repairs part 1:


Part 2:


CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Unta
thanks CHAD...Awesome..priceless info. well 10,000 usd worth anyway.
Sean Harrington
educate.
 
http://www.untacoffee.com
endlesscycles
that element, the best shot is the main still in the second video, I wonder how it compares to this:
http://www.graing...Pid=search
-Marshall Hance
Asheville, NC
 
allenb
It's similar in that it's also meant for duct heater applications. My guess is Sivetz had to do a whole bunch of R&D to get the air inlet holes sized just so and in just-so locations to not have premature burnouts.

If you notice in the video he only has air entering around the perimeter which is tricky. If you don't get them located perfectly you end up with hot spots.

The duct heater from Graingers might work fine but would take some playing around with to get the right size plenum and air flow path. You can't have the air flow across the large cross section but has to flow in-line along it's length to achieve sufficient heat exchange.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Unta
Might someone comment on the construction of the elements, he has four coils per wire frame, and one of the coils is wound tighter then the rest... WHY?
Sean Harrington
educate.
 
http://www.untacoffee.com
seedlings
I wondered the same thing Sean. A heatgun or popper has a small element to drop voltage to a fan, but I'm with you - don't understand this one.

CHAD
Edited by seedlings on 05/01/2010 6:41 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
endlesscycles
allenb wrote:
... You can't have the air flow across the large cross section but has to flow in-line along it's length to achieve sufficient heat exchange.

Allen


Could you explain this, please?
-Marshall Hance
Asheville, NC
 
allenb
Looking at the pic of the Graingers heating element you'll see it's a single layer. If you flow air from bottom to top (vertical as you view the photo) you're passing air across the single layer where the air cannot build (enough) heat.

If you build a plenum not much thicker than the single layer and pass air across the coils horizontally, not allowing much bypass, you will build to a sufficient temp with proper cfm.

Can you give some details as to how you were planning the plenum ducting?

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Unta
thats how i was intending to orient the unit that i have, though im still skeptical of its capability. the unit that both marshall and i have shown is 10.8 to 14.4 but was never intended to generate the temps we are looking to achieve. It may work though i think your point is well taken that surface area and contact are going to be the key to making the best of it. Sean..
Sean Harrington
educate.
 
http://www.untacoffee.com
allenb
If you remove everything but the element from the sheet metal flange and punch a series of holes (into the flange) directly in-line with the element which will have the air flow coming through the flange holes up across the elements sort of like Sivetz did with the 14kw you should be fine. The only difference would be the holes on yours would be directly below the element allowing the air to flow directly across them which would be an improvement over the Sivetz model.

You can then box-in the element coils with a plenum not much bigger than the element itself.

Maybe this was already your plan anyway.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
endlesscycles
Watts are watts, and heat transference is relative to temperature differential. Those two facts alone work in tandem to suggest that blowing across the broadest cross section is the most efficient means of moving energy.
-Marshall Hance
Asheville, NC
 
allenb
Elementary my dear Wattson! Some watts are hot, some watts are not depending on quite a lot!

You are quite right in that a single layer, if done properly, can achieve a perfectly efficient heat transfer.

For argument sake, let me show a couple of scenarios where heat transfer is good and not so good.

1. Take a 20 gauge coiled resistive heating element stretched to 2 times its closed length, lets say 2 ft. long, and at 120 V has a rating of 1000 watts. (this is all hypothetical). Now place it across a 2 ft. x 1 ft. duct, run 10-15 cfm past it while the element is powered up. Now measure the discharge temperature exiting a smaller hole to make sure its blended for an accurate read. With an ambient inlet temperature of 72 F you might be lucky to get 85-90 F discharge temp.

2. Now duplicate the test but with the element within a 2 ft. x 3/4" duct leaving little area for air to bypass around the element. You now have very good efficiency and probably hitting several hundred degrees.

As we all know, most modern popcorn poppers use a donut style coiled element with a single loop and leaving almost no path for the air to bypass around the coil. This arrangement can achieve very high efficiency in transferring heat from the nichrome to the air by preventing bypass air.

The reason heatgun style elements can achieve sufficient heat transfer with a seemingly large bypass area is that the air has to flow across several successive layers of coils bringing the air temp crossing the coils up to 900-1200 F but when mixed with the bypassing air around the coils it averages between 500-900 F or higher depending on heatgun.

I could be wrong but I think if you try and flow the air across the grainger element large cross section (single layer) with it's very large bypass area, you will have trouble achieving an efficiency high enough to produce roasting temps.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
endlesscycles
Heat coils are engineered inefficiency; nearly all watts are heat.
Very close to, but not precisely:

Temperature Increase = Watts / CFM
-Marshall Hance
Asheville, NC
 
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Unta
Allen you are the man..thanks for the breakdown.
BEST.
SEan
Sean Harrington
educate.
 
http://www.untacoffee.com
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