Ramp=draft

[tonka]

I'm just curious about something and want to hear your guys take on it. Do you guys think that a ramp improves draft?

[Brian]

No it don't control draft but it does control the heat and were it goes. Heat travels the path with least resistance.

[ecolbeck]

The sole purpose of a ramp is to direct flue gasses (and the heat they contain) up against the bottom of the pan (or flues). There are recommended designs depending on your situation.

[berkshires]

I'm just curious about something and want to hear your guys take on it. Do you guys think that a ramp improves draft?

You mean like if you had an evaporator where there was no ramp, just like an even 2" all the way from the fire to the stack? Would that have worse draft? Is that your question?

No, I don't think so. If anything the ramp creates a tiny bit of back-pressure on the fire. But it should be almost none. Mostly it forces the fire up onto the pan/through the channels.

GO

[RileySugarbush]

In general, gradual changes in flow path for gases will have less pressure loss than abrupt ones. So a ramp probably has some small benefit in increasing natural draft.
My arch has no ramp at all, the firebox just jumps right up to an inch from the bottom of my drop flues. One benefit of that is it can protect the end of the flues from over enthusiastic loading. But I am sure it does decrease draft a bit. Thats not a big issue with under fire forced air, but it can make the firebox harder to seal up. More draft restriction means higher firebox pressure, and maybe a little ash will shoot out any small gaps.

One advantage of the ramp is it lets the radiative heat from the fire hit more of the pan surface, which might increase efficiency a bit.

[tonka]

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In my home built cooker I have the firebox and then straight up to the bottom of my tube pan. I'm still doing some tweaking to it. The pan size is 4x10 tube pan and 2 2x4 syrup pan. I'm currently boiling almost 300 gph. Will be making a preheater for it by this coming season. The highest stack temp I've seen is 650 degrees. So I wasn't quite sure if a ramp helped with draft or not. I currently have an old furnace flower blowing under the fire(dont know the cfms) will be looking to get a blower atleast 1,000 cfm for under the fire, I'd rather have too much then not enough. I do have air blowing over fire as well which I think I have that part good.

[RileySugarbush]

650°F is an indicator of good efficiency, especially if it is the actual internal temp measured with a probe thermometer! I wouldn't mess with more air unless you want to trade lots more wood for a faster rate. Your rate looks good for the size of your pans if I read you right that you have a 4x14 total pan area. Over 5 gph per sq feet of pan. We max out at about 4 gph per sq. foot.

Love that tube flue pan, it's like an old locomotive boiler.!! Thats a lot of heat transfer area. I aways wanted to make one. Share some more pics!

[tonka]

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A steam engine was what I built my cooker based of off. I thought its gotta be a the right way to go since steam engines were build to efficiently make steam, steam is what is needed in order for the machine to do its work.

I figured it could be anywhere from 400 to 500 gallons an hour. When I figured it out it comes out to be about 480 sq ft of heated surface going off of 1 sq ft will cook off 1 gallon water per hour.

[RileySugarbush]

That is wonderful!! Congratulations on a fine build..

[ir3333]

what are you asking when you say increase draft?
Are you wondering if it increases volume or velocity?