Capacity of exaust fan

I'm setting up my bluing room. I need to choose an exhaust fan. The room (the loo) is 9'-4" square and 8' high, 692 cubic feet. I'll have as much as

160,000 BTU's of burners cooking under 5 6"X40" tanks, as little as maybe 25-35K BTU's under 2 tanks. I'm looking at a Grainger blower # 7C039, 1005 CFM @ 0.0 static pressure, 850CFM @ .5 " SP and 480 CFM @ 1.25" SP. The blower will suck through a 90 deg. elbow and 1' of 10" dia. plastic pipe and blow straight up through maybe 6' of plastic pipe through the roof to the great outdoors. Will this blower be adequate or should I step up in CFM?
Reply to
Tom Wait
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That's about one change of air per minute, give or take. 2 minutes worst case. Seems to me that it'd keep things reasonable in there.

Your booklet is on the way, by the way. Blue Streak / Silver Streak. No idea when it's from but it has that 50's-ish look to it?

Reply to
Dave Hinz

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Here's a link to the fan. Tom

Reply to
Tom Wait

Thanks a bunch, Dave. I figured the air change alright, what I can't figure is how fast the room is going to heat up with all that propane burning. I did a test light-up on the big burner and that sucker throws a lot of heat out fast. It's 45K btu by itself. Tom

Reply to
Tom Wait

Work it up in tons of cooling (heating in this case), and figure 800cfm per ton for adequate ventilation performance. More for dangerous fumes, less (400cfm/ton) for ordinary HVAC application.

LLoyd

Reply to
Lloyd E. Sponenburgh

Let me re-do that with the numbers -- say 4 tons minimum for the two tanks only, up to 13 tons for the full load.

At 400 cfm (HVAC flow) for the 13 tons, that's 5200cfm. Double that for comfortable ventilation-only cooling, and double that again for noxious fumes removal.

(it takes a lot of air to move that much heat)

HOWEVER... if the tanks have hoods over them, and most of the rising heat is captured by hoods, rather than just 'sloshing' the air around in the room, you can probably do the whole job with about 1000cfm.

LLoyd

LLoyd

Reply to
Lloyd E. Sponenburgh

Well, you probably could model it, but after all the math you might end up just doing a "fire it up and see how it goes" anyway. I've done some pretty lengthy calculations only to verify it empirically anyway...

Hm. Blueing, you say? I might have some pieces to do next time you run a batch...

Reply to
Dave Hinz

You aren't going to like that fan. It is closer to vacumn cleaner specs than to funace blower specs. Running the main blower wheel at 1750 will really howl. (I have the next size smaller one, I know!)

Th>>I'm setting up my bluing room. I need to choose an exhaust fan. The room

Reply to
RoyJ

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I looked at that fan, the next size smaller uses an 1140 rpm motor. A 2 or 3 speed motor would be ideal with that blower, I think, if the cfm is high enough. Thanks for your thoughts. Tom

Reply to
Tom Wait

Yeah, but the fan is going to cost over 300 clams, if it's too small, I'm screwed. Lloyd seems to think 1000 cfm would do the trick. Thats about where I was thinking too.

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Whatcha got in mind, you have some credit coming. Tom

Reply to
Tom Wait

Well, you can always put another one in parallel with it?

I'm building some parts of a 1927a1 as an exercise in, well, seeing how well I can do. I'm not pleased with my cold-blueing tests, even with the Birchwood-Casey gel type blueing. Just little stuff to toss in when you're running a batch, if it works that way?

No rush, haven't finished machining yet. Making some of this up as I go along.

Reply to
Dave Hinz

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