#11  
Old 10-17-2011, 03:21 PM
brickie in oz's Avatar
Il Pizzaiolo
 
Join Date: Mar 2009
Location: Whittlesea
Posts: 3,455
Default Re: secondary chimney vent?

Quote:
Originally Posted by Faith In Virginia View Post
No Al, I have not tried a blast door what are the benefits?
It increases the draw dramatically at start up, a piece of cardboard with a cut out at the bottom across the opening will give you an idea of the effect.
__________________
The English language was invented by people who couldnt spell.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #12  
Old 10-17-2011, 03:27 PM
benguilford's Avatar
Laborer
 
Join Date: Dec 2010
Location: Melbourne
Posts: 99
Default Re: secondary chimney vent?

Being the impatient soul that I am, I usually start a pretty decent sized fire straight away, and I was definitely having issues with smoke giving my decorative arch the 'rustic look' that I wasn't really going for!

My neighbor Dave has a very simple solution for this problem; Cut a piece of solid timber as though you were making a door for your oven - mine looks like a semi-circle (see attached sketch). Then, to allow fresh air to be drawn in, cut decent sized gaps in the base of this semi-circle. If you sit this in the doorway just inside your decorative arch, it will ensure the smoke goes straight up the flue without staining the front of the oven. This door can then be removed once your flue has heated to the point that it is drawing good and hard. Simple and effective.
Attached Files
File Type: pdf Baffle Door Drawing.pdf (22.2 KB, 139 views)
Reply With Quote
  #13  
Old 10-17-2011, 03:28 PM
Journeyman
 
Join Date: May 2009
Location: Detroit
Posts: 383
Default Re: secondary chimney vent?

The second calculator on this page is perfect for your question. Simply plug in some numbers and find out.

Air Flow and Velocities due to Natural Draft

Quote:
Originally Posted by GianniFocaccia View Post
I am currently designing my flue and in particular, the size and shape of the flue gather, or vent. I understand that the longer a given flue is the higher the pressure and draw it will provide. Is it incorrect to assume a shorter but larger diameter flue would not provide the same amout of pressure that the longer/narrower flue could?
Reply With Quote
  #14  
Old 10-17-2011, 03:34 PM
brickie in oz's Avatar
Il Pizzaiolo
 
Join Date: Mar 2009
Location: Whittlesea
Posts: 3,455
Default Re: secondary chimney vent?

Quote:
Originally Posted by benguilford View Post
Simple and effective.
Its a blast door, there are lots of oven users using them..
__________________
The English language was invented by people who couldnt spell.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #15  
Old 10-17-2011, 03:39 PM
brickie in oz's Avatar
Il Pizzaiolo
 
Join Date: Mar 2009
Location: Whittlesea
Posts: 3,455
Default Re: secondary chimney vent?

Quote:
Originally Posted by GianniFocaccia View Post
I am currently designing my flue and in particular, the size and shape of the flue gather, or vent. I understand that the longer a given flue is the higher the pressure and draw it will provide. Is it incorrect to assume a shorter but larger diameter flue would not provide the same amout of pressure that the longer/narrower flue could?
Not sure if thats correct, if you read up on fluid dynamics you will see that the longer the pipe the more friction and resistance you will get and thats with pressurized fluids.
Smoke from your oven isnt pressurized so has to coaxed to find the flue.

My last oven had a very short flue of about 400mm and worked fine, my current flue is over 2M tall and works fine.

It comes down to internal sizing over door opening size plus any restrictions like incorrect flue gather.
__________________
The English language was invented by people who couldnt spell.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #16  
Old 10-17-2011, 04:27 PM
benguilford's Avatar
Laborer
 
Join Date: Dec 2010
Location: Melbourne
Posts: 99
Default Re: secondary chimney vent?

Quote:
Originally Posted by brickie in oz View Post
Its a blast door, there are lots of oven users using them..
Thanks Brickie! (I've been wondering what the heck a blast door was, lesson learnt! )
Reply With Quote
  #17  
Old 10-17-2011, 04:32 PM
GianniFocaccia's Avatar
Il Pizzaiolo
 
Join Date: Jun 2009
Location: Disneyland, CA
Posts: 1,312
Default Re: secondary chimney vent?

Thanks Shuboyje and Al. I just did the Natural Draft Calculator on the Engineering Toolbox this morning and confirmed that when comparing flues of equal volume, the taller one wins. I actually have a 48" (hot water heatere rigid duct) smokestack on my 30" smoker. It looks funny but works a treat.

I think I'm gonna go with a 36" 304 stainless steel flue that starts out 10"x8" where it attaches to the top of the vent and tapers upward to finish at 8"x8". My bro works in steel and can get it welded up for me.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
vent and chimney jersey Pompeii Oven Construction 7 03-31-2011 08:01 AM
Chimney and Vent Transition measurements that count dinoforno Design Styles, Chimneys and Finish 10 11-17-2009 10:22 AM
Refractory Chimney vent & Choke THX1138 Introductions 12 01-23-2009 07:06 PM
Vent chimney and insulation complete KCJones Pompeii Oven Construction 3 10-21-2007 07:40 AM
Vent and chimney design JoeT62 Pompeii Oven Construction 0 07-13-2007 11:04 AM


All times are GMT -7. The time now is 06:36 PM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC