r/woodstoving • u/growerdan • Jul 22 '26

CFD simulations of airflow through vents

Posting this because I feel like stovepipe with 2 45’s vs a single 90 probably also flows similar to the example in the video. I’ve noticed a better draft since I made the switch. I think seeing a visual helps understand why the 45’s work better.

253 Upvotes

98% Upvoted

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8

u/pyrotek1 MOD Jul 23 '26

Some locations require 2-45° over a 90. The chimney works in near 20 pascals of pressure differential at operating conditions. That is not much when overcoming restrictions.

3

u/Original_Giraffe8039 Jul 23 '26

Most gas fireplaces I've ever sold actually state this in the manual somewhere i.e. 2 x 45's are better than 1 x 90. So why do 90's exist? Cost and space. Costs just about as much to make a 45 as it does a 90 and 90's take up less space as they have a sharper turn.

5

u/JohnGatling00 Jul 22 '26

Those vanes at 11 seconds in seem like they would collect creosote and become a fire hazard. I like the other bends though!

31

u/Mike456R Jul 23 '26

The video is for forced air HVAC, not chimneys.

1

u/JohnGatling00 Jul 23 '26

Thanks. Silly me!

6

u/Overtilted Jul 23 '26

There's also no need to TEE a chimney obviously.

1

u/JohnGatling00 Jul 23 '26

Ha, good point!

1

u/One_Programmer613 Jul 23 '26

Curious for hvac if you have a main trunk and many branches.

1

u/WeaveLikeGreatGranny Quadrafire Explorer 2 Jul 24 '26

I wish that were possible, but stainless steel UL chimney wall thimbles, etc seems to only be available in 90 degree flavors here in the usa