When I took my stuff to the workshop to build a mockup, I took some of the flexible stainless ducting with me. Ernie said I couldn't use it for the complete run, but might be able to get by using it for elbows and U's. He said something about "recovery time". He said if the flexible ducting was used for an elbow it would take a certain amount of straight smooth ducting for the flow rate to recover.
I'm pretty good at leaps of logic (aka "connecting the dots") but I think we need to ask Ernie to weigh in on this, don't you?
I'd like to compare the effect on air flow of a commercial elbow versus the same radius/length of the stainless flexible ducting. Maybe when I get to the point of doing testing I'll be able to do that, but don't hold me to it. I'm building a 7" system and the flexible ducting I have is 6", so I won't be using it for this system.
Chris, it sounds like you're confusing flow rates, with heat delivery. The exhaust fan site that Nori found would not likely be talking about heat delivery - I think she's worried about maintaining good flow, and her RMH has a couple of unusual dimensions that might give her problems if she puts too much resistance on the outbound exhaust flow.
What exactly is the claim? That an elbow and it's associated mass will absorb the heat equivalent of 10 feet of run?
I'm building a 7" system and the flexible ducting I have is 6", so I won't be using it for this system.
I'm pecking away at my planning and understanding of RMHs. Part of understanding is to read as much as I can on things smokey. Today I ran across something on an exhaust fan page that says 90° elbows = 10' of straight run. Is that what y'all see in your construction?
Chris K e n d a l l wrote:
I'm a shop guy so I can design and build duct and fittings