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Subject Author Date
Flow / Pressure Question still just me 01-05-2008
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Posted by still just me on January 5, 2008, 6:24 pm
Slightly OT, not fully an HVAC question, but I know you guys have the
answers! (Well, I hope so).

With relatively low pressure air (like hot air supply off a furnace)
there are major drops in pressure if you turn 90 degrees, even
smoothly... with every bend sucking up more of your flow.

What about with high pressures? If I have air coming out of a
compressor at 80-100psi, do 90 degree bends make much of a difference
in pressure? Or does the loss factor decrease as pressures are
increased?

Posted by ftwhd on January 5, 2008, 9:49 pm
On Sat, 05 Jan 2008 23:24:25 GMT, still just me

>Slightly OT, not fully an HVAC question, but I know you guys have the
>answers! (Well, I hope so).
>
>With relatively low pressure air (like hot air supply off a furnace)
>there are major drops in pressure if you turn 90 degrees, even
>smoothly... with every bend sucking up more of your flow.
>
>What about with high pressures? If I have air coming out of a
>compressor at 80-100psi, do 90 degree bends make much of a difference
>in pressure?

yes

>Or does the loss factor decrease as pressures are
>increased?

no or yes. :)



Posted by CJT on January 6, 2008, 12:47 am
still just me wrote:

> Slightly OT, not fully an HVAC question, but I know you guys have the
> answers! (Well, I hope so).
>
> With relatively low pressure air (like hot air supply off a furnace)
> there are major drops in pressure if you turn 90 degrees, even
> smoothly... with every bend sucking up more of your flow.

Not necessarily.
>
> What about with high pressures? If I have air coming out of a
> compressor at 80-100psi, do 90 degree bends make much of a difference
> in pressure? Or does the loss factor decrease as pressures are
> increased?

As the other poster indicated, flow rate is the key.

If you're really interested, Google "Reynolds number" and follow some
links.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.

Posted by tony on January 6, 2008, 12:14 pm
it depends on volume of flow


> Slightly OT, not fully an HVAC question, but I know you guys have the
> answers! (Well, I hope so).
>
> With relatively low pressure air (like hot air supply off a furnace)
> there are major drops in pressure if you turn 90 degrees, even
> smoothly... with every bend sucking up more of your flow.
>
> What about with high pressures? If I have air coming out of a
> compressor at 80-100psi, do 90 degree bends make much of a difference
> in pressure? Or does the loss factor decrease as pressures are
> increased?



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