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Author Topic: "In loss" and "out loss"option in HVAC model  (Read 2557 times)

Georges

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"In loss" and "out loss"option in HVAC model
« on: January 20, 2014, 10:08:20 am »

Hi,

I need some clarifications concerning the loss factors in ducts:

For "In loss": is it equivalent to the K factor for an entering flow (for example K=0.5 for a square entrance)

Concerning a node at the intersection on several pipe, I am guessing it is not necessary to specify the "forward loss" and $revers loss" if the roughness and diameter are known. Is thei assumption correct?

Thank in advance fr you help

Georges



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swenson

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Re: "In loss" and "out loss"option in HVAC model
« Reply #1 on: January 20, 2014, 11:44:50 am »

Your are correct that you do not need to specify additional duct "forward loss" and reverse loss" if the roughness and diameter are known.

My understanding is that in addition to duct loss, each node should be assigned the appropriate fitting loss. For example, the loss for a round 90 degree elbow with r/D=1.5 and D=6 inches is 0.14. The ASHRAE Handbook - Fundamentals is one source of this data. However, I am not an HVAC engineer, so please take this statement with caution.

I have successfully run the HVAC option in FDS using only duct loss terms.

We do have an HVAC news post and example problem on the PyroSim web site.
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Georges

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Re: "In loss" and "out loss"option in HVAC model
« Reply #2 on: January 22, 2014, 03:23:03 am »

Hi Swenson,
Thanks for your quick reply
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