[Bldg-sim] pressure difference in large extract system

chris.malcolm.yates at gmail.com chris.malcolm.yates at gmail.com
Wed Apr 17 04:34:59 PDT 2024

Hello all!


I'm modelling an extract system for a rail maintenance depot (RMD). It'll be
sucking about 50m3/s (106,000 cfm).


The client wishes to investigate solutions regarding intake air louvres. The
main resulting variable is the zone's resulting internal pressure. I've
calculated, based on their stock louvre selection, and based on many
assumptions (e.g., leakiness, backflow through non-operable fans, etc) that
this will be in the range of minus 10 to 25 Pa.


Does this sound reasonable? I'm unaware of any standards relating to
maintenance sheds anywhere.


Also, considering the range 10 to 25 Pa, what discharge coefficients and
flow exponents would be normally considered? I've usually worked to Cd ~
0.62 and ~ 0.5 respectively, but this could be more variable as the pressure


Many thanks



PS. X-posted in AIVC linkedin group

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