Fan Static Pressure
Fan Static Pressure
Fan Static Pressure
The Fan Static Pressure is expressed as the Fan Total Pressure minus the velocity pressure at the fan discharge, or:
outlet
- P v discharge
Where P v discharge = Velocity Pressure at the Fan Discharge For Exhaust Systems !ith resistance only on the inlet side, the fan static pressure is:
P s fan = P t loss
For exhaust system: P v system outlet = P v discharge For Supply Systems !ith resistance on the outlet side, the fan static pressure is:
The diagram "elo! illustrates the difference "et!een exhaust and supply systems
Pressure Calculations
Methodology
Brea the system into sections! $ ne! section occurs at: %& 'hanges in duct si(e )& 'hange in air volume Calculate losses for each section! *egin at the section farthest from the fan and !or+ to!ards the fan For each section: "! #rite do$n or calculate all no$n varia%les! $ir Flo! ,ate -.& Duct 'ross/Sectional $rea of the section -$& 'enter/0ine 0ength of the section -0& $ir Velocity through the section -V=.1$& Velocity Pressure -Pv = -V12##3&)& #rite do$n or calculate all pressure losses in the section! a' List the Component Losses/Gains! 4ncurred "y hoods, 5SPs, filters, dampers, etc %' Calculate the Dynamic Losses/Gains! 6ccur through el"o!s, transitions, tees, or any other type of fitting 7se the $S8,$5 Fitting Diagrams to find Dynamic 0oss 'oefficients for fittings Be sure to factor in System Effect( c' Calculate Frictional Losses/Gains! 7se the $S8,$5 Friction 'hart for 9standard: galvani(ed duct!or+ 7se the Darcy/Weis"ach 5;uation for 9non/standard: duct such as flex duct Sum up the Component* +ynamic* and Frictional Pressure for the section! Sum up the pressure losses for all of the sections!
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