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K_extract_branch_90



The K_extract_branch_90(V1overV3, A1overA3) function returns the resistance coefficient for a 90 degree extract branch.  The coefficient returned is for the branch and should be applied to the downstream main duct velocity.  The coefficient is a function of the ratio of the branch to downstream volumetric flow rates and the branch to downstream areas.  The correlation is for circular ducts.  Note that the function DuctExtractBranch90_CL in the component library implements the dimensional version of this function.  

Inputs: 
V1overV3 = ratio of branch to downstream flow rates
A1overA3 = ratio of branch to downstream areas

Example:
$UnitSystem SI C kPa Degree
$VarInfo DELTAP units=Pa
$VarInfo rho units=kg/m^3
V1overV3=0.7
A1overA3 = 0.5
K=k_extract_branch_90(V1overV3, A1overA3)
vel = 10 [m/s]
P = Po#
T = 20 [C]
F$ = 'Air'
rho=density(F$,P=P,T=T)
DELTAP = rho*vel^2/2*K

{Solution:
DELTAP=112.0 [Pa]
K=1.86
}


Reference:
Legg, R., 2017, "Chapter 14: Ducted Air Systems" in Air Conditioning System Design, Butterworth-Heinemann

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