Contents - Index

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 ratio of 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

Minor Losses Index