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K_90deg_bend
The K_90deg_bend(r,D,RelRough) function returns the resistance coefficient for a 90 degree bend having a diameter of D and a radius of curvature r, as shown in the figure. The relative roughness must also be supplied as a parameter. This parameter should be set to 0 for smooth tubes and it should be less than 0.002 for this function. The dependence of relative roughness indicates that the resistance factor is applicable to turbulent flow.
The radius and diameter are expected to be entered in m or ft, depending on the unit system setting in EES. However, it is their ratio that is needed, so the units are not important.
Example:
$UnitSystem SI K Pa J
$VarInfo DELTAP units=Pa
$VarInfo h_L units=m
r=0.25 [m]
D=0.05 [m]
RelRough=0
K=k_90deg_bend(r,D,RelRough)
V_tilde=10 [m/s]
rho=1000 [kg/m^3]
g=g#
h_L=K*V_tilde^2/(2*g)
DELTAP=h_L*rho*g
{Solution:
DELTAP=4,980 [Pa]
h_L=0.5078 [m]
K=0.0996
}
Reference:
Pipe Friction Manual, Hydraulic Institute, New York, 1962
Minor Losses Index