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DuctFlow_f

Procedure DuctFlow_f( Fluid\$, T, P, m_dot, H, W, L, RelRough: h_T, h_H, DELTAP, Nusselt_T,  f, Re) returns the pressure drop and friction factor for mass flow m_dot through a rectangular duct of height H, width W, and length L.  The procedure is applicable for developing flow or fully-developed flow in the laminar, transitional or turbulent flow regimes.  Properties are evaluated at a bulk temperature T and pressure P and used to calculate the Reynolds number. Units of the inputs and outputs depend upon the unit settings in EES.

Inputs:
Fluid\$ can be any fluid in the EES database.  The fluid can be an ideal gas, a real fluid, a brine, or a fluid from the Solid-Liquid property library.
T - the bulk temperature of the fluid  in [C], [K], [F], or [R].
P -  pressure can be in [Pa], [kPa], [bar], [MPa], [atm], or [psia].   (Note that for brines, this parameter provides the concentration in %)
m_dot  -  mass flow rate in [kg/s] or [lbm/hr]
H - duct height [m] or [ft]
W - duct width [m] or [ft]
L - length of the duct [m] or [ft]
RelRough - the ratio of the dispersions on the walls of the duct to the hydraulic diameter  of the duct (must be between 0 and 0.05).  The hydraulic diameter is 2 W H/(W + H).

Outputs: {only the first output is required}
DELTAP - pressure difference between the inlet and outlet of the duct in the pressure units set in the EES Unit System dialog
f -  friction factor [-]
Re - Reynolds number [-]

Notes:
The procedure will determine if the flow is laminar or turbulent.  Transitional flow is assumed to occur for Reynold's numbers between 2300 and 3000 and interpolation is applied between the laminar and turbulent correlations.

Example:
\$unitSystem SI Pa K J
\$VarInfo DELTAP units=Pa
\$TabStops 2.5 in
T=363 [K] "average temperature of fluid in duct"
P=101300 [Pa]               "pressure of air in duct"
m_dot=0.005 [kg/s]       "flow rate"
H=0.1 [m]                      "duct height"
W=0.5 [m]                     "duct width"
L=5 [m]                         "duct length"
RelRough=0.005 [-]        "relative roughness"
Call ductflow_f('air',T,P,m_dot,H,W,L,RelRough:DELTAP, f, Re)

{Solution:
DELTAP=0.02058
f=0.1334
Re=779.6 }

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Minor Losses Index