Screens
The function
Screens(Fluid$, m_dot, d, m, A_fr, L, T, P: f, h, NTU, DP)
returns the friction factor (f), heat transfer coefficient (h) and the number of transfer units for a perfectly stacked array of woven screens.
Inputs:
Fluid$ - string variable indicating a specific fluid in EES database or in the Solid-Liquid_Props fluids list
m_dot - mass flow rate of fluid [kg/s] or [lbm/min]
d - diameter of wire comprising screen [m] or [ft]
m - the number of mesh openings per unit length [1/m] or [1/ft]
A_fr - the frontal area of the screen exposed to fluid flow [m^2] or [ft^2]
L - length/depth of stacked screens [m] or [ft]
T - temperature of the fluid [C], [K], [F], [R]
P - pressure of the fluid at the inlet [Pa], [kPa], [bar], [MPa], [atm], or [psia]
Ouputs:
f - friction factor [-]
h - heat transfer coefficient [W/m^2-K] or [Btu/hr-ft^2-R]
NTU - number of transfer units on the flow side [-]
DP - pressure drop [Pa], [kPa], [bar], [MPa], [atm], or [psia]
Notes: This function determines the fluid properties at the stated pressure and temperature, and the Reynold's number from the screen mesh and wire diameter. In order to determine the Reynold's number, the porosity is needed. The idealized equations relating the screen mesh and diameter to porosity were based on those provided on page 52 of Ackermann (1997). With the Reynold's number and porosity calculated, the non-dimensional function Screens_ND is called to determine the values for the Colburn j and friction factor. The Colburn j factor is interpreted by Screens and returned as a heat transfer coefficient. It is assumed that the screens are perfectly arranged, i.e. the thickness of a single screen is exactly twice the wire diameter, and there is no gap between successive screens. The pressure drop is determined based on frictional considerations. Pressure drop due to fluid acceleration is not included.
Example:
$UnitSystem SI K Pa J
Fluid$='air'
m_dot=9.5 [kg/s] "air flow rate"
d=0.069 [mm]*convert(mm,m) "wire diameter"
A_fr=3.5 [m^2] "frontal area"
L=0.024 [m] "length in the flow direction"
T=650 [K] "inlet temperature"
P=101300 [Pa] "inlet pressure"
m=3900 [1/m] "mesh openings per unit length (100 mesh)"
Call Screens(Fluid$, m_dot, d, m, A_fr, L, T, P: f, h, NTU, DP)
{Solution:
f=2.477
h=1,138 [W/m^2-K]
NTU=116
DP=10074 [Pa]
}