terminal velocity in a spray dryer

[kuds]

I am working on a problem involving spray dryers. The material to be dryed would be injected through a rotating nozzle with multiple openings from the top. Hot air would be blown from the dryer's bottom part. I was wondering how can I approach the problem to find out the particle's terminal velocity and how is terminal velocity related to reynolds number.any help will be appreciated.

thanks

 

[m777182]

There are many empirical relations describing incipient fluidization velocity or minimum fluidization velocity or critical Re.You can find them in numerous books and papers. The equations will give you a range of values that may differ quite a lot.Here I've got some of them from one of my spread sheets

fuidization Re:
*Vane?ek,*Pavlov
Re=Ar/ [1400 +5,22*sqrt(Ar)]
*Rhodes (eq. 8) from:
Ar=1406 *Remf+27,3 * Remf**2
Geldart (p24 eq. 2.26) from:
Ar=1650*Remf+24,5*Remf**2
*Wen & Yu from:
Ar=1652*Remf+24,5*Remf**2

minimum fluidization velocity
*Rhodes (eq.10)
Re_mf=33,7*[SQRT(1+3,59e-5*Ar) -1]
Rhodes (eq. 7)
Re_mf =[-150*(1-epsilon)+-sqrt((150*(1-epsilon))**2+4*1,75*epsilon**3*AR)]/( 2*1,75)

*Kneule p.320
Re L =[1830 + 0,571*epsilon_L**3*Ar/(1-epsilon_L)**2]**1/2 - 42,8
*Kneule p.320
u_mf=Re_L*(1 - epsilon)*viscosity/d_p
Geldart (p24 eq. 2.27)
u_mf=m / (ro_fl*d_p) * [sqrt(1135,7+0,0408*Ar)-33,7]
Bulk Solids Physical Properties Guide
u_mf=420*ro_p*d_p**2

incipient fludization velocity
*Rhodes from:
Ar=150*(1-epsilon)*epsilon**3*Re_mf+1,75/e**3*Re_mf
*Rhodes from:
Re_mf=33,7*[SQRT(1+3,59e-5*Ar) -1] ---->u_mf

*Pavlov p.123:
v_cr=Re_cr*viscosity_fl/d_p

Re.. Reynolds number
Ar-Arhimedes number
epsilon -porosity
e_L- porosity
u_mf-minimum fluidization velocity
ro-density
viscosity
d_p- particle diameter
ro_fl-fluid density
v -velocity
index fl--fluid
index cr-critical
index mf-minimum fluidization

If you need citated papers it will take me some time to find them.

m777182