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terminal velocity in a spray dryer

terminal velocity in a spray dryer

terminal velocity in a spray dryer

(OP)
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

RE: terminal velocity in a spray dryer

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


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