# Chapter 7:Liquid Mixing¶

## Example no:7.2,Page no:286¶

In :
#Variable declaration
rho_sol=1650                   #Density of the solution
Meu_sol=50e-3                  #Viscosity of the solution
Dt=2.28                        #Density of the tank
D=0.5                          #Diameter of the propeller mixer
H=2.28                         #Liquid depth
Za=0.5                         #Height of the propeller
N=2                            #Rotational speed

#Calculation
Re=D**2*N*rho_sol/(Meu_sol)
Fr=N**2*D/9.81
#From figure 7.6
Np=0.5
P=Np*rho_sol*N**3*D**5

#Result
print"Power provided by propeller to the liquid =",round(P),"W"

Power provided by propeller to the liquid = 206.0 W


## Example no:7.3,Page no:286¶

In :
#Variable declaration
d=0.6 #tank diameter
N1=4.0 #Rotor dpeed in Hertz
P1=0.15 #Power consumption
Re1=160000 #Reynold's number
D1=d/3.0

#Calculation
import math
D2=6*D1
N2=math.pi*N1*D1/(math.pi*D2)
P2=7.32*N2**3*D2**5
#For thermal similarity, that is the same temperature in both systems:
Re2=Re1*(N2*D2**2/(N1*D1**2))
V2=(math.pi/4.0)*(6*d)**3
P=V2*0.884
N=(P/(7.32*(6*0.6/3.0)**5))**(1.0/3.0)
Re=Re1*(N*D2**2/(N1*D1**2))

#Result
print"The new rotor speed =",round(N2,2),"Hz"
print"The new power required =",round(P2,2),"kW"
print"The new reynolds number =",Re2
print"\n\n For Constant power input per unit volume:"
print"The new power required =",round(P,1),"kW"
print"The new rotor speed =",round(N,2),"Hz"
print"The new reynolds number =%d"%Re

print"NOTE:Wrong values of Reynolds numbers in book"

The new rotor speed = 0.67 Hz
The new power required = 5.4 kW
The new reynolds number = 960000.0

For Constant power input per unit volume:
The new power required = 32.4 kW
The new rotor speed = 1.21 Hz
The new reynolds number =1744643
NOTE:Wrong values of Reynolds numbers in book