CHAPTER 6:Condensers and Cooling Towers

Example 6.1,PAGE NUMBER:77

In [1]:
# Variable declaration
Q_1=12;# Heat load in kW
T_c1=50;# The condensing temperature in °C
T_o1=35;# The maximum outdoor temperature in °C
T_o2=15;# The reduced outdoor temperature in °C
Q_2=8;# The reduced heat load in kW

# Calculation
deltaT=T_c1-T_o1;# Temperature Difference in K
CR=Q_1*10**3/deltaT;# Condenser Rating in W/K
CR=CR*10**-3;# Condenser Rating in kW/K
deltaT_15=Q_2/CR;# Temperature Difference at 15°C 
T_c2=T_o2+deltaT_15;#The Condensing temperature at 15°C
print"Cooling Rating=",round(CR,1),"kW/K"
print"Temperature Difference at 15°C=%2.0f°C"%deltaT_15
print"The Condensing temperature at 15°C=%2.0f°C"%T_c2

Cooling Rating= 0.8 kW/K
Temperature Difference at 15°C=10°C
The Condensing temperature at 15°C=25°C

Example 6.2,PAGE NUMBER:80

In [2]:
# Variable declaration
deltaT=5.2;# The temperature rise in K
E=930;# Total duty at the condenser in kW
C_pw=4.187;# The specific heat of water in kJ/kg K

# Calculation
mdot=E/(deltaT*C_pw);# The amount of water required in kg/s
print round(mdot,0),"kg/s water flow is required."

43.0 kg/s water flow is required.

Example 6.3,PAGE NUMBER:80

In [3]:
# Variable declaration
E_t=880;# Total duty at the condenser in kW
E_wcp=15;# Total duty at water-circulating pump in kw

# Calculation
E=E_t+E_wcp;# Total tower duty in kW
w_er=E*0.41*10**-3;# Evaporation rate in kg/s
Cr_80=30;# Circulation rate in kg/s
Cr_160=60;# Circulation rate in kg/s
w_air=E*0.06;# Air flow rate in kg/s
print"\nEvaporation rate=%0.2f kg/s \nCirculation rate,80times=%2.0f kg/s \nCirculation rate,160times=%2.0f kg/s \nAir flow rate=%2.0f kg/s"%(w_er,Cr_80,Cr_160,w_air)

Evaporation rate=0.37 kg/s 
Circulation rate,80times=30 kg/s 
Circulation rate,160times=60 kg/s 
Air flow rate=54 kg/s

Example 6.4,PAGE NUMBER:85

In [4]:
# Variable declaration
Cc=700;# The cooling capacity in kW
P_c=170;# The compressor power in kW
c_b=0.0012;# Concentration of solids in bleed-off (kg/kg)
c_m=0.00056;# Concentration of solids in make-up water in kg/kg

# Calculation
E_tc=Cc+P_c;# Cooling tower capacity in kW
h_fg=2420;# Latent heat of water vapour in kJ/kg
w_e=E_tc*10**3/h_fg;# Rate of evaporation in g/s
w_m=(w_e*(c_b))/(c_b-c_m);# Rate of make up in kg/s
w_bo=w_m-w_e;# Rate of bleed off in kg/s
print"\nRate of make up=%0.2f kg/s \nRate of bleed off=%0.2f kg/s"%(w_m/1000,w_bo/1000)

Rate of make up=0.67 kg/s 
Rate of bleed off=0.31 kg/s