Chapter 6: Heat Exchanger Pipes and Tubes

ILLUSTRATIVE EXAMPLE 6.1, Page number: 73

In [1]:
#Variable declaration:
NPS = 2                     #Nominal pipe size (inch)
SN = 40                     #Schedule number

#Calculation:
#From Table 6.2, we obtain that the inside diameter of steel pipe is ID = 2.067 in.
ID = 2.067

#Result:
print "The inside diameter of steel pipe is :",ID," in."

The inside diameter of steel pipe is : 2.067  in.

ILLUSTRATIVE EXAMPLE 6.2, Page number: 73

In [2]:
#Variable declaration:
NPS = 3                     #Nominal pipe size (inch)
SN = 40                     #Schedule number

#Calculation:
#From Table 6.2, we obtain that the inside diameter of steel pipe is ID = 3.068 in, outside diameter OD = 3.5 in, wal thickness WT = 0.216 in, and pipe weight PW = 7.58 lb/ft.
ID = 3.068
OD = 3.5
WT = 0.216
PW = 7.58

#Result:
print "The inside diameter of steel pipe is :",ID," in"
print "The outside diameter of steel pipe is :",OD," in"
print "The wall thickness of steel pipe is :",WT," in"
print "The weight of steel pipe is :",PW," lb/ft."

The inside diameter of steel pipe is : 3.068  in
The outside diameter of steel pipe is : 3.5  in
The wall thickness of steel pipe is : 0.216  in
The weight of steel pipe is : 7.58  lb/ft.

ILLUSTRATIVE EXAMPLE 6.3, Page number: 73

In [3]:
#Variable declaration:
ID = 0.957                  #Inside diameter of pipe (in)
OD = 1.315                  #Outside diameter of pipe (in)
WT = 0.179                  #Wall thickness of pipe (in)
PW = 2.17                   #Weight of pipe (lb/ft)

#Calculation:
#From Table 6.2, it indicates that the steel pipe is 1 inch schedule 80.
NSP = 1
SN = 80

#Result:
print "The nominal size of the pipe is :",NSP," in."
print "The schedule number of the pipe is:",SN,"."

The nominal size of the pipe is : 1  in.
The schedule number of the pipe is: 80 .

ILLUSTRATIVE EXAMPLE 6.4, Page number: 75

In [4]:
#Variable declaration:
S = 3/4                         #Tube size (in)
BWG = 16                        #Birmingham Wire Gauge number (gauge)

#calculation:
#From table 6.3, we get:
ID = 0.620                      #Internal diameter of tube (in)
WT = 0.065                      #Wall thickness of tube (in)
OD = ID+2*WT                    #Outside diameter of tube (in)
EA = 0.1963                     #External area per foot (ft)

#Result:
print "The inside diameter is :",ID," in"
print "The wall thickness is :",WT," in"
print "The outside diamater is :",OD," in"
print "The external area per foot per foot :",EA," ft."

The inside diameter is : 0.62  in
The wall thickness is : 0.065  in
The outside diamater is : 0.75  in
The external area per foot per foot : 0.1963  ft.

ILLUSTRATIVE EXAMPLE 6.11, Page number: 81

In [11]:
#Variable declaration:
a = 1                           #Length of cross-section (m)
b = 0.25                        #Width of cross-section (m)
v = 1*10**-5                    #Kinematic viscosity of air (m^2/s)
Re = 2300.0                     #Reynolds Number
cm = 100                        #Cenitmeters in a meter

#Calculation:
Dh = 2*a*b/(a+b)                #Hydraulic diameter of duct (m)
V = Re*v/Dh*cm                  #Maximum air velocity (cm/s)

#Result:
print "The maximum air velocity before the flow becomes turbulent is :",round(V,1)," cm/s."

The maximum air velocity before the flow becomes turbulent is : 5.8  cm/s.

ILLUSTRATIVE EXAMPLE 6.12, Page number: 82

In [12]:
#Variable declaration:
q = 0.486                       #Flow rate of fluid (ft^3/s)
D = 2.0/12.0                    #Diameter of tube in feet (ft)
pi = 3.14                       #Value of pi
p = 70.0                        #Density of fluid (lb/ft^3)
u = 0.1806                      #Viscosity of fluid (lb/ft)

#Calculation:
V = 4*q/pi/D**2                 #Flow velocity (ft/s)
Re = D*V*p/u                    #Reynolds Number

#Result:
if(Re<2100):
    print "The flow is laminar."
elif(Re>2100):
    print "The flow is turbulant."

The flow is laminar.

ILLUSTRATIVE EXAMPLE 6.13, Page number: 82

In [22]:
#Variable declaration:
#From example 6.12, we have:
D = 2.0/12.0                    #Diameter of pipe in feet (ft)
Re = 1440.0                     #Reynolds number

#Calculation:
Lc = 0.05*D*Re                  #Length of pipe (ft)

#Result:
print "The pipe length to ensure a fully developed flow is:",Lc," ft."
print "This is an abnormally long calming length for a pipe (or tube) in a heat exchanger."

The pipe length to ensure a fully developed flow is: 12.0  ft.
This is an abnormally long calming length for a pipe (or tube) in a heat exchanger.

ILLUSTRATIVE EXAMPLE 6.14, Page number: 82

In [14]:
#Variable declaration:
u = 6.72*10**-4                     #Viscosity of water (lb/ft.s)
p = 62.4                            #Density of water (lb/ft^3)
#For laminar flow:
Re = 2100.0                        #Reynolds number
#From table 6.2, we have:
D = 2.067/12.0                      #Inside diameter of pipe (ft)

#Calculation:
V = Re*u/D/p                        #Average velocity of water flowing (ft/s)

#Result:
print "The average velocity of water flowing is:",round(V,2)," ft/s."

The average velocity of water flowing is: 0.13  ft/s.