In [3]:

```
import math
# Variables
Tm = 70.; # Average air temperature in degF
Tw = 60.; # Pipe wall temperature in degF
thm = Tm-Tw; # Mean temperature difference in degF
# Thm is so small that the fluid properties may be based on 70 degF
v = 30.; # Velocity in ft/sec
L = 1000.; # Length of pipe
D = 3./12; # Diameter in ft
y = 0.15; # Specific weight in lb/ft**3
p = 0.15/32.2; # Density in slug/ft**3
u = 0.00137; # Vismath.cosity in slug/ft/hr
# Calculations and Results
Nre = v*3600*D*p/u; # Reynolds number
f = 0.08/(Nre)**.25; # Nusselt number
delp = 2*f*L*p*(v**2)/D; # Pressure drop in lb/sq.in
print "The pressure drop is %d lb/sq.ft "%(delp);
cp = 0.24*32.2; # Specific heat capacity in slug/degF
Cp = 0.24*0.15; # Heat capacity in Btu/ft**3-degF
k = 0.0148; # Thermal conductivity in Btu/ft-hr-degF
Npr = u*cp/k; # Prandtls number
phi = math.sqrt(Npr)/(1+(750*math.sqrt(Npr)/Nre)+7.5*(Npr**0.25)/math.sqrt(Nre));
A = math.pi*L*D; # Area in ft**2
q = phi*f*Cp*A*v*thm*3600/(2*Npr); # Heat loss in Btu/hr
print "Heat loss per hour of air is %.3f Btu/hr "%(phi);
h = q/(A*thm); # Film coefficient
print "The film coefficient of heat transfer on the inner pipe wall is %.1f Btu/hr-ft**2-degF"%(h);
# note : rounding off error.
```