Chapter 15: GETTING STARTED IN HEAT TRANSFER: MODES, RATE EQUATIONS AND ENERGY BALANCES

Example 15.01, page: 343

In [1]:
from __future__ import division
import math

# Initialization  of  Variable
k = 1.7 #W/m.K
T1 = 1400 #K
T2 = 1150 #K
L = 0.15 #m
W = 1.2 #m
H = 0.5 #m

#calculations:
qx2 = k*(T1-T2)/L
#heat flux
qx = H*W*qx2

#Results
print  "the rate of heat transfer through a wall is", qx,"W"

the rate of heat transfer through a wall is 1700.0 W

Example 15.02, page: 347

In [2]:
from __future__ import division
import math

# Initialization  of  Variable
Tinf = 25 #degC
h = 15 #W/m2.K
D = 70 #mm
Ts = 200 #degC
e = 0.8
Tsur = 25 #degC
sigma = 5.67E-8 #W/m2.K4

#calculations:
E = e*sigma*(Ts + 273)**4
G = sigma*(Tsur + 273)**4
#heat transfer per Unit length
q1 = h*(math.pi*D/1000)*(Ts - Tinf) + e*(math.pi*D/1000)*sigma*((Ts+273)**4 - (Tsur+273)**4)

#Results
print "Emissive Power, E =", round(E,0),"W/m2"
print  "Irradiation, G =", round(G,0),"W/m2"
print  "Heat  transfer  per  unit  length, q' = ", round(q1,0),"W/m"

Emissive Power, E = 2270.0 W/m2
Irradiation, G = 447.0 W/m2
Heat  transfer  per  unit  length, q' =  998.0 W/m

Example 15.05, page: 352

In [3]:
from __future__ import division
import math

# Initialization  of  Variable
k = 1.2 #W/m.K
T2 = 100 #degC
e = 0.8
L = 0.15 #m
Tinf = 25 #degC
Tsur = 25 #degC
h = 20 #W/m2.K
sigma = 5.67E-8 #W/m2.K4

#calculations:
#inner wall temperature
T1 = T2 + 273 + L/k*(h*(T2 - Tinf) + e*sigma*((T2+273)**4 - (Tsur+273)**4))

#Results
print  "inner  wall  temperature is", round(T1,0),"K"

inner  wall  temperature is 626.0 K

Example 15.06, page: 353

In [4]:
from __future__ import division
import math

# Initialization  of  Variable
Tsur = 30 #degC
Tinf = 20 #degC
h = 15 #W/m2.K
Glamp = 2000 #W/m2
alamp = 0.8
e = 0.5
sigma = 5.67E-8 #W/m2.K4

#calculations:
#coating Temp
Ts = Tinf + 273 + (alamp*Glamp - e*sigma*((104+273)**4 - (Tsur+273)**4))/h

#Results
print "coating Temperature is", round(Ts,0),"K"

coating Temperature is 377.0 K