Appendix E Thermal Radiation

Example E.1 Page no 446

In [4]:
#Given
K=380                               #W/m/K
A=7.85*10**-5                       #m**2
x=0.19
a1=100
a2=30
t=600                               #sec

#Calculation
Q=(K*A*(a1-a2)*t)/x

#Result
print"Amount of heat is",round(Q*10**-3,1),"*10**3 J"

Amount of heat is 6.6 *10**3 J

Example E.2 Page no 446

In [14]:
#Given
K=0.1674                            #j/a/m/degree C
A=3600                              #cm**2
x=0.04
L=336.0*10**3                         #J/Kg
a1=27
a2=0

#Calculation
A1=6*A
Q=K*A1*(a1-a2)/x
m=Q/L

#Result
print"Rate of flow of heat is",round(Q*10**-4,2),"J"
print"Mass of ice melted per second is",round(m*10**-1,3),"*10**-3 Kg/sec"

Rate of flow of heat is 244.07 J
Mass of ice melted per second is 0.726 *10**-3 Kg/sec

Example E.3 Page no 447

In [20]:
#Given
K=0.26                           #cal/s/cm/degree C
r=1
x=200                            #cm
a1=250                            #degree
Q=0.5

#Calculation
import math
A=math.pi*r**2
a2=a1-(Q*x/(K*A))

#Result
print"Temperature of other end is", round(a2,1),"Degree C"

Temperature of other end is 127.6 Degree C

Example E.4 Page no 447

In [23]:
#Given
K=1                            #W/m/K
A=0.5                          #m**2
t=3600                          #sec
x=6*10**-3                      #m
a1=24                           #degree
a2=2

#Calculation
Q=K*A*t*(a1-a2)/x

#Result
print"Heat is",Q*10**-5,"*10**5 J"

Heat is 66.0 *10**5 J

Example E.5 Page no 448

In [27]:
#given
T=2100                        #K
er=0.5
a=5.67*10**-8                 #W/m**2/K**4

#Calculation
E=er*a*T**4

#Result
print"Power radiated per unit area is",round(E*10**-5,1),"*10**5 W/m**2"

Power radiated per unit area is 5.5 *10**5 W/m**2

Example E.6 Page no 448

In [33]:
#Given
E=315                       #W/m**2
T=273.0                       #K
t=60                          #sec
r=10*10**-2

#Calculation
import math
a=E/T**4
T1=1000+T
E=a*4*math.pi*r**2*T1**4*t

#Result
print"Heat radiated is",round(E*10**-5,2),"*10**5 J"

Heat radiated is 11.23 *10**5 J

Example E.7 Page no 448

In [40]:
#Given
r=6*10**-2
T1=1200+273                             #K
T2=500+273
a=5.7*10**-8

#Calculation
import math
E=a*4*math.pi*r**2*(T1**4-T2**4)

#Result
print"Rate of loss of heat is",round(E*10**-3,1),"*10**3 W"

Rate of loss of heat is 11.2 *10**3 W