# Chapter 1 : Basic Concepts¶

## Example 1.1 Page No : 9¶

In [1]:
# Variables
L = 0.02;		    	#Thicness of stainless steel plate in m
T = [550,50];			#Temperatures at both the faces in degree C
k = 19.1;		    	#Thermal Conductivity of stainless steel at 300 degree C in W/m.K

# Calculations
q = ((k*(T[0]-T[1]))/(L*1000));			#Heat transfered per uni area in kW/m**2

# Results
print 'The heat transfered through the material per unit area is %3.1f kW/m**2'%(q)

The heat transfered through the material per unit area is 477.5 kW/m**2


## Example 1.2 Page No : 11¶

In [2]:
# Variables
L = 1.;			#Length of the flat plate in m
w = 0.5;			#Width of the flat plate in m
T = 30.;			#Air stream temperature in degree C
h = 30.;			#Convective heat transfer coefficient in W/m**2.K
Ts = 300.;			#Temperature of the plate in degree C

# Calculations
A = (L*w)               			#Area of the plate in m**2
Q = (h*A*(Ts-T)/(1000));			#Heat transfer in kW

# Results
print 'Heat transfer rate is %3.2f kW'%(Q)

Heat transfer rate is 4.05 kW


## Example 1.3 Page No : 11¶

In [1]:
# Variables
T = 55.			#Surface temperature in degree C

# Calculations
q = (5.6697*10**-8*(273+T)**4)/1000;			#The rate at which the radiator emits radiant heat per unit area if it behaves as a black body in kW/m**2

# Results
print 'The rate at which the radiator emits radiant heat per unit area is %3.2f kW/m**2'%(q)

The rate at which the radiator emits radiant heat per unit area is 0.66 kW/m**2


## Example 1.5 Page No : 20¶

In [4]:
# Variables
k = 0.145;			#Thermal conductivity of Firebrick in W/m.K
e = 0.85;			#Emissivity
L = 0.145;			#Thickness of the wall in m
Tg = 800.;			#Gas temperature in degree C
Twg = 798.;			#Wall temperature ion gas side in degree C
hg = 40.;			#Film conductance on gas side in W/m**2.K
hc = 10.;			#Film conductance on coolant side in W/m**2.K
F = 1.; 			#Radiation Shape factor between wall and gas

# Calculations
R1 = (((e*5.67*10**-8*F*((Tg+273)**4-(Twg+273)**4))/(Tg-Twg))+(1./hg));			#Thermal resistance inverse
R2 = (L/k);     	    		#Thermal resistance
R3 = (1./hc);	    	    	#Thermal resistance
U = 1./((1./R1)+R2+R3);			#Overall heat transfer coefficient in W/m**2.K

# Results
print 'Overall heat transfer coefficient is %3.3f W/m**2.K'%(U)

Overall heat transfer coefficient is 0.906 W/m**2.K


## Example 1.6 Page No : 21¶

In [5]:
# Variables
D = 0.05;			#Outside diameter of the pipe in m
e = 0.8;			#Emmissivity
T = 30;			#Room Temperature in degree C
Ts = 250;			#Surface temperature in degree C
h = 10;			#Convective heat transfer coefficient in W/m**2.K

# Calculations
q = ((h*3.14*D*(Ts-T))+(e*3.14*D*5.67*10**-8*((Ts+473)**4-(T+273)**4)));			#Heat loss per unit length of pipe in W/m

# Results
print 'Heat loss per unit length of pipe is %3.1f W/m'%(q)

Heat loss per unit length of pipe is 2231.3 W/m


## Example 1.7 Page No : 21¶

In [7]:
# Variables
A = 0.1;			#Surface area of water heater in m**2
Q = 1000.;			#Heat transfer rate in W
Twater = 40;			#Temperature of water in degree C
h1 = 300;			#Heat transfer coefficient in W/m**2.K
Tair = 40;			#Temperature of air in degree C
h2 = 9;			#Heat transfer coefficient in W/m**2.K

# Calculations
Tsw = (Q/(h1*A))+Twater;			#Temperature when used in water in degree C
Tsa = (Q/(h2*A))+Tair;			#Temperature when used in air in degree C

# Results
print 'Temperature when used in water is %3.1f degree C  \n \
Temperature when used in air is %i degree C'%(Tsw,Tsa)

Temperature when used in water is 73.3 degree C
Temperature when used in air is 1151 degree C