# Chapter 1:Introduction¶

## Example 1.1 , Page no:5¶

In :
#Variable declaration
v=28.8*10**-6; #the viscosity of water at 100 degree Celsius in kgf s/m^2
g=9.81; #Acceleration due to gravity in m/s^2

#calculations
v=28.8*10**-6*g; # Conversion of unit

#result
print ("The viscosity of water at 100 degree Celsius = {:.4e}".format(v)),"N s/m^2 (or kg/m s)"

The viscosity of water at 100 degree Celsius = 2.8253e-04 N s/m^2 (or kg/m s)


## Example 1.2, Page no:14¶

In :
#variable declaration
i=950; # radiation flux [W/m^ 2 ]
A=1.5; # area [m^ 2 ]
Ti=61; # inlet temperature
To=69; # outlet temperature
m=1.5; # mass flow rate
M=1.5/60; # kg/sec
Qconductn=50; # W
t=0.95; # transmissivity
a=0.97; # absoptivity
Cp=4183; # J/kg K

#calculations
q=M*Cp*(To-Ti); # heat gain rate
n=q/(i*A); # thermal efficiency
n_percent=n*100; # thermal efficiency

#result
print "Useful heat gain rate is ",round(q,4),"W"
print "Thermal efficiency is",'%.4E'%n,"i.e",round(n_percent,3),"%"
print "The rate at which energy is lost by re-radiation and convection is ", round(Qreradiated,6),"W"


Useful heat gain rate is  836.6 W
Thermal efficiency is 5.8709E-01 i.e 58.709 %
The rate at which energy is lost by re-radiation and convection is  426.5375 W


## Example 1.3, Page no:16¶

In :
#variable declaration
vi=10; # velocity at inlet in m/s
q=1000; # heat in w
di=0.04; # inside diameter in m
do=0.06; # outside diameter in m
den1=0.946; # density in kg/m^3 at 100 degree C
Cp=1009; # specific heat in J/kg k
den2=0.773; # specific heat at To=183.4 degree C

#calculations
m=den1*(3.14/4)*(di**2)*vi; # kg/s
dh=q/m; # j/kg
To=dh/Cp+100; # Exit Temperature
vo=m/(den2*(3.14/4)*(do)**2); # Exit velocity
dKeKg=(vo**2-vi**2)/2; # Change in Kinetic Energy per kg

#result
print "Exit Temperature is",round(To,4),"degree C"
print "Exit velocity is ",round(vo,4),"m/s"
print "Change in Kinetic Energy per kg =",round(dKeKg,5),"J/kg"

Exit Temperature is 183.4119 degree C
Exit velocity is  5.4391 m/s
Change in Kinetic Energy per kg = -35.20795 J/kg