#An electrically heated vertical plate, 5 in square has a temperature of
#150 F and is being cooled by natural convection in 50 F air. What is the
#heat transfer rate from both sides of the plate?
import math
#initialisation of variables
d= 5. #ft
Tw= 150. #F
T= 50 #F
Pr= 0.72
k= 0.015 #Btu/hr ft F
r= 1.76*1000000. #(F ft^3)^-1
#CALCULATIONS
D= d*(0.42/5.) #Diameter
dt= Tw-T #change in temp
Gr= r*D*D*D*dt #Grashof number
z= Gr*Pr
h= 0.59*(math.pow(z,(0.25))) *(k/D) #Heat transfer coefficient
q= (2*h*dt*d*d)/144. #Heat transfer rate
#RESULTS
print '%s %.2f' % ('Heat transfer rate from both sides of the plate (Btu/hr) = ',q)
raw_input('press enter key to exit')
#Cooling water at an average temperature of 70 F flows through a tube of
#0.9 in ID, with an average velocity of 7 ft/s. What is the heat transfer
#coefficient when the flow is fully developed?
#initialisation of variables
import math
T= 70. #F
l= 0.9 #in
v= 7. #ft/s
d= 62.3 #lbm/ft^3
m= 6.58*math.pow(10,-4) #lbm/ft s
Pr= 6.82
k= 0.347 #Bt/hr ft F
#CALCULATIONS
l1= l*0.075/l
Re= (d*v*l1)/m #Reynold's number
Nu= 0.023*math.pow(Re,0.8)*math.pow(Pr,0.4) #Nusselt number
h= Nu*k/l1 #Transfer coefficient
#RESULTS
print '%s %.2f' % ('Heat transfer coefficient when the flow is fully devoloped (Btu/hr ft^2 F) = ',h)
raw_input('press enter key to exit')
#Air at 1 atm pressure and a mixing cup temperature of 450k flows through
#a 3 cm diameter tube with a velocity of 6 m/s. determine the heat transfer
#rate per unit length if tube if a constant heat flux condition is maintained
#at the tube wall and the wall temperature is 10 C above the air temperature
import math
#initialisation of variables
P= 1 #atm
d= 0.783 #Kg/m^3
K= 0.0371 #W/m C
m= 2.48*math.pow(10,-5) #Ns/m^2
Pr= 0.683
D= 0.03 #m
v= 6 #m/s
T= 10 #C
#CALCULATIONS
Re= d*v*D/m #Reynolds number
Nu= 0.023*math.pow(Re,0.8)*math.pow(Pr,0.4) #Nusselt number
h= Nu*K/D #Heat transfer coefficient
ql= h*math.pi*D*T #Heat transfer rate
#RESULTS
print '%s %.2f' % ('Heat transfer rate per unit lenght (W/m) = ',ql)
raw_input('press enter key to exit')
#Air at 1 atm pressure and 25 C flows past a horizontal 5 cm diameter with
#a velocity of 46 m/s. If the surface of the cylinder is kept at 135 C, determine
#the rate of heat flow from the cylinder
import math
#initialisation of variables
T= 25 #C
P= 1 #atm
v= 46 #m/s
d= 5 #cm
T1= 135 #C
d1= 0.998 #kg/m^3
k= 0.03 #W/m C
m= 2.08*math.pow(10,-5) #Kg/s m
c= 0.024
n= 0.81
#CALCULATIONS
Tf= (T+T1)/2. #Final temp.
D= d/100.
Re= d1*v*D/m #Reynolds number
h= c*math.pow(Re,0.81)*k/D #Heat transfer coefficient
dt= T1-T #temp diff.
ql= h*math.pi*D*dt #Heat transfer rate
#RESULTS
print '%s %.2f' % ('Heat transfer rate per unit lenght of cylinder (W/m) = ',ql)
raw_input('press enter key to exit')