In [1]:

```
import math
#Variable
v = 1. #m/s
#temprature
T = 25. # degree celcius
#length of plate,l = 1m
l = 1. #m
#width of plate,w = 0.5m
w = 0.5 #m
#angle of incidence,theta = 0 degree
theta = 0. #degree
#Calculation
#for water at 25 degree celcius ,momentum diffusivity,
MD = 8.63*(10**-7) # m**2/s
#local Reynold no.
x = 0.5 #m
Re = x*v/MD
#from Eq. 11.39,the boundary layer thickness is
t = 5*x/(Re**0.5)
#Results
print "i) Boundary layer thickness is %.4f m"%(t)
#local drag coefficient
#CD = local drag force per unit area (F)/kinetic energy per unit volume(KE)
#F = 0.332*rho*v**2*Re**0.5 and KE = 0.5*rho*v**2
CD = 0.332*v**2*(Re**-0.5)/(0.5)*v**2
print "Local drag coefficient is %.2e "%(CD)
#From eq 11.44, the drag force acting on one side of the plate is
#kinetic viscocity
mu = 8.6*(10**-4)
fd = 0.664*mu*v*(l*v/MD)**0.5*w
#the total force acting on both sides of the plate
tfd = 2*fd
print "total drag force is %.3f N "%(tfd)
#shear stress at any point in the boundary layer
#at a point in the boundary layer,
x = 0.5 #m
y = t/2
# n = blasius dimensionless variable
n = y/(MD*x/v)**0.5
#From table 11.1, at n = 2.5,f"(n) = 0.218
#shear stress = tau
fn = 0.218 #f"(n) = fn
tau = (mu*v*(v/(MD*x))**0.5)*fn
print "Shear stress is %.3f N/m**2"%(tau)
```

In [2]:

```
#Variable
Ts = 200. # C,temp. of air
Ta = 30. #C, temp .of surface
Va = 8. #m/s, velocity of air
d = 0.75 #m, dismath.tant from leading edge
#Calculation and Results
Tm = (Ts+Ta)/2 #C, Mean temp. of boundary layer
mu = 2.5*10**-5 #m**2/s, vismath.cosity
P = 0.69 #prndatl no.
k = 0.036 #W/m c, thermal conductivity
Re = d*Va/mu #reynold no.
t = 5*d/(Re**0.5*P**(1./3)) #m, thermal boundary layer thickness
print "Thermal boundary layer thickness is %.1f mm "%(t*10**3)
N = (0.332*Re**(0.5)*P**(1./3)) #Nusslet no.
h = k*N/d #heat transfer coefficent
print "heat transfer coeff is %.1f W/m**2 C"%(h)
```

In [1]:

```
# Variables
#Free strean velocity (v1) and temp.(t1) on side 1
v1 = 6. #m/s
t1 = 150. #degree celcius
#same on side 2
v2 = 3. #m/s
t2 = 50. #degree celcius
#dismath.tant
x = 0.7 #m
#The plate temp. is assumed to be equal to the mean of the bulk air temp on the two sides of the plates
T = 100. #degree celcius
# Calculations
#Side 1
#mean air temp.
tm1 = (T+t1)/2
#From thermophysical properties:kinetic vismath.cosity (kv),Prandtl no.(P), thermal conductivity (k)
kv1 = 2.6*10**-5 #m**2/s
P1 = 0.69
k1 = 0.0336 #W/m degree celcius
#Reynold no.
Re1 = x*v1/kv1
#Nusslet no(N1)
a = 1/3.
N1 = 0.332*(Re1)**0.5*P1**a
h1 = k1*N1/x
#Side 2 of the plate
tm2 = (T+t2)/2
#Similarly
kv2 = 2.076*(10)**-5 #m**2/s
P2 = 0.70
k2 = 0.03 #W/m degree celcius
Re2 = x*v2/kv2
N2 = 0.332*(Re2)**0.5*P2**a
h2 = k2*N2/x
#overall heat transfer coeff.
U = h1*h2/(h1+h2)
#The local rate of heat exchange
RH = U*(t1-t2)
# Results
print "Local rate of heat exchange is %.0f W/m2"%(RH)
#the plate temp is given by
TP = t2+(t1-t2)*U/h2
print "Plate temperature is :%.0f Celsius "%(TP)
```

In [5]:

```
import math
# Variables
T1 = 120. #C, initial temp.
T2 = 25. #C, Final temp.
Tm = (T1+T2)/2 #C, mean temp.
rho = 8880. #kg/m**3, density of plate
#Properties of air at mean temp.
mu = 2.07*10**-5 #m**2/s, vismath.cosity
Pr = 0.7 #Prandtl no.
k = 0.03 #W/m C, thermal conductivity
l = 0.4 #m, length of plate
w = 0.3 #m, width of plate
d = 0.0254 #m, thickness of plate
Vinf = 1. #m/s, air velocity
Re = l*Vinf/mu #REynold no.
#from eq. 11.90 (b)
Nu = 0.664*(Re)**(1./2)*(Pr)**(1./3) #average Nusslet no.
#Nu = l*h/k
h = Nu*k/l #W/m**2 C, heat transfer coefficient
#Rate of change of temp. is given by
A = 2*l*w #m**2. area of plate
t = 1*3600. #s, time
cp = 0.385*10.**3 #j/kg K, specific heat
m = l*w*d*rho #kg, mass of plate
#-d/dt(m*cp8dt) = A*hv*(T1-T2)
#appling the boundary condition
T = (T1-T2)*math.exp(-A*h*t/(m*cp))+T2
print "The temprature of plate after 1 hour is %.0f C"%(T)
```

In [6]:

```
import math
# Variables
#Reynold no (Re),friction factor(f),Prandlt no. (P)
Re = 7.44*(10**4)
f = 0.00485
P = 5.12
x = P-1 #assume
# Calculations
#according to Von Karmen anamath.logy
N = ((f/2)*Re*P)/(1+(5*math.sqrt(f/2))*(x+math.log(1+(5./6)*x)))
# Results
print "Nusslet no is: %.0f "%(N)
```