In [7]:

```
import math
# Variables
Tsat = 100.; #Saturation temperature of water in degree C
p1 = 957.9; #Density of liquid in kg/m**3
Cpl = 4217.; #Specific heat in J/kg.K
u = (279.*10**-6); #Dynamic viscosity in N.s/m**2
Pr = 1.76; #Prantl number
hjg = 2257.; #Enthalpy in kJ/kg
s = (58.9*10**-3); #Surface tension in N/m
pv = 0.5955; #Density of vapour in kg/m**3
m = 30.; #Rate of water in kg/h
D = 0.3; #Diameter in m
# Calculations
q = round((m*hjg*1000)/(3600*math.pi*D**2/4)); #Heat transfer in W/m**2
Ts = Tsat+(((q/(u*hjg*1000))*math.sqrt(s/(9.81*(p1-pv)))))**0.33
# Results
print 'Temperature of the bottom surface of the pan is %3.2f degree C'%(Ts)
# NOte: answer in book is wrong.
```

In [2]:

```
# Variables
Tsat = 100; #Saturation temperature of water in degree C
p1 = 957.9; #Density of liquid in kg/m**3
Cpl = 4217; #Specific heat in J/kg.K
u = (279*10**-6); #Dynamic vismath.cosity in N.s/m**2
Pr = 1.76; #Prantl number
hjg = 2257; #Enthalpy in kJ/kg
s = (58.9*10**-3); #Surface tension in N/m
pv = 0.5955; #Density of vapour in kg/m**3
m = 30; #Rate of water in kg/h
D = 0.3; #Diameter in m
# Calculations
q = (0.18*hjg*1000*pv*((s*9.81*(p1-pv))/pv**2)**0.25)/10**6; #Burnout heat flux in MW/m**2
# Results
print 'Burnout heat flux is %3.3f MW/m**2'%(q)
```

In [3]:

```
# Variables
D = 0.0016; #Diameter of the wire in m
T = 255; #Temperature difference in degree C
p1 = 957.9; #Density of liquid in kg/m**3
Cpl = 4640; #Specific heat in J/kg.K
u = (18.6*10**-6); #Dynamic viscosity in N.s/m**2
hjg = 2257; #Enthalpy in kJ/kg
k = (58.3*10**-3); #Thermal conductivity in W/m.K
pv = 31.54; #Density of vapour in kg/m**3
Ts = 628; #Surface temperature in K
Tsat = 373; #Saturation temperature in K
# Calculations
hc = (0.62*((k**3*pv*(p1-pv)*9.81*((hjg*1000)+(0.4*Cpl*T)))/(u*D*T))**0.25); #Convective heat transfer coefficient in W/m**2.K
hr = ((5.67*10**-8)*(Ts**4-Tsat**4))/(Ts-Tsat); #Radiative heat transfer coefficient in W/m**2.K
hm = (hc+(0.75*hr)); #Mean heat transfer coefficient in W/m**2.K
Q = (hm*3.14*D*T)/1000; #Power dissipation rate per unit length of the heater in kW/m
# Results
print 'Mean heat transfer coefficient is %3.1f W/m**2.K \n \
Power dissipation rate per unit length of the heater is %3.3f kW/m'%(hm,Q)
```

In [3]:

```
# Variables
Ts = 10.; #Surface temperature in degree C
p1 = 10.; #Pressure of water in atm
# Calculations
hp = (5.56*Ts**0.4); #Heat transfer coefficient in kW/m**2.K
hp1 = (5.56*(2*Ts)**3*p1**0.4); #Heat transfer coefficient in kW/m**2.K
hp2 = (5.56*Ts**3*(2*p1)**0.4); #Heat transfer coefficient in kW/m**2.K
x1 = (hp1/hp)/1000; #Ratio of heat transfer coefficients
x2 = (hp2/hp)*100; #Ratio of heat transfer coefficients
# Results
print 'Heat transfer coefficient becomes %.f times the original value in the first case\n \
Heat transfer coefficient is increased only by 32 percent in the second case'%(x1)
```

In [13]:

```
import math
# Variables
p = 6.; #Pressure of water in atm
D = 0.02; #Diameter of the tube in m
Ts = 10.; #Wall temperature in degree C
L = 1.; #Length of the tube in m
# Calculations
p1 = (p*1.0132*10**5)/10**6; #Pressure in MN/m**2
h = (2.54*Ts**3*math.exp(p1/1.551)); #Heat transfer coefficient in W/m**2.K
Q = (h*math.pi*D*L*Ts); #Heat transfer rate in W/m
# Results
print 'Heat transfer rate is %3.1f W/m'%(Q)
# note : rounding off error.
```

In [17]:

```
# Variables
p = 2.45; #Pressure of dry saturated steam in bar
h = 1; #Height of vertical tube in m
Ts = 117; #Tube surface temperature in degree C
d = 0.2; #Distance from upper end of the tube in m
# Calculations
Tsat = 127; #Saturation temperature of water in degree C
p1 = 941.6; #Density of liquid in kg/m**3
k1 = 0.687; #Thermal conductivity in W/m.K
u = (227*10**-6); #Dynamic vismath.cosity in N.s/m**2
hfg = 2183; #Enthalpy in kJ/kg
pv = 1.368; #Density of vapour in kg/m**3
q = round((((4*k1*u*10*d)/(9.81*p1*(p1-pv)*hfg*1000))**0.25)*1000,2); #Thickness of condensate film in mm
h = (k1/(q/1000)); #Local heat transfer coefficient at x = 0.2 in W/m**2.K
# Results
print 'Thickness of condensate film is %3.2f mm \n \
Local heat transfer coefficient at x = 0.2 is %3.0f W/m**2.K'%(q,h)
```

In [21]:

```
import math
# Variables
D = 0.05; #Diameter of the tube in m
L = 2; #Length of the tube in m
Ts = 84; #Outer surface temperature in degree C
Tsat = 100; #Saturation temperature of water in degree C
Tf = (Tsat+Ts)/2; #Film temperature in degree C
p1 = 963.4; #Density of liquid in kg/m**3
u = (306*10**-6); #Dynamic vismath.cosity in N.s/m**2
hfg = 2257; #Enthalpy in kJ/kg
pv = 0.596; #Density of vapour in kg/m**3
k1 = 0.677; #Thermal conductivity in W/m.K
# Calculations
hL = (1.13*((9.81*p1*(p1-pv)*k1**3*hfg*1000)/(u*16*L))**0.25); #Heat transfer coefficient in W/m**2.K
Ref = ((4*hL*L*2)/(hfg*1000*u)); #Reynolds nmber
Q = (hL*math.pi*D*L*10); #Heat transfer rate in W
m = (Q/(hfg*1000))*3600; #Condensate mass flow rate in kg/h
# Results
print 'Heat transfer rate is %3.0f W \n \
Condensate mass flow rate is %3.1f kg/h'%(Q,m)
# note : rounding off error.
```

In [26]:

```
# Variables
h = 2.8; #Height of the plate in m
T = 54.; #Temperature of the plate in degree C
Tsat = 100.; #Saturation temperature of water in degree C
Tf = (Tsat+T)/2; #Film temperature in degree C
p1 = 973.7; #Density of liquid in kg/m**3
u = (365.*10**-6); #Dynamic viscosity in N.s/m**2
hfg = 2257.; #Enthalpy in kJ/kg
pv = 0.596; #Density of vapour in kg/m**3
k1 = 0.668; #Thermal conductivity in W/m.K
# Calculations
Re = (0.00296*((p1*9.81*(p1-pv)*k1**3*(Tsat-T)**3*h**3)/(u**5*(hfg*1000)**3))**(5./9)); #Reynolds number
hL = (0.0077*((9.81*p1*(p1-pv)*k1**3)/u**2)**(1./3)*Re**0.4); #Heat transfer coefficient in W/m**2.K
Q = (hL*h*(Tsat-T))/1000; #Heat transfer rate per unit width in kW/m
# Results
print 'Heat transfer rate per unit width is %3.2f kW/m'%(Q)
# note : rounding error.
```

In [13]:

```
# Variables
T = 100; #Temperature of dry steam in degree C
Do = 0.025; #Outer diameter of the pipe in m
Ts = 84; #Surface temmperature of pipe in degree C
Tf = (T+Ts)/2; #Film temperature in degree C
p1 = 963.4; #Density of liquid in kg/m**3
u = (306*10**-6); #Dynamic viscosity in N.s/m**2
hfg = 2257; #Enthalpy in kJ/kg
pv = 0.596; #Density of vapour in kg/m**3
k1 = 0.677; #Thermal conductivity in W/m.K
# Calculations
h = (0.725*((9.81*p1*(p1-pv)*k1**3*hfg*1000)/(u*(T-Ts)*Do))**0.25); #Heat transfer coefficient in W/m**2.K
q = (h*3.14*Do*(T-Ts))/1000; #Heat transfer per unit length in kW/m
m = (q/hfg)*3600; #Total mass flow of condensate per unit length in kg/h
# Results
print 'Rate of formation of condensate per unit length is %3.2f kg/h'%(m)
```

In [14]:

```
# Variables
m = 50; #Mass of vapour per hour
n = 100; #Number of tubes
D = 0.01; #Diameter of the tube in m
L = 1; #Length of the tube in m
n1 = 10; #Array of 10*10
# Calculations
mr = ((0.725/1.13)*(L/(n1*D))**0.25); #Ratio of horizontal and vertical position
mv = (m/mr); #Mass flow rate in the vertical position in kg/h
# Results
print 'Mass flow rate in the vertical position is %3.2f kg/h'%(mv)
```