In [1]:

```
import math
# Variables
T = 25.+273; # Temperature in degK
p = 1.; # Pressure in atm
Va = 18.9; # Molecular volume of water vapour in cm**3/gm-mol
Vb = 29.9; # Molecular volume of air in cm**3/gm-mol
Ma = 18.; # Molecular weight of water vapour in gm/mol
Mb = 29.; # Molecular weight of air in gm/mol
# Calculations
Dab = 0.0043*(T**1.5)*math.sqrt((1/Ma)+(1/Mb))/(p*(Va**(1./3)+Vb**(1./3))**2);
# Results
print "The diffusion coefficient is %.3f cm**3/sec "%(Dab);
```

In [2]:

```
import math
# Variables
T = 25.+273; # Temperature in degK
p = 1.; # Pressure in atm
Va = 96.; # Molecular volume of benzene in cm**3/gm-mol
Vb = 29.9; # Molecular volume of air in cm**3/gm-mol
Ma = 78.; # Molecular weight of benzene in gm/mol
Mb = 29.; # Molecular weight of air in gm/mol
# Calculations
Dab = 0.0043*(T**1.5)*math.sqrt((1/Ma)+(1/Mb))/(p*(Va**(1./3)+Vb**(1./3))**2);
# Results
print "The diffusion coefficient is %.3f cm**3/sec "%(Dab);
```

In [3]:

```
import math
# Variables
x = 0.1/12; # thickness of still air layer in ft
T = 77.+460; # temperature in degR
p = 1.; # Atmospheric pressure in atm
pa1 = 0.3; # Pressure of ammonia in still air in atm
pb1 = p-pa1; # pressure of air in atm
pa2 = 0; # pressure of ammonia in the absorption plane
pb2 = p-pa2; # pressure of air in absorption plane
# Calculations
pbm = (pb2-pb1)/(math.log(pb2/pb1)); # Logarithmic mean pressure
D = 0.914; # Diffusion coefficient for ammonia
R = 0.729; # Gas consmath.tant in ft**3-atm/lb-mole-degR
N = D*p*(pa1-pa2)/(R*T*x*pbm);
# Results
print "The amount of ammonia diffusing through the stagnant air is %.1f lb-mol/hr-ft**2"%(N);
```

In [5]:

```
import math
# Variables
ri = 3./96; # Inner radius of pipe in ft
ro = 1./24; # Outer radius of pipe in ft
Ca1 = 0.0003; # Concentration at the inner hose of pipe in lb-mol/ft**2
Ca2 = 0; # Concentration at the outer surface
# Calculations
D = 0.7*10**-5; # Diffusion coefficient of hydrogen in rubber in ft**2/hr
N = 2*math.pi*D*(Ca1-Ca2)/math.log(ro/ri); # Rate of diffusion in lb-mol/hr
# Results
print "The rate of diffusion iof hydrogen in rubber is %.2f*10**-8 lb-mole/hr"%(N*10**8);
# note : rounding off error.
```

In [6]:

```
import math
# Variables
u = 0.0437; # Vismath.cosity in lb/hr-ft
rho = 0.077; # Density in lb-ft**2
D = 0.992; # Diameter of pipe in ft
v = 4.*3600; # Velocity in ft/sec
L = 6./12; # Length of pipe parallel to direction of air flow in ft
p = 14.7; # Atmospheric pressure in psi
T = 460.+65; # Temperature in degR
# Calculations
# Heat transfer equation for laminar flow of a flat surface
Nre = L*v*rho/u; # Reynolds number
Ns = u/(rho*D); # Schimdt mumber
Nnu = 0.662*(Ns)**(1./3)*math.sqrt(Nre); # Nusselt number
hmc = Nnu*D/L; # Heat transfer coefficient
pv1 = 0.144; # Vapour pressure at 40% humidity
pv2 = 0.252; # Vapour pressure at saturation
pa1 = p-pv1; # Absolute pressure of air at 40% rel. humidity in psi
pa2 = p-pv2; # Absolute pressure of saturated air in psi
pbm = (pa1+pa2)/2; # Log mean pressure in psi
R = 1544.; # Universal gas consmath.tant in ft**3-psi/lbmol-degR
N = hmc*p*(pa1-pa2)*144/(R*T*pbm);
# Results
print "The amount of water evaporated per hour is %.4f lb mol/hr-ft**2"%(N);
```

In [7]:

```
# Variables
u = 0.047; # Vismath.cosity in lb/hr-ft
rho = 0.069; # Density in lb-ft**2
D = 0.992; # Diameter of pipe in ft
v = 7.5*3600; # Velocity in ft/sec
L = 2.; # Length of pipe parallel to direction of air flow in ft
M = 0.992; # Molecular weight
p = 14.696; # Atmospheric pressure in psi
T = 460.+65; # Temperature in degR
M = 29.; # molecular weight of air
M2 = 18.; # Molecular weight of water vapour
A = 4.; # Area of water surface in ft**2
# Calculations
# Heat transfer equation for laminar flow of a flat surface
Nre = L*v*rho/u; # Reynolds number
# Assuming the case that of a fluid flowing parallel to a flat plate , jm = 0.0039
jm = 0.0039;
Ns = u/(rho*D); # Schimdt mumber
Gm = v*rho/M; # Mole flow rate
pv1 = 0.672; # Vapour pressure at 40% humidity
pv2 = 0.600; # Vapour pressure at saturation
pa1 = p-pv1; # Absolute pressure of air at 40% rel. humidity in psi
pa2 = p-pv2; # Absolute pressure of saturated air in psi
pbm = (pa1+pa2)/2; # Log mean pressure in psi
hmp = jm*Gm/(pbm*144*Ns**(2./3)); # Heat transfer coefficient in lbmol/ft**2-hr-psi
N = hmp*(pv1-pv2)*144; # Mass transfer rate in lb mol/hr-ft**2
W = N*A*M2;
# Results
print "The amount of water evaporated per hour is %.3f lb mol/hr-ft**2"%(W);
```

In [8]:

```
import math
# Variables
u = 3.82*10**-7; # Vismath.cosity in lb-sec/ft**2
rho = 2.3*10**-3; # Density in lbsec**2/ft**4
A = 1.; # Area in ft**2
Cp = 0.24; # Specific heat capacity in abtu/lbm-degF
v = 4.*3600; # Velocity in ft/sec
k = 0.015; # Thermal conductivity in Btu/hr-ft-degF
p = 14.7; # Atmospheric pressure in psi
M = 29.; # Avg. molecular weight of air
T1 = 70.+460; # Temperature of still air in degF
T2 = 90.+460; # temperature of surface of water in degF
L = 1.; # For characteristic of 1 ft
D = 0.992; # Diffusivity in ft**2/sec
# Calculations
# Heat transfer equation for laminar flow of a flat surface
Ngr = 32.2*L**3*((T2/T1)-1)/(u/rho)**2; # Grasshops number
Npr = u*3600*Cp*32.2/k; # Prandtls number
Nnu = 0.75*(Ngr*Npr)**.25; # Nusselt number
h = Nnu*k/L; # Heat transfer coefficient
Ns = u*3600/(rho*D); # Schimdt mumber
hmc = h*D*(Ns/Npr)**0.25/k; # Heat transfer coe
pv1 = 0.18; # Vapour pressure at 40% humidity
pv2 = 0.69; # Vapour pressure at saturation
pa1 = p-pv1; # Absolute pressure of air at 40% rel. humidity in psi
pa2 = p-pv2; # Absolute pressure of saturated air in psi
pbm = (pa1+pa2)/2; # Log mean pressure in psi
R = 1544; # Universal gas consmath.tant in ft**3-psi/lbmol-degR
T = (T1+T2)/2; # Average temperature in degR
N = hmc*p*(pv2-pv1)*144/(R*T*pbm)*18; # mass transfer rate in lbmol/hr-ft**2
# Results
print "The amount of water evaporated per hour is %.4f lb mol/hr-ft**2"%(N);
```

In [10]:

```
# Variables
Td = 70.+460; # Dry bulb temperature in degR
Tw = 60.+460; # Wet bulb temperature in degR
a = 0.26; # Ratio of coefficients ie. h/hmw from table
L = 1059.9; # Latent heat Btu/lbmol
p = 14.7; # Atmospheric pressure in psi
pa = 0.259; # Partial pressure of water in psi
Ma = 18.; # Molecular weight of water vapour
Mb = 29.; # Molecular weight of air
# Calculations
Wwb = pa*Ma/(Mb*(p-pa)); # Absolte dry bulb humidity of air
Wdb = Wwb-(a*(Td-Tw)/L); # Absolte dry bulb humidity of air
# Results
print "The humidity of air at dry conditions is %.5f lbm/lbm of dry air"%(Wdb);
# rounding off error.
```

In [11]:

```
# Variables
v = 20.; # Velocity of air ammonia mixture in ft/sec
Npr = 0.72; # Prandtls number
Ns = 0.60; # Schimdt number
pbm = 14.7; # math.log mean pressure in psi
Mm = 29.; # Molecular weight of mixture
Mv = 17.; # Molecular weight of ammonia
Ma = 29.; # Molecular weight of air
Cp = 0.24; # specific heat capacity in Btu/lbm-degF
h = 8.; # Heat transfer coefficient
p = 1.; # Atospheric pressure in atm
# Calculations
hmp = h*Mv*(Npr/Ns)**(2./3)/(Cp*p*Ma); # Mass transfer coefficient based on pressure
# Results
print "The mass transfer coefficient based on pressure is %.1f lbm/hr-ft**2-atm"%(hmp);
```