In [ ]:

```
#In a dew point apparatus a metal beaer is cooled by gradually adding ice water
#to the water initally in the beaker at room temp. The moisture from the room
#circulating around the beaker beins to condense on the beaker when its temp
#is 70 F and the pressure is 15 psia, find (1) the partial pressure of water
#vapor in the room air and (2) the parts by mass of the same.
#initialisation of variables
P= 15.0 #psia
T= 55 #F
P1= 0.2141 #psia
ma= 29. #lb
mb= 18. #lb
P2= 0.2141 #psia
P3= 0.3631 #psia
#CALCULATIONS
dp= P-P1 #Change in pressure
r= (dp*ma)/(P1*mb) #parts by mass
r1= r/(r+1) #ratio
r2= 1/(r+1) #ratio
r4= r2/r1 #specific humidity
P= P2/P3 #relative humidity
#RESULTS
print '%s %.2f' %('relative humidity= ',P)
print '%s %.4f' %(' \n specific humidity (lb vapour/lb air) = ',r4)
raw_input('press enter key to exit')
```

In [1]:

```
#Air supplied to a furnacce has RH 75%, T=80 F and P=10 in of water. The
#barometer reads 29.5 in of mercury. How many pounds of water vapor enter
#the furnace per pound of dry air?
#initialisation of variables
h= 29.5 #in
n= 75.
T= 80 #F
h1= 10 #in
mw= 0.380*18
ma= 14.47*29
d= 13.6 #kg/m^3
P= 0.5069 #psi
#CALCULATIONS
Pw= (n/100.)*P #partial pressure
P= (h+(h1/d))*(0.491) #Total pressure
pa= P-Pw #partial pressure of air
r= mw/ma # pounds of water
#RESULTS
print '%s %.4f' %('Pounds of water vapour enter the furnance per pound of dry air (lb vapour/lb air) = ',r)
raw_input('press enter key to exit')
```

Out[1]:

In [2]:

```
#A mixture of air and water vapor at 75 F and 14.7 psia has RH 0.5; find its
#specific humidity and its dew-point temp.?
#initialisation of variables
n= 0.5
T= 75 #F
P= 14.7 #psia
pg= 0.4298 #psia
pw= 0.2149 #psia
#CALCULATIONS
pw1= n*pg #partial pressure of water
pa= P-pw1 #partial pressure of air
r= 0.622*pw/pa #RH
#RESULTS
print '%s %.5f' %('relative humidity (lb water/lb dry air) = ',r)
```

In [3]:

```
#In the process shown, the air is received at 1 atm, 40 F and Rh 60% and it is
#desired to discharge it at 70 F, RH 50%. How much water at 45F must be supplied
#per pound of dry air passing through the apparatus?
#initialisation of variables
r2= 0.0078 #lb water /lb dry air
r1= 0.0032 #lb water /lb dry air
h2= 25.33 #Btu/lb
h1= 12.9 #Btu/lb
pg= 0.1217 #psia
p= 14.7 #psia
h3= 13 #Btu/lb
n= 60.
t2=70.
t1=40.
cpa=0.240
R2= 0.00788 #lb/lb of dry air
w1= 0.00477 #lb/lb of dry air
#CALCULATIONS
print '%s' %('Method 1')
w= r2-r1 #water to be supplied
q= h2-h1-w*h3 #energy supplied
print '%s %.2f' %('\n In method 1, Enthalpy (Btu/lb of dry air) = ',q)
print('\n Method 2')
R1= 0.622*(n/100.)*(pg/(p-pg)) #Gamma 1
R2=0.00788 #Gamma 2
w2=R2-R1 #weight 2
#All constants are obtained from steam tables
Q=cpa*(t2-t1)+R2*(1092.6)-R1*(1079.6) -w2*h3
print '%s %.2f' %('In method 2, Enthalpy (btu/lb of dry air) = ',Q)
raw_input('press enter key to exit')
```

Out[3]:

In [4]:

```
#Air at 1 am,75F,70% relative humidity is to be brought to 70 F and 60 % RH
#. To what temp. must the mixture be cooled?How much heat must be removed by
#the cooling coil and how much be supplied by the heatin coil per pound of dry
#air?what fraction of the heat removed in the cooling coil is required to cool
#and condense the water removed?
#initialisation of variables
P= 1. #atm
n= 70.
T= 75 #F
T1= 70 #F
Td=55.3 #F
r1= 0.0131 #lb water/lb dry air
r2= 0.0093 #lb water/lb dry air
h1= 32.36 #Btu/lb dry air
h2= 27.03 #Btu/lb dry air
hd2= 23.40 #Btu/lb dry air
hf= 23.4 #Btu/lb dry liquid
hg= 1094.5 #Btu/lb dry liquid
#CALCULATIONS
R1= r1-r2 #Gamma 1
Qc= hd2-h1+R1*hf #Cooling
Qh= h2-hd2 #Heating
x= R1*(hg-hf) #Mole fraction
y= x/(-Qc) #fraction of heat removed
#RESULTS
print '%s %.2f' %('The mixture must be cooled to the dew point temperature (F) = ',Td)
print '%s %.2f' %('Heat removed by the cooling coil (Btu/lb dry air)= ',Qc)
print '%s %.2f' %('Heat supplied by the heating coil (Btu/lb dry air)= ',Qh)
print '%s %.2f' %('Fraction of heat removed in the coil = ',y)
raw_input('press enter key to exit')
```

Out[4]: