Chapter 23 - Gas Vapor mixtures

Example 1 - Pg 505

In [1]:
#calculate the specific humidity
#Initalization of variables
pv=0.3631 #psia
pa=14.7 #psia
cp=0.24
tw=70 #F
td=80 #F
hv1=1096.6 #Btu/lb
hfb=38.06 #Btu/lb
#calculations
sh=0.622*pv/(pa-pv)
sh1=(cp*tw -cp*td + sh*1054.3)/(hv1-hfb)
#results
print '%s %.5f %s' %("Specific humidity =",sh1," lb/lb")

Specific humidity = 0.01342  lb/lb

Example 2 - Pg 509

In [2]:
#calculate the relative humidity
#Initalization of variables
rel=0.9
p1=0.0396 #psia
p2=0.3631 #psia
#calculations
act=rel*p1
RH=act/p2 *100.
#results
print '%s %.1f %s' %("Relative humidity =",RH," percent")

Relative humidity = 9.8  percent

Example 3 - Pg 509

In [3]:
#calculate the final temperature
#Initalization of variables
pa=14.2
rel=0.9
sh=0.012 #lb/lb
#calculations
pv=(pa*sh)/(0.622-sh)
sat=pv/rel
tf=64.34 #F
#results
print '%s %.2f %s' %("From steam tables, by interpolation, Final temperature =",tf," F")

From steam tables, by interpolation, Final temperature = 64.34  F

Example 4 - Pg 509

In [4]:
#calculate the heat rate addition per min
#Initalization of variables
pa=14.7
pv=0.0356
pv2=0.04
cp=0.24
t1=70 #F
t2=15 #F
R=53.35
V=8000 #ft^3
#calculations
sh=0.622*pv/(pa-pv2)
hm2=cp*t1+ sh*1092.3
hm1=cp*t2+sh*1068.4
Q=hm2-hm1
m=144*(pa-pv2)*V/(R*(t2+460.))
Q2=Q*m
#results
print '%s %d %s' %("Heat added per min =",Q2,"Btu/min")
print '%s' %("The answer is a bit different due to rounding off error in the textbook")

Heat added per min = 8821 Btu/min
The answer is a bit different due to rounding off error in the textbook

Example 5 - Pg 511

In [5]:
#calculate the Temperature
#Initalization of variables
rel=0.45
p1=0.4747 #psia
print '%s' %("From steam table data,")
#calculations
act=rel*p1
t2=54.94 #F
#results
print '%s %.2f %s' %("Temperature =",t2,"F")

From steam table data,
Temperature = 54.94 F

Example 6 - Pg 511

In [6]:
#Calculate the tonnage
#Initalization of variables
rel=0.6
p1=0.6982 #psia
pa=14.7 #psia
t1=90 #F
t2=54.94 #F
cp=0.24
p2=0.2136 #psia
vol=4000 #ft
t3=538 #R
R=53.35
#calculations
act1=rel*p1
sh1=0.622*act1/(pa-act1)
hm1=cp*t1+sh1*1100.9
sh2=0.622*p2/(pa-p2)
hm2=cp*t2+sh2*1085.8
con=sh1-sh2
enth=con*23.01
heat=hm1-hm2-enth
mass=144*(pa-p2)*vol/(R*(t3))
tonnage=mass*heat/200
#results
print '%s %.1f %s' %("Tonnage =",tonnage,"tons ")

Tonnage = 26.6 tons

Example 7 - Pg 514

In [7]:
#calculate the tonnage
#Initalization of variables
p1=0.541 #psia
rel=0.48
pa=14.7 #psia
t1=82 #F
cp=0.24
m1=0.75 #lb
m2=0.25 #lb
hm4=23.15 #Btu/lb
mass=291 #lb
#calculations
p2=rel*p1
sh=0.622*p2/(pa-p2)
hm1=cp*t1 + sh*1097.5
hm2=m1*hm1
hm3=m2*41.67
heat=hm2+hm3-hm4
tonnage=heat*mass/200
#results
print '%s %.2f %s' %("Tonnage =",tonnage," tons")

Tonnage = 16.35  tons

Example 8 - Pg 516

In [8]:
#calculate the volume of entering air and amount of make up water
#Initalization of variables
ce=0.8
t1=115 #F
tc=75 #F
td=85 #F
pa=14.7 #psia
p1=0.43 #psia
p2=0.9492 #psia
m1=159600
m2=31.65
R=53.35
T=545 #R
#calculations
t2=t1-ce*(t1-tc)
Pv=0.4298- (pa-p1)*(td-tc)/(2800- 1.3*tc) 
sh1=0.622*Pv/(pa-Pv)
sh2=0.622 *p2/(pa-p2)
mda=m1/m2
V=mda*R*T/(144*(pa-Pv))
amount=mda*(sh2-sh1)
#results
print '%s %d %s' %("Volume of entering air =",V,"cfm")
print '%s %.1f %s' %("\n Amount of make up water =",amount,"lb/min")
print '%s' %('The answers are a bit different due to rounding off error in textbook')

Volume of entering air = 71087 cfm

 Amount of make up water = 134.0 lb/min
The answers are a bit different due to rounding off error in textbook