Drafts Fans Blowers and Compressors

Example 10.1,Page 515

In [1]:
# Initialization of Variable
from math import pi
from math import atan, cos
from numpy import *
hb=29.0 #in of Hg
sg=0.491 #specific gravity
Ra=53.3
Ta=460+40.0 #R
Tg=540+460.0 #R
H=300 #ft
gam=62.4 #lb/cu ft

#calculations
pb=hb*sg*144
rhoa=pb/(Ra*Ta) #density
rhog=pb/(Ra*Tg) #density
dp=H*(rhoa-rhog)
D=dp/(gam)

#results
print "Theoretical draft in psf",round(dp,3)
print " Draft in ft H2O",round(D,3)

Theoretical draft in psf 11.541
 Draft in ft H2O 0.185

Example 10.2,Page 516

In [2]:
# Initialization of Variable
from math import pi
from math import atan, cos
from numpy import *
md=15.0 #lb per lb of coal
x=0.1
mss=1.0 #basis
rea=29.0 #in of Hg
sg=0.491
R=53.3
T=540+460.0 #R
V=25.0 #fps
gam=0.038 #lb/ft^3

#calculations
m=mss-mss*x+md
ms=m
rhog=rea*0.491*144/(R*T) #density
A=ms/(gam*V)

#results
print "stack area in sq ft",round(A,3)

stack area in sq ft 16.737

Example 10.3,Page 526

In [11]:
# Initialization of Variable
from math import pi
from math import atan, cos
from numpy import *
p=144*29*0.491 #psf
R=53.3
T=70+460.0 #R
gamw=62.4 #lb/ft^3
gama=0.073 #lb/ft^3
hw=3.0/12 #ft
hw2=3.5/12 #ft
hv=32.2 #ft/s^2
ms=9.0 #lb
g=32.2 #ft/s^2

#calculations
rhoa=p/(R*T)
hs=hw*gamw/gama
ht=hw2*gamw/gama
hv=ht-hs
V=sqrt(2*g*hv)
msv=ms*V*60.0
mm=msv*gama
airhp= ht*mm/33000.0

#results
print "Velocity head in ft of air",round(hv,3)
print " velocity of air in the duct in fps",round(V,3)
print " volume in cu ft per min",round(msv,3)
print " Mass flow rate in lb/min",round(mm,3)
print " Air horsepower in hp",round(airhp,3)
print "The answers in the textbook are a bit different due to rounding off error in the textbook Please use a calculator"

Velocity head in ft of air 35.616
 velocity of air in the duct in fps 47.893
 volume in cu ft per min 25861.99
 Mass flow rate in lb/min 1887.925
 Air hp in hp 14.263
The answers in the textbook are a bit different due to rounding off error in the textbook Please use a calculator

Example 10.4,Page 528

In [12]:
# Initialization of Variable
from math import pi
from math import atan, cos
from numpy import *
A2=9.0 #sq ft
p2=3.0/12 *62.4 #psf
p1=-1.0/12 *62.4 #psf
ms=20000.0 #cfm
A1=16.0 #sq ft
gam=0.075 #lb/ft^3
g=32.2 #ft/s^2
inp=17.0 #hp

#calculations
V2=ms/60 *1/A2
V1=ms/60 *1/A1
ht=(p2-p1)/gam +(V2**2 -V1**2)/(2*g)
airhp=ht*ms*gam/33000
eta=airhp/inp *100

#results
print "Total head in ft of air",round(ht,3)
print " Air horsepower in hp",round(airhp,3)
print " Effifciency in percent",round(eta,3)

Total head in ft of air 291.894
 Air hp in hp 13.268
 Effifciency in percent 78.047

Example 10.5,Page 532

In [13]:
# Initialization of Variable
from math import pi
from math import atan, cos
from numpy import *
n1=400.0 #rpm
mv1=10000.0 #lb
mv2=15000.0 #lb
h1=2.0 #in of water
hp1=4.0 #hp

#calculations
n2=mv2/mv1 *n1 #speed
h2=h1*(n2/n1)**2 #pressure height
hp2=hp1 *(n2/n1)**3 #power

#results
print  "The speed in rpm",round(n2,3)
print " The pressure in inch of water",round(h2,3)
print " Power in hp",round(hp2,3)

The speed in rpm 600.0
 The pressure in in of water 4.5
 Power in hp 13.5

Example 10.6,Page 546

In [8]:
# Initialization of Variable
from math import pi
from math import atan, cos
from numpy import *
m=100000.0 #lb/hr
p1=1.0 #psia
x=0.8
p2=14.7 #psia
t2=300.0 #F

#calculations
#"from table A3 and A2"
h2=1192.8 #Btu/lb
hf=69.7 #Btu/lb
hfg=1036.3 #Btu/lb
h1=hf+x*hfg
W=h2-h1
power=m*W
hp=power/2545.0

#results
print "Power required in hp",round(hp,3)

11554.42 Power required in hp

Example 10.7,Page 546

In [14]:
# Initialization of Variable
from math import pi
from math import atan, cos
from numpy import *
p1=14.7 #psia
t1=60.0 #F
p2=60.0 #psia
t2=440.0 #F
m=10.0 #lb/sec

#calculations
#"From mollier charts"
h2=216.3 #Btu/lb
h1=124.3 #Btu/lb
W21=h2-h1
power=W21*m
hp=power*3600/2545
cp=0.237
W212=cp*(t2-t1)
power2=W212*m
hp2=power2*3600.0/2545.0

#results
print "Power required in hp",round(hp,3)
print " Power required in hp",round(hp2,3)
print " Work done in Btu/lb",round(W212,3)

Power required in hp 1301.375
 Power required in hp 1273.933
 Work done in Btu/lb 90.06