Chapter 15 - Vapor cycles and processes

Example 1 - Pg 276

In [1]:
#calculate the Thermal efficiency and Furnace efficiency
#Initialization of variables
p1=600. #psia
p2=0.2563 #psia
t1=486.21 #F
t2=60. #F
fur=0.75
#calculations
print '%s' %("from steam tables,")
h1=1203.2
hf1=471.6
hfg1=731.6
h2=1088
hf2=28.06
hfg2=1059.9
s1=1.4454
sf1=0.6720
sfg1=0.7734
s2=2.0948
sf2=0.0555
sfg2=2.0393
xd=(s1-sf2)/sfg2
hd=hf2+xd*hfg2
xa=0.3023
ha=hf2+xa*hfg2
wbc=0
wda=0
wcd=h1-hd
wab=ha-hf1
W=wab+wcd+wbc+wda
Wrev=hfg1- (t2+459.7)*sfg1
etat=(t1-t2)/(t1+459.7)*100
eta=fur*etat
#results
print '%s %d %s' %("Thermal efficiency =",etat,"percent")
print '%s %.1f %s' %("\n Furnace efficiency =",eta," percent")

from steam tables,
Thermal efficiency = 45 percent

 Furnace efficiency = 33.8  percent

Example 2 - Pg 277

In [2]:
#calculate the Thermal and Overall efficiency
#Initialization of variables
dhab=-123.1
etac=0.5
ha=348.5
etaf=0.75
eta=0.85
hf=471.6
hfg=731.6
hc=1203.2
dhcd=452.7
#calculations
dwabs=dhab/etac
hbd=ha-dwabs
dwcds=dhcd*eta
dqa=hc-hbd
etat=(dwcds+dwabs)/dqa*100.
eta=etat*etaf
#results
print '%s %.1f %s' %("Thermal efficiency =",etat," percent")
print '%s %.1f %s' %("\n Overall efficiency = ",eta," percent")

Thermal efficiency = 22.8  percent

 Overall efficiency =  17.1  percent

Example 3 - Pg 277

In [3]:
#calculate the Thermal and Overall efficiency
#Initialization of variables
t=60 #F
J=778.16
p1=600 #psia
p2=0.2563 #psia
etaf=0.85 
#calculations
print '%s' %("From steam tables,")
vf=0.01604 #ft^3/lbm
dw=-vf*(p1-p2)*144/J
ha=28.06 #Btu/lbm
hb=29.84 #Btu/lbm
hd=1203.2 #Btu/lbm
he=750.5 #Btu/lbm
dqa=hd-hb
dqr=ha-he
dw=dqa+dqr
dwturb=hd-he
dwpump=ha-hb
etat=dw/dqa*100.
eta=etat*etaf
#results
print '%s %.1f %s' %("Thermal efficiency =",etat," percent")
print '%s %.1f %s' %("\n Overall efficiency =",eta,"percent")
    

From steam tables,
Thermal efficiency = 38.4  percent

 Overall efficiency = 32.7 percent

Example 4 - Pg 278

In [4]:
#calculate the Thermal and Overall efficiency
#Initialization of variables
dhab=-1.78
etac=0.5
ha=28.06
eta=0.85
hf=471.6
hfg=731.6
hd=1203.2
dhcd=452.7
#calculations
dwabs=dhab/etac
hbd=ha-dwabs
dwcds=dhcd*eta
dqa=hd-hbd
etat=(dwcds+dwabs)/dqa*100.
eta=etat*eta
#results
print '%s %.1f %s' %("Thermal efficiency =",etat,"percent")
print '%s %.1f %s' %("\n Overall efficiency =",eta,"percent")

Thermal efficiency = 32.5 percent

 Overall efficiency = 27.7 percent

Example 5 - Pg 287

In [5]:
#calculate the thermal efficiency
#Initialization of variables
p2=600 #psia
p1=44 #psia
te=486.21 #F
tb=273.1 #F
J=778.16
p3=0.25 #psia
#calculations
hc=241.9
hj=834.6
y=1-0.805
v1=0.0172
v2=0.016
ha=28.06
hd=hc+v1*(p2-p1)*144/J
hb=ha+v2*(p1-p3)*144/J
hh=1374
Qa=hh-hd
Qr=(ha-hj)*(1-y)
etat=(Qa+Qr)/Qa*100.
#results
print '%s %.1f %s' %("thermal efficiency =",etat,"percent")

thermal efficiency = 42.6 percent