# Chapter 4 : principles of energy analysis¶

## Example 4.1 pg : 79¶

In [1]:

# Variables
m = 1.
he = 1148.8 			#B/lbm
hi = 1357. 			#B/lbm
Ve = 100. 			#ft/sec
Vi = 800. 			#ft/sec

# Calculations
dW =  m*(he-hi) + m*(Ve**2 - Vi**2)/(2*32.2*778)
dWhr = dW*3600
hp = -dWhr/2545.

# Results
print "Horsepower output  =  %d hp"%(hp+1)

Horsepower output  =  313 hp


## Example 4.2 pg:79¶

In [2]:

# Variables
rate = 80. 			#lbm/min
T1 = 100. 			#F
P1 = 100. 			#psia
P2 = 1000. 			#psia

# Calculations
v = 0.01613 			#ft**3/lbm
W = rate*(P2-P1)*144*v

# Results
print "Work done  =  %.2f ft-lbf/min"%(round(W,-3))

Work done  =  167000.00 ft-lbf/min


## Example 4.3 pg : 81¶

In [3]:

# Variables
hi = 1279.1 			#B/lbm

# Calculations
u2 = hi
T2 = 564. 			#F

# Results
print "Temperature of steam  =  %d F"%(T2)

Temperature of steam  =  564 F


## Example 4.4 pg : 82¶

In [5]:

# Variables
import math
P1 = 20. 			#psia
P2 = 100. 			#psia
V = 3. 	    		#ft**3
T = 560. 			#R
ma = 0.289

# Calculations
ma = P1*V/(53.35*T)
Wa = -ma*53.35*T*math.log(P1/P2)
Qa = -Wa
Va2 = 3/5.
V2s = V-Va2
hi = 1279.1 			#B/lbm
T2s = 536. 			#F

# Results
print "Final temperature  =  %d F"%(T2s)

Final temperature  =  536 F


## Example 4.5 pg : 87¶

In [7]:
import math

# Variables
P1 = 200. 			#psia
P2 = 100. 			#psia
T1 = 300.+460 			#R
g = 1.4
cp = 0.24

# Calculations
T2 = (T1)*(P2/P1)**((g-1)/g)
V2 = math.sqrt(2*32.2*778*cp*(T1-T2))

# Results
print "Final velocity   =  %d ft/sec"%(V2)


Final velocity   =  1281 ft/sec


## Example 4.6 pg : 88¶

In [8]:

# Variables
T1 = 500.+460 			#R
P1 = 50. 			#psia
P2 = 15. 			#psia
g = 1.4
cp = 0.24

# Calculations
T2 = T1*(P2/P1)**((g-1)/g)
W = cp*(T2-T1) + (T1-460)**2 /(2*32.2*778)

# Results
print "Net work output from turbine  =  %.1f B/lbm"%(W)

Net work output from turbine  =  -62.1 B/lbm


## Example 4.7 pg : 91¶

In [9]:

# Variables
T1 = 150.+460 			#R
T1 = 40.+460 			#R

# Calculations
h2 = 43.850 			#B/lbm
hf2 = 17.273
hfg2 = 64.163
x2 = (h2-hf2)/hfg2

# Results
print "Quality of freon vapor  =  %.3f"%(x2)

Quality of freon vapor  =  0.414