# Chapter 5 The first law and the dynamic open system¶

## Ex:5.2 Pg:105¶

In [1]:
## Initialization of variables
rate= 5 #lbm/sec
Q=50 #Btu/s
h2=1020 #Btu/lbm
h1=1000 #Btu/lbm
V2=50 #ft/s
V1=100 #ft/s
J=778
g=32.2 #ft/s**2
gc=g
Z2=0
Z1=100 #ft
#calculations
dw=Q/rate -(h2-h1) -(V2**2- V1**2)/(2*gc*J) -g/gc *(Z2-Z1)/J
power=dw*rate
#results
print "work done by the system = %.1f Btu/lbm"%(dw)
print "\n Power = %.1f Btu/s"%(power)

work done by the system = -9.7 Btu/lbm

Power = -48.6 Btu/s


## Ex:5.3 Pg:106¶

In [4]:
#Initialization of variables
V=100.0 #ft/s
v=15 #lbm/ft**3
m=5 #lbm/s
#calculations
A=m*v/V
#results
print "Area of inlet pipe = %.2f ft**2"%(A)

Area of inlet pipe = 0.75 ft**2


## Ex:5.4 Pg:106¶

In [5]:
#Initialization of variables
P=100.0 #psia
#calculations
print "From table B-4"
h=1187.2 #Btu/lbm
t1=328 #F
t2=540 #F
dt=t2-t1
#results
print "Final temperature of the steam = %d F"%(t2)
print "\n Change in temperature = %d F"%(dt)

From table B-4
Final temperature of the steam = 540 F

Change in temperature = 212 F