Chapter 15: Refrigeration and Air Conditioning

Exa 15.1

In [1]:
#Estimate how much the temperature is lowered when the steam at 7 bar and 
#260C is throttled to 1.4 bar. What is the approximate Joule-Thomson 
#initialisation of variables
P= 7. 				#bar
P1= 1.4 			#bar
T= 260. 			#C
T1= 251. 			#C
h= 2974.9 			#J/gm
#CALCULATIONS
dT= T-T1 			#Change in Temp. 
Mj= dT/(P-P1) 		#Joule-Thomson coefficient
#RESULTS
print '%s %.2f' % ('Joule-Thomson coefficient (C/bar) = ',Mj)
raw_input('press enter key to exit')

Joule-Thomson coefficient (C/bar) =  1.61
press enter key to exit
Out[1]:
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Exa 15.2

In [2]:
#A vapor compression refrigiration system, using Refrigirant 12, works between
#n evaporator temperature of 10F and a condenser temp. of 110F. The pumping
#rate for the refrigrant is 180 lbm/hr. Determine (a) the refrigirating 
#effect, (b) the coefficient of performance,and (c) the capacity of refrigiration
#in tons
#initialisation of variables
T= 10. 						#F
T1= 110. 					#F
Pr= 180. 					#lbm/hr
h1= 78.335 					#Btu/lbm
h3= 33.531 					#Btu/lbm
h2= 91. 					#Btu/lbm
L= 12000. 					#Btu/hr per ton
#CALCULATIONS
h4= h3
QL= h1-h4 					#Refrigerating effect
W= h2-h1 					#Work done
COP= QL/W 					#Coffecient of performnance
C= QL*Pr/L 					#Capacity of refrigeration in tons
#RESULTS
print '%s %.2f' % ('Refrigerating effect (Btu/lbm) = ',QL)
print '%s %.2f' % (' \n Coffecient of performnance= ',COP)
print '%s %.2f' % (' \n Capacity of refrigeration in tons (ton) = ',C)
raw_input('press enter key to exit')

Refrigerating effect (Btu/lbm) =  44.80
 
 Coffecient of performnance=  3.54
 
 Capacity of refrigeration in tons (ton) =  0.67
press enter key to exit
Out[2]:
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