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TRG-TRC011-EN 17
period one
Absorption Refrigeration Cycle
notes
Starting at the absorber, the dilute lithium bromide solution leaves the absorber
($) at 105°F [40.6ºC] and 59% concentration. This solution passes through the
heat exchanger, where it is preheated to 175°F [79.4°C] (%). (Notice that there is
no change in concentration as the solution passes through the heat exchanger.)
In the generator, the solution absorbs heat from the steam or hot water flowing
through the tubes. Initially, this only sensibly heats the solution to &, that is, the
temperature of the solution increases while the concentration stays the same.
At this point, the refrigerant begins to boil (vaporize) and separate from the
solution. This increases the concentration of the lithium bromide solution as the
temperature continues to increase (').
The concentrated solution ('), now at 215°F [101.7ºC] and 64.5%, passes
through the heat exchanger where it is cooled to 135°F [57.2ºC] ((). This cooled,
concentrated solution (() is then mixed with dilute solution from the absorber
($), and this intermediate solution ()) (118°F [47.8ºC] and 62% concentration) is
pumped to the absorber spray trees. In the absorber, refrigerant vapor is
absorbed by the intermediate solution, decreasing its concentration to 59%,
while heat is transferred to the cooling water. The resulting cooled, dilute
solution ($) returns to the generator to repeat the cycle.
This chart also can be used to demonstrate the operating pressures of the cycle.
In this example, the low-pressure sections of the cycle are operating at
approximately 0.15 psia [1.034 kPa], and the high-pressure sections are
operating at approximately 1.5 psia [10.34 kPa].
6
5
6
5
6
0
6
0
5
5
5
5
5
0
5
0
4
0
4
0
50°F
50°F
[10°C]
[10°C]
100°F
100°F
[37.8°C]
[37.8°C]
150°F
150°F
[65.6°C]
[65.6°C]
200°F
200°F
[93.3°C]
[93.3°C]
$
$
%
%
&
&
'
'
(
(
)
)
15
15
psia
psia
[103.4
[103.4
kPa
kPa
]
]
5
5
psia
psia
[34.5
[34.5
kPa
kPa
]
]
1
1
psia
psia
[6.9
[6.9
kPa
kPa
]
]
0.1
0.1
psia
psia
[0.69
[0.69
kPa
kPa
]
]
LiBr
LiBr
solution
solution
v
a
p
o
r
p
r
e
s
s
u
r
e
v
a
p
o
r
p
r
e
s
s
u
r
e
concentration
concentration
concentration
solution temperature
solution temperature
1.5
1.5
psia
psia
[10.3
[10.3
kPa
kPa
]
]
Figure 20