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1.
Principle of Absorption Chiller-heater
1.1 Vacuum
The earth on which we are living is compressed by the weight of air layer surrounding the earth
approximate 10km above. It is called the atmospheric pressure and the lower pressure than the
pressure is called vacuum.
To talk about vacuum in absorption chiller-heater, it is necessary to know the relation between the
pressure and the water evaporating temperature. It is well
the air pressure is over the atmospheric pressure and it also evaporates at less than 100 ℃ in
vacuum. The higher pressure than the atmospheric pressure can be confirmed by boilers and the
drop of evaporating temperature can be confirmed by climbing up a high mountain. For example,
water boils at about 89 ℃ at the top of Mt. Fuji so that rice cannot be cooked well. Thus, the lower
the pressure or in vacuum, at the lower temperature water boils or evaporates. The relation between
the pressure and water evaporating temperature is shown in Table 1.
Table-1 Pressure & Saturation Temperature
Gauge
pressure
kg/㎠ (atg)
Over
20
atmosphere
10
8
5
1
0
Atmosphere
Vacuum
1.2 Principle of Absorption Chiller-heater
The absorption chiller-heater is a machine to produce chilled water and hot water by using heat such
as steam, hot water, gas, oil and so on, and by using pure water as refrigerant and lithium bromide
solution as absorbent.
There are two kinds of absorption chillers, single-effect absorption chiller and double-effect
absorption chiller with two-stage heat exchangers (two generators) to increase heat efficiency and
reduce heating energy. However, there is no difference in its principle between the two absorption
chillers.
1.2.1 Reason why heating can produce chilled water
Chilled water is produced by the principle that liquid, which evaporates easily, absorbs heat from
surroundings when it evaporates.
For example, when alcohol is put on your arm, you feel cool on the part. It is because alcohol is
warmed by your body's heat to absorb the heat when it evaporates.
Absolute
Saturation
pressure
temperature
kg/㎠ (ata)
(℃)
21
213.86
11
183.20
9
174.53
6
158.09
2
119.61
760 mmHg
100.00
634.0
95
355.2
80
149.4
60
92.5
50
55.3
40
17.5
20
9.2
10
7.5
7
6.5
5
6.1
4
5.7
3
61
known that water boils at 100 ℃ when
Double effect steam pressure
Single effect steam pressure
(about 730 mmHg)
Pressure in condenser
(about 57 mmHg)
Pressure in evaporator
(about 6mmHg)
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