period two
Absorption Chiller Types
to the absorber reduces the flow rate of cooling water required through the absorber.
The chiller shown in Figure 27 is steam-fired and includes an additional heat exchanger. This condensate heat exchanger transfers heat from the hot condensed steam, leaving the high-temperature generator, to the cooler intermediate solution returning to the high-temperature generator. Notice that this heat exchanger is in parallel with the high-temperature heat exchanger and only a portion of the intermediate solution passes through each one. Again, a double-effect absorption chiller operating with hot water would not include the condensate heat exchanger.
The precooled, concentrated solution leaving the high-temperature heat exchanger then mixes with the rest of the intermediate solution that is returning from the low-temperature generator, before traveling to the low-temperature heat exchanger.
| high-temperature | low-temperature |
| generator |
| generator |
| |
high-temperature 
generator pump
absorber
low-temperature generator pump | Figure 28 |
|
All double-effect absorption chillers are constructed from the same basic components: high-temperature generator, low-temperature generator, condenser, evaporator, absorber, two solution heat exchangers, and several pumps. There are, however, three common methods in which the solution can be circulated through the chiller: series, parallel, and reverse-series. The double-effect chiller used in the previous example employs the reverse-series flow cycle.
In a reverse-series flow cycle, the dilute solution leaving the absorber is pumped to the low-temperature generator, where it is partially concentrated. Part of this intermediate solution is then pumped to the high-temperature generator, where it is further concentrated. The remaining intermediate solution, leaving the low-temperature generator, is mixed with the concentrated solution, leaving the high-temperature generator, before returning to the absorber.
The reverse-series flow cycle requires two generator pumps. This, however, makes it easier to control in part-load conditions.
