ENVIRONMENTALLY FRIENDLY TECHNOLOGY
Absorption cooling cycle
The SANYO super absorption machine applies the same basic absorption
The absorption cycle operates in a vacuum. This permits the liquid refriger-
SUPER ABSORPTION
D. High temperature generator section
principles but enhances the cycle by adding additional heat exchangers and a second generator to recover all the available energy of the system and maximize the unit's COP (see Figure 2).
ant to boil at a lower temperature, transferring the latent heat of evaporation from the entering chilled water to cooling the chilled water.
Below is a component description of the absorption cycle with reference to the D¨uhring diagram shown in Graph 10 at page 16.
The diluted solution from the heat exchangers is heated by the burner or steam upon entering the high temperature generator and separates into re- frigerant vapor and intermediate solution (see Figure 6).
Line D' to E of Graph 10 shows the heating and concentration process in the high temperature generator. The diluted solution at point D' is heated at a
constant concentration to point D, where the refrigerant vapor is released and the solution becomes concentrated to 60.8% (point E, Graph 10). Following the intermediate solution, Line E to F' of Graph 10 shows heat transfer from the intermediate solution to the diluted solution in the high tem- perature heat exchanger (see Figure 5).
Figure 4. Lower shell
Liquid refrigerant
Concentrated solution
Chilled water outlet 
Chilled water inlet
Evaporator Absorber
E. Low temperature generator section
The refrigerant vapor from the high temperature generator passes through the heat transfer tubes of the low temperature generator (see Figure 7). The intermediate solution from the high temperature heat exchanger passes to the low temperature generator where it is heated by the refrigerant vapor. The heated intermediate solution releases additional refrigerant vapor and becomes concentrated to its final level. The condensed refrigerant in the heat transfer tubes and the refrigerant vapor of the low temperature genera- tor section then flows to the condenser.
Line F' to F to G of Graph 10 shows the concentrating process in the low
temperature generator. The intermediate solution enters the low tempera- ture generator and is heated by the refrigerant vapor from the high tempera- ture generator. Additional refrigerant vapor is released and the intermediate solution becomes concentrated into its final concentration level of 63.7% (point G, Graph 10).
Following the concentrated solution, Line G to A' of Graph 10 shows the process of temperature reduction in the low temperature heat exchanger by heat transfer to the diluted solution (Figure 5). Line A' to A shows the tem- perature reduction of the concentrated solution entering the absorber.
Diluted solution
Refrigerant pump |
|
Absorbent pump | Cooling water inlet |
Figure 6. High temperature generator
Exhaust gas
Refrigerant vapor
A. Evaporator section
Liquid refrigerant entering the evaporator is dispersed uniformly on the chilled water evaporator tubes (see Figure 4).
The low pressure of the evaporator causes the refrigerant to be boiled, thus
B. Absorber section
Concentrated solution entering the absorber is dispersed uniformly on the cooling water tubes (see Figure 4). The concentrated solution in the absorber section absorbs the refrigerant vapor from the evaporator section of the ves- sel.
Cooling water flowing through the absorber section heat transfer tubes ex- tracts the heat generated by this absorption process. The concentrated solu- tion, after absorbing the refrigerant vapor from the evaporator, becomes a diluted solution.
C. Low and high temperature heat exchangers
The diluted solution, after leaving the absorber section, passes through the low temperature heat exchanger (see Figure 5) where it is heated by the concentrated solution. The diluted solution then passes through the high tem- perature heat exchanger where it is further heated by intermediate solution. The intermediate and concentrated solutions are cooled by the diluted solu-
vaporizing the refrigerant and causing the latent heat of the vaporized refrig- erant to cool the chilled water.
Line A to B of Graph 10 describes the process in the absorber. The concen- tration of the lithium bromide solution entering the absorber section is 63.5% (all concentration levels and temperatures are approximate). The lithium bro- mide solution then absorbs the refrigerant vapor from the evaporator section and is cooled from 50° C to 37° C by the cooling water. This causes the bro- mide solution to become diluted and it then leaves the absorber at a concen- tration of 57.7% (point B, Graph 10).
tion. This cooling process of the concentrated solution allows for greater ab- sorbing power due to its lower temperature.
Line B to C to D' of Graph 10 shows the temperature rise of the diluted solution in the low and high temperature heat exchangers.
High temperature generator
Burner
Intermediate solution | Diluted solution |
Figure 5. Heat exchangers
Concentrated Intermediate
solutionsolution
Diluted solution
Low temperature | High temperature |
heat exchanger | heat exchanger |
12 | 13 |
