Absorption Refrigeration Systems

Absorption Refrigeration Systems Two main absorption systems are used in industrial application lithium bromide-water and ammonia-water. Lithium bromide-water systems are hmited to evaporation temperatures above freezing because water is used as the refrigerant, while the refrigerant in an ammonia-water system is ammonia and consequently it can be applied for the lower-temperature requirements. 

Steam and cooling water requirements for ammonia absorption refrigeration systems are shown in Table 1 for single-stage and two-stage units. The tables are based upon cooling water to the condenser of 85°F with 100°F condensing temperature. Water from the condenser is used in the absorbers. 

Steam and Cooling Water Required for Ammonia Absorption Refrigeration Systems... 

Figure 11-18. Lithium bromide absorption refrigeration system concept water is the refrigerant. Actual commercial and industrial process flows reflect various heat recovery arrangements.

Figure 11-19. Lithium bromide hermetic absorption refrigeration system, double effect, liquid chiller/heater. As shown in chilling mode, water is the refrigerant under low absolute pressure (boiling at 40°F) (Used by permission Cat. 521-606, form 16DF-1 PD, 1994. Carrier Corporation, a United Technologies Company.)...

The thermal compression or absorption refrigeration systems are less common. They do not require a compressor. Their energy source is steam, natural gas, or waste heat. This system requires much more cooling water than the previous one, but may be economical if a large amount of waste heat is available.21 See references 20 and 21 to determine heat and cooling water requirements. 

Absorption refrigeration systems (ARS), 21 550-552 advantages of, 21 551 industrial and domestic use of, 21 552 Absorption separation systems, design of, 20 751... 

How does an absorption refrigeration system differ from a vapor compression refrigeration system ... 

Another kind of absorption refrigerant system employs aqueous lithium bromide as absorbent and circulating water as the refrigerant. It is used widely for air conditioning systems, in units of 600-700 tons producing water at 45°F. 

In a vapor-absorption refrigeration system, there are no moving parts. The added energy comes from a gas or liquid fuel burner or from an electrical heater, as heat. rather than from a compressor, as work. See Fig. 2. The refrigerant used in this example is ammonia gas. which is liberated from a water solution and transported from one region to another by the aid of hydrogen, The total pressure throughout the system is constant and therefore no valves axe needed. 

The most commonly used absorption-refrigeration system operates with water as the refrigerant and a lithium bromide solution as the absorbent. This system is obviously limited to refrigeration temperatures above the freezing point of water. It is treated in detail by Perry and Green.t For lower temperatures the usual system operates with ammonia as refrigerant and water as the solvent. 

Alien a process requires temperatures lower than those attainable by cooling water (less than 10(FF), refrigeration must be used. Most refrigeration systems use compression refrigeration, but occasionally absorption refrigeration systems are employed if an inexpensive low-level heat source is available. 

ABSORPTION REFRIGERATION SYSTEM - One in which the refrigerant, as it is absorbed in another liquid, maintains the pressure difference needed for successful operation of the system. 

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