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Absorption refrigeration systems operate using thermal energy. They use the principle of liquids evaporating already at low temperatures when pressure is reduced. This basic principle is demonstrated in the experimental unit ET 480 with the example of an ammonia-water solution with the ammonia acting as refrigerant.
In the evaporator the liquid ammonia evaporates and withdraws heat from the environment. To keep the evaporation pressure low, the ammonia steam in the absorber is absorbed by the water. In the next step, ammonia is permanently removed from the high concentration ammonia solution to prevent the absorption process from being halted. For this purpose, the high concentration ammonia solution is heated in a generator until the ammonia evaporates again. In the final step, the ammonia steam is cooled in the condenser to the base level, condenses and is returned to the evaporator. The low concentration ammonia solution flows back to the absorber. To maintain the pressure differences in the system, hydrogen is used as an auxiliary gas.
In process technology systems the resulting waste heat can be used for cooling. In small mobile systems, such as a camping refrigerator or minibar in a hotel, the required heat is generated electrically or by gas burner. Another benefit of absorption refrigeration systems is their silent operation.
ET 480 demonstrates the functional principle of an absorption refrigeration system with its main components: evaporator, absorber, boiler as generator with bubble pump, condenser. The boiler can alternatively be operated with gas or electrically. Another electric heater at the evaporator generates the cooling load.
Temperatures in the refrigeration circuit and the heating power at the boiler and at the evaporator are recorded and displayed digitally.
The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.
Learning Objectives / Experiments
- demonstrate the basic principle of an absorption refrigeration system
- absorption refrigeration system and its main components
- operating behaviour under load
 operation of an absorption refrigeration system
 main system components: evaporator, absorber, boiler with bubble pump, condenser
 ammonia-water solution as working medium, hydrogen as auxiliary gas
 boiler to separate ammonia
 bubble pump for transportation in the circuit
 adjustable electrical heater at the evaporator serves as cooling load
 boiler is alternatively heated by electrical heater or gas burner
 piezoelectric igniter for gas operation
 digital displays for temperature and power
Working medium: ammonia-water solution
Auxiliary gas: hydrogen
Electric heater: 125W
Gas burner, adjustable: propane gas
Evaporator heater, adjustable: 50W
- temperature: 4x -80...180°C
- power: 0...150W
Dimensions and Weight
Weight: approx. 47kg Required for Operation
230V, 50/60Hz, 1 phase or 120V, 60Hz/CSA, 1 phase; Propane gas: 30...50mbar
Scope of Delivery
1 experimental unit
1 pressure reducer
1 set of instructional material