Installation year



Nominal capacity


 16 kW

Cooling capacity


 20 kW

Thermal COP


 COP = 1.1

Adsorption material



Hot water inlet temperature



Heat driven chillers produce chilled water, which can be distributed in local air conditioning units or can be used in central air conditioning units. The technology used by heat driven chillers is called absorption or adsorption.

The absorption chillers are usually installed in small hotels, office buildings and hospitals. Ideally, the thermal energy required for the regenerator unit can be produced by renewable energy sources, such as waste recovery or solar thermal systems.

The difference between double effect and single effect absorption chillers is the thermal efficiency of the process and the temperature of the chilled water produced. Specifically, double effect chillers can produce water of much lower temperature and have greater thermal COPs. However, they require much higher inlet temperature of hot water and therefore, the potential use of renewable energy sources is limited.

The double effect absorption chiller installed at the premises of the Laboratory serves research and educational purposes. Mathematical models have been developed that simulate the chiller performance. Experimental data from the installation has been used for the model validation.   










Operational principle

This unit uses lithium bromide LiBr as absorbent material, water as refrigerant and natural gas as the heat source. In the evaporator, the pressure is substantially lower than the pressure in the condenser. As the water flows into the evaporator, it boils on the surface of the chilled water coil. The latent heat is removed from the recirculating water, which is chilled to 5°C. The water vapor flows to the absorber. There, the water is absorbed by the concentrated LiBr solution, as it flows down the surface of the absorber coil. Heat of condensation and dilution are removed by the cooling water. The dilute LiBr solution is preheated through the heat exchanger before returning to the high temperature generator. There, the gas burner heats the dilute LiBr solution and the produced water vapor is driven to the separator. The semiconcentrated solution is precooled and then flows to the low-temperature generator. There, hot water vapor from the separator heats the semiconcentrated solution. Water vapor flows then to the condenser, while the concentrated solution flowis again to the absorber. In the condenser, water vapor is condensed on the surface of the cooling coils and latent heat is rejected to a cooling tower. Water is then driven into the evaporator.