Michihiko Aizawa

Development of an Air Cooled Double Effect Absorption Chiller Heater

Double effect absorption chiller heaters have become popular and they now represent the majority of air conditioners in large scale buildings. Their absorbers and condensers are water cooled. However, there is a strong need to elimitate the cooling water. It is extremley difficult to realize an air cooled double effect absorption chiller with a water-lithium bromide pair working medium because of the increasing cooling temperature that leads to crystallization of the lithium bromide and an increasing cycle pressure. This paper describes our development to overcome these difficulties. The key factor is an air cooled absorber that consists of vertical absorbing tubes and air cooled fins installed outside the tubes. The absorbent solution flows down 4-paths in the absorber. By using an absorber of this type, we achieved an air cooled absorption refrigeration cycle that is the same as the conventional water cooled type. The cooling capacity of the prototype is 14kW and its COP is 0.9 when the ambient air temperature is 35°C, and the chilled water outlet temperature 7°C.