Adsorption (AD) Technology - Cooling

In the adsorption technology, water is used as the refrigerant, and silica gel as the adsorbent within the system.

The machines consist of two compartments; namely the evaporator and condenser. While the adsorbent (silica gel) in the first compartment is regenerated using hot water (heated with waste heat/solar energy), the adsorbent in the second compartment adsorbs the water vapour entering from the evaporator. The second compartment is then cooled to enable a continuous adsorption. Due to the low pressure condition in the evaporator, the refrigerant in the evaporator is transferred into the gas phase by taking up the evaporation heat from the chilled water loop and thus producing the useful chilling effect. If the adsorbent in the adsorption compartment is saturated with water vapour, the chambers are then switched over in their respective functions.

Absorption (AB) Technology - Cooling

Similar to AD chiller, the AB Chiller also makes use of water as the refrigerant, but lithium bromide as the absorbent. The key difference between the AD & AD chillers is the absorbent used. Although the lithium bromide solution is relatively inexpensive, it is highly corrosive and its disposal has to be closely controlled.

The main components of an absorption chiller are the generator, the condenser, the evaporator and the absorber. The cooling effect is based on the evaporation of the refrigerant (water) in the evaporator at very low pressure. The vaporised refrigerant is absorbed in the absorber, thereby diluting the H2O/LiBr solution. The solution is continuously pumped into the generator, where the regeneration of the solution is achieved by applying the driving heat such as from hot water supplied by a solar collector. The refrigerant leaving the generator by this process condenses through the application of cooling water in the condenser and circulates by means of an expansion valve again into the evaporator.

Adsorption (AD) vs Absorption (AB) Technology