Modelling the absorption refrigeration cycle using partially miscible working fluids by group contribution methods

Abstract

The present study concerns the cycle performance modelling of a particular configuration of an absorption refrigeration machine based on phase separation as well as development of a strategy for computer aided design of absorbents. The model uses predictive methods based on the group contribution concept for the computation of the thermodynamic phase equilibria involved such as liquid–liquid and vapour–liquid as well as enthalpy–concentration diagrams. The proposed absorbents computer-aided design strategy is based on the exploration of a number of structural group combinations obtained from a selected set of functional groups, according to the chemistry laws. The model was tested on four different absorbent–refrigerant pairs reported in the literature, namely (benzyl ethyl amine–glycerol), (water–hexanoic acid), (water–2-hexanone) and (water–ethyl propionate) as well as on pairs where the absorbent compound is generated by the proposed absorbent design strategy and the refrigerant is water. The results show that quite good values of the coefficient of performance (COP) can be obtained, indicating that this cycle configuration is promising and energetically efficient, mainly due to hardware savings, i.e. absence of condenser. However, other working fluid combinations have to be tested using the proposed model.