Thermodynamic study on absorption refrigeration systems using ammonia/ionic liquid working pairs

Identifier:  TDX:2392

Handle: https://hdl.handle.net/20.500.11797/TDX2392

Authors:  Ariyadi, Hifni Mukhtar

Abstract:
This thesis was aimed to analyse the feasibility and the performance of ionic liquids as an absorbent for ammonia refrigerant in absorption refrigeration systems. Ionic liquids, novel and tailor-made absorbents, can be used with ammonia as working pairs for absorption refrigeration cycles and give some advantages such as elimination of the rectification process in ammonia/water systems. The performances of several ammonia/ionic liquid mixtures working pair available in the literature were then theoretically studied and analysed for absorption refrigeration applications using selected NRTL model. In addition, new selected ammonia/ionic liquid mixtures working pair for absorption refrigeration applications were also theoretically studied and analysed. The results show that the coefficient of performance (COP) of the absorption systems working with ammonia/ionic liquid working fluids were about similar when compared with ammonia/LiNO3 at same cooling capacity and operation conditions. Among all of selected ammonia/ionic liquid working fluids studied in this thesis, only [N1113][NTf2] presented higher COP that that of ammonia/LiNO3 at certain operation conditions. The COP of the systems with other ionic liquids as absorbents follows an order of [EtOHmim][BF4] > [N111(2OH)][NTf2] > [EtOHmim][NTf2] at all operation conditions. Finally it can be concluded that the ionic liquid has a great potential to be an alternative absorbent for ammonia refrigerant. The ammonia/ionic liquid working fluid can provide competitive performance in comparison with conventional absorbent for ammonia refrigerant. However, some drawbacks were still remains to be solved such as relatively low solubility of ammonia into ionic liquids which affects to the solution circulation mass flow ratio and relatively high viscosity of ionic liquid in comparison with other conventional absorbent which may affects to the performance of absorber and solution pump.