Abstract

A district cooling system (DCS), that generally operates with vapor compression refrigeration (VCR) chillers, is superior to conventional air conditioning as it helps to reduce energy consumption and to protect the environment by reducing carbon dioxide emissions. The advantages of the district cooling plant can be further enhanced by integrating the VCR system with a vapor absorption refrigeration system (VAR). In this context, this paper presents the comparative assessment of a VCR chiller and two configurations of an integrated VCR and VAR chiller, consisting of the parallel and the cascade configuration. Two refrigerant-absorbent mixtures in the VAR system are considered, namely the conventional NH3/H2O and the novel acetaldehyde/N,N-dimethylformamide (Acet/DMF). The energy, exergy, environmental and economic analysis of the systems have been performed considering the coefficient of performance (COP), the exergy efficiency (ηexergy), the total equivalent warming impact (TEWI) and the cost rate (Ċtot) as performance indicators. It is observed that the connection of the evaporator of the VAR with the condenser of the VCR in the cascade configuration increases the COP of the VCR unit by 292% compared to the stand-alone VCR system. Overall, the COP of the parallel and the cascade refrigeration system with the novel Acet/DMF is better than that of NH3/H2O. This performance can further be improved by enhancing the exergy efficiency. Overall, the thermodynamic, environmental and cost benefits of the novel Acet/DMF with the cascade arrangement of the VCR and the VAR system are superior to those of NH3/H2O.

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