Performance of a triple-pressure level absorption/compression cycle

The performance of the triple-pressure level (TPL) single-stage absorption cycle operated with various organic refrigerants and absorbents showed many advantages over the common double-pressure level (DPL) absorption cycle. In order to enhance these advantages (increased COP and decreased generator temperature); the jet ejector was replaced by a mechanical compressor and a mixing device. In the modified triple-pressure level absorption cycle, the compressor was inserted in the super heated refrigerant line between the evaporator and the absorber. The influence of the elevated pressure on the performance of the TPL absorption cycle with the working fluid pentafluoroethane (R125) and N,N′-dimethylethylenurea (DMEU) was predicted by a computerized simulation program. The performances of the TPL absorption cycle operated with mechanical compressor or jet ejector and the DPL absorption cycle were compared. Based on the analysis the following advantages were achieved: a significant reduction of the required generator temperature (i.e., ability to use low grade heat source such as solar energy), increased coefficient of performance (COP), reduction in the circulation ratio (f) and the reduction of the actual size of the solution heat exchanger. The disadvantage of inserting the compressor is increased electricity consumption.