Hybrid single-stage triple pressure level absorption/compression cycle operated by low grade heat sources

The performance of the triple-pressure level (TPL) single stage absorption cycle operated with organic refrigerants and absorbents showed many advantages over the common double pressure level (DPL) absorption cycle. In order to enhance these advantages (increased COP) a mechanical compressor and a mixing device were 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'-dimethylethylurea (DMEU) was predicted by a computerized simulation program. The performances of two configurations of the TPL absorption cycle operated with mechanical compressor were compared; a) with common solution heat exchanger (HS) and b) divided solution heat exchanger (pApG). Based on the analysis, in the first configuration a significant reduction of the required generator temperature with increased coefficient of performance (COP), reduction in the circulation ratio (f) and reduction of the actual size of the solution heat exchanger was found. In the second configuration a significant increasing of the COP with less reduction of the required generator temperature but with increased actual size of the solution heat exchanger was found. The disadvantage of inserting the compressor is the increased electrical consumption.