Energy saving performance assessment of the hybrid refrigeration cycle with working pairs of HFCs and organic absorbents

摘要

With the aim to developing the potential working pairs for the absorption-compression hybrid refrigeration cycle, the energy saving performance of nine different working pairs composed of fluorohydrocarbon refrigerants (HFCs) and organic absorbents have been evaluated. The investigated refrigerants in this work include 1,1,1,2-tetrafluoroethane (R134a), 1,1-difluoroethane (R152a), difluoromethane (R32) and various organic compounds such as N,N-dimethylfomamide (DMF), N/N-dimethylacetamide (DMAC) and dimethylether diethylene glycol (DMEDEG) constitute the absorbents. Especially, the thermodynamics properties of the systems R134a + DMAC, R152a + DMF, R152a + DMAC, R152a + DMEDEG, R32 + DMAC and R32+DMEDEG have been measured and evaluated in our previous works. Firstly, with the aid of Aspen Plus software, the overall coefficient performance (COP_(HC)) and circulation ratio (f) of the hybrid refrigeration cycle were calculated for the nine working pairs. Then the systems R32 + DMF, R32 + DMAC, R152a + DMAC and R134a + DMF were selected as the potential working pairs based on above cycle performance for further simulation study. In addition, on the basis of two new cycle evaluation criterions, the heat powered coefficient of performance (ω) and electricity saving rate (η), the effects of generator temperature, absorber temperature and compressor outlet pressure ratio (λ) on the energy saving performance were also discussed. The results show that the ω and η values increase with increasing generator temperatures, but decrease with increasing absorber temperatures. It is also found that the systems R152a + DMAC and R134a + DMF exhibit obvious advantage in electricity saving benefits than others when the generator temperature is higher than 80°C. What's more, under the specified working conditions, there is an optimum compressor outlet pressure ratio which corresponds to the maximum ω and η values of the hybrid refrigeration cycle. The maximum electricity saving rate value 66.33% is obtained by the system R152a + DMAC, followed by R134a + DMF, R32 + DMF and R32 + DMAC systems, the maximum electricity saving rate values of them are 62.65%, 50.01% and 46.03%, respectively. In terms of overall energy saving performances, the systems R152a + DMAC and R134a + DMF are better options to be investigated and developed as the working pairs for the hybrid refrigeration cycle.