Numerical evaluation of thermal performances of diffusion-absorption refrigeration using 1,3-dimethylimidazolylium dimethylphosphate/methanol/helium as working fluid

The thermal performances of diffusion-absorption refrigeration using 1,3-dimethylimidazolylium dimethylphosphate/methanol/helium as working fluid were numerically analyzed. The operating characteristics of bubble pump, boiler, and evaporator were investigated. The variations in the coefficient of performance and exergy efficiencies with different heat inputs of the bubble pump and boiler were simulated and discussed. The thermal performances were compared with those of the butane/nonane/helium and lithium bromide/water/helium systems. The trend of variation in coefficient of performance is accordance to that of the experimental results for butane/nonane/helium system. The optimal coefficient of performance of the proposed system was lower than that of the lithium bromide/water/helium system. But the proposed system possessed the advantages of non-crystallization and non-corrosion, and it could operate at a higher boiler temperature. The exergy losses of each component were calculated and compared with one another. The largest four exergy losses occurred in the condenser, absorber, boiler, and bubble pump, which accounted for approximately two thirds of the total exergy input. The main reason for the exergy loss of the diffusion absorption refrigeration system was the heat transfer with temperature difference.