Thermodynamic analysis of a novel sodium hydroxide-water solution absorption refrigeration, heating and power system for low-temperature heat sources

Abstract

A novel sodium hydroxide-water solution absorption refrigeration, heating and organic Rankine cycle power system is proposed for low-temperature heat source utilization. The sodium hydroxide-water solution absorption refrigeration is employed as top cycle which directly absorbs heat from low-temperature heat source. While R218 organic Rankine cycle and heating subsystem are adopted to produce power and heating as designed in bottom cycles. Under the considered condition, model results indicate that refrigeration, heating and electricity efficiency are 0.8244, 0.4019 and 0.03437 with the capacity of 945.2, 460.8 and 39.41 kW, respectively. Energy and exergy efficiency of refrigeration, heating and electricity are also theoretically analyzed with various condensation temperature, evaporation temperature, turbine inlet pressure, split ratio and mass fraction of rich sodium hydroxide solution. Sensitivity of parameters to system performance is also analyzed and results indicate that energy and exergy efficiency are remarkably influenced by operating parameters. A comparison between the proposed system and three independent electrical refrigeration, heating and power systems shows that the proposed system has superior performance and the maximum primary energy saving ratio can reach approximately 0.4889. In conclusion, with the multi-productions of refrigeration, heating and electricity, the proposed polygeneration system provides a more rational and effective energy utilization from a single low temperature heat source at suitable level.