Thermodynamic analysis of a novel chemical heat pump cycle based on the physical-chemical thermal effects of reversible reaction

摘要

Heat pump is an effective technology for the utilization and upgrading of low-grade heat in building and industrial heating. A novel chemical heat pump based on the reversible reaction of ammonium carbamate (AC) is proposed. Different from the exiting AC -based thermal management system, the proposed cycle can realize the upgrading of low-grade heat. Compared with conventional heat pumps, it is more efficient and environmentally friendly. A thermodynamic model for this cycle is established based on the experimental data of AC reaction equilibrium. The influences of some key parameters, such as the intermediate pressure of the two-stage compressors, the concentration of the mixed solution and the effectiveness of the internal heat exchangers, on the cycle coefficient of performance (COP) are investigated. The results show that the internal heat recovery (intercooler and recuperator) has a huge impact on cycle performance. It can reduce 78.5% of the heat and cold offset loss and improve the cycle COP by 35.6% compared with the cycle without internal heat recovery. The performance comparison with the conventional vapor compression heat pump shows that the proposed cycle has the potential to obtain higher COP thanks to the comparatively higher reaction heat. Under the condition of temperature lift Delta t = 40 degrees C and exothermic temperature t(k) = 50 similar to 100 degrees C, the COP of the proposed cycle is 37.1% and 7.8% higher than that of the conventional cycle with R1234yf and R600 on average, respectively. However, the proposed cycle suffers from large theoretical suction volume and high exhaust temperature for compressor, which can be improved with the increase of endothermic temperature and decrease of temperature lift, respectively.