利用液化天然气余冷与氨供冷的低温制冷系统性能对比

目的:对比研究利用液化天然气(LNG)余冷和氨供冷的低温制冷系统性能。方法:利用MATLAB建立两个系统的热力学和经济学模型,在基本参数下,选择适合LNG低温制冷系统的工质质量分数,同时分别改变冷间温度和制冷量,对两系统的热经济性进行对比分析。结果:随着乙二醇质量分数增加,LNG质量流量、系统功耗、蓄冷量增加,制冷系统性能系数(COP)减小,而乙二醇质量流量不变;随着冷间温度的升高,系统COP增大,而工质质量流量、功耗随之降低。同样,随着制冷量的增大,质量流量、功耗均升高,而氨低温制冷系统COP不变,LNG低温制冷系统COP增加,在5~20 kW时LNG低温制冷系统COP低于氨低温制冷系统,而20~30 kW时相反。经济性能对比表明:LNG低温制冷系统的投资费用远低于氨低温制冷系统。结论:在相同工况下,利用LNG余冷的低温制冷系统的热力学性能和经济学性能优于传统的氨低温制冷系统。

Performance comparison of cryogenic refrigeration system using LNG wasted cold and ammonia refrigeration

bjective:To compare the performance of cryogenic refrigeration system using LNG wasted cold and ammonia cooling.Methods:The thermodynamic and economic models of the two systems were established by MATLAB. Under the basic parameters, the working medium concentration suitable for LNG low-temperature refrigeration system was selected, and the cold storage temperature and refrigeration capacity were changed respectively. The thermal economy of the two systems was compared and analyzed.Results:With the increase of ethylene glycol concentration, LNG mass flow, system power consumption and cold storage capacity increased, COP decreased, but ethylene glycol mass flow remained unchanged; With the increase of cold storage temperature, the system COP increased, while the working medium mass flow and power consumption decrease. Similarly, with the increase of refrigeration capacity, the mass flow and power consumption increase, while the COP of ammonia low-temperature refrigeration system remained unchanged and the COP of LNG low-temperature refrigeration system increased. In the range of 5~20 kW, the COP of LNG low-temperature refrigeration system was lower than that of ammonia low-temperature refrigeration system, and the opposite was true in the range of 20~30 kW. The comparison of economic performance showed that the investment cost of LNG cryogenic refrigeration system was much lower than that of ammonia cryogenic refrigeration system.Conclusion:Under the same working conditions, the thermodynamic and economic performance of the low-temperature refrigeration system using LNG wasted cold is better than that of the traditional ammonia low-temperature refrigeration system.