关键词: 工业余热利用, 高温热泵, 压缩-吸收耦合热泵, 混合工质, 经济性分析

Abstract:

There is insufficient research on working fluid optimization， thermodynamic characteristics and economic performance analysis of existing coupled heat pumps providing 150 ℃ heat supply. Therefore， a 150 ℃ compression-absorption coupled high-temperature heat pump unit was proposed， to improve the utilization rate of low-temperature waste heat， lower the energy consumption in industrial high-temperature heat supply and decrease the operational costs of the unit. A system mathematical model was established based on steady-state thermodynamics， and pure working fluids on the high-pressure side and binary mixed working fluids on the low-pressure side were screened. The effects of evaporator-condenser temperature， heating temperature， waste heat outlet temperature， and compression ratio of the water vapor compressor on the thermodynamic performance of the unit were analyzed， and comparison of economic efficiency was conducted. The results showed that the optimal working fluid on the high-pressure side was trans-1-chloro-3，3，3-trifluoropropene， the optimal mixed working fluid on the low-pressure side was n-Pentane（R601）/cis-1，3，3，3-tetrafluoropropene， the optimal mole fraction of R601 was 0.69， and the coefficient of performance （COP） of the system was 5.16. When the evaporator-condenser temperature increased from 85 ℃ to 95 ℃， the COP decreased from 2.16 to 2.02， while the heating capacity increased from 739.29 kW to 761.26 kW. When the heating temperature increased from 140 ℃ to 160 ℃， the COP decreased from 2.22 to 1.97， while the heating capacity increased from 727.00 kW to 774.95 kW. When the waste heat outlet temperature increased from 40 ℃ to 50 ℃， the COP increased from 1.91 to 2.14， while the heating capacity decreased from 1 314.83 kW to 617.46 kW. When the compression ratio of the water vapor compressor increased from 1.20 to 1.70， the COP decreased from 2.14 to 2.06， the mass fraction of concentrated lithium bromide solution increased from 54.16% to 58.02%， and the circulation ratio decreased from 6.56 to 4.79. Under the same heating capacity， the hourly operating cost of the coupled heat pump system was reduced by 55.6% and 72.8% compared to gas boilers and electric boilers， respectively. The findings indicate that the coupled heat pump unit shows good thermodynamic performance and economic efficiency， and has promising application prospects in deep recovery of industrial medium- and low-temperature waste heat and substitution for high-temperature heat supply.

Key words: industrial waste heat utilization, high-temperature heat pump, compression-absorption coupled heat pump, mixed working fluid, economic analysis