Abstract
Aiming at exploring advanced absorption power generation (APG) cycles using ammonia-water as working solution, the present study has studied one double-effect, one half-effect and one ejector-combined APG cycles based on one of the most widely studied APG cycles – Kalina KCS-11. The performance of these advanced cycles were numerically analyzed and compared against KCS-11 in terms of power output, energy and exergy efficiencies. An optimal mass fraction of ammonia-water solution used in KCS-11 has been identified to achieve the maximum energy and exergy efficiencies, which were 0.09–0.14 and 0.65–0.72 respectively when using 70.0–100.0°C boiling temperature; however, the corresponding power output was only 23.0–48.0% of its maximum potential. The double-effect APG cycle could effectively improve the energy and exergy efficiencies by 3.6–12.6%, 10.7–28.2% and 19.0–900.0% respectively when using 100.0°C, 120.0°C and 140.0°C boiling temperature; but its power output capacity was about 43.0–63.0% lower. The half-effect cycle could provide larger pressure ratio for power generation, which amplified the power output by 50.0–85.0% but sacrificed its energy and exergy efficiencies by 4.0–45.0% compared to that of KCS-11. To pursue higher energy and exergy efficiencies without a bulky two-stage system, one can replace the throttling valve and mixer in KCS-11 by an ejector to form a ejector-combined APG cycle, which could improve the system energy efficiency by 2.9–6.8% when using 80.0–100.0°C boiling temperature, while the power output capacity was only slightly influenced.
Highlights
The global fossil energy usage grows rapidly in the last few decades, resulting in severe economic and environmental issues
Hettiarachchi et al [9] concluded that KCS-11 generally had better heat source and working fluid utilization efficiencies comparing to organic Rankine cycle (ORC), and there existed an optimal ammonia mass fraction of the basic working solution to yield best system energy efficiency at a given turbine inlet pressure
The present work has studied three different advanced absorption power generation (APG) cycles based on KCS-11, including one doubleeffect cycle, one half-effect cycle and one ejector-combined cycle, the corresponding performance including work output, energy efficiency and exergy efficiency were numerically investigated and compared
Summary
The global fossil energy usage grows rapidly in the last few decades, resulting in severe economic and environmental issues. Hettiarachchi et al [9] concluded that KCS-11 generally had better heat source and working fluid utilization efficiencies comparing to organic Rankine cycle (ORC), and there existed an optimal ammonia mass fraction of the basic working solution to yield best system energy efficiency at a given turbine inlet pressure. KCS-11 cycle could have the maximum thermal efficiency at 12.95% when its turbine inlet pressure was at 40.0 bar and the basic working solution had the ammonia mass fraction at 0.8, the overall energy efficiency of the coal-fire power plant was improved by 0.277%. Elsayed et al [14] revealed that the KCS-11 using the ammonia-water solution with 0.55 ammonia mass fraction could achieve 20.0–40.0% higher thermal efficiency than that of ORC under the conditions of 15.0 bar turbine inlet pressure, 100.0 °C heat source and 10.0 °C heat sink. The present work has studied three different advanced APG cycles based on KCS-11, including one doubleeffect cycle, one half-effect cycle and one ejector-combined cycle, the corresponding performance including work output, energy efficiency and exergy efficiency were numerically investigated and compared
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