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The Optimal Evaporation Temperature of Subcritical ORC Based on Second Law Efficiency for Waste Heat Recovery
Key Laboratory of Low-grade Energy Utilization Technologies and Systems of Ministry of Education, College of Power Engineering, Chongqing University, Chongqing 400030, China
Renewable Energy School, North China Electric Power University, Beijing 102206, China
* Author to whom correspondence should be addressed.
Received: 1 February 2012; in revised form: 23 February 2012 / Accepted: 27 February 2012 / Published: 6 March 2012
Abstract: The subcritical Organic Rankine Cycle (ORC) with 28 working fluids for waste heat recovery is discussed in this paper. The effects of the temperature of the waste heat, the critical temperature of working fluids and the pinch temperature difference in the evaporator on the optimal evaporation temperature (OET) of the ORC have been investigated. The second law efficiency of the system is regarded as the objective function and the evaporation temperature is optimized by using the quadratic approximations method. The results show that the OET will appear for the temperature ranges investigated when the critical temperatures of working fluids are lower than the waste heat temperatures by 18 ± 5 K under the pinch temperature difference of 5 K in the evaporator. Additionally, the ORC always exhibits the OET when the pinch temperature difference in the evaporator is raised under the fixed waste heat temperature. The maximum second law efficiency will decrease with the increase of pinch temperature difference in the evaporator.
Keywords: organic Rankine cycle; OET; second law efficiency; waste heat temperature; pinch temperature difference; waste heat recovery
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MDPI and ACS Style
Liu, C.; He, C.; Gao, H.; Xu, X.; Xu, J. The Optimal Evaporation Temperature of Subcritical ORC Based on Second Law Efficiency for Waste Heat Recovery. Entropy 2012, 14, 491-504.
Liu C, He C, Gao H, Xu X, Xu J. The Optimal Evaporation Temperature of Subcritical ORC Based on Second Law Efficiency for Waste Heat Recovery. Entropy. 2012; 14(3):491-504.
Liu, Chao; He, Chao; Gao, Hong; Xu, Xiaoxiao; Xu, Jinliang. 2012. "The Optimal Evaporation Temperature of Subcritical ORC Based on Second Law Efficiency for Waste Heat Recovery." Entropy 14, no. 3: 491-504.