A NEW APPROACH FOR EVALUATING THE RANKINE CYCLE THROUGH ENTROPY GENERATION

Increasing oil prices, the growing demand for energy, the adoption of new regulations for greenhouse gases and other harmful particulate emissions, as well as political instabilities and crises have necessitated the design of more efficient and environmentally-friendly plants. This paper presents a useful combination of mean cycle irreversibility (MCI) for thermodynamically optimizing the Rankine cycle using the MCI as the currently proposed criterion. The thermal irreversibilities and physical size of a system are evaluated together using the criterion that aims to minimize the ratio of the thermal irreversibilities or exergy destruction to a specified size that is characterized as the difference between the maximum and the minimum specific volumes of the cycle. The analyses consider the effects of different boiler-outlet or turbine-inlet pressures and temperatures, different condenser pressures, and different isentropic efficiencies on cycle performance. The results show that increasing the inlet temperature for a constant turbine-inlet pressure increases the MCI and increasing the turbine-inlet pressure at a constant inlet temperature decreases the MCI. With boiler pressure at 500 kPa, the boiler temperature increases from 500K to 600K, the MCI value increases nearly seven-fold, and thermal efficiency increases from 14% to nearly 16%. Also, the results show that the criterion gives more beneficial information to designers and engineers in terms of exergy destruction for designing more environmentally friendly and smaller thermal systems.

Keywords:

Rankine Cycle Entropy Generation, Exergy Density,

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[1] Bejan, A. (1996). Entropy generation minimization: The new thermodynamics of finite-size devices and finite-time processes. J. Appl. Phys., 79(3), 1191–1218.
[2] Bejan, A. (2012). Entropy generation minimization, exergy analysis, and the constructal law,” Arab. J. Sci. Eng., 38(2), 329–340.
[3] Martins, J. J. G., Ribeiro, B. S., & Ion, V. (2009). Thermodynamic analysis of spark ıgnition engines using the entropy generation minimisation method. Int. J. Exergy, 6(1), 93.
[4] Haseli, Y. (2013). Performance of ırreversible heat engines at minimum entropy generation. Appl. Math. Model., 37(23), 9810–9817.
[5] Tchanche, B. F., Lambrinos, G., Frangoudakis, A., & Papadakis, G. (2011). Low-grade heat conversion into power using organic Rankine cycles - A review of various applications. Renew. Sustain. Energy Rev., 15(8), 3963–3979.
[6] Zhang, X., Wu, L., Wang, X., & Ju, G. (2016). Comparative study of waste heat steam SRC, ORC, and S-ORC power generation systems in medium-low temperature. Appl. Therm. Eng., 106, 1427–1439.
[7] Andreasen, J., Meroni, A., & Haglind, F. (2017). A comparison of organic and steam Rankine cycle power systems for waste heat recovery on large ships. Energies, 10(4), 547.
[8] Sahin, B., Kodal, A., & Yavuz, H. (1995). Efficiency of a Joule-Brayton engine at maximum power density. J. Phys. Appl. Phys., 28(7), 1309.
[9] Üst, Y., Sahin, B., & Kodal, A. (2005). Ecological coefficient of performance (ECOP) optimization for generalized irreversible Carnot heat engines. J. Energy Inst., 78(3), 145–151.
[10] Ust, Y., Sogut, O. S., Sahin, B., & Durmayaz, A. (2006). Ecological coefficient of performance (ECOP) optimization for an ırreversible Brayton heat engine with variable-temperature thermal reservoirs,” J. Energy Inst., 79(1), 47–52.
[11] Yeğiner, Y., Kenç, S., Özkol, I., & Kömürgöz, G. (2013). ECOP-based comparative study of thermodynamic cycles. Appl. Mech. Mater., 390, 655–659.
[12] Chen, L., Zhang, W., & Sun, F. (2007). Power, efficiency, entropy-generation rate and ecological optimization for a class of generalized ırreversible universal heat-engine cycles. Appl. Energy, 84(5), 512–525.
[13] Karakurt, A. S., & Sahin, B. (2019). A new method for the size and performance analyses and optimization of thermal systems: The exergy density. Sigma J. Eng. Nat. Sci., 37(2), 573–583.
[14] Gunes, U., Karakurt, A. S., & Sahin, B. (2019). The effect of size on entropy generation for waste heat recovery boiler. Paper presented at The 32nd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy System (pp. 809–818). Wroclaw, Poland
[15] Klein, S. A., & Alvarado, F. L. (2019). EES-engineering equation solver. F-Chart Software, 4406 Fox Bluff Rd., Middleton, WI.
[16] Karakurt, A. S. (2018). A new method for the size and performance optimization of thermal systems: The exergy density (unpublished doctoral dissertation). Yildiz Technical University, Istanbul Turkey.
[17] Üst, Y., Sahin, B., & Kodal, A. (2005). Ecological coefficient of performance (ECOP) optimization for generalized ırreversible Carnot heat engines. J. Energy Inst., 78(3), 145–151.

Başlangıç: 2015
Yayıncı: YILDIZ TEKNİK ÜNİVERSİTESİ

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