Thermodynamic and Exergoeconomic Performance Evaluation of Single and Double-Flash Steam Cycles With Heat Exchanger Integration: Exergetic and Economic Optimization

Öz

Liquid-dominated geothermal energy sources with temperatures above 150 °C provide suitable conditions for flash steam production due to their high pressure. Geothermal energy is considered as an environmentally friendly and sustainable renewable energy source due to its minimal greenhouse gas emissions compared to fossil fuel-based energy sources. Improving the thermodynamic and economic performance of these energy systems is crucial, particularly for increasing overall system efficiency and long-term sustainability. In this study, mathematical models of the proposed single and double-flash steam cycles were created using EES software and the performances of these systems were compared. The exergy efficiency and sum unit cost of the product (SUCP) of the proposed systems were considered as objective functions. The mass flow rate of the geothermal fluid directed to the heat exchanger and the flashing pressures in the high and low pressure regions were selected as the decision variables. The optimum design conditions were determined as a result of multivariate, single-objective optimizations performed with the genetic algorithm method. The results show that the optimum points obtained from exergetic and economic optimizations are quite close to each other. As a result of the exergetic optimization of the single-flash steam cycle, energy efficiency, exergy efficiency, and SUCP was calculated as 10.52%, 44.4%, and 4.3 dollars/GJ, respectively. The electrical power output produced by the system was determined as 11,422.5 kW. In addition, 32.08% of the total exergy entering the system was destroyed due to irreversibility, while 23.52% was discharged as exergy losses. In the double-flash steam cycle, energy efficiency, exergy efficiency, and SUCP were determined as 12.59%, 53.1%, and 3.98 dollars/GJ, respectively. The electrical power output produced by the system was determined as 13,660.5 kW. Also, 35.92% of the total exergy entering the system was destroyed due to irreversibility, while 10.98% was discharged as exergy losses. Exergetic optimization results indicate that the double-flash steam cycle generated 2,238 kW more power than the single-flash steam cycle, resulting in a 19.6% increased in exergy efficiency and a 7.4% decreased in SUCP. The findings show that careful optimization of the proposed design parameters in flash steam cycle systems has a significant impact on overall system performance. In addition, the waste energy released at the end of the process can be recovered and utilized as a heat source in applications such as district heating, greenhouse heating, food drying, and low-temperature Organic Rankine Cycle systems, thereby enhancing the overall energy recovery potential of the system.

Anahtar Kelimeler

• Geothermal energy
• Flash steam cycle
• Genetic algorithm
• Optimization

Kaynakça

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