Parameter significance in exergy destruction: Comparative analysis of working fluid and temperature effects in low-temperature geothermal energy conversion

Abstract

bahadiryuce@uludag.edu.tr This study analyzed the effect of the refrigerant type selection, condenser and evaporator temperatures on thermal efficiency, network output, second-law efficiency, and exergy destruction values obtained with an advanced approach to exergy analysis. The thermal source was considered a low-temperature geothermal resource at 90 degrees C. The refrigerants R11, R123, and R245ca were used as a working fluid. The evaporator and condenser temperatures investigated were 76 degrees C, 80 degrees C, 84 degrees C, and 26 degrees C, 31 degrees C, and 36 degrees C, respectively. Firstly, the thermodynamic aspects were validated by using the literature study. Then, the L27 orthogonal array was created, and further the Taguchi method was applied to objectives. The ranking order of parameters and optimum cases were obtained by calculating signal-to-noise (S/N) ratios. Subsequently, the ANOVA method was applied, yielding satisfactory R2 values and allowing for the determination of the impact ratios of the parameters. Because of the diverse nature of objectives, the contribution ratios of parameters have different values. The contribution ratio results showed that the working fluid is the most important and dominant parameter for net work output (95.1%) and endogenous (97%), avoidable (97.6%), and unavoidable (95%) exergy destructions. Alternatively, the condenser temperature is the most important parameter for thermal efficiency (66.6%), second-law efficiency (66.6%), and exogenous exergy destruction (62.2%). The results showed the rank order of the parameters and the contribution ratio values are largely compatible.