The binary-flashing cycle (BFC) is supposed to be a promising technology for geothermal recovery due to the full use of geofluid. For further performance improvement, the potential of using mixtures of a hydrocarbon and a retardant in the BFC system is investigated. R245fa is selected as a retardant and blended with R600 to form zeotropic mixtures. With the thermal efficiency (ηth), exergy efficiency (ηex), net power output per ton geofluid (PRW), and exergy destruction rate (Ed) as evaluation indexes, the flowsheet modeling and optimization are conducted to explore the optimal compositions and operating parameters. It is revealed the optimal mass fraction of R600/R245fa is 0.44/0.56, at which the flammability of R600 is suppressed, the global warming potential (GWP) of R245fa is reduced. The maximum ηex and PRW are higher than those of component fluids. The maximum Ed occurs in the heat exchanger, which should be optimized. The recommended generation pressures are 1200–1430, 1240–1480, 1220–1460, and 1170–1420 kPa, respectively, for R600 mass fraction of 0.2, 0.4, 0.6, and 0.8. In addition, the flashing temperature is also optimized. Although the mixtures do not always yield superior performance, it is still beneficial to apply the mixtures to the BFC system through systematic consideration of safety and environmental friendliness.

中文翻译：

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共沸混合物为工作流体的地热二元闪蒸循环研究

由于充分利用了地流，二元闪蒸循环（BFC）被认为是一种有前途的地热回收技术。为了进一步提高性能，研究了在BFC系统中使用碳氢化合物和阻燃剂的混合物的潜力。选择R245fa作为阻燃剂，并与R600共混以形成共沸混合物。以热效率（ηth），火用效率（ηex），每吨土流的净功率输出（PRW）和火用破坏率（Ed）作为评估指标，进行了流程建模和优化，以探索最佳组成和运行参数。结果表明，R600 / R245fa的最佳质量分数为0.44 / 0.56，可抑制R600的可燃性，降低R245fa的全球变暖潜能。最大ηex和PRW高于组分流体的最大ηex和PRW。最大Ed发生在热交换器中，应对其进行优化。对于R600质量分数为0.2、0.4、0.6和0.8的建议生成压力分别为1200–1430、1240–1480、1220–1460和1170–1420 kPa。另外，闪蒸温度也被优化。尽管混合物并不总是能产生优异的性能，但通过系统地考虑安全性和环境友好性，将混合物应用于BFC系统仍然是有益的。