The transcritical CO power cycle has been recognized as a highly promising technique for reducing carbon emissions in heat utilization. However, this technology is limited because of the critical parameters of pure CO (including low critical temperature and high critical pressure). To overcome these limitations, one potential solution is to introduce a new working fluid consisting of a blend of hydrofluoroolefins (HFOs) and CO. Precise knowledge of the critical parameters is essential for accurately evaluating the effectiveness and capacity of CO+HFO mixtures. In this study, the critical properties of the CO + R1336mzz(Z) (cis-1,1,1,4,4,4-hexafluoro-2-butene) blend were determined using a metal-bellows variable volumeter. The critical point was identified by visually observing the critical opalescence and the reappearance of the vapor-liquid meniscus. The Modified Wilson method and the Redlich-Kister method were used to fit critical data. Our results reveal that the CO + R1336mzz(Z) mixture can elevate the critical temperature in comparison to pure CO. The highest critical pressure is achieved when the mole fraction of CO is approximately 0.82. For the critical temperature, critical pressure, critical density, and mole fraction, the expanded combined uncertainties were below 50 mK, 21 kPa, 0.6 %, and 0.004 ( = 2, 95 %), respectively. Meanwhile, the Modified Extended Chueh-Prausnitz (MECP) method and a simplified MECP method were used to predict critical properties of the CO + R1336mzz(Z) binary mixture. Finally, the critical locus of the CO + R1336mzz(Z) mixture was compared with other CO + HFO mixtures.

中文翻译：

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CO2 + R1336mzz(Z) (cis-1,1,1,4,4,4-六氟-2-丁烯)二元混合物关键参数的实验研究和CO2 +氢氟烯烃体系的关键轨迹分析

跨临界二氧化碳动力循环已被认为是一种非常有前途的减少热利用中碳排放的技术。然而，由于纯CO的临界参数（包括低临界温度和高临界压力），该技术受到限制。为了克服这些限制，一个潜在的解决方案是引入一种由氢氟烯烃 (HFO) 和 CO 混合物组成的新工作流体。准确了解关键参数对于准确评估 CO+HFO 混合物的有效性和容量至关重要。在本研究中，使用金属波纹管可变体积计测定了 CO + R1336mzz(Z)（顺式 1,1,1,4,4,4-六氟-2-丁烯）混合物的关键特性。通过目视观察临界乳光和汽液弯月面的再现来确定临界点。采用改进的 Wilson 法和 Redlich-Kister 法来拟合关键数据。我们的结果表明，与纯 CO 相比，CO + R1336mzz(Z) 混合物可以提高临界温度。当 CO 的摩尔分数约为 0.82 时，可以达到最高临界压力。对于临界温度、临界压力、临界密度和摩尔分数，扩展组合不确定度分别低于 50 mK、21 kPa、0.6 % 和 0.004 ( = 2, 95 %)。同时，采用改进的扩展Cueh-Prausnitz (MECP)方法和简化的MECP方法来预测CO + R1336mzz(Z)二元混合物的临界性质。最后，将 CO + R1336mzz(Z) 混合物的临界轨迹与其他 CO + HFO 混合物进行了比较。