有机工质热稳定性的离解能预测方法

Dissociation Energy Prediction Method for the Working Fluid Thermal Stability

有机朗肯循环(Organic Rankine Cycle,ORC)在可再生能源和工业余热等领域有着广泛的应用,目前热源温度范围更高的超临界ORC由于其高效率、低损失等优势得到广泛的关注。随着热源温度的提高,有机工质的热稳定性成为更为重要的工质性质,是工质筛选工作中需要首先确定的关键因素。目前针对有机工质热稳定性的研究主要集中在实验方面,而要对上百种适用工质进行筛选,合适的理论预测方法是必要的。本文提出了一种对有机工质热稳定性进行预测的离解能预测方法,可以实现对于不同种类有机工质热稳定性的理论预测。计算结果表明工质的最小离解能能够很好的表征工质热稳定性的相对大小;同时选择HFE7100作为验证对象对预测方法进行实验验证,发现实验结果与预测结果相符合。同时通过对最小离解能的计算对不同官能团对工质热物性的影响以及不同种类工质在超临界ORC中的适用性进行了分析讨论。

The Organic Rankine Cycles （ORCs） have wide application prospects in the renewable energy utilization and industry waste heat recovery. The high temperature （150-350°） ORCs have attracted much interest due to their high efficiencies and less losses. The working fluid thermal stability is the primary limitation for the high temperature ORCs due to the decomposition of working fluids at high temperatures. A proper theoretical prediction method for thermal stability is needed due to hundreds of potential working fluids, which were hard to be measured experimentally. This paper presented a dissociation energy prediction method for thermal stability, which was suitable for various kinds of working fluids. The minimum dissociation energyvalues were consistent with the relative values of existing experimental decomposition temperatures. A decomposition experiment was designed to verify the prediction method with HFE7100 as test fluid. The results showed that the pre- diction result was consistent with the experimental result. The effects of different functional groups on fluid thermal stability and the applicability of different fluids for supercritical ORCs were also analyzed.