Organic Rankine Cycles (ORCs) are recognized as suitable systems to convert the thermal energy from low-grade heat sources to electricity. However, their performance and reliability are subjected to several deficiencies especially at micro-to-small scales. In this work, the impact of the expander lubricant oil on the performance of the heat exchangers and the scroll expander of a non-regenerative, micro-scale ORC unit is investigated. In particular, the oil circulation rate (OCR) is theoretically assessed for each experimental data set based on the thermal balance between the hot and cold streams of the condenser. Then, the performance of the other components is assessed using the lubricant-R134a mixture properties, assuming the same OCR.

Results have shown that the presence of the lubricant oil leads to 5–15% capacity loss of the evaporator and the condenser of the studied ORC system. The calculated mass charge of the evaporator can also be underestimated up to 6.5% approximately if the oil is neglected. In addition, neglecting the lubricant oil may lead to over-estimation of the expander mechanical efficiency and under-estimation of its volumetric efficiency up to about 50% in very low shaft speeds. Hence, despite it is usually neglected in the literature, the results of the present analysis show that the impact of expander oil is relevant in micro-scale ORC systems.

有机朗肯循环（ORC）被认为是将低级热源的热能转化为电能的合适系统。但是，它们的性能和可靠性存在一些缺陷，特别是在微型到小规模的情况下。在这项工作中，研究了膨胀剂润滑油对非再生微型ORC单元的热交换器和涡旋膨胀器性能的影响。特别地，理论上基于冷凝器的热流和冷流之间的热平衡为每个实验数据集评估油循环速率（OCR）。然后，使用相同的OCR，使用润滑剂R134a的混合物性能评估其他组件的性能。

结果表明，润滑油的存在导致所研究的ORC系统的蒸发器和冷凝器的容量损失5–15％。如果忽略了机油，则蒸发器的计算出的装料量也可能被低估约6.5％。另外，在极低的轴转速下，忽略润滑油可能会导致膨胀机机械效率的高估，而其容积效率的低估可能高达50％。因此，尽管在文献中通常忽略了它，但本分析结果表明，膨胀油的影响在微型ORC系统中是相关的。