Organic Rankine cycle (ORC) is an effective way for low to medium grade heat to power conversion. A suitable cycle form (subcritical or trans-critical, whether to use a regenerator) is the guarantee of good cycle performance. The selection of cycle forms strongly depends on the heat source conditions. In this work, the heat source types and ORC forms are introduced firstly. Then the cycle form selection criteria are obtained through theoretical derivation, directly from the heat source parameters and getting rid of the working fluid properties, thus, having more universal applicability. The main criteria include: when $T_{\text{hs,out}}>\frac{T_{\text{hs,in}}+\Delta T_{\text{p}}+T_{\text{cd}}}{2}$(T_hs,out is the outlet temperature of the heat source, T_hs,in is the inlet temperature of the heat source, $\Delta T_{\text{p}}$ is the pinch temperature difference between the heat source and the working fluid, T_cd is the working fluid condensation temperature), subcritical ORC has better thermodynamic performance than trans-critical cycle; when $T_{\text{hs,out}}>\frac{2T_{\text{hs,in}}+\Delta T_{\text{p}}+T_{\text{cd}}}{3}$, a regenerator is needed to improve the cycle performance. At last, simulation results of 35 working fluids for four typical heat sources are used to verify the theoretical criteria.

有机朗肯循环 (ORC) 是一种有效的中低档热能转换方式。合适的循环形式（亚临界或跨临界，是否使用再生器）是良好循环性能的保证。循环形式的选择很大程度上取决于热源条件。在这项工作中，首先介绍了热源类型和 ORC 形式。然后通过理论推导，直接从热源参数中，剔除工质性质，得到循环形式选择标准，具有更普遍的适用性。主要标准包括：当${吨}_{\text{hs,out}}>\frac{{吨}_{\text{小时，输入}}+\Delta {吨}_{\text{磷}}+{吨}_{\text{光盘}}}{2}$（T _hs,out为热源出口温度，T _hs,in为热源入口温度，$\Delta {吨}_{\text{磷}}$为热源与工质的夹点温差，T _cd为工质冷凝温度），亚临界 ORC 比跨临界循环具有更好的热力学性能；什么时候${吨}_{\text{hs,out}}>\frac{2{吨}_{\text{小时，输入}}+\Delta {吨}_{\text{磷}}+{吨}_{\text{光盘}}}{3}$，需要一个再生器来提高循环性能。最后利用4种典型热源的35种工质的仿真结果对理论判据进行验证。