Abstract Dual-pressure organic Rankine cycle (DPORC) is a technology with great potential to solve energy problems. This paper performs constructal thermodynamic optimization (CTO) for the DPORC based on a combination of constructal theory and finite-time thermodynamics. The tube outside diameters of the heat exchangers, such as high- and low-temperature evaporators (HTE and LTE) and condenser, and the volume ratio of the high-pressure turbine are the design variables, the system net power output (POW) is the optimization function, and the total volume of the turbines and total heat transfer area (HTA) of the heat exchangers are the constraints. The influences of some parameters, such as the HTA ratios of the HTE and LTE, and the total mass flow rate (MFR) of the working medium on the CTO results are studied. The performance comparison between the DPORC and single-pressure ORC (SPORC) is carried out under the same conditions. The results demonstrate that the system net POWs after the four stepwise CTOs are improved by 1.70%, 3.01%, 5.80% and 8.84% over against the initial system net POW, respectively. Reducing the HTA ratios of the HTE and LTE and increasing the total MFR of the working medium can increase the system net POW. Compared with the performance of the SPORC, the system net POW and system net thermal efficiency of the DPORC are increased by 4.91% and 5.51%, respectively. The optimization results can be used to guide the optimal designs of the low-temperature waste heat utilization systems.

中文翻译：

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余热利用系统双压有机朗肯循环的构型热力学优化

摘要 双压有机朗肯循环（DPORC）是一项在解决能源问题方面具有巨大潜力的技术。本文结合构造理论和有限时间热力学，对 DPORC 进行构造热力学优化 (CTO)。高低温蒸发器（HTE、LTE）、冷凝器等换热器管外径、高压汽轮机容积比为设计变量，系统净输出功率（POW）为优化函数，涡轮机的总体积和换热器的总传热面积（HTA）是约束条件。研究了HTE和LTE的HTA比、工质总质量流量(MFR)等参数对CTO结果的影响。DPORC和单压ORC（SPORC）的性能比较是在相同条件下进行的。结果表明，经过四次逐步 CTO 后的系统净 POW 比初始系统净 POW 分别提高了 1.70%、3.01%、5.80% 和 8.84%。降低 HTE 和 LTE 的 HTA 比率并提高工作介质的总 MFR 可以提高系统净 POW。与SPORC的性能相比，DPORC的系统净POW和系统净热效率分别提高了4.91%和5.51%。优化结果可用于指导低温余热利用系统的优化设计。结果表明，经过四次逐步 CTO 后的系统净 POW 比初始系统净 POW 分别提高了 1.70%、3.01%、5.80% 和 8.84%。降低 HTE 和 LTE 的 HTA 比率并提高工作介质的总 MFR 可以提高系统净 POW。与SPORC的性能相比，DPORC的系统净POW和系统净热效率分别提高了4.91%和5.51%。优化结果可用于指导低温余热利用系统的优化设计。结果表明，经过四次逐步 CTO 后的系统净 POW 比初始系统净 POW 分别提高了 1.70%、3.01%、5.80% 和 8.84%。降低 HTE 和 LTE 的 HTA 比率并提高工作介质的总 MFR 可以提高系统净 POW。与SPORC的性能相比，DPORC的系统净POW和系统净热效率分别提高了4.91%和5.51%。优化结果可用于指导低温余热利用系统的优化设计。DPORC的系统净POW和系统净热效率分别提高了4.91%和5.51%。优化结果可用于指导低温余热利用系统的优化设计。DPORC的系统净POW和系统净热效率分别提高了4.91%和5.51%。优化结果可用于指导低温余热利用系统的优化设计。